GHANA JOURNAL OF FORESTRY - CSIR-FORIG · The Ghana Journal of Forestry (ISSN 0855-1707) is...

VOLUME 31, 2015

ISSN 0855-1707

GHANA JOURNAL OF FORESTRY, VOL. 31, 2015

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Seedling abundance, composition and growth forecastunder two logging intensities in a moist tropical forest in GhanaA.Duah-Gyam�, B. Kyereh, V. K. Agyeman, K. A. Adam K. O. Afriyie and M. D. Swaine.....1 - 20

Methodology for e�cient survey of pests in smallholder tree plantations: �e case of the Community Forestry Management Project in GhanaP. P. Bosu, M. M. Apetorgbor and E. E. Nkrumah….............………………………………….….21 - 33

�e signi�cance of medicinal plants in a valley rice growing eco-system (Sawah): �e case of Ahafo-Ano South District, Ghana E. Nutakor ........................................................................................................................34 - 44

In�uence of indole-3-butyric acid concentrations on rooting of Cinnamomum camphora (L.) Presl marcotsE. A. Owusu, C. M. Asare and S. Ackon…………………………………….................................45 - 50

Calori�c values and gravimetric yield of six wood fuelspecies in the Forest Transition Zone of GhanaJ. K. Korang, B. D. Obiri, H. Appiah and S. Awuku…………………………………............……51 - 61

E�ects of land use changes on �ora diversity in Oban Division of the Cross River National Park, NigeriaE. T. Ikyaagba, S. O. Jimoh and J. I. Amonum…………………………………………….............62 - 77

VOLUME 31, 2015

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Ghana J. Forestry, Vol. 31, 2015 ISSN 0855-1707

GHANA JOURNAL OF FORESTRY

CSIR-FORESTRY RESEARCH INSTITUTE OF GHANA

P. O. BOX UP 63, KNUST

KUMASI, GHANA


VOLUME 31, 2015

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CONTENTS Seedling abundance, composition and growth forecast

under two logging intensities in a moist tropical forest in Ghana

A.Duah-Gyamfi, B. Kyereh, V. K. Agyeman, K. A. Adam

K. O. Afriyie and M. D. Swaine……………………...……………………………................1 - 20

Methodology for efficient survey of pests in smallholder

tree plantations: The case of the Community Forestry

Management Project in Ghana

P. P. Bosu, M. M. Apetorgbor and E. E. Nkrumah…..……………………………………21 - 33

The significance of medicinal plants in a valley rice

growing eco-system (Sawah): The case of Ahafo-Ano

South District, Ghana

E. Nutakor .....................................................................................................................34 - 44

Influence of indole-3-butyric acid concentrations on

rooting of Cinnamomum camphora (L.) Presl marcots

E. A. Owusu, C. M. Asare and S. Ackon……………………………………......................45 - 50

Calorific values and gravimetric yield of six wood fuel

species in the Forest Transition Zone of Ghana

J. K. Korang, B. D. Obiri, H. Appiah and S. Awuku………………………………………51 - 61

Effects of land use changes on flora diversity in Oban Division

of the Cross River National Park, Nigeria

E. T. Ikyaagba, S. O. Jimoh and J. I. Amonum…………………………………………….62 - 77

Seedling abundance, composition and growth forecast in a moist tropical forest in Ghana A. Duah-Gyamfi et al.

Ghana J. Forestry, Vol. 31, 2015, 1 – 20 1

SEEDLING ABUNDANCE, COMPOSITION AND GROWTH FORECAST

UNDER TWO LOGGING INTENSITIES IN A MOIST TROPICAL FOREST IN

GHANA

A. Duah-Gyamfi1, B. Kyereh2, V. K. Agyeman,3, K. A. Adam4, K. O. Afriyie1and M. D. Swaine5

1CSIR-Forestry Research Institute of Ghana, University P. O. Box 63, Kumasi, Ghana

2 Faculty of Renewable Natural Resources, Kwame Nkrumah University of Science and Technology,

Kumasi, Ghana, 3Council for Scientific and Industrial Research (CSIR), Secretariat, Accra

4Ghana Timber Millers’ Organization, Kumasi, Ghana 5Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, U K

Email: [email protected];[email protected]

ABSTRACT

Timber species differ in their response to logging disturbance. Knowledge about the impacts of different

logging intensities is necessary to determine levels of timber extraction compatible with species responses

in order to refine management interventions. We examined the effects of two logging intensities on the

abundance and composition of tree seedlings in gaps in Pra Anum Forest Reserve within a Moist Semi-

deciduous forest in Ghana. In addition, we assessed seedling growth by forecasting the probability of

locating a seedling (≥ 55 cm) in the two logging intensities compared to controls. Logging was carried

out experimentally at two intensities, 26 m3/ha (1 AAC) and 52 m3/ha (2 AAC) of extracted timber, in a

128 ha compartment. Twenty plots each of 60 m2 were randomly established in gaps in each of the

logging treatments and in the unlogged forest. These plots were monitored for number of seedlings and

height growth of timber tree species for 33 months in four different enumerations. We used mixed effect

models to assess the abundance of seedlings over time. A non-metric multidimensional scaling (NMDS)

was used to determine the shifts in species composition. Seedling abundance was significantly different in

gaps for both high and low logging intensities, however, a significant interaction effect between

abundance and time was found only in the low intensity treatment. There was a significant difference in

the rate of change in species composition between the high intensity and unlogged forest (P = 0.03) but

the rate of change between the low intensity and unlogged forest was not significant (P = 0.27). After 3

years, we predicted that it was approximately three and two times more likely to locate a seedling (≥ 55

cm) in the low and high intensity treatments, respectively compared to controls. An explanation for this is

that the high intensity treatment enhanced competition from herbaceous weeds, which affected the

survival and growth of tree seedlings. Based on this result, we recommend enforcement of silvicultural

prescriptions to the management of logged forests in order to achieve the level of forest manipulation

needed to ensure productivity.

Keywords: Abundance, Composition, Gaps, Logging intensity, Model, Selective logging



INTRODUCTION

Timber harvesting is a major land use type in the

tropics and important to the economies of most

tropical countries through its contributions to

Gross Domestic Product (GDP) and foreign

exchange earnings. In 2011, the forest sector

contributed about 1% to GDP worldwide with the

global trade in forest products estimated as US$

421 billion (FAO, 2014). In Ghana, between 2012

and 2014 the forest sector consistently accounted

for about 2% of GDP and a 38% increase in the

value of timber exports from US$ 131.0 to US$

181.2 million (Ghana Statistical Service, 2016).

Despite their recognition as an important resource,

the forests in Ghana as elsewhere in the tropics are

threatened by increasing rates of deforestation and

degradation (Asner et al., 2005, 2009; FAO,

2016). Selective logging of commercially valuable

tree species and unsustainable management

practices have been flagged as major contributors

to the high deforestation rates in Ghana (Damnyag

et al., 2011; Oduro et al., 2011).

Throughout the tropics, selective logging,

involving the harvesting of high-value timber

species and a variable number of stems per hectare

depending on species, is the widely adopted

system for timber harvesting (Appanah, 1998;

Werger, 2011). In Ghana, logging intensity is

generally low, with two to three trees harvested

per hectare in a 40-year felling cycle. While this

low intensity logging may appear ecologically

compatible with sustainable forest management

aspirations, the lack of a standard silvicultural

system accompanying logging poses a serious

challenge to the achievement of quality

regeneration and maintenance of forest

productivity in the production forests. A recent

study by Hawthorne et al., (2012) concluded that

logging practices in Ghana under the current 40-

year felling are not sustainable. If this is true, then

it places in doubt the sustainability of the current

logging practices in the country. Studies such as

the one reported here are required to provide

further insights into the understanding of the

selection system in Ghana.

One of the most evident changes caused by timber

harvesting is the creation of canopy gaps, which

are of fundamental and silvicultural importance to

forest regeneration. Canopy gaps allow more light

into the forest and below the forest canopy in

logged forest (van der Meer et al., 1999). The

increased light levels in turn can induce significant

changes in the microclimate within the forest

(Denslow, 1987; Brown, 1993) and also affect the

pattern of tree seedling recruitment (Brokaw,

1985; Denslow, 1987; Hawthorne, 1993; Nichols

et al., 1998; Chazdon, 2003; Medjibe et al., 2014).

However, the type of species recruited has been

found to be influenced by gap conditions and gap

size (Swaine and Whitmore, 1988; van der Meer

et al., 1999; Medjibe et al., 2014). Large gaps

characterized by increased irradiance and

temperature on the gap floor following logging

favour the germination, establishment and growth

of light demanding pioneers (Brokaw, 1985;

Hawthorne, 1993) as well as saplings of non-

pioneer light demanders (Hawthorne, 1993).

Consequently, shifts in species composition

following disturbances can arise from differences

in species-specific pattern of regeneration through

the logging disturbance. By contrast, other studies

have shown that individual species are not strictly

adapted to gaps of different sizes. For instance,

Brown and Whitmore (1992) found that regardless

of species, seedling size was the most important

determinant of the survival and growth of

seedlings. Kennedy and Swaine (1992) also

reported that gap size had virtually no effect or

influence on the number of germinating seeds.

Felling gaps can also enhance regeneration of fast-

growing herbaceous and woody species,

particularly weeds and lianas, which compete with

newly recruited seedlings for available resources

and can inhibit recruitment (Schnitzer et al, 2000;

Pinard et al., 2000; Fredericksen and Pariona,

2002).



Logging impacts on the forest ecosystem are

variable and depend on factors such as harvest

intensity, harvesting methods and skill of field

personnel, site differences due to soil, topography,

and biota. Some studies have reported a direct

relationship between felling intensity and area

damaged (Hendrison, 1990; Sist et al., 2014). On

the other hand, the direction of the effects of

logging on forest communities is not consistent

among different forests and different species

groups. It is expected that plant species

composition changes would increase

proportionally with logging intensity, particularly

pioneer species which colonize disturbed sites

immediately after logging. Similarly, there is a

positive relationship between felling intensity and

canopy opening, therefore, depending on which

species guild is to be favoured in a particular

compartment, felling intensity may vary (low,

medium or high) in view of the fact that species

with different regeneration strategies respond

differently to logging (Hawthorne, 1993;

Chazdon, 2003). However, studies are needed to

determine appropriate thresholds of low, medium

and high intensity felling in different forest types

(Osho, 1995; Pena-Claros et al., 2008). In

addition, given that logging disturbance increases

the number of available sites for species

regeneration and these sites may be filled only by

species abundant at the right place and time

(Hubbell et al., 1999), it is therefore important to

examine the effects of logging intensity on the

abundance and composition of tree seedlings over

time. This has scarcely been tested in Ghana and

in most West African countries despite the

increasing importance of logging in the subregion.

The objective of this study was to determine the

abundance and composition of tree seedlings in

felling gaps under two logging intensities in a

moist tropical forest in Ghana. We also sought to

predict seedling height growth under the different

logging intensities. The lack of a standard

silvicultural system in the management of Ghana’s

natural forests calls for research to test the

sustainability of the current system. Studies have

shown that whilst regeneration of tree species may

be profuse in the first few years following logging

(Hawthorne, 1993; Duah-Gyamfi et al., 2014a,

2014b), it is not sustained due to the proliferation

of herbaceous weeds and climbers in logging

gaps. Thus, logging without silvicultural practices

cannot attain the desired level of forest

manipulation needed to ensure productivity.

The questions we addressed in this paper and the

corresponding hypothesis were: (i) Are abundance

and composition of timber tree seedlings related to

logging intensity? We expected that the

abundance and composition of tree seedlings

increase with increasing logging intensity, as long

as the forest recovers over time from logging

disturbance. (ii) How does logging intensity

influence height growth of tree seedlings

overtime? In keeping with the results of other

studies, we predicted faster seedling height growth

to be most likely in the most intensively logged

treatment.

The work described in the present paper

complements that of Adam (2003) who examined

ecological and silvicultural considerations in tree

selection in selective logging for natural forest

management in Ghana, and Duah-Gyamfi et al.

(2014b) who compared regeneration on disturbed

sites following logging but did not test the effects

of the logging treatments imposed in the design of

the silvicultural experiment as reported in this

paper.

MATERIALS AND METHODS

The Study Area

Data were collected from the Research Working

Cycle (RWC) of Pra Anum Forest Reserve (6o 16'

N, 1o 12' W) in the South-east sub-type of Moist

Semi-deciduous (MSSE) forest in Ghana (Hall

and Swaine, 1981). Covering an area of about

12,332 ha, Pra Anum has served as timber

production area and silvicultural research station



since 1954 (FIP, 1989). Total mean annual rainfall

and temperature recorded for the period 2000 –

2010 ranged between 98.0 and 170.6 cm and 23.0

and 27.5 °C, respectively. Soils are deeply

weathered and composed of forest oxysol-

ochrosol intergrades (Brammer, 1962). The

relative abundance of common timber species in

the research compartment for trees ≥ 70 cm dbh

are Triplochiton scleroxylon (17.6%), Celtis

mildbraedii (15.4%), Cylicodiscus gabunensis

(8.5%), Turreaenthus africanus (6.9%) and Ceiba

pentandra (6.2%).

Experimental Design and Field Methods

Four experimental blocks approximately 32 ha

each were established in the research

compartment. Each block was designed to be

randomly subjected to one of four types of logging

intensity: low intensity - harvesting of small

stems[i.e. 1 Annual Allowable Cut (AAC = 26.3

m3 ha-1,× small stems)]; low intensity – harvesting

of large stems[i.e. 1 Annual Allowable Cut (AAC

= 26.3 m3 ha-1, × large stems)]; high intensity -

harvesting of small stems [i.e. 2 Annual Allowable

Cut (AAC = 52.6 m3 ha-1, × small stems)], and

high intensity [i.e. 2 Annual Allowable Cut (AAC

= 52.6 m3 ha-1, × large stems)]. However,

permission was not granted by the Forest Services

Division (FSD) for inclusion of smaller stems

below the minimum-felling diameter (MFD).

Therefore, all trees selected for felling, either large

or small diameter stem, were necessarily within

the MFD for the respective species (50 - 110 cm

dbh). For purposes of the present paper, the

logging treatments imposed in the four blocks can

be categorized into two broad types: high or low

intensity.

In August 2000, immediately following

harvesting, 20 sample plots were randomly

established in felling gaps in each of the treatment

blocks (hereinafter referred to as Gap-High or

Gap-Low depending on treatment block). Felling

gaps were laid in the direction of tree fall from

stump to crown zone and measured approximately

30 m × 2 m. Control plots were set up in an

identical fashion in unlogged parts of the forest.

Digital hemispherical photograph 1 m above each

plot center was taken with a Nikon F2 digital

camera to determine canopy openness.

Using an ocular estimation, soil condition was

assessed on a 4-point scale: 1= no disturbance; 2 =

topsoil slightly disturbed but intact; 3 = slightly

disturbed and displaced, ≤ 20 cm; 4 = topsoil

moderately disturbed, 20 ≤ x < 50 cm.

In this study, we adopted a more practical, field-

based definition for seedlings: germinating seeds

with open cotyledons and up to young plants < 1m

tall and < 1 cm dbh (Zagt, 1997). Seedling

censuses were carried out within each plot at 0.5,

4.2, 10 and 33 months (mo) after logging. At the

time of the first census, each seedling was

identified to species level and tagged (using

consecutive numbers) to ensure accurate re-

identification. Seedlings were mapped and vertical

height from the ground to the apical bud measured

with a meter tape or telescopic rod when

necessary. In subsequent censuses, surviving

tagged seedlings were re-measured, dead or

missing seedlings noted and new recruits tagged,

identified, height measured and their positions in

the plots mapped to the nearest centimeter. In

December, 2012, a random assessment of the

ground layer composition was carried out in 10

randomly selected gaps using 1m × 1m quadrats.

Within each gap, the quadrat was placed at the

North, East, South and West directions and the

number of ground herbaceous and woody species

identified and recorded. Total heights of tallest

tree species in each plot were also estimated using

a vertex and a transponder.

Data Analysis

Response Function Modeling (Modeling

Seedling Abundance)

To examine the effects of the logging treatments

on seedling abundance over time, we used a



generalized linear mixed model as implemented in

the statistical interface R (R Development Core

Team, 2015). In this study, we settled on mixed

effects statistical method, an extension of

regression models, for these reasons: (1) we were

interested in trends and comparisons in seedling

abundance; (2) based on (1) above, it was possible

to investigate directly the interaction between

treatment and time given the temporal and spatial

autocorrelation between seedling abundance and

time; (3) we could use the totality of the data,

given the hierarchical structure in our

experimental design (Pinheiro and Bates, 2000;

Zuur et al., 2009; Maindonald and Braun, 2012;

Crawley, 2013), thus, increasing the power of

statistical tests implemented in our analysis. We

identified significant treatment effects and trends

by determining the best model among a

hierarchical set of alternatives. Our experimental

design suggested temporal or spatial correlation

might be present (Pinheiro and Bates, 2000;

Schabenberger and Pierce, 2002; Zuur et al.,

2009; Crawley, 2013), therefore, to determine a

robust model to answer our first question, we

sought first to ensure we had correctly specified

the error structure, and afterwards tested for a

contribution by effects of interest (Zuur et al.,

2007; 2009). This step is very important in mixed-

model building. If the random effects are poorly

chosen, the error introduced affects the values and

quality of the fixed effects as the random effects

work their way into the standard deviation of the

slopes of the fixed effects and vice versa (Zuur et

al., 2009). We evaluated statistical significance

using likelihood ratio tests and compared models

using Akaike’s Information Criterion (AIC) and

estimated log-likelihoods (LL) (Burnham and

Anderson, 2002). Unless otherwise indicated,

model parameters were estimated using maximum

likelihood (ML) in the R package Non-linear

Mixed Effects (nlme) (Pinheiro and Bates, 2000).

We examined four alternative response functions

for tree seedling abundance (aij, number of

seedlings in block i and plot j) as a function of

treatment (Control, Gap-Low and Gap-High) and

time (months since logging) (Table 1).

Table 1: Comparisona of alternative models for the natural logarithm of seedling abundance [aij+ 1]

Model no. Model AIC LL P-value

1

2

3

4

aij = (βo +β2 · t ) + (β1 +β3 · t ) xij + ɛijk

aij = (βo +b0i + b0j) + β2 · t + (β1 +β3 · t ) xij + ɛijk

aij = (βo +b0i + b0j) + β2 · t + (β1 +β3 · t ) xij + CAR1+ɛijk

aij = (βo +b0i + b0j) + ɛijk

693.4

620.3

608.5

665.7

-339.7

-301.1

-294.3

-328.8

<0.001b

<0.001c

<0.001c

n.a.

aLikelihood ratio test statistics compare successive models; i.e., model 1 versus 2, model 2 versus 3 and model 3

versus 4 b Test based on model estimated using restricted maximum likelihood c Test based on model estimated using maximum likelihood

where

i denotes block, j denotes plot, k and t are month and time since logging, respectively.

AIC Akaike’s information criterion,

LL log likelihood,

CAR (1) continuous autocorrelation error structure

n.a. not applicable



Model 1 was a fixed-effects only specification for

abundance as a function of treatment (xij, for the

ith block and jth) plot and time (t, months since

logging). Model 2 was the same as model 1, but

was augmented with the random effects b0i for

block and b0j for plot within block. Model 3 was

an extension of Model 2, augmented with a first-

order continuous autoregressive correlation error

structure, [CAR (1)], a correction for the unequal

time interval. Model 4 was an intercept-only

variant of Model 3, which implies no treatment or

time effects. As in classical model building in

regression analysis, standard diagnostics were

used to evaluate regression assumptions (Neter et

al., 1996).

Change in Community Composition

We used non-metric multidimensional scaling

(NMDS) ordination as implemented in R package

vegan 2.3 (Oksanen et al., 2015) and PC-ORD

version 6.2 (McCune and Mefford, 2011) to

examine tree seedling species composition among

treatments over time. We conducted the NMDS

using Sorensen’s (Bray-Curtis) distance measure

in PC-ORD’s autopilot mode (slow and through)

and a random starting configuration (McCune and

Grace, 2002). According to McCune and Grace

(2002), the procedure automatically determines

dimensionality by comparing final stress values to

determine the best solution for the NMDS

ordination. Seedling abundance data were square-

root transformed to reduce the stress and over

influence of sample plots with high seedling

abundance to improve the interpretability of the

NMDS ordination (McCune and Grace, 2002).

Rare species with a frequency of < 5% were

excluded from the analysis. The square-root

transformation and removal of rare species

reduced the stress of the best solution from 24.9 to

16.7, which is an improvement from an

unacceptable to acceptable level of stress

(McCune and Grace, 2002). Kendall’s τ rank

correlation coefficient was used to examine

relationships between each axis and the

environmental variables, canopy openness and soil

condition.

To test for differences in species composition

between treatment types, a Multiple Response

Permutation Procedure (MRPP) was employed.

MRPP compares within-group to between-group

distances between sample units (McCune and

Grace, 2002). To carry out this analysis, a distance

matrix was computed followed by an effect size

(chance-corrected within-group agreement, A) that

describes the observed within-group homogeneity

compared to expected homogeneity due to chance.

Values of A range from 1 when there is complete

agreement within groups, to 0 when within group

heterogeneity equals random expectation. We

used Sorenson’s distance measure to maintain

consistency with the distance measure used in the

NMDS ordination. We carried out two separate

MRPP analyses to test for compositional changes

between treatments at the initial and final

censuses. If a difference was found in the MRPP

analysis, then, an indicator species analysis (ISA)

(Dufrene and Legendre, 1997) was used to

determine which species were more prevalent in a

given treatment. In ISA, an indicator value (IV) is

computed for each species in each treatment by

multiplying relative abundance by relative

frequency and multiplying by 100. To determine if

a species’ maximum IV was significant, we

conducted a Monte Carlo test of significance with

10,000 randomizations (McCune and Grace,

2002). An alpha level of 0.05 and minimum IV of

25 were set to determine significance (Dufrene

and Legendre, 1997).

We examined differences in the rates of change in

species abundance over time by computing

successional (directional) vectors between plot-

level NMDS ordination scores for the initial and

final censuses. Successional vectors show

movements of sample units in species space and

since we were interested in trends (McCune and

Mefford, 2006), we assessed whether control plots

moved in a different direction and or rate than



gaps. Differences in mean length of gap and

control vectors were compared with a pooled t-

test.

Prediction of Height Growth

For forests recovering from logging, growth

would be expected to be accelerated in gaps

relative to unlogged sites, due to increased

recruitment of seedlings into saplings and

subsequently into adult size classes under gap

conditions. We used binary logistic regression to

examine the probability that a plot (gap) had a

seedling (>55 cm tall) in the final census (2004) as

a function of initial (2000) canopy openness and

soil disturbance. We chose >55 cm given the slow

growth of seedlings in controls, which served as

the baseline for comparison with gaps. The

analysis was carried out in the R statistical

interface using a generalized linear model (GLM)

with the binomial family and the package ggplot2

(Wickham, 2009). Generalized linear models are

applications of linear regression model which

allow for the response variable to have

distributions other than the normal distribution

(Zuur et al., 2009).

RESULTS

Changes in Seedling Abundance

The treatments imposed in this study had a

significant effect on seedling abundance

throughout the study (Tables 1 and 2; Figure 1).

Because of substantial temporal autocorrelation in

the abundance data, models including random

effects and CAR (1) error structure were

statistically superior to models without these

components (models 3 vs. 2; models 3 vs. 4; P<

0.001; Table 1) and were preferred by AIC and LL

(Table 2). Given the obvious trend, it was not

surprising that the intercept-only model 4 was

inferior to the more complex alternatives. Thus,

model 3, which included random effects for block

and plot within block, and a CAR (1) error

structure, was identified as the best

characterization for tree seedling abundance over

time (Table 2).

Table 2: Model 3 term effects (±1S.E.) and

statistical significance.

Model term (effect) Abundance

Value

Intercept

Month

Gap-High

Gap-Low

Gap-High x month

Gap-Low x month

1.92 (0.206)**

0.03 (0.007)**

1.22 (0.247)**

1.26 (0.287)**

-0.02 (0.010)

-0.05 (0.010)**

** Statistical significance is specified at the < 0.01 level

A detailed examination of model 3 reveals an

interesting result - a significant interaction effect

for Gap-Low and time (Table 2). By contrast,

there was no significant interaction effect for Gap-

High and time (Table 2). In general, the treatments

imposed had a significant effect on seedling

abundance and stimulated divergent responses in

abundance among some species overtime.

As is expected, shade bearers were consistently

abundant in unlogged forest while the NPLD

response switched dominance between Gap-High

and Gap-Low at different periods of the study.

Celtis mildbraedii, a shade bearer and dominant

species in the research compartment, was

consistently dominant in the unlogged forest

throughout the study. Contrary to the increase in

abundance of the non-pioneers, there was a

decline in the abundance of pioneers in all

treatments throughout the study but consistently dominant in Gap-Low (Figure 1).

Changes in Seedling Composition

The NMDS ordination resulted in a three-axis

solution explaining 78.5% of the variation in the

data structure, and with a final stress of 16.7 and

an instability of < 0.001 in 380 iterations.



Figure 1: Changes in the proportion of seedlings

(±1S.E.) over time for pioneer, non-

pioneer light demander (NPLD) and

shade bearer (SB) in control (●), Gap-

Low (Δ), and Gap-High (*).

Axes 1 and 2 were most informative, representing

the highest proportions of the variance, 0.412 and

0.228, respectively. Axes 1 was positively

correlated with soil condition (τ = 0.436) and

negatively correlated (τ = -0.396) with initial

canopy openness. Axis 2 was negatively

correlated with both soil condition (τ = -0.089)

and canopy openness (τ = -0.045). Axis 1

separated species into ecological guilds with non-

pioneers drawn away from initial canopy openness

and soil disturbance (Figure 2). Based on the

MRPP, plant communities varied significantly by

treatment at 0.5 mo (A = 0.072, p < 0.001) and 33

mo (A = 0.170, p < 0.001). The ISA revealed

different dominant species for each treatment type,

with all indicators of control being non-pioneers

(Tables 3 and 4) and for the Gap-High, pioneers.

Indicator species for Gap-Low were a mix of

pioneers and non-pioneers. Successional vectors

revealed that the compositional trajectories of tree

seedlings in gaps and unlogged forest were

generally unidirectional, however, NMDS plot

scores between the initial plot and final plot scores

in species space revealed species composition

changed more rapidly in Gap-High compared to

Gap-Low and the unlogged forest.

There was a significant difference in the rate of

change in species composition between Gap-High

and unlogged forest (P = 0.03) but the rate of

change between Gap-Low and unlogged forest

was not significant (P = 0.27).

Prediction of Height Growth

At a given initial canopy openness and level of

soil disturbance, a combination of Gap-Low and

moderate soil disturbance and Gap-High and high

soil disturbance, were approximately 3 (2.72) and

2 (2.01) times, respectively more likely to have a

tall seedling in 2004 than controls (Gap-Low: log-

likelihood = -18.9, n = 40, P = 0.008; Gap-High:

log-likelihood = -20.4, n = 40, P = 0.017).



Figure 2: Nonmetric multidimensional scaling (NMDS) ordination bi-plots with species scores for axis 1

plotted against axis 2 (a) and successional vectors representing trajectories of sample plots in

species space (b, c, d). Vectors indicate direction and magnitude of sample plot movement in

NMDS space between the initial and final censuses. Arrow lengths indicate magnitude of plot

movement between the initial and final censuses, an indication of relative changes in species

composition over time.



Table 3: Relative density m-2 of tree seedlings recorded in control (C), low intensity (L) and high intensity (H) treatments at

each census.

Species Guild Mean relative density

Census 1 Census 2 Census 3 Census 4

C L H C L H C L H C L H

Albizia zygia

Alstonia boonei

Pouteria altissima

Antiaris toxicaria

Blighia sapida

Canarium schweinfurthii

Cedrela odorata

Ceiba pentandra

Celtis mildbraedii

Cleistopholis patens

Cola gigantea

Cylicodiscus gabunensis

Dialium aubrevillei

Distemonanthus

benthamianus

Entandrophragma angolense

Guarea cedrata

Hymenostegia afzelii

Khaya spp.

NPLD

P

NPLD

NPLD

NPLD

P

P

P

SB

P

NPLD

SB

SB

P

NPLD

SB

SB

NPLD

NPLD

0.24

-

-

0.14

0.07

-

-

0.35

0.47

-

-

-

0.02

-

-

-

-

-

0.35

-

-

-

-

-

-

-

0.74

0.06

0.10

-

-

-

-

-

-

-

-

-

-

-

-

0.04

-

0.17

-

0.46

0.12

0.05

-

-

-

-

-

-

-

-

0.23

0.22

-

-

0.09

0.14

-

-

0.33

0.44

-

-

-

0.02

-

-

-

-

-

0.30

-

0.06

-

-

-

-

-

0.60

0.05

0.09

-

-

-

-

-

-

-

-

-

-

0.10

-

0.03

-

0.07

-

0.46

0.13

0.05

-

-

-

-

-

-

-

-

0.10

0.40

-

-

0.12

-

-

0.27

0.19

0.26

-

-

-

-

-

-

-

0.09

-

0.15

0.21

0.05

-

0.07

-

-

0.06

0.41

0.08

0.07

-

-

-

-

-

0.05

-

-

-

0.17

0.07

0.03

0.02

-

-

0.13

0.35

0.11

0.05

-

-

-

-

0.02

-

0.07

-

0.10

0.17

-

0.14

0.12

0.10

-

-

0.10

0.30

-

-

-

-

0.08

-

-

0.04

0.15

0.13

0.29

0.10

-

0.19

-

-

0.28

0.31

0.21

0.15

0.08

-

-

-

-

0.04

-

-

-

0.16

0.10

0.08

0.06

0.17

-

0.16

0.10

0.23

0.06

-

-

-

0.05

0.05

-

-

-

0.15



Mansonia altissima

Milicia excelsa

Nauclea diderrichii

Nesogordonia papaverifera

Petersianthus macrocarpus

Piptadeniastrum africanum

Pterygota macrocarpa

Ricinodendron heudelotti

Sterculia rhinopetala

Strombosia glaucescens

Terminalia superba

Triplochiton scleroxylon

Turreanthus africanuus

P

P

SB

P

NPLD

NPLD

P

NPLD

SB

P

P

SB

-

-

0.32

-

-

-

-

0.12

-

-

-

0.12

-

-

0.17

-

-

-

0.23

-

-

-

-

0.02

-

-

0.07

-

-

-

0.41

-

-

-

-

0.24

-

-

0.43

-

-

-

-

0.09

-

-

-

0.41

0.20

-

-

-

-

-

0.15

0.17

-

0.07

-

-

0.13

0.05

0.04

-

-

0.02

0.21

0.05

0.04

0.02

-

0.25

-

-

0.12

-

0.12

-

0.16

0.05

-

-

-

0.16

0.24

-

0.16

-

-

0.10

0.12

0.02

-

0.07

0.06

0.06

0.11

0.03

0.06

0.04

0.01

0.03

0.09

0.03

0.03

0.03

0.01

0.11

-

-

0.20

-

0.18

0.08

-

0.15

0.09

-

-

0.33

0.15

-

0.20

-

-

0.23

0.18

0.15

0.20

0.07

0.42

-

0.08

-

0.11

-

0.03

0.05

0.08

0.17

0.06

0.04

0.02

0.27

Guilds: P, pioneer; NPLD, shade bearer; SB, shade bearer



Table 3: Significant indicator species by treatment type 0.5 mo after logging

Species Guild Treatment Obs. IVa Rand. IVb p

C. pentandra

R. heudelotti

C. mildbraedii

M. altissima

C. patens

P

P

SB

NPLD

P

Gap-Low

Gap-High

Control

Control

Gap-Low

52.6

46.1

33.8

29.3

27.5

35.3 (3.05)

26.9 (4.68)

20.4 (4.70)

13.9 (4.83)

12.2 (4.55)

<0.001

0.003

0.016

0.011

0.006

a Observed importance value b Mean importance value from randomized groups; standard deviation in parentheses; Monte Carlo test with 10,000

permutations

Table 4: Significant indicator species by treatment type 33 mo after logging


T. africanus

C. mildbraedii

C. odorata

C. pentandra

M. excelsa

C. patens

SB

SB

P

P

P

P

Control

Gap-Low

Gap-High

Gap-Low

Gap-High

Gap-Low

50.7

44.3

43.4

36.7

35.9

25.3

19.4 (4.96)

31.9 (4.10)

15.6 (4.86)

22.6 (4.75)

20.2 (4.78)

14.7 (4.60)

<0.001

0.010

0.009

0.011

0.009

0.032 a Observed importance value b Mean importance value from randomized groups; standard deviation in parentheses; Monte Carlo test with 10,000

permutations.

The p-values suggest that our best logistic curve

for growth forecast as a whole fits significantly

better than a null or empty model with the

combination Gap-Low and moderate soil

disturbance as our best model (Figure 3).

DISCUSSION

Our results illustrate the complex role of

disturbance on the dynamics of seedlings in gaps

following logging (Hubbell et al., 1999; Sheil and

Burselem, 2003). In our study, the treatments had

a significant effect on seedling abundance but

stimulated divergent responses in abundance

among seedlings of ecological guilds overtime.

The decline in the abundance of pioneers in all

treatments could be due to several factors. The

canopy gaps formed as a result of logging initially

created conditions suitable seed germination and

seedling growth - increased light and associated

irradiance, temperature as well as soil disturbance

- for the recruitment of pioneers especially in Gap-

High and Gap-Low sites (Brown, 1993; van der

Meer et al., 1999; Pinard et al., 2000). Canopy

openness was significantly higher in gaps (mean ±

se: Gap-High, 15.7 ± 1.38%; Gap-Low, 13.6 ±

1.03%; unlogged, 5.4 ± 0.56%) compared to the

unlogged forest (P< 0.05). The increased radiation

and temperatures associated with the high canopy

openness and soil disturbance following logging

(Brown, 1993; van der Meer et al., 1999; Pinard et

al., 2000) might have provided suitable conditions

for the recruitment of weeds as well particularly

lianas/climbers and herbaceous plants to compete



for these resources with the pioneers (Schnitzer et

al., 2000; Fredericksen and Pariona, 2002).

An examination of the ground layer of Gap-High

12 years after logging revealed that the most

abundant species were lianas and herbs with C.

mildbraedii being the only timber tree species

(Figure 4). In terms of plant height, two invasive

species, B. papyrifera, and C. odorata were

among the tallest/leading species in Gap-High

(Figure 4). The presence of lianas, herbs, and

invasive species in the high intensity gaps might

have produced a stiffer competition against tree

pioneers and created shade detrimental to their

survival (Swaine and Whitmore, 1988) hence their

low abundance in Gap-High compared to Gap-

Low where the dominance of weeds and lianas in

the ground layer was moderate (Figure 4). This is

in agreement with Schnitzer et al. 2004, who

reported that in Cameroon lianas recruited heavily

into logging gaps within 1 year and many survived

for longer than 6 years. Similar results were

reported by Thompson et al. (1998) who observed

an increase in density of herbs and sprouts, four

times greater in large gaps than in small and

unlogged forests few months after gap creation in

a tropical forest in Brazil.

Figure 3: Fitted logistic regression curves of square root transformed canopy openness versus seedling

height probability estimates for different levels of soil disturbance. The figure shows the best fit

logistic curve, with a characteristic “S” shape, for moderate soil disturbance and Gap-Low.



Figure 4: Boxplots of heights (a and b) and relative abundances (c and d) of dominant life forms in the

understoreys of Gap-High and Gap-Low, respectively, 12 years after logging. Species in

alphabetical order: Atacon, Ataenidia conferta (herb); Bapnit, Baphia nitida (SB); Bropap,

Broussonetia papyrifera (P), Calafr, Calycobolus africanus (liana); Cedodo, Cedrela odorata

(P); Ceipen, Ceiba pentandra (P); Celmil, Celtis mildbraedii (SB), Culsca, Culcasia scandens

(climber); Eryivo, Erythrophleum ivorense (NPLD), Grisim, Griffonia simplicifolia (climber);

Milrho, Millettia rhodantha (SB); Nespap, Nesogordonia paparivefera (SB); Oxyspe,

Oxyanthus speciosus (SB); and Trimon, Trichilia monadelpha (NPLD).



The authors also observed that for large gaps the

number of recruits for some species was generally

low and concluded that conditions were not

favourable for their germination and establishment

because of higher light, temperatures, or soil-

surface dryness (van der Meer et al., 1999). A

similar reasoning could be espoused for the low

abundance of pioneers in Gap-High compared to

Gap-Low observed in the current study. Although,

none of the pioneers survived in the unlogged

forest throughout the study, recruitment was

evident and this concurs with the observation of

Kyereh et al. (1999) that several Ghanaian forest

trees believed to be pioneers do germinate but

soon die under forest shade. This characteristic of

pioneers could probably be due to their negative

carbon balance (Swaine et al., 1997; Kyereh et al.,

1999).

Contrary to the decline in seedling abundance

observed in pioneers, the non-pioneers slowly but

steadily increased in abundance in gaps overtime.

Whereas SBs were consistently abundant in

unlogged forest, the NPLDs switched dominance

between Gap-High and Gap-Low at different

periods of the study. Our results agree with a

study in Bia Forest Reserve (Hawthorne, 1993), in

which regeneration of most light-demanders in

selectively logged forests including NPLDs were

favored by gaps in disturbed areas compared to

unlogged forest.

The results of the present study suggest a

significant interaction only between Gap-Low and

time in the mixed-model; indeed, the model

suggests that overall abundance was slightly lower

in Gap-Low compared to control. Given the rapid

colonization of high intensity gaps by weeds and

other species coupled with the lack of silvicultural

practices following logging, then the significant

interaction between Gap-Low and time is

interesting. While this result may be encouraging,

it is unclear how long this interaction will persist

considering the increase in abundance of

herbaceous and invasive tree species which can

slow the rate of succession.

We observed a shift in the composition of the

seedling community within treatments towards

increased representation by non-pioneers (Figure

2). Despite the compositional convergence,

logging treatments were dissimilar, though not as

drastic as at 0.5 mo, due to the observed variation

in dominant species (even within an ecological

guild) among treatments. Our observation was

elucidated by the indicator species analysis within

and between treatments. For instance, at 33 mo C.

mildbraedii, a shade bearer, was an indicator

species in Gap-Low while C. odorota, a pioneer,

was dominant in Gap-High (by contrast the second

and third ranked indicator species in Gap-Low

were pioneers, C. pentandra and C. patens,

respectively (Table 5). On the basis of this result,

the study does not entirely support the notion that

species of ecological guilds are adapted to gaps of

a certain size. The observed variations within

individual species belonging to different

ecological guilds make it unlikely that a species is

best adapted to one gap size. Our finding accords

with other studies in tropical forests (Brown and

Whitmore, 1992; Kennedy and Swaine, 1992;

Thompson et al., 1998) that reported no evidence

for gap partitioning as a means of differentiation

in rain forest species.

Gaps in low intensity logging with moderate soil

disturbance represented the most likely

combination to find a seedling (≥ 55 cm). This

observation compliments the significant

interaction between Gap-Low and time. Since the

species composition of gaps was dominated by

non-pioneers at 33 mo, it was not surprising that

moderate soil disturbance fitted in our growth

forecast. We believe that growth forecast would

have been higher if silvicultural interventions had

been applied to our plots. This assertion is based

on increased growth rates of species in logged

forests following the application of silvicultural

interventions after logging (D’Oliveira, 2000).



Table 5: Significant indicator species by treatment type 33 mo after logging


T. africanus

C. mildbraedii

C. odorata

C. pentandra

M. excelsa

C. patens

SB

SB

P

P

P

P

Control

Gap-Low

Gap-High

Gap-Low

Gap-High

Gap-Low

50.7

44.3

43.4

36.7

35.9

25.3

19.4 (4.96)

31.9 (4.10)

15.6 (4.86)

22.6 (4.75)

20.2 (4.78)

14.7 (4.60)

<0.001

0.010

0.009

0.011

0.009

0.032

a Observed importance value b Mean importance value from randomized groups; standard deviation in parentheses; Monte Carlo

test with 10,000 permutations.

CONCLUSIONS

In conclusion, our results show that both high and

low logging intensities significantly affected

seedling abundance, however, the interaction

effect of abundance and time was only significant

for the low intensity logging. The implies that the

growth and survival seedlings are retarded

probably due to the dominance of fast-growing

herbaceous species in the high intensity gaps even

12 year after logging. Gaps in our low intensity

treatments seemed to favour seedlings of both

pioneer and non-pioneer light demanders over

time.

However, as the current selection system in Ghana

lacks standard prescriptions following logging, it

is unclear how long this interaction will persist

considering the high growth rate of herbaceous

and invasive tree species which can slow the rate

of succession (Putz et al., 2012; Sist et al., 2014).

Future research should explore the extent of this

interaction. After three years of logging, species

composition in our treatments consisted mainly of

non-pioneers as pioneers showed a gradual decline

in all gaps - a clear demonstration of the need to

improve the existing forest management system in

Ghana by enforcing the application of some level

of forest manipulation to logged forests to ensure

productivity. As per our findings, if we are to

sustainably manage the research compartment,

then silvicultural interventions such as enrichment

planting of pioneers and liberation thinning to free

liana and weed infested stems would need to be

employed, though it comes at a cost.

At the species level, our results show the presence

of C. mildbreadii in all sites throughout the

period. One explanation for this is that the species

is common in Pra Anum, which was classified as a

Celtis-Triplochiton association (Taylor, 1960),

therefore, dispersal and recruitment might not be a

problem but a key factor necessary for the

establishment of this species. Continue pleaseThis

is in line with Hubbell et al (1999) who argue that

for some species, dispersal and successful

recruitment at the right place and time rather than

disturbance structure their communities. By

contrast, T. scleroxylon, a common species in the

reserve, was recorded in gaps in later stages of the

study. This could probably be due to its erratic

characteristic as it fruits once in four years

(Hawthorne, 1995). Mechanisms driving the

regeneration of other species are less clear. For

example, Terminalia superba was recorded in



gaps in later enumerations. This late arrival could

be due to seeds not finding suitable germination

sites, dispersal from distant sources, or decline in

population at the study area. Further studies

should be carried out on potential factors (e.g.

litter accumulation, dispersal, soil nutrients)

limiting the regeneration and establishment of

common timber species in the research

compartment.

ACKNOWLEDGEMENTS

We thank Peter Amoako, Asumadu Kwaku,

Jonathan Dabo, Vincent Berko, and Dominic

Bosompem for their assistance with fieldwork and

the CSIR–Forestry Research Institute of Ghana for

logistic support. This research was funded jointly

by the University of Aberdeen, the British

Ecological Society and Tropenbos International,

the Netherlands, under the Tropenbos-Ghana

(TBI-Ghana) Programme.

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Efficient survey of pests in smalholder tree plantations: Case of the CFM project in Ghana P. P. Bosu et al.


METHODOLOGY FOR EFFICIENT SURVEY OF PESTS IN SMALLHOLDER

TREE PLANTATIONS: THE CASE OF THE COMMUNITY FORESTRY

MANAGEMENT PROJECT IN GHANA

P. P. Bosu, M. M. Apetorbgor and E. E. Nkrumah

CSIR-Forestry Research Institute of Ghana, University P.O. Box 63, Kumasi Ghana.

Email: [email protected]

ABSTRACT

The challenges of forest pest surveys in smallholder tropical plantations can be different from those

encountered in large scale industrial plantations making it necessary to develop more appropriate survey

methods. In this article, we report on non-conventional approaches used to assess pest and disease status

in smallholder plantations established under the Community Forestry Management Project in Ghana. A

combination of interviews, focus group discussions, and follow-up field assessments were employed to

determine pests and disease incidences in the plantations. The interviews were conducted with the aid of

pictures and samples of potential key pests, as well as pictures of symptomatic trees to elicit forest health

conditions as perceived by farmers. Twenty-three communities and over 2,000 hectares of taungya-type

plantations that were planted with two exotic species Tectona grandis (teak) and Cedrela odorata

(cedrela), and two indigenous species Terminalia superba (ofram) and Ceiba pentandra (ceiba) were

surveyed. A wide range of tree health problems that included biotic, abiotic and human-induced stresses

were recorded. Coleopterous stem borers of pole-size trees, grasshopper (Zonocerus variegatus)

defoliation of actively growing saplings and retardation of growth due perhaps to nutrient deficiency,

were the key problems observed on teak. Stem canker and dieback were observed on C. odorata and C.

pentandra, respectively. We noted that involvement of the communities in the survey process greatly

increased our ability to detect pest in the plantations. We concluded that pest surveys in smallholder

plantations should not only focus on the technical aspects, but also the cultural and socioeconomic

orientations of the local community, as well as engender their active participation in the process.

Keywords: Survey methods, plantation damage agents, smallholder plantations, community forest

management

INTRODUCTION

In phytosanitary terminology, a “survey” is an

official procedure conducted over a defined period

to determine the characteristics of a pest

population or to determine which species occur in

an area (FAO, 2011). Its meaning is different from

“surveillance” which also is an official process for

collecting and recording data on pest occurrence

or absence by survey, monitoring or other

procedures such as literature reviews (FAO,

2011). A survey is therefore a component of

surveillance. The purpose for surveillance may

vary but will usually include detecting new pests

for rapid eradication or containment, facilitation of

trade by providing information about pests and

their distribution within a country’s borders, or

justification for use of regulations to prevent the

entry of a pest that does not occur in the country

of importation. Surveillance and survey activities

are conducted for early detection of pest incidence

in designated areas before they escalate. Pest

surveys are often conducted in forested

mailto:[email protected]



landscapes, botanic gardens, and ports to prevent

entry and spread of invasive pests.

Forest pest surveys are not routinely conducted in

Ghana. This may be largely attributed to logistical

and financial constraints. But also because

plantation forestry did not receive serious

attention in the past. As a result of persistent pest

and disease problems on high-value indigenous

species such as Milicia excelsa, Milicia regia,

Khaya ivorensis, Khaya anthotheca , Pericopsis

elata (Wagner, et al., 2008), and Terminalia

ivorensis (Ofosu-Asiedu, 1988; Ofosu-Asiedu and

Canon, 1976) attention shifted to the planting of

exotic tree species. With few pest and disease

problems, teak (Tectona grandis), cedrela

(Cedrela odorata), and various species of

Eucalyptus became the exotic species of choice

for plantation development in Ghana. Statistics

from the Forestry Commission (FC) of Ghana

indicate that teak now constitutes about 70% of

Ghana’s forest plantation estate (FC, 2013).

However, few years into the implementation of

the National Forest Plantations Development

Programme (NFPDP) which was launched in

2001, reports of pests and disease incursions of

economic proportions emerged from across the

country. Somehow, the reports included pest

incidences on teak, cedrela and other exotic

species which hitherto were rarely attacked (Bosu

and Apetorgbor, 2009). This obviously required

surveying of the plantations to better understand

the pest and disease situation before any

management interventions could be prescribed.

Ghana’s forest plantation estate was estimated at

estimated at 60,000 hectares in year 2000 (FC,

2013). According to the FC some 185,088 ha of

new plantations had been added to the plantation

estate by the end of 2014 (FC, 2015). The rapid

increase in the area under plantations in Ghana

was as a result of the implementation of the

NFPDP, which targeted the planting of some

20,000 ha annually. The objectives for

establishing the plantations were various, and

included restoration of degraded forest landscapes,

increase in wood supply in the country,

employment generation and by extension

reduction of rural poverty, improving

environmental quality, carbon sequestration and

food security improvement. The programme was

implemented under various components as per the

funding source. They include the Modified

Taungya System (MTS), Community Forestry

Management Project (CFMP), the Highly-

Indebted Poor Country Initiative (HIPC) of the

World Bank, and several others implemented by

private or quasi-private developers or the Forest

Services Division (FSD) (FC, 2013).

As expected, the sudden increase in plantation

estate resulted in the emergence of pests and

disease problems (Bosu and Apetorgbor, 2009).

While several of the pest problems encountered in

the new plantations were known, a few were

completely new to forestry in Ghana (Wagner, et

al., 2008). Identifying forest pests and disease

problems, and understanding the scale and scope

of the problems is a necessary first step towards

effective management in all situations. Thus, a

setting-up of a pest surveillance system to ensure

adequate protection against pests and diseases

became obvious. Without a history of systematic

forest pest surveillance in Ghana, and with no

existing guidelines or protocols forest pest

surveillance in the country, managers needed to

start from scratch. A complementary study

reported by Apetorgbor and Roux (2015), was

broader in scope and focused more on tree

diseases in plantations scattered throughout the

southern half of the country.

The CFMP was initiated as part of the several

national forest plantation development projects

aimed at expanding the plantation base. The

CFMP also had as one of its key objectives to

restore degraded forest reserves. As a result, the

plantations were established under collaborative

arrangements between the FSD, Ministry of Food

and Agriculture (MoFA), and farming



communities living within or near selected

degraded forest reserves. The reserves were

located in three of the ten administrative regions

of Ghana namely the Ashanti, Eastern, and Brong

Ahafo Regions. They included Afram Headwaters

(AHFR), Asubima (ASFR), Yaya (YAFR),

Worobong South (WSFR), and Esubone Forest

Reserves (ESFR) (Table 1).

In this article, we report on a pest and disease

survey we conducted in the plantations, present an

overview of the results obtained, and discuss the

results with particular focus to the methodology

used and its implications for survey and

monitoring of pests and diseases in smallholder

plantations. A credible survey is necessary if the

results are to be accepted by all stakeholders,

including especially trading partners. According to

provisions of the International Standards for

Phytosanitary Measures (ISPM No. 6), a good

survey should among others include a technically

valid methodology (FAO, 2006).

METHODOLOGY

Study Area

Our surveillance study was conducted in forest

plantations established within the tropical high

forest zone, located in the southern half of Ghana

(Hall and Swaine, 1981) (Figure 1). The area also

falls within three of Ghana’s ten administrative

regions, namely Ashanti, Brong Ahafo, and

Eastern Regions. The plantations were on

degraded forest reserves, and were established

jointly by the FC and local communities,

following government’s policy to restore degraded

forest reserves through the Community Forestry

Management Project.

Figure 1: Map of southern part of Ghana showing locations of the reserves where small holder plantations

under the Community Forestry Management Project (CFMP) were established.



Reconnaissance Visits

Prior to the start of the full scale monitoring

activities, reconnaissance visits were made to the

communities and plantation sites to obtain inputs

necessary for designing an appropriate survey

methodology. The visits revealed that using a

conventional survey approach would not

adequately provide information/data on the

incidence of pests and diseases in the plantations.

This was because we realized at the very

beginning that some farmers were hesitant to

engage with our team without permission by their

elders or taungya head, and it looked like it was

going to be difficult to have access to the farms.

Again, farms were small in size and in most places

scattered over the landscape so that following

conventional approaches was going to be

logistically very difficult. Thus, a new

methodology was needed. This included a

combination of interviews, focus group

discussions, field survey of plantations, and post-

survey discussion or validation with affected

plantation owners or community.

Field Survey

Communities involved in the project surrounded

the five forest reserves (AHFR, ASFR, YAFR,

WSFR, and ESFR) (Table 1). Most of the

plantations were established between 2002 and

2005, and the survey was conducted between June

2006 and October 2007. In total about 2,300 ha of

plantations, and about 23 communities were

visited. The survey team consisted of a forest

entomologist, a plant pathologist and two field

assistants. Prior to visiting each community, the

survey crew interacted with the District Manager

of the FSD for a briefing on the status of forest

plantation development and general forest health

issues in the District. Thereafter, the team moved

into the community to undertake the survey as

described below.

Interactions with Community Heads and

Farmers

On arrival in each community, the survey team

met with the chiefs, elders, assembly member(s)

(local government representative), and the leader

of the CFMP farmers group (also known as

Taungya Head), to formally inform them of the

purpose of the visit and seek their permission to

work in the communities. Such courtesy meetings

are customary in Ghana and are essential to the

successful execution of projects in rural

communities.

Table 1: List of villages involved in the Community Forestry Management Project (CFMP) visited during

the study.

Forest Reserve Communities Forest Zone

Afram Headwaters Ada Nkwanta, Akrofoa, Daban, Kwapanin Dry Semi-deciduous

Asubima Asunkwa, Atabourso I, Atabourso II,

Aworopataa, Woraso

Dry Semi-deciduous

Esuboni Kofi Dade, Nyamenti, Owusukwae, Small

London

Moist Semi-Deciduous,

South East

Worobong South Ankesu, Ayigbetown, Feyiase, Kumferi,

Mianya, Owusukrom

Moist Semi-deciduous

South East

Yaya Asuakwaa, Ayigbekrom, Mallamkorum,

Owusukrom

Dry Semi-deciduous



Focus Group Discussion

After the meeting with the chiefs and elders, an

announcement was made, usually through the

local information centre or by word of mouth, for

a town-hall style meeting with farmers involved in

the plantation project. This meeting was usually

conducted in the vernacular and facilitated by the

Taungya head. Here, the team interacted with the

tree growers asking pertinent questions on tree

pest and disease problems with the aid of a pre-

prepared checklist. The questions were structured

to capture information on the nature of plantation,

history of establishment, forest issues, nursery

pest problems, and other relevant information. In

order to help the farmers understand the

discussion, interviewers carried pictures of

plantation tree species showing symptoms and

signs of potential damage caused by insects and

diseases, as well as pictures of the insect pests

commonly associated with the planted trees. These

aids helped clarify the nature of the damage seen

and elicited farmer’s recall of past and/or current

pest problems. Information provided by farmers

was carefully recorded, including the name(s) of

farmers reporting the particular pest problem,

nature of the problem, and approximate location

of the farm(s).

Field Inspection

Once interviews were completed, a list of

potential pest problems, their locations, and

affected farmers was compiled for field

inspection. Follow-up field inspections were then

conducted, within a few days of obtaining the

information to verify and assess the claims. In

addition to the survey team, the inspection usually

included the taungya head and the farmer or

farmers who had observed symptoms in their

plantations. Where the symptoms reported were

also observed in the plantation, an assessment of

the severity of the infestation/infection was

conducted by the survey crew. The assessment

included estimates of number of plants attacked

and severity of the attacks. In addition, a quick

inspection was made of nearby plantations to

determine whether the infestation had spread.

Severity of tree damage were classified

qualitatively as minor (signs of pest or disease

attack present but no physical evidence of impact

on tree growth), moderate (signs of pest or disease

attack, with physical evidence of impact on tree

health/growth; e.g. defoliation, leaves are necrotic,

sap flow, stunted growth), severe (damage to tree

very visible, affecting 50% or more of tree; e.g.

trees heavily or completely defoliated, heavy flow

of sap/cracks, latter stages of dieback, etc), or

death of trees.

Post-field Inspection Discussion

(Validation)

Once the inspection was over, further discussion

with the farmer(s) was done to clarify any issues

that might have arisen during the assessment. The

validation phase often began in the field and was

completed within the community with as many

farmers as possible involved. Underlying causes

or predisposing factors of the attack were

discussed along with strategies on how the attack

could be controlled or managed. Here, farmers

were educated on basic principles of integrated

pest management (IPM) approaches. At least one

follow-up or monitoring visit was made to the

communities where attacks were recorded.

Summarizing the Results on Forest

Health?

The results of the study were summarized under

two main subheadings namely, the stages and

steps involved in the survey, and the data and

information on the pest/disease incidence

observed in the plantations.

RESULTS

Survey Methodology

The stages or steps involved in the present survey

may be summarized with a flow chart as shown in



Meet local authorities

Figure 2. Key steps involved were (i) Planning

and designing stage, (ii) Meeting with the

leadership of local community, (iii) Focus group

or town-hall type meeting with participating

farmers, (iv) Follow-up field inspections or

validation of reported cases, (v) Expert

preliminary recommendations on pest

management interventions to farmers (vi) Design,

planning and implementation of systematic forest

health monitoring programme for the affected

communities.

Figure 2: Schematic representation of the stages involved in the survey of pests in

smallholder community plantations in Ghana.

Planning and Design

Planning and Design

Focus group meeting

with farmers

Conduct follow-up

field inspections

Recommend control

measures

Return later for

monitoring

No pest problems

reported Create/increase awareness on

integrated pest management

Pest problems

reported Pest problems not

confirmed

Pest problems

confirmed



Damage Agents

Pest and disease problems were encountered in all

except ESFR. At the time of the survey only two

hectares of plantation had been established within

the Esubone Forest Reserve. Teak, cedrela, ofram

and ceiba were the species planted in the CFMP

plantations. Farmers reported a suite of pests and

related forest health problems in the informant

interviews and focus group discussions, and nearly

all their reports were confirmed during the follow-

up field assessments.

Worobong South Forest Reserve (WSFR)

The plantations at WSFR were mixtures of cedrela

and ofram, or teak monocultures. No major pest

damage or symptoms were found on the one-year

old plantations in this area. However, drought-

related stunting of saplings in plantations two

years old or older appeared to be quite common on

teak and cedrela.

This was quite widespread in sites with dry

weather or generally poor soil conditions. Other

factors that contributed to stunting include the use

of poor quality planting material and late season

planting. Stem-boring likely caused by the

coleopterous beetles Apate monachus and Apate

terebrans was recorded on teak and cedrela

(Figure 3). Similar symptoms of borer activities

were observed in plantations at AHFR and YAFR.

Some farmers reported wind-throw of cedrela,

which we later confirmed in the field. Factors that

might have predisposed the trees to wind-throw

include loosening of the soil following heavy

downpours, and/or weakening of root systems by

pathogenic agents (Table 2). At WSFR, we also

observed initial stages of cedrela stem canker on

at least three trees in small roadside plantation in

the village of Bosuso, on the main Koforidua-

Begoro road. The symptoms we observed had also

been reported previously in a cedrela plantation at

the ASFR near Bibiani in the Western Region.

Figure 3: Coleopterous beetle Apate spp killed in the process of attack of a 5-year old Cedrela odorata

tree near Kwapanin in the Afram Headwaters Forest Reserve. Heavy exudation of gum and frass

following boring into stem of vigorously growing trees often kills the insect.



Table 2: Forest health threats to smallholder plantations in the Worobong South Forest Reserve, Ghana

during 2006/2007.

Forest

health

problem

Species

affected

Age/habit

of plant

Severity Probable

cause

Distribution of

affected plants

Remarks

Stem-

boring

Tectona

grandis

Cedrela

odorata

Pole-size

trees

Moderate Coleopterous

borers and

including

probably

Apate spp,

Isolated cases in

plantations within

the reserve CFMP

plantations not

affected

No mortality

recorded

Stem

canker

Cedrela

odorata

Pole-size

trees

Minor Pathogenic

fungi

3 infected trees

observed outside of

the reserve

No mortality

recorded.

Potentially

serious problem

if it reaches an

outbreak level.

Stunting T. grandis

1-yr old

saplings

Moderate Late season

planting,

drought,

door site

conditions

Limited to few

farms

Stunting T. superba 1-year old Moderate Insect or

disease

attack

Isolated cases -

Wind-

throw

C. odorata Pole-size

trees

Minor Loose soil,

or

pathogenic

causes

Isolated -

Mistletoe T. superba Pole-size

trees

Minor - Isolated -

Dieback Ceiba

pentandra

Pole-size

trees

Severe Pathogenic

fungi

Widespread Infection starts

at the nursery

stage.



Few problems were reported or observed on ofram

at WSFR except for isolated cases of stunting of

some of the young plants. We associated the

stunting with stress caused by activities of

arboreal ants, which nests we found on the

affected ofram plants. It did not appear as though

the ants were actively feeding on the plants. In

other places in the reserve, we recorded various

stages of serious dieback of ceiba in 2-3 year older

plantations. Dieback of ceiba at the nursery stage

and in plantations is well known in Ghana.

In addition to the cases reported above, the staff of

the FSD at the District Office at Begoro reported

poor tending, presence of powdery substances on

teak, oozing of sap from bark of another native

tree plantation species mahogany (Khaya spp.),

and destruction of new plantations by cattle of

nomadic herdsmen as some other forest health

problems in plantations. While most of the

damage symptoms we observed during the field

survey were mentioned by the farmers during the

interview, there were a few inaccuracies and

inconsistencies with the intensities and/or

distribution of the damage levels reported.

Yaya Forest Reserve (YAFR)

Teak dieback of varying intensity was observed in

plantations within YAFR (Table 3). However, it

was only in a few instances that this had resulted

in tree death although tree growth and quality

were seriously affected. In many other instances

trees suffering from dieback were found re-

sprouting vigorously at the base of the stem.

Trees were planted during 2003-2004. However, it

was observed that stands were generally poorly

stocked due to widespread seedling mortality

during the early stages of plantation establishment.

Dieback occurred either in isolated instances or, in

some cases, included pockets of trees averaging

between 2 and 10 per hectare. The exact cause of

dieback was not known, however it could have

been a consequence of several predisposing

factors including poor soil, dry weather

conditions, weed competition, termite attack,

lightening, or mechanical damage. Human-caused

injuries such as slashing with cutlass, and poorly

timed or ill-executed pruning might also

predispose trees to dieback.

Table 3: Forest health threats to smallholder plantations in the Afram Headwaters Forest Reserve, Ghana

during 2006/2007.

Forest health

problem

Species

affected

Age/habit

of plant

Severity Probable cause Distribution of

affected plants

Remarks

Tree mortality Tectona

grandis

2-4 years Moderate Insect or

disease attack

Scattered cases

reported from

one community

Mortality is

often sudden

with no prior

visible

symptoms of

attack

Stem-boring C. odorata 1-year Moderate Coleopterous

borers

Scattered Borer

unknown

Stunting C. odorata 1-2 years Moderate - Isolated -

Wind

bending/throwing

C. odorata 1-2 years Minor Wind possibly

aided by

pathogenic

root infection

Isolated -



Apart from dieback and tree mortality, it was

observed that a number of trees exhibited signs of

various stages of stress as a result of bad farming

practices adopted by some of the farmers. At

Ayigbe Kurom, for example, we noted that some

yam farmers were relying on the pole-sized teak

trees as live stakes for their yam vines. In other

places excessive cutting of teak branches by

farmers to open the canopy for food crop

cultivation was stressing the trees and leading to

needless tree deaths. In cases where pruning was

done on saplings in younger plantations high

levels of mortality was observed leading to very

low stocking levels in the plantations.

Stem boring of cedrela by an unknown insect was

the principal damage recorded in farms near

Nhyiayem. No mortalities were recorded and trees

did not show any physiological abnormalities as a

result of the attack. However, the presence of an

insect borer was clearly evident by the frass

deposited at the base of the stem. Damage due to

human causes included indiscriminate slashing of

trees, and burning within mature stands during site

preparation by farmers.

Afram Headwaters Forest Reserve

(AHFR)

Plantations at Nkwanta, Akrofoa, Daban and

Kwapanin were surveyed in AHFR. The

plantations were mostly teak, except for

Kwapanin, where both cedrela and teak have been

planted. As was observed in YAFR, dieback of

teak was also recorded in these plantations (Table

4). However, unlike at YAFR, dieback incidence

was isolated in the teak plantations and the

intensities were low, giving no cause for concern

to farmers. However, we observed what appeared

to be serious damage to the stems of some 4-5

year old teak trees. After careful analyses, we

concluded that the deep cracks and knots of the

bark, as well as the curly leaves we observed were

likely the reaction of the trees to exposure to

excessive herbicide application. Similar symptoms

of cedrela stem canker which we had previously

recorded in several other plantation sites were also

observed at AHFR. We also recorded stem boring

activities on 4-5 year old trees of cedrela, by what

looked like ambrosia beetles attacks.

Table 4: Forest health threats to smallholder plantations in Yaya Forest Reserve, Ghana during

2006/2007.

Forest health

problem

Species

affected

Age/habit

of plant

Severity Probable

cause

Distribution of

affected plants

Remarks

Stem-borer Tectona

grandis

Pole-size

trees

Moderate Insect Scattered

Defoliation T.

grandis

Year Moderate Grasshopper Pockets Seasonal

Defoliation Cedrela

odorata

1-2 years Moderate Unidentified

insects

Scattered

Dieback C.

odorata

1-2 years Moderate Pathogenic Scattered No mortality

recorded but

attack leads to

growth of

epicormic shoots.

Stunting C.

odorata

1-2 years Minor Drought-

stress

Scattered



Asubima Forest Reserve (ASFR)

No serious pest problems or forest health issues

were noted in ASFR. This was because very few

plantations had been established or were readily

accessible for survey. A newly established

plantation near the village of Wuraso was poorly

stocked as a result of poor seedling survival.

From the reports of farmers during the key

informant and focus group, it was gathered that

the pest or forest health challenges in the

plantations were not too different from those in

the AHFR and YAFR.

DISCUSSION

The survey revealed several latent forest health

problems in the CFMP plantations. While the

problems could not generally be described as

serious, several including the sudden death of teak

trees, defoliation of teak seedlings, dieback of

cedrela, as well as stem canker on cedrela were of

major concern to affected farmers. Also, abiotic

factors such as drought and poor site, planting

issues such as use of poor quality planting

material and poor timing of planting, and damage

from pruning were setbacks to the efforts of some

of the communities, especially those with

plantations in dry sites (Speight and Wylie, 2001).

However, proper management backed by effective

supervision from the FSD should help mitigate

future tree damage or mortality.

The design and approach of the survey provide

useful lessons for effective surveillance of pests

and diseases in smallholder tropical plantations in

Ghana and elsewhere. Forest health challenges of

small holder plantations are obviously different

from those in large scale industrial plantations.

Firstly, plantations often start as agroforestry or

taungya systems, including both trees and food

crops. Which means that, pest problems and their

management may be more complicated than in

pure tree plantations (Schroth, et. al., 2000; Singh,

1995; Singh and Singh, 1988; Epila, 1986). It also

means that forest health experts should be familiar

with pests of commonly grown crops in order to

provide technical assistance to farmers whose

problems could be on both tree and food crops, or

possibly on food crops alone.

Secondly, as the name implies, smallholder farms

are small in size, and in our study most were less

than 2.5 ha per farmer and were mostly

established on the landscape in a mosaic pattern.

Such a situation requires that the system of survey

and monitoring adopted should be all-inclusive,

involving all farmers within a catchment area.

Such an approach helps to quickly identify any

pest problems and underlying causes. It also helps

to achieve effective and cost-efficient control, if

needed.

Thirdly, pest surveys in smallholder plantations

should be participatory. Conventional survey

approaches in large scale plantations are often

systematic and somewhat mechanical. Experts

usually set up plots or monitor the forest

systematically using ground (often with vehicles)

and/or aerial surveys (usually with light aircraft)

(Woodall, et al., 2010; Speight and Wylie, 2001).

They are usually aided by sophisticated data

recording and photographic equipment, with very

little if any non-expert involvement. Such a

system cannot be applied to small holder

plantations, especially in developing countries

where resources are limited. As can be seen from

our study, involvement of local authorities,

farmers, and opinion leaders was critical in

obtaining results. Otherwise, access to the

plantations alone could have been a challenge to

survey crew.

Fourthly, effective surveillance in smallholder

plantations should be done concurrently with

technical assistance for the control/management of

the affected plantations. It should also include

awareness and education on integrated pest

management (IPM) strategies in the communities.

Farmers’ commitment to tree planting projects is

often low and therefore they need to be



encouraged and motivated continually to sustain

their interest. Any serious pest outbreak left

unattended, to the point of threatening the

plantations, or the time or resources invested by

the farmer can lead to abandonment of the project.

Finally, FHM programme in smallholder

plantations should be amenable to the local

situation. It is important to first consider the

prevailing condition in the locality in order to

design the survey approach. In the present study,

plantations were established in degraded forest

reserves by adjoining communities. In addition to

land for planting, the farmers were organized by

the Forest Plantations Development Centre, and

given logistical, financial and technical assistance

to undertake the project. Again, they were

organized into groups to facilitate the process of

project monitoring and evaluation. It was therefore

relatively easy to gain access to the communities,

the farmers, their farms and relevant information.

This may not necessarily be the same in other

situations. Thus, it is essential that analysis is done

before the initiation of survey programme in

smallholder plantations in the tropics.

CONCLUSION

The conditions under which this study was

conducted contributed greatly to the outcome

obtained. The CFMP project was a donor-funded

project being implemented by the FC so the

circumstances under which farmers were

operating were different from normal. Farmers

were given access to degraded portions of the

forest reserves for cultivation. In addition, they

received financial, logistical and technical

assistance from the FC to motivate them to

undertake the taungya activities. Also, the taungya

conditions were modified from what pertained in

the past, where farmers were allowed to grow their

crops and tend the trees for a few years, after

which they were ejected when the tree canopy

closed. Under the present modified taungya

system, farmers were required to continue with the

maintenance of the plantations even when they

stopped crop cultivation until the trees matured.

According to the new benefit sharing scheme

under the MTS, farmers are then entitled to 40%

of the proceeds from the trees at the end of the

rotation. Such a system was is a strong motivation

for farmers to commit to the project and

collaborate/ support any moves that appear to

increase the success of the project. The support

and commitment received by the project team

might not necessarily be the same if farmers were

working on their own accord, outside of the forest

reserves, and without any form of technical or

logistical support.

This study has shown that surveillance of pest

status in smallholder tropical plantations should

not only focus on the technical aspects, but should

be amenable to suit the local cultural and

socioeconomic conditions. Such a system should

also be designed to concurrently advice farmers on

how to control the observed pest problems, as well

as education and creation of awareness on IPM

strategies.

ACKNOWLEDGEMENT

Funds for the study were provided by the National

Forest Plantation Development Programme

(NFPDP), under the Community Reforestation

Programme On-farm Research Project of the

Ministry of Lands and Natural Resources, Ghana.

The authors wish to thank Dr. Victor K. Agyeman,

Director-General of the Council for Scientific and

Industrial Research (CSIR), formerly Director

(CSIR-Forestry Research Institute of Ghana,

FORIG) and Manager of NFPDP. Gratitude also

goes to Dr. Ernest G. Foli, who was the

Coordinator of the CFMP On-farm Research

Project at CSIR-FORIG and several anonymous

reviewers.

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pests in tropical forestry. 1st edition. CAB

International, Wallingford, UK. 307 pp.

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(2008). Forest Entomology in West Tropical

Africa: Forest Insects of Ghana. 2nd Edition.

Springer. The Netherlands. 244pp.

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Significance of medicinal plants in a valley rice growing eco-system (Sawah) E. Nutakor


THE SIGNIFICANCE OF MEDICINAL PLANTS IN A VALLEY RICE

GROWING ECOSYSTEM (SAWAH): THE CASE OF AHAFO-ANO SOUTH

DISTRICT, GHANA.

E. Nutakor

CSIR-Forestry Research Institute of Ghana, University P.O. Box 63, KNUST, Kumasi, Ghana

Email:[email protected]

ABSTRACT

The technology for wet valley rice production or Sawah, has gained increased popularity in Ghana as it

holds promise for improved food production and poverty reduction. However, there is concern that this

system could have negative implications for wetland ecosystems especially in the provision of medicinal

plants (MPs) for human health. The study identified medicinal plants and their utilization by local people

in 3 Sawah pilot communities in Ahafo-Ano South District, Ghana. It assessed their perceptions of the

Sawah system in relation to distribution, diversity and availability of medicinal plants in the ecosystem.

Data was collected using participatory research approach. In terms of distribution and diversity of MPs,

the results revealed that, out of 84 different plant species mentioned, 48% were found in the Sawah

system, while 61%, 38% and 30% were in upland farms, forests and homesteads/gardens, respectively.

The Sawah system was ranked (perceived as) second in the availability of medicinal plants by 32% of

respondents compared to other land use types such as farms (39%); forest (17%) and homestead/gardens

(12%). Availability of MPs varied across land use types with farms and homesteads/gardens having the

highest mean availability indices of 2.64 and 2.36 respectively with the Sawah system ranking slightly

above forest lands with least availability index. The MPs are generally on the decline in the ecosystem,

thus there would be the need for interventions to conserve them in the ecosystem.

Keywords: Medicinal plants, wet valley rice production system, Sawah, perception, utilization.

INTRODUCTION

“Sawah” (Indonesian term for wet rice-field) is an

inland valley rice production technology used in

lowland areas where rice fields are bunded and

leveled with inlet and outlet for irrigation and

drainage. Sawah system is gaining increasing

popularity in Ghana due to its associated increased

production output compared to the traditional

upland systems (Oladele and Wakatsuki, 2010;

Wakatsuki, et al., 1998; Obeng, 1994). Rice

productivity analysis of rice production in Ghana

shows that the Sawah technology increased output

from 1.0 t/ha under traditional system to over 5

t/ha under the “Sawah” system (Buri et al., 2008;

Buri et al., 2012). Thus, Sawah (wet valley rice

production) is considered as a promising

sustainable rice production system that addresses

Ghana’s domestic rice demand, huge rice imports,

quest to increase rice productivity and ensure food

security (Alarima et al., 2013). Besides, the Sawah

system is perceived to conserve and enhance

wetland ecosystem services (Oladele and

Wakatsuki, 2010). Generally, 15% of rice growing

areas and 68% of irrigated rice areas practice the

Sawah system (Ragasa et al., 2013). The current

rate of diffusion is said to be limited (ranked third

in terms of rice management practices in Ghana)

compared Asia (Ragasa et al., 2013). However, to

improve the adoption and diffusion of Sawah rice



production system, dissemination activities are

being intensified. The fact is that, as more farmers

adopt the Sawah system, there would be

increasing conversion of inland valley wetlands to

rice fields in Ghana. This could have potential

detrimental effect on other services or uses that

inland valley wetland ecosystems offer such as

biodiversity and provision of medicinal plants.

Medicinal plants have significant socio-cultural

values to local communities with limited access to

orthodox medical care. Local people rely on

herbal medicines to treat many common ailments

endemic in their communities. Mahomoodally

(2013) notes that in many parts of rural Africa,

traditional healers prescribing medicinal plants are

the most easily accessible and affordable health

resource available to the local community and at

times the only therapy that is available to the

people. Studies show that demand for medicinal

plants has been increasing in Africa (Oviedo et al.,

2007; Rukangira, 2001). While, global policy

direction of the World Health Organization

(WHO) of the United Nations supports initiatives

to promote the use of traditional herbal medicine

especially in rural communities that usually have

very limited access to orthodox modern medical

facilities (WHO, 2002). Hence, the need to

conserve and protect medicinal plant resources,

and their habitats in order to increase their

availability to rural communities (Salafsky and

Wollenberg, 2000). In relation to medicinal plants

habitats, Cole, (1996) showed that wetland

ecosystems provided habitat for 3% of 439 species

medicinal plants surveyed in West Africa.

Although low compared to other ecosystems,

nevertheless, it underscores the importance of

inland valley as important source of medicinal

plants for fringed dwellers and the detrimental

socioeconomic effect of habitat loss due

conversion of inland valleys to rice fields.

Therefore, the need for basic data and scientific

information on medicinal plants in the Sawah rice

production system in Ghana cannot be

overemphasized. Information on availability,

abundance, diversity, use and management of

medicinal plants is important in assessing the

effect of adoption of Sawah rice production

technology on medicinal plants and exploring

need for in-situ conservation of medicinal plants

in the Sawah system. Ecological and ethno-

botanical studies of medicinal plants in the Sawah

rice production system are essential to ascertain its

perceived attribute of conservation and

enhancement of wetland ecosystem and their

services (Oladele and Wakatsuki, 2010),

nonetheless, most studies have focused on farm

adoption trials, factors affecting Sawah rice

production system and adoption and dissemination

of Sawah rice technology (e.g. Oladele et al.,

2011; Alarima et al., 2011; Oladele and

Wakatsuki, 2011). Research studies on effect of

practice of Sawah rice production system on

provision of important ecosystem services of

inland valley ecosystems such as medicinal plants

are generally lacking. Consequently, this study

assesses perception of diversity, distribution and

availability of medicinal plants in the “Sawah

ecosystem” in selected Sawah pilot communities.

Results of the study is relevant to researchers,

policymakers, farmers and users of herbal

medicines on the best approach for ensuring

sustainable provision of multiple ecosystem goods

and services particularly medicinal plants in the

dissemination and adoption of Sawah rice

production system.


Study Area

The study was conducted in the rice growing areas

of Ahafo-Ano South District in the Ashanti

Region, Ghana. The district was selected for

inland valley rice development project (IVRDP) in

years 2004-2009 with the aim of raising rice

production from 1.5 tons/ha to 4.5 tons/ha (ADF).

It was also the target district for the introduction

and adoption of Sawah rice production



technology. The district recorded rice yield of

5.17-5.44 tons/ha in the yeas 2000-2005. The

district recorded the highest rice yield in all

seventeen (17) districts in the Ashanti region in

the same period (Oladele and Wakatsuki, 2010b).

Three (3) rice-producing communities in the

district were selected for the study, namely:

Adugyama, Amakom and Biemso No. 1. The

district falls within the moist semi-deciduous

forest zone of Ghana (Hall and Swaine, 1981). It

is located on Latitude 6 42'N, 7 10'N and

longitude 1 45'N and 2 20'.

Data Collection and Analysis

Data for the study was collected using

questionnaire and interviews involving farmers

and herbalists. Random sampling method was

used in selecting a total of 40 respondents for the

study. The respondents comprised farmers who

cultivated rice using the the Sawah technology as

well as farmers who cultivated crops other than

rice, and herbalists that operate within the selected

communities. An initial list of farmers and

herbalists was generated from which thirty (31)

farmers and nine (9) herbalists were randomly

selected.

The questionnaire survey and interviews focused

on gathering information on availability, diversity

and distribution of medicinal plants. Data

generated from the questionnaires and interviews

were analyzed by means of descriptive statistics

and presented in graphs and tables using Statistical

Package for Social Scientists (SPSS, version 16,

IBM) and Windows Microsoft Excel (2010).

Quantitative ethno-botany tools of multivariate

and statistical methods (Höft et al., 1999) were

used for data analysis.

Assessing Perception of Distribution,

Diversity and Availability of Medicinal

Plants

To determine perception of availability, diversity

and distribution of medicinal plants in the Sawah

system, respondents were asked questions such as

‘what medicinal plants have you collected and

used in recent years (at most 5 years)?; where did

you collect the above-mentioned medicinal

plants?; what is level of availability at the

source(s) mentioned?.

Perception of distribution and diversity of

medicinal plants: Respondents were asked to

mention medicinal plants they have harvested and

used, including their sources in recent years (at

most 5 years). The identified medicinal plants

were categorized in relation to their sources with

their frequency compared across sources. Sources

with higher number of different number of species

were determined to be highly diverse. For

example, a land use containing 10 species would

be more diverse than another with 5 species

(Gotelli and Colwell, 2001; Butler and Chazdon,

1998). Also, the cross-comparison gave an

indication of the distribution of medicinal plants

Sawah ecosystem and other land use types.

Perception of level of availability of medicinal

plants: Respondents were asked per their

knowledge to indicate the level of availability of

the identified medicinal plants with respect to their

sources on four-point scale. The four-point scale

and its respective score is described as follows:

‘Abundant = 3, Less Abundant = 2, Scarce = 1

Unavailable = 0’.

RESULTS AND DISCUSSION

Plants of Medicinal Value and their

Utilization

In all, sixty (60) different plant species were

mentioned by the respondents. The most

mentioned species include Morinda lucida,

Alchornea cordifolia, Rauvolfia vomitoria,

Spathodea campanulata, Ficus exasperata,

Zanthoxyllum leprieurii, Khaya sppand

Pycnanthus angolensis. Notably, the most

frequently mentioned species in terms of usage

was Paullinia pinnata, cited by 58% of the



respondents (Annex 1, column 4). Paullinia

pinnata which has multiple uses is applied in

treating dysentery, stroke, hypertension and body

wounds.

Distribution and Diversity of Medicinal

Plants in Sawah Ecosystem

Sixty (60) different medicinal plant species were

identified to have been collected and used by

respondents. The medicinal plants were accessed

in crop farms, Sawah ecosystem, forests and home

gardens. In terms of distribution, the results

showed that, respondents perceived medicinal

plants to be more distributed in farms and thus

more accessible to them (43%) and Sawah

ecosystem (27%) compare to other land uses

(Figure 1). As a result of the high diversity of MPs

in these land-use types they would be the most

frequented places for the collection of medicinal

plants for use by the communities which is likely

to place great pressure on the resource.

Figure 1: Diversity of medicinal plants in land-use

systems of the Sawah ecosystem: where

plants are mostly found and collected.

The Sawah zone is additionally the place where

harvesting may continue even in the dry season.

Annex 1 indicates in columns 6-8 the popular

sources for collecting the various medicinal plants

that were mentioned by respondents. The

presentation also indicates how more likely they

are to be found in a particular location in the

ecosystem; for instance, Paullinia pinnata, was

more likely to be found in the Sawah land-use area

than in the upland farms. Ficus exasperata was

perceived as being equally distributed in the

Sawah and the farms.

In terms of diversity, the results showed that, out

of the different species identified and collected by

respondents, 61% were found in the farmlands

located on the higher grounds, 48% in the Sawah

system while, 38% and 30% were located in

forests and homesteads/gardens respectively

(Table 1). Naturally, one would expect relatively

higher diversity of plant species in the wetlands

but it was speculated by respondents in focus

group discussions that the application of

chemicals to control weed in the rice farms had

led to reduction or the extermination of many

plants in that zone.

Table 1: Respondents’ perception of diversity of

medicinal plant species in different

land-use types in the Sawah ecosystem.

Land use

types in the

ecosystem

No. of different

Species found in

use-type

Percentage of

all species

found in

ecosystem

Sawah 40 47.62

Farm 51 60.71

Forest 32 38.10

homes 25 29.76

N = 60

Sawah

27%

Farms

43%

Forest

20%

Home gardens

10%



The relative diversity of MPs in the two land use

systems (farms and Sawah) is corroborated by the

fact that, respondents also identified the two land-

use systems as the most popular locations for

collection of MPs. Even though Sawah is seen as

high yielding, studies indicate that there are real

environmental concerns particularly in terms of

chemical applications and their impact of

environment (flora and fauna) as well as on

human health that must be considered for

sustainable management and availability of

biodiversity (Killebrew and Wolff, 2010).

Severally, therefore it is suggested by experts that

scientists and policy actors must try to quantify

the benefits of the natural use of wetlands against

the benefits to be derived from conversion to rice

production.

Availability of Medicinal Plants in the

Sawah Ecosystem

The overall nominal availability (abundant,

declining, endangered or extinct) of MPs indicated

by respondents revealed that, 57% of MPs were

perceived to be abundant, while 17% were

endangered. Respondents perceived that 14% of

plants were declining and 12% were reported to be

extinct in all the four land-use systems (Figure 2).

However, the availability status of medicinal

plants in each land use system showed that, farms

and Sawah system were perceived as land use

system with the most abundant MPs. As shown in

Figure 3, thirty-nine percent (39%) of respondents

indicated farms as the land-use with most

abundant MPs while Sawah (32%), forest (17%)

and homestead/gardens (12%) followed

respectively. It is also probable that collection

behavior may influence this result; farmers would

naturally look for MPs on their own farms first,

mostly up-land, before traveling farther to

wetlands for scarce varieties. As to why farms

(cocoa and food crop farms) ranked highest in

relation to abundance of MPs compared to Sawah

and other land use systems may be a question of

access, suitable growth conditions for MPs and

degradation.

Figure 2: Perception of abundance of medicinal

plants by land use types.

Figure 3: Respondents’ perception of the most

abundant source or land-use type for

harvesting medicinal plants in the

Sawah ecosystem.

Sawah

32%

Farm 39%

Forest

17%

Home

12%

57%

Declined

14%

Endangered 17%

Extinct

12%

Abundant



As noted at the focus group discussions, the wet

valley areas where Sawah rice production system

is practiced were reported to have come under

increasing agro-chemical application, while

forests have become less accessible to people for

collection of non-timber forest products such as

medicinal plants due to forest degradation. In

terms of access, majority of farmers with farms

and farm lands would access these areas for MPs

than trek long distances to the forest and valley

areas to collect MPs. It is also possible most

farmers may have domesticated some of the most

important and commonly used MPs in their farms

thereby increasing its abundance and distribution

over larger land area compare to homesteads or

gardens. The home gardens have not also been the

most popular sources for the ten most important

MPs shown in Annex 1. In Sawah system

(commercialized rice cultivation), there is an

increasing use of agricultural chemicals

unfavorable to growth and development of

medicinal plants. The low level of diversity and

abundance of MPs in the forests in the study area

may be due to degradation and deforestation or

even restricted access and distance.

Generally, farms having high level of abundance

of MPs should make them of special interest

among conservationists with regards to

availability of biodiversity. Also, not to be

neglected is the Sawah system since respondents

at focus group discussions and during key

informant interviews indicated that the wet valley

areas are an important source of MPs during the

dry seasons.

Overall, MPs’ availability index for all land-use

types was determined as 1.97 (Table 2) along the

continuum (3-0). For individual land-use systems,

crop farms scored the highest mean availability

index (2.64) followed by the homesteads/gardens

(2.36). Sawah system and forest scored the least

indices of 1.58 and 1.45 respectively. Crop farms

and home-gardens would be expected to have high

score of availability indices if important plants are

domesticated and protected to ensure their

availability (Rukangira, 2001; Cunningham,

1997).

Table 2: Score of availability of medicinal plants

in the Sawah ecosystem.

Land use

types in the

ecosystem

N Mean

score

Std.

Deviation

Sawah 81 1.58 1.25

Farm 72 2.64 0.72

Forest 71 1.45 1.31

Home 50 2.36 0.80

274 1.97 1.19

This however does not necessarily mean that these

areas should have higher plant diversity. It could

simply mean that over the period under

assessment the perception was that there had been

only a certain trend (increase or decline etc.) of

change in availability of the plants. Although,

homesteads/gardens scored the second highest

availability index, it can be argued that, the score

may partly be attributed to the smallness of N for

this group. A look at the availability scores of the

Sawah system and forest zone shows that MPs

seem to be on the decline in these land use types

since their means were generally below the overall

mean availability index of (1.97). Obviously, this

makes the case for investing in availability actions

targeted at improving availability of medicinal

plants in these land use types.

CONCLUSION

The study has assessed the perception of

distribution, availability and relative diversity of

MPs in the Sawah eco-system in the pilot

communities of Ahafo-Ano South District, Ghana.

The study revealed that a wide variety of MPs

were collected and used for various and multiple



purposes with in the communities. Multiple parts

including roots of plants are harvested for use. The

harvesting of roots and peeling of tree bark are

practices that have serious implications for the

survival of MPs and thus the sustainable

management of the resource.

The perception is that majority of medicinal plants

mentioned are between abundant and declining

within the ecosystem. The most bio-diverse and

popular harvesting sources are the farms and wet

lands, the latter now being prone to chemical

application. The popularity of collection sites

could be due to plant diversity and not necessarily

abundance of any particular MPs in that site.

Thus if a particular MP can be found only in the

Sawah for instance, albeit scarce, that would still

drive people to the location to harvest that MP.

In terms of abundance of medicinal plants, Sawah

system was ranked second to farms. However,

availability of MPs varied across land use types

with farms and homesteads/gardens having the

highest mean availability indices of 2.64 and 2.36

respectively. Sawah system was slightly above

forest with regards to land use types with least

availability index. The implication is that MPs are

on the decline in the Sawah and forest land use

types. This calls for investing in availability

actions targeted at improving availability of

medicinal plants in these land use types.

The emerging commercial rice farming in the wet

lands is a challenge to sustainability of the eco-

system and survival of medicinal plant diversity

and availability. The Sawah technology could

promote excessive chemical usage (herbicides

especially) if not checked with other improved

farm practices. Nonetheless, it is worth noting

that, the observed results were perceptions based

on collection experience of respondents for all

species identified. It would subsequently be more

revealing to examine the influence of social and

cultural factors on perception of the identified

species. For instance, access to some locations

may be influenced significantly by gender, social

status, management regime, occupation, among

others.

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Annex1: List of medicinal plants identified in the study areas.

Botanical name Local name %

respondents

Source1 Availability2

1st 2nd 3rd

Paullinia pinnata Tuantini 57.5 W Fa Fr 2.6

Morinda lucida Konkroma 47.5 Fa Fr W 2.5

Alchornea cordifolia Gyama 45 Fa W

Fr

H 3

Rauvolfia vomitoria Kakapenpen 45 Fa W

H

Fr

2.5

Spathodea campanulata Akuakuanesuo 42.5 Fa W

H

2.5

Ficus exasperata Nyakyerenee 30 W

Fa

Fr H 3

Zanthoxylum leprieurii Oyaa 30 Fr

Fa

1.6

Khaya spp Mahogany 27.5 Fa Fr 1.3

Pycnanthus angolensis Otie 25 Fa Fr W 2.3

Solanum erianthum Pepediewuo 22.5 W Fa

H

2.4

Phyllanthus capillaries Awobe 20 W Fr 3

Hoslundia opposita Nunumnini 20 H W

Fa

Fr

0.9

Alstonia boonei Nyamedua 20 Fr Fa W 2.4

Senna alata Simpe 20 H 1.5

Mallotus oppositifolia Nyanyanforowaa 17.5 Fa 2

Chromolaena odorata Acheampong 15 W Fa 3

Vitex grandifolia Dusinkro 15 W Fr 1.3

Teminalia ivorensis Emire 15 Fr Fa 1.3

Petersianthus

macrocarpus

Esia 15 Fa 1

Microdesmis puberrula Afema /

Owudifokete

12.5 W Fr 3

Bombax buonopozense Akata 12.5 Fa 3

Bambusa vulgaris Mpampro 12.5 W Fa 2.6

Trilepisium

madagascariense

Okureokore /

Okure

12.5 Fa W

Fr

H

2.6

Mezoneuron

benthamianum

Akoboowere 10 W 2.5

Blighia sapida Akye 10 W Fa Fr 3



Thalia geniculata Babadua 10 W 2.5

Phyllanthus uninaris Bowomaguwakyi 10 W Fa 1

Piper guineense Esorowisa 10 Fa Fr 2

Momordica charantia Yanya 10 Fa W

Fr

2.7

Persea americana Paya (pear) 10 Fa Fr 3

Tetrapleura tetraptera Prekese 10 Fa H 3

Psydrax subcordata Tetieadupon 10 Fa Fr

H

2.3

Ricinodendron heudelotii Wama 10 Fa 2

Albizia ferruginea Awiem

Foursamina

7.5 Fa Fr 2.3

Kigelia africana Nufuten 7.5 W Fr 1.5

Terminalia superba Ofram 7.5 Fr 1

Sida acuta Tweata /tweta 7.5 W 2

Parquetina nigrescens Abakambo 5 W Fa 2.5

Solanum torvum Abeduro 5 Fa 3

Dialium guineense Akosuatuntum 5 H 3

Hilleria latifolia Anafraneku 5 Fa H 1

Citrus aurantifolia Ankaatware 5 Fa 2.5

Guarea thompsonii Basiko/kwadwuma

/Kwabohirinini

5 Fr 1

Lonchocarpus

cyanescens

Edwene 5 H 2

Glyphaea brevis Foto 5 W 0

Psidium guajava Guava (leaves) 5 W H 1

Jatropha curcasa Nkrandua 5 H 3

Griffonia simplicifolia Kegya 5 Fa Fr 3

Lannea welwitschii Kumanii 5 Fa 3

Capsicum frutescens Mesewa 5 Fa 3

Senna occidentalis Nkwadaakwada

Abodea

5 H 2.5

Ficus sur Adoma 5 Fa 3

Abrus precatoriius Odwiankyene 5 H 3

Achomanes difformis Ope 5 W Fa 2

Clausena anisata Samanobi 5 H 3

Nicotiana tobacum Bonto 5 W 3

Raphia farinifera Tonto 5 W 3

Voacanga africana Ofruma/bedaa/obo

Nawa

5 Fr 0

1W = Sawah; Fa=Farm; Fr = forest; H = homestead 2Abundant = 3; declining = 2; endangered = 1; extinct = 0

Influence of indole-3-butyric acid concentrations on cinnamomium camphora E. O. Owusu et al.


INFLUENCE OF INDOLE-3-BUTYRIC ACID CONCENTRATIONS ON

ROOTING OF CINNAMOMUM CAMPHORA (L.) PRESL MARCOTS

E. O. Owusu, C. M. Asare and S. Ackon

CSIR-Plant Genetic Resources Research Institute, Bunso


ABSTRACT

In this study, marcotting technique was used to reproduce camphor tree (Cinnamomum camphora (L.)

Presl) at the Council for Scientific and Industrial Research Plant Genetic Resources Research Institute at

Bunso. The aim of the study was to determine indole-3-butyric acid (IBA) concentration that promotes

rooting in marcotted camphor tree. One hundred shoots of similar girth (0.9 cm) were sampled on the

only C. camphora tree at Bunso and marcotted by girdling 2.5 cm-wide strip of the bark at 15 cm from

the apex. Thereafter, a set of 25 girdled strips were each treated with 2000 mg/l, 4000 mg/l, 6000 mg/l or

0 mg/l (control) IBA concentration. Two handfuls of moistened river sand and decomposed palm fiber

mixture (1:2 v/v) root substrate, was placed in 25 cm2 transparent polyethylene film and wrapped around

the girdled surface. Data collected after 12 weeks indicated that IBA concentrations had effect on rooting

of the marcots. Number of survived marcots, rooted marcots, root length and sprouted marcots differed

significantly (p ≤ 0.05) amongst marcots of different IBA concentrations. Differences in callus formation

were however not significant amongst the different concentrations. Rooting and shoot performance of

marcotted camphor were highest at 4000 mg/l IBA concentration. Marcotting camphor tree without IBA

or applying of 6000 mg/l IBA resulted in poor rooting.

Keywords: Cinnamomum camphora, vegetative propagation, marcotting, indole-3-butyric acid.

INTRODUCTION

Vegetative propagation techniques have been

instrumental in tree improvement programmes

over the years. New plants are produced from

vegetative organs of parent plants to generate

offspring with similar parental genotype (Zobel

and Talbert, 1984; Ofori et al., 1996). It is a useful

and reliable method for multiplying tree species of

superior genotype as it bars any somatic mutation

(Hartmann et al., 2011). It also ensures rapid

maturity of desirable tree species for early

utilization (Hartmann et al., 2011). Propagation by

grafting, budding, marcotting and cuttings are

some of the most common techniques in

vegetative propagation which are amateur-friendly

and require simple inexpensive equipment

(Hartmann et al., 2011; JICA, 2002).

Plants of the Lauraceae family like Cinnamomum

camphora (L.) Presl have been propagated

vegetatively over the years. This is because seed

propagated plants are genetically diverse and have

long juvenile periods (Hartmann et al., 2011).

Cinnamomum camphora is native to China,

Taiwan, and Japan (Li and Bai, 1982; Rabuil et

al., 2011). It is evergreen, large and grows up to

20-30 m tall with a round dense crown. The leaves

are simple, ovate and alternate with pinnate

venation along entire leaf margin and about 6-12

cm long and 2.5-5.5 cm wide. Leaves are glossy

green, thin and leathery textured and give off

camphor aroma when crushed. The stem and



branch of young trees are bright green, tinged with

red, maturing into a dark grey-brown and rugged-

looking trunk which appears almost black when

wet. Trunk and branch structure of older trees are

similar to mature live oak. Flowers are tiny,

inconspicuous and yellow and appear from April –

May. The tree produces profuse, small, fleshy

black berry fruits which is 1.3 cm in diameter

from August-November (Cerveny et al., 2006).

Camphor tree has been underexploited due to over

reliance on artificial sources of fragrances and

flavour. However, recent demand for natural

sources of fragrances and flavour call for

propagation techniques aimed at increasing

populations of natural sources of fragrances and

flavours like the camphor tree to meet future

demand. Essential oils from C. camphora have

been identified to be among the most important

oils in world trade. Camphor oils are extracted

from the roots, branches, leaves and wood of the

tree for pharmaceutical use and flavouring. The

fruit core is about 40% oil which has industrial

and medicinal uses. The wood is good for

construction, ship building and cabinet-making (Li

and Bai, 1982).

Vegetative propagation techniques such as

marcotting have been widely used for commercial

propagation of lychee (Litchi chinensis Sonn.)

(Hartmann et al., 2011). Misra and Jaiswal (1993)

studied the propagation of Anthocephalus

chinensis (Sonn) by marcotting with the aid of

Indole-3-butyric acid (IBA) and reported that all

marcots showed callusing but only those treated

with IBA showed rooting. Plant auxins are known

to promote root formation in vegetative plant parts

(Aminah et al., 2006). The auxins increase cell

wall elasticity which accelerates cell division and

consequently enhance rooting through

translocation of carbohydrate and other nutrients

to the rooting zone (Middleton et al., 1980).

Marcotting is considered as one of the simplest

and oldest methods of plant multiplication. It is

one of the safest because while the prepared plant

is making roots, the parent plant continues to

provide nourishment until it can fend for itself

when sufficient new roots have been formed

(Sicuranza et al., 2005).

Marcotting was therefore considered as a viable

method for reproducing C. camphora (camphor

tree) on the premises of Council for Scientific and

Industrial Research, Plant Genetics Resources

Research Institute (CSIR-PGRRI). The study was

carried out to determine the optimum IBA

concentration that would promote root initiation

and survival of marcotted C. camphora.


Experimental Site and Design

The experiment was carried out at CSIR-PGRRI,

Bunso in the Eastern Region of Ghana between

April and August, 2013. Bunso lies on 06⁰ 17' 19"

N, 00⁰28' 05" W and elevation of 226 m.

Temperature ranges from 24°C to about 28°C and

average rainfall is about 1750 mm. Marcotting

was initiated on selected branches of the only C.

camphora tree on the campus of CSIR-PGRRI. At

the time of the experiment, the tree had a dbh

(diameter at breast height) of 94.30 cm and height

of 3.22 m. The experiment was set up in a

completely randomized design with four

treatments, each replicated 25 times. The

treatments were indole-3-butyric acid (IBA)

concentrations of 2000 mg/l, 4000 mg/l and 6000

mg/l and a control (0 mg/l) where no IBA was

applied. Thus, a total of 100 shoots were

marcotted. In order to avoid bias, each shoot

selected for marcotting was allocated randomly to

the treatments by use of a table of random

numbers (Johnson and Bhattacharyya, 2006).

Preparation of Rooting Hormone

Indole-3-butyric acid of concentrations of 2000

mg/l, 4000 mg/l and 6000 mg/l were used as

rooting hormone for the treatments. Indole-3-

butyric acid concentration of 2000 mg/l was



prepared by dissolving 200 mg of powdered stock

IBA in 100 ml of 50% ethanol solution in a

volumetric flask .The same process was followed

for preparation of the 4000 ml/l and 6000 mg/l

IBA concentrations

Preparation of Rooting Medium

River sand and decomposed oil palm fibres

collected from a decomposing palm tree were

mixed thoroughly in proportions of 1: 2 v/v on

thick sheet of polythene. Stones and other foreign

materials were removed and the mixture sterilized

by autoclaving at 121°C and 15 psi for 15 minutes

in sealed glass jars.

Selection of Leafy Shoots for Marcotting

Leafy shoots measuring 15 cm in length from the

apex and approximately 0.9 cm in diameter

(Hartmann et al., 2011) were selected from

healthy branches of the C. camphora tree. Barks

of selected shoots were girdled by removing 2.5

cm-wide strip. The debarked surfaces were

scraped of all phloem and cambium tissues to

retard healing of the exposed surfaces, after which

the IBA solution was then applied. Two handfuls

(180 cm3) of moistened rooting media was placed

in 25 cm2 transparent polyethylene sheet and

wrapped around the girdled surface. Monitoring of

the setup was done weekly for 12 weeks. The

marcots were excised from the plant with a pair of

secateurs after 12 weeks for examination. The

transparent polyethylene sheet and the rooting

medium were removed, and the marcots examined

for callus formation, roots and shoot sprouts.

Callus forms as a result of dedifferentiation of

tissues indicated by bulging of the girdled areas of

the marcots.

Data Collection

Marcotted shoots that had green leaves and stem

after 12 weeks were considered alive. Marcots that

were alive were counted for the different IBA

treatments. Data collected included survived

marcots, rooted marcots, root length, sprouted

marcots and callused marcots. Root length

measurements were done with a metric measuring

rule.

Statistical Analyses

Data were transformed using square root

transformation where applicable before Analysis

of Variance (ANOVA). GenStat package software

Version 12 was used for the analysis. The

Duncans multiple range test was used to separate

the differences between means at 5% level of

significance.

RESULTS

Survival and Callus Formation

Marcots survival was highest in the 4000 mg/l

IBA concentrations and least in the control (Table

1). There was callus formation in all the survived

marcots. There was callus formation in 19 out of

24 survived marcots with the 4000 mg/l IBA

concentration as compared to the least, 11 out of

21 survived marcots with the 6000 mg/l IBA

concentration (Table 1). Survived marcots with

IBA concentrations 2000 mg/l and the control

both had 18 callused marcots as shown in Table 1.

Shoot Sprout

There were considerable numbers of new shoot

sprout in marcots of all the IBA concentrations.

Even though the control formed more new shoots

per unit marcot, the percentage of marcots that

formed new shoots was higher in those treated

with IBA (Table 2). Shoot formation in marcots

ranged from 24 marcots in IBA concentration of

4000 mg/l with a mean shoot sprout per marcot of

17.88 to 20 marcots in IBA concentration of 0

mg/l (control) with a mean shoot sprout per

marcot of 20.05 (Table 2).



Table 1: Percent survival and callus formation of 12-week old C. camphora marcots.

IBA concentration

(mg/l)

Number of

marcots (n)

Number of

Survived marcots

Number of

callused marcots

% callused

marcots

0 mg/l 25 20 a 18 a 72 a

2000 mg/l 25 21 a 18 a 72 a

4000 mg/l 25 24 b 19 a 76 a

6000 mg/l 25 21 a 11 b 44 b

Note: n=number of sample units per treatment. Figures with the same letter are not significantly different at (p ≤

0.05) according to Duncans multiple range test.

Table 2: New shoot sprouts in 12-week old C. camphora marcots.

IBA concentration (mg/l) Number of

marcots (n)

Number of sprouted

marcots

Mean number of new

shoot per sprouted marcot

0 mg/l 25 20a 20.05a

2000 mg/l 25 21a 19.62a

4000 mg/l 25 24b 17.88b

6000 mg/l 25 21a 19.48a

Note: n=number of sample units per treatment. Figures with the same letter are not significantly different at (p ≤

0.05) according to Duncans multiple range test.

Root Formation

Roots were formed in marcots of all treatments.

Marcots with IBA concentration 4000 mg/l

recorded the highest rooted marcots while marcots

with IBA concentration 6000 mg/l recorded the

least (Table 3). Although marcots with IBA

concentrations of 2000 mg/l and the control

recorded equal number of rooted marcots, the

former recorded a higher number of roots per

marcot (Table 3).

DISCUSSION

Survival and Callus Formation

The minimum survival recorded in the control

treatment agrees with a study by Rahman et al.

(2000) in the propagation of Litchi chinensis. The

decline in survival of camphor marcots treated

with 6000 mg/l IBA conforms to Sharma et al.’s

(1990) observation that increasing IBA

concentration increases survival of Litchi

chinensis marcots however, higher IBA

concentrations reduced survival of marcots. Callus

formed in all the camphor marcots. Number of

callused marcots increased with increasing IBA

concentration. There was however a sharp decline

in the number of callused marcots treated with

IBA of 6000 mg/l. A Similar finding was reported

by Holt and Chism (1988) in the propagation of

Oxalis corniculata leading to the conclusion that

higher concentrations of auxins have phytotoxic

effect.



Table 3: Rooting of 12-week old C. camphora marcots.

IBA concentration

(mg/l)

Number of

marcots

(n)

Number of

rooted marcots

Mean number of

roots per rooted

marcot

Mean root length per

rooted marcot (cm)

0 mg/l 25 18a 9a 15.5a

2000 mg/l 25 18a 11a 35.0b

4000 mg/l 25 19a 28b 89.7c

6000 mg/l 25 11b 7a 30.8b

Note: n=number of sample units per treatment. Figures with the same letter are not significantly different

at (p ≤ 0.05) according to Duncans multiple range test.

Callus precedes root initiation and is a sign of

tissue dedifferentiation at the marcotted area

(Blythe et al., 2004; Hartmann et al., 2011).

Root Formation and Shoot Sprout

Roots formed were more in IBA treated marcots

than untreated ones. Plant auxins are known to

promote root formation in vegetative plant parts

(Aminah et al., 2006). Indole-3-butyric acid is

reported to enhance rooting through translocation

of carbohydrate and other nutrients to the rooting

zone (Middleton et al., 1980; Hartmann et al.,

2011). The abrupt decline in rooting percentage

with IBA concentration greater than 4000 mg/l is

an indication that plant auxins can also inhibit root

initiation (Leakey et al., 1990). Thus, ensuring

optimal hormone concentration is an important

consideration in vegetative propagation for

inducing adventitious root formation.

There was profuse sprouting of new shoots in the

form of buds and leaflets in marcots of all the

different treatments. Shoot sprouting in the

marcots was influenced by IBA in a similar

fashion as in root formation. This could be

attributed to the increased rooting resulting in

increased shoot sprout due to easy translocation of

water and mineral nutrients to the meristematic

tissues of the marcots and subsequently, to rapid

growth and formation of shoots (Hartmann et al.,

2011).

CONCLUSION

The results show that IBA has effect on root

formation and shoot sprouting of C. camphora

marcots. IBA concentration of 4000 mg/l was

most effective in promoting root formation and

shoot sprout in C. camphora marcots. Marcotting

camphor tree without IBA or applying of 6000

mg/l resulted in poor rooting.

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dependant on rooting stem cuttings of Phaseous

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and Grace, J. (1996). Vegetative propagation of

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https://www.cabdirect.org/cabdirect/search/?q=do%3a%22Indian+Journal+of+Horticulture%22

Calorific values and gravimetric yield of six wood fuel species in Ghana J. K. Korang et al.


CALORIFIC VALUES AND GRAVIMETRIC YIELD OF SIX WOOD

FUEL SPECIES IN THE FOREST TRANSITION ZONE OF GHANA

J. K. Korang, B. D. Obiri, H. Appiah and S. Awuku

CSIR- Forestry Research Institute of Ghana, University P. O. Box 63, Kumasi, Ghana.


ABSTRACT

The biomass and energy-calorific values of six of the most common tree species used for wood fuel

production in the Transition Forest Zone of Ghana were assessed. Moisture content (mc), volatile matter

(vm), ash content (ash), fixed carbon (fc) and calorific value (cv) were determined for the species;

Azadirachta indica, Senna siamea, Anogeissus leiocarpus, Afzelia africana, Pterocarpus erinaceus and

Khaya senegalensis. Results showed that A. africana, K. senegalensis, P. erinaceus and A. indica have

the highest mc, vm, ash content and fixed carbon content, respectively. P. erinaceus gave the highest

gravimetric yield (gy) of 33.30% during carbonization, which correlated very well with green density of

the species. A. africana and A. indica posses the highest (5.17 kcal/g) and lowest (3.39 kcal/g) calorific

values for fuel wood, respectively. Similarly, A. indica and A. africana have the highest (6.79 kcal/g) and

lowest (6.07 kcal/g) calorific values for charcoal respectively. Contrary to the assertion that fast growing

species produce poor quality wood fuel, this work has shown that exotic fast growing species such as S.

siamea produces good quality charcoal.

Keywoods: Wood fuel, charcoal, fuel wood, calorific value, fuel index value

INTRODUCTION

Bioenergy in different forms is one of the most

common and easily accessible energy in the world

(Nielsen et al., 2009; Antal et al., 1990;

Chandrasekaran et al. 2012; Finco et al., 2010). In

developing countries like Ghana, wood fuel is the

most important source of bioenergy (Okello et al.,

2001), contributing between 50 to 90% of all

energy consumed (Mensah et al. 2014). Although

wood fuels are perceived as cheap source of

energy, they have a greater economy cost to the

environment. It has been reported as the cause of

forest degradation and eventually deforestation in

some countries.

The overexploitation of the forest for charcoal

production, firewood and furniture making has

resulted in the depletion of forest reserves at a

faster rate, estimated at 3% per year (Foley, 1985).

According to Emerhi (Emerhi, 2011), in sub-

Saharan countries overexploitation has resulted in

the shortage of preferred indigenous tree species

for wood fuel, and as a result wood fuel producers

have to travel longer distances to obtain preferred

species. Wood fuel consumption has led to the

depletion of over 75% of the total forest cover in

many sub-Saharan countries and thus leading to

environmental crises. The demand for bioenergy

especially wood fuel is estimated to double

between 2010 and 2030, and as such a shift to

sustainable production of biomass for wood fuel is

urgently needed for developing countries (Lund,

2007, Duku et al., 2011). The sustainability of

biomass for wood fuel will become even more

important in the coming decades, from the



environmental, economic and societal points of

view.

Switching from fuel wood to charcoal has proven

to be more conducive for most urban lifestyles as

charcoal is more convenient to use, produces less

noxious fumes when burnt and is easier to

transport. Even those households that have

switched to fossil fuels (mainly Liquefied

Petroleum Gas, LPG) use wood fuel occasionally,

often for specific traditional preparations.

According to the Ghana Statistical Service Ghana

Demographic Health Survey by Ghana Statistical

(2009), about 56% of urban households use

charcoal compare to 14% for fuel wood. Unlike

fuel wood where dead wood or tree branches are

collected, wood is harvested from the forest

through clear felling and selective logging for

charcoal production (Hosier, 1993).

The utilization of wood as a source of energy has

significantly increased during the past decade and

charcoal remains the major product. Charcoal is a

wood fuel made from burning wood in a low-

oxygen environment (pyrolysis). The yield of

charcoal is related to tree species (Ramos et al.,

2008; Bourque, et al., 2009; Shah et al., 1992).

Obiri et al. (2014) listed the preferred tree species

for wood fuel in Ghana. These tree species are

known to possess good characteristics of wood

fuel (Houehanou et al., 2011).

The chemical composition of biomass changes

between tree species (Chandrasekaran et al. 2012;

Bao et al., 2001; Oduor et al., 2013) and affects

the energy properties of wood fuel. High lignin

and extractive content of tree species are very

good candidate for wood fuel (Stevens et al.,

2010; White, 1987). Volatile matter and fixed

carbon content are the properties used to represent

the combustible chemical composition of wood

fuel (Nurmi, 1992). These components undergo

combustion to release energy during use. Tree

species with very high volatile matter and fixed

component couples with low moisture and ash

content are favorable for good wood fuel.

Little information exists on the characteristics of

some important tree species used for fuel wood in

Ghana and other developing countries. The

objective of this study was to evaluate energy

characteristics of indigenous tree species used

commonly in agroforestry farming systems and

fuel wood plantations.

METHOD AND MATERIALS

Collection of Wood Species

Wood samples for the study were obtained from

the Kintampo North District, within the Forest

Transition zone of Ghana. The area produces large

quantities of wood fuel, which are transported for

sale mainly in Accra, Kumasi and other major

towns and cities throughout the country. Six (6)

tree species, comprising two (2) exotics

(Azadirachta indica, Senna siamea) and four (4)

indigenous (Anogeissus leiocarpus, Afzelia

africana, Pterocarpus erinaceus and Khaya

senegalensis) were used in the study. Two small-

sized logs of each tree species with diameter

ranging from 10-12 cm and average length were

collected from the Kintampo North District of

Ghana. The samples were stored under shed for

eight (8) weeks to dry before measurements were

taken.

Wood Density Measurements

Basic density and moisture content of the wood

were determined based on International standards

(ASTM D2395-07a (R08), ASTM D2974-14). An

average of 50 cube samples of dimensions 2 x 2 x

2 cm (width x thickness x length) were cut for

both density and green moisture content

determination. Each cube was soaked in water

until it sunk or became swollen. The weight of the

container and the water it contained were

determined. The wood specimen was submerged



in the water, and the mass of container plus water

plus specimen was again determined. The increase

in mass of the container and its contents was equal

to the mass of water displaced by the specimen in

grams and that was numerically equal to the

volume of water (cm3) displaced by the wood

sample (ASTM D2395-07a (R08)). The wood

blocks were then oven-dried at 101±3oC to

constant mass and the oven dry mass determined.

The Green Moisture Content (gmc%) and the

Basic Density (gd), Swollen Density (sd) and

Green Density (gd) were estimated.

Physico-Chemical Properties of Wood Fuel

The wood and the charcoal cubes were milled and

sieved to determine their quality by proximate

analysis, including moisture content (mc), volatile

matter (vm), ash content (Ash) and fixed carbon

content (fc) according to the international standard

ASTM D 1762-84 (ASTM 2001a).

Moisture Content

The moisture content (mc) was found by weighing

1.00 g of the sample into a crucible. The sample

was placed in oven at 100±3°C until the mass of

the sample was constant. The sample was then

cooled in a desiccator and reweighed.

Moisture content (mc %) =Initial weight of sample

Initial weight of sample - Weight of ovendry sample

Volatile Matter The volatile matter (vm) was determined by

weighing 1.00 g of the oven-dry sample into a

crucible. The sample was then kept in a furnace at

a temperature of 550°C for 5 min, cooled in a

desiccator and re-weighed.

Volatile matter (mc %) =Weight of ovendry sample

Weight of ovendry sample - Weight of residue

Ash Content The ash content was determined by returning the

crucible into the furnace at 550°C for 30 min for

combustion. After complete combustion, the

sample was removed and cooled in a desiccator

and before weighing to obtain the weight of ash.

Ash content (Ash %) =Weight of ovendry sample

Weight of Ash

Fixed Carbon Content

Fixed carbon (fc) was computed using the formula below:

Fixed carbon (fc %) = 100 % - (Volatile matter + Ash content)

Determination of Calorific Values

The cv was determined with a bomb calorimeter

using the milled and sieved wood and charcoal

products; about 0.50 g of oven-dried sample, was

completely combusted under a pressurized (3000

kPa) oxygen atmosphere. The change in

temperature of the system was used to calculate

the calorific value.



Fuel Value Index (fvi)

The fvi was estimated using a modified formula

developed by Nasser et al., (2013) below by

considering Basic Density (bd), Moisture Content

(mc) and Calorific Value.

FVI =Moisture content

Calorific value * Basic density

Carbonization of the Wood Species

The carbonization was carried out in an electric

furnace. The charcoal was produced from wood

cubes (2 x 2 x 2 cm). The sample was heated until

450oC for 30 min in the electric furnace at

controlled presence of oxygen. The gravimetric

yield was determined according to the following

equation: Where,

Gravimetric yield (gy %) =Mbio

Mcharx 100%

Mchar = Mass of charcoal (g), and

Mbio = Mass of wood (g)

RESULTS

The results of the basic properties of the species

including green moisture content (gmc), green

density, swollen density and basic density are

reported in Table 1. The results shows that gmc

values of the six wood species ranged from

45.03% to 80.62%, in descending order from A.

Africa, S. siamea, A. leiocarpus, K. senegalensis,

P. pterocarpus to A. indica. In terms of Green

density, the highest was A. leiocarpus with 1.10

gcm-3, whereas the lowest value of 0.89 gcm-3 was

recorded for K. senegalensis.

Tables 2 and 3 show the values obtained for the

proximate analysis of the six wood species for fuel

wood and charcoal. The proximate analysis

involves the measurement of the following

parameters; moisture content (mc), volatile matter

(vm), ash content (ash), and fixed carbon (fc). The

mc result for fuel wood shows, A. indica with the

highest value of 11.24% and A. leiocarpus with

the lowest value of 7.58%. The mc was generally

very low for charcoal with P. pterocarpus with the

highest of 8.00% and K. senegalensis with the

lowest at 0.97%. The vm ranges from 33.52 to

69.68% with A. indica having the lowest and K.

senegalensis the highest. The fc in fuel wood

ranged from 29.64 to 66.29% with A. indica

having the highest and K. senegalensis the lowest.

Similarly the fc for charcoal ranged from the

lowest of 66.80% for A. africana to the highest of

76.80% for A. indica. The ash content is the non-

combustible component of the wood fuel. The ash

content increased from 0.20% to 2.67%, with A.

indica (0.60%) and P. erinaceus (6.78%) having

the lowest and highest, respectively.

The calorific value (cv) of the six wood species

ranged from 3.39 to 5.17 kcal/g for fuel wood, and

between 6.07 to 6.79 kcal/g for charcoal,

respectively. The fuel wood with the highest

energy was A. africana with cv of 5.17 kcal/g and

A. indica had the highest energy for the charcoal

with cv of 6.17 kcal/g. The gravimetric yield (gy)

of charcoal is reported in Table 4, the gy indicates

the yield of charcoal after carbonization. The

average gy was 30.93% with P. erinaceus having

the highest of 33.30% and K. senegalensis with

the lowest of 29.20%.

The suitability of a particular species for either

fuel wood or charcoal based on fuel index value

(fvi) is also shown in Table 4. In Figure 1, the

ranking of the six species studied according to

their estimated fvi are also reported. The

correlation between gy, cv (fuel wood and

charcoal) and the basic density as well as some



proximate analysis parameters of the six species is

reported in Table 5.

Table 1: Physical properties of six wood fuel species from the Transition Zone of Ghana.

Scientific names Local Names Green mc

(%)

gd

(g/cm3)

sd

(g/cm3)

bd

(g/cm3)

Exotic

Species

Azadirachta indica Neem 45.03 0.98±0.07 1.09±0.04 0.67±0.05

Senna siamea Cassia 74.18 1.02±0.03 1.09±0.03 0.59±0.04

Indigenous

Species

Anogeissus

leiocarpus

Kane

61.98 1.10±0.02 1.13±0.02 0.68±0.02

Afzelia africana Papao 80.62±0.01 1.03±0.06 1.12±0.07 0.57±0.04

Pterocarpus

erinaceus

Krayie

(Rosewood)

48.20±0.01 1.08±0.05 1.16±0.04 0.73±0.06

Khaya

senegalensis

Mahogany 59.10±0.01 0.89±0.04 1.09±0.03 0.56±0.03

*Green Moisture Content (gmc) is based on wet basis

Table 2: Moisture Content (mc), volatile matter (vm), Ash, Fixed Carbon (fc) and Calorific Value (cv) of

six fuel wood species from the Transition Zone of Ghana.

Scientific names mc

(%)

vm

(%)

Ash

(%)

fc

(%)

cv

(kcal/g)

Azadirachta

indica

11.24 33.52 0.20 66.29 3.39

Senna siamea 10.55 62.41 1.08 36.51 4.47

Anogeissus

leiocarpus

7.58 35.25 2.60 62.15 5.09

Afzelia africana 9.25 58.66 1.32 40.02 5.17



Pterocarpus

erinaceus

10.74 59.12 2.67 38.21 4.47

Khaya

senegalensis

9.96 69.68 0.69 29.64 4.94

Table 3: Moisture Content, Volatile Matter (vm), Ash, Fixed Carbon (fc) and Calorific Value (cv) of

charcoal from six species from the Transition Zone of Ghana.

Scientific

names

mc

(%)

vm

(%)

Ash

(%)

fc

(%)

cv

(kcal/g)

Azadirachta

indica

3.56 22.6 0.60 76.8 6.79

Senna siamea 1.61 30.2 2.75 67.0 6.48

Anogeissus

leiocarpus

2.26 26.2 6.78 67.0 6.38

Afzelia africana 1.71 26.7 6.44 66.8 6.07

Pterocarpus

erinaceus

8.00 24.1 5.63 70.2 6.69

Khaya

senegalensis

0.970 19.3 6.05 74.6 6.53

DISCUSSION

The densities of all the species investigated were

very high and can be classified as medium (> 0.58

g/cm3) and heavy (0.725-0.90 g/cm3), according to

Ofori, et al. (2009). The density values of both the

exotic and indigenous species were higher than

popular wood fuel species such as Eucalyptus

tereticornis (0.59 g/cm3), Tectona grandis (0.62

g/cm3) and Acacia mellifera (Khider et al., 2012,

Chow et al., 1988). The basic density has the best

correlation with gy, which indicates that wood

species with high basic density will produce more

charcoal. Density is also expected to influence the

fvi of wood fuel, as density has a positive

correlation with fvi. This supports the use of

denser wood for wood fuel production.

The proximate analyses in Tables 2 and 3 give the

essential properties of wood that affect the

preference for a particular species for wood fuel

(Sadiku et al, 2016). Both mc and ash content

have negative correlation with the cv and fvi of

the wood fuel, whilst fc and vm have positive

correlation with cv and fvi. There were no major



variations in the proximate analysis results. The

mc was generally lower for charcoal, since the

production of charcoal involves heating of fuel

wood at elevated temperature that causes the loss

of moisture. In contrast, carbonization results in an

increase in the ash content and fc of charcoal. The

cv is the most important property and gives the

amount of heat expected from any fuel product

(Telmo et al., 2011). The cv for species

investigated was generally high. There was not

much difference between the cv among both the

exotic and indigenous species. The cv results were

similar to the findings of other investigators

(Chow et al., 1988; Khider et al., 2012; Mainoo et

al., chow et al., 1988; Khider et al., 1996.

Table 4: Gravimetric yield (gy) and Fuel Value Index (fvi) of wood fuel species from the Transition Zone

of Ghana.

Scientific names gy (%) fvi (Fuel wood) fvi (charcoal)

Azadirachta indica 29.90±0.05 0.30 1.87

Senna siamea 29.20±0.07 0.43 4.11

Anogeissus leiocarpus 34.10±0.05 0.74 3.11

Afzelia Africana 29.90±0.09 0.58 3.66

Pterocarpus erinaceus 33.30±0.09 0.45 0.90

Khaya senegalensis 29.20±0.07 0.44 5.99

Table 5: Correlation coefficient between Volatile matter (vm), Ash content, Fixed Carbon (fc) and,

Gravimetric yield and calorific value (cv) of charcoal.

Woodfuel properties Green Density Fixed carbon Volatile

matter

Ash Content

Gy 0.8005 0.3271 0.0797 0.4544

cv (Charcoal) 0.1904 0.7205 0.4270 0.6161

cv (Fuel wood) 0.1648 0.4728 0.4385 0.4894



In general wood fuel with high cv, high density,

low ash and low mc are considered good wood

fuel species, however, the best indicator for

quantifying the best or worst wood fuel species is

fvi. The fvi is a ratio that takes into account both

the best and worse properties of the wood fuel

(Bhatt et al. 1992). The fvi for the fuel was very

low with the highest fvi value (0.740) for A.

leiocarpus. The fvi gave a better rating of the

species for use as fuel wood or to produce

charcoal, as shown in Figure 1. The results

revealed very good relationship between gy and

density (R = 0.80). The relation between gy and

the other properties were not very good. The green

density is the best physical property for predicting

the gy.

Figure 1: Ranking of fuel wood and charcoal of six Transition Zone species from Ghana using fuel value

index.



The green density however had a very poor

correlation with cv. The fc rather had a good

correlation (R = 0.70) with cv, making fc a good

indicator for predicting the energy property for

charcoal but not for fuel wood from the species

investigated. This result is similar to the findings

of Pereira et al. (2013), where significant

correlation was found between density, fc and cv.

CONCLUSION

The yield of charcoal production can be predicted

from the density of wood. The correlation between

density, fixed carbon, ash content and calorific

value were better for charcoal compared to fuel

wood. In terms of fuel index value, the best wood

fuel species are A. leiocarpus followed by A.

africana, P. erinaceus, K. senegalensis, S. siamea,

and A. indica, for fuel wood.

Similarly, the best species for charcoal production

are as follows from the best to the worst; K.

senegalensis, S. siamea, A. africana, A.

leiocarpus, A. indica and P. erinaceus. The exotic

species are very good wood fuel species and

comparable to the indigenous trees species

investigated.

ACKNOWLEDGEMENT

The authors want to thank the International

Tropical Timber Organization (ITTO) for their

funding.

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Effects of land use changes on flora diversity in Oban Division E. T. Ikyaagba et al.


EFFECTS OF LAND USE CHANGES ON FLORA DIVERSITY IN OBAN

DIVISION OF THE CROSS RIVER NATIONAL PARK, NIGERIA

E. T. Ikyaagba1, S. O. Jimoh2 and J. I. Amonum3

1Department of Social and Environmental Forestry, University of Agriculture, Makurdi. Nigeria.

2Department of Forest Resources Management, University of Ibadan, Ibadan, Nigeria. 3Department of Forest Production and Products, University of Agriculture, Makurdi. Nigeria.

Email: [email protected], [email protected]

ABSTRACT

The Oban Division of the Cross River National Park, Nigeria, is a globally renowned biodiversity

hotspot. The area is experiencing rapid land use changes and little efforts have been made to document

the effects of the changes on biodiversity. The study investigated the effects of different land use types on

flora composition, distribution and diversity in the area with a view to generating data that will support

conservation decisions. The area was stratified into four: primary forest (core), secondary forest (buffer),

farm fallow and plantation. Ten transects of 2 km length each were systematically located in each land

use type. Four sample plots of 50×50 m were located on each transect at an interval of 500 m. Each plot

was subdivided into 10×10 m subplots; and nine subplots were randomly selected for the enumeration of

trees, shrubs and climbers. A 1×1 m miniplot was then located at the centre of each subplot for herb

enumeration. Flora species composition was estimated across the land use types using species diversity

indices and Jaccard similarity indices. Composition, species richness and diversity of trees, shrubs and

climbers all decreased from the core to plantation. However, herb species composition, richness and

diversity increased from core to farm fallow. Significant differences in species composition were obtained

across land use types at 5%. The highest tree species similarities were recorded between core and buffer.

The highest similarities for shrubs, herbs and climbers were recorded between farm fallow and

plantation. The absence of species previously recorded in the core, and in the other land use types makes

it imperative that conservation efforts be improved and extended to areas beyond the core in order to

save the remaining flora diversity in this forest.

Keywords: Flora, species composition, species diversity, conservation

INTRODUCTION

Tropical rainforest is the most diverse terrestrial

ecosystem in the world (Richard, 1996; Gillespie

et al., 2004). Tropical forests of Africa harbour

unique biota, much of which is distributed in

forest isolates that have been poorly investigated.

Hence our current knowledge of species diversity

and distribution patterns in such ecosystems is still

limited (Norris et al., 2010). The Guinean forests

of West Africa are recognised as a biodiversity hot

spot (Myer et al., 2000), supporting about a

quarter of the African mammal fauna and

displaying significant endemism across a range of

animal and plant groups.

Understanding how biodiversity responds to

human-induced habitat change is pivotal for

conservation efforts in the region. Limited

scientific work has been conducted on biodiversity

in human-modified forest landscapes in West

Africa compared with Amazonia or South East





Asia (Gardner et al., 2009). Oban Division of

Cross River National Park (CRNP) in Nigeria is

located within the Guinean forests of West Africa

which is known to be among the top 25

biodiversity hot spots in the world (Myer et al.,

2000). Oban Division of CRNP is the only area in

the sub-region with near intact largest block of

contiguous forest and high level of endemism

(Oates et al., 2004). Bergl et al. (2007) listed some

taxa in the area that show high level of species

richness and endemism to including primates,

amphibians, birds, butterflies, dragonflies, fish and

vascular plants.

Despite the biological value of the forest of this

area the future of the area is not secured. This is

because the Park is surrounded by 39 enclave

communities with high population density (Fa et.

al., 2006). As a consequence, the remaining

forests are becoming increasingly degraded and

fragmented. Oates et al. (2004) tag the area as

“understudied” with little efforts being made to

document the biological effects of land use

changes going on in the area. Onadeko (2006)

concluded that basic data needed to support the

management and conservation of Oban Division

of CRNP is scarce and certain taxa remain

understudied. Therefore, the effects of different

land use types on flora species composition,

distribution and abundance was investigated with

a view to generating data that will support

conservation efforts in the area.

The Study Area

The Oban Division of CRNP was carved out of

Oban group Forest Reserve in 1991. It is located

in Cross River State, Nigeria, within latitudes

05o15' and 05o25'N, and longitudes 08o30' and

08o45'E (Figure 1). The total area (including

buffer zones), is about 3,000 km2. The area of

farm fallow and plantation is not specified as they

occur in several locations and in varying sizes at

the periphery of the park. The park shares a

boundary with Korup National Park, Cameroon, in

the east. Annual rainfall ranges between 2,500 and

3,000 mm (Oates et al., 2004; Bisong and Mfon,

2006; Jimoh et al., 2012).

Relative humidity is about 75-95% in January, but

towards the end of the year, it reduces gradually to

below 70% as a result of the harmattan (Bisong

and Mfon, 2006, Jimoh et al., 2012). Altitude

ranges from 100 to over 1,000 m above sea level

(Oates et al., 2004). Four vegetation types are

distinguishable within the park. These include

high forest, ridge forest, secondary forest (buffer

zone) and swamp forest. Patches of oil palm and

cocoa plantations as well as farm fallows exist in

various locations at the periphery of the park.

Schmitt (1996) identified 1,303 species of plants,

141 lichens, and 56 mosses within the park.

Seventy seven of these are endemic to Nigeria.

Fauna diversity includes 134 mammals, 318 birds,

42 snakes, and over 1,266 butterflies (Schmitt,

1996).

Some of the typical tree species found in the area

include; Pericopsis elata (Harms) Van Meeuwen,

Amphimas pterocarpoides Harms, Enantia

chlorantha (A DC) van Setten and Maas,

Entandrophragma spp, Hannoa klaineana Pierre

and Engl, Irvingia spp (Aubry-Lecomte) Bail,

Khaya grandifoliola C.DC. Lophira alata Banks

exGaertn.f. Milicia excelsa(Welw.) C.C. Berg,

Piptadeniastrum africanum (Hook.f) Brenan,

Piptostigma pilosum Oliv,. Strombosia schefflei

Engl. Tabernaemontana spp, Terminalia spp and

Treculia spp, (Jimoh et al., 2012).

Study Design and Data Collection

Oban Division of CRNP is divided into two

corridors, the West and East corridors. The

Western corridor is made up of eight villages,

while the Eastern Corridor has 31 villages. With

the permission of the management of the park, the

study was conducted in all the corridors. Five

villages: Obung (Erokut), Old Ekuri and Ifumkpa

in the West and Aking/ Osomba and Ekang in the

East were purposively selected from these

corridors based on their proximity to the park as



shown in Figure1.

Figure 1: Map of the Cross River National Park showing the study locations.



The study was conducted in the four major land

use types in the Oban Division of CRNP namely;

primary forest (core), secondary forest (buffer),

farm fallow and plantation. Ten transects of 2 km

length each were systematically located in each

land use type at a regular interval of 2 km apart,

this was to cover different gradients present in the

study area (Walter et al., 2006). Four sample plots

of 50 × 50 m were located on each transect at an

interval of 500 m. Each plot was sub-divided into

10×10 m subplots and nine subplots were

randomly selected for trees, shrubs and climbers

enumeration. A 1×1 m miniplot was then located

at the centre of each subplot (Sullivan et al., 2005;

Turyahabwe and Tweheyo, 2010). Within the 50 x

50 m plots, trees with diameter at breast height

(DBH) ≥ 10 cm and climbers were enumerated.

Trees with DBH of ≤ 10 cm considered as shrubs

and saplings and they were enumerated within the

10 x10 m subplots (Sullivan et al., 2005;

Turyahabwe and Tweheyo, 2010). All the herbs

and seedlings within the 1 x 1 m sub-plots were

also enumerated. Each of the trees encountered

was assigned a class based on DBH (Sullivan et

al., 2005, Turyahabwe and Tweheyo, 2010).

Diameters of trees were measured using a

diameter tape. Where there were cases of irregular

features such as buttresses, diameters were taken

above those features (Turyahabwe and Tweheyo,

2010).

The identification of plant samples was carried out

using flora field guides (Keay, 1989; Akobundu

and Agyakwa, 1998; Arbonnier, 2004). A

taxonomist was engaged for the identification of

the plants on the field. Those that could not be

identified on the field were preserved in wooden

press and taken to the Forestry Research Institute

of Nigeria Ibadan Herbarium for proper

identification. Identified species were grouped

into species, genera and families.

Floristic composition in the various land use types

were estimated using density, species richness,

diversity and evenness.

Density was estimated:

Density = Number of individuals species

Area sampled

Species richness was computed using Margalef

Index Magurran (2004) as follows:

N

SD

ln

1 ………………...................(1)

Where, D = species richness index (Margalef

Index), S = number of species and N = the total

number of individuals.

Species diversity was estimated using the

Shannon-wiener diversity index as cited

Turyahabwe and Tweheyo (2010). The Shannon-

wiener diversity index equation is stated as:

i

s

i

i ppH ln1

……………………………………......(2)

Where H′ = species diversity index, pi = the

proportion of individuals or the abundance of the

ith species expressed as a proportion of the total

abundance. The use of natural logs is usual

because this gives information in binary digits.

Species evenness was estimated using Pielou’s

evenness (equitability) index (Pielou, 1975) as

cited by Turyahabwe and Tweheyo (2010) as

follows:

Species evenness was estimated using Pielou’s

evenness (equitability) index (Pielou, 1966) as

cited by Odiwe et al. (2012) as follows:

SIn

HJ

…………………..................................(3)

J′ = Pielou’s evenness index Where S is the total

species number, H is the diversity index and ln=

natural logarithm.



Jaccard similarity coefficient:

cba

aSJ

………………………………………..(4)

SJ = Jaccard similarity coefficient,

a = number of species common to (shared

by) quadrats,

b = number of species unique to the first

quadrat, and

c = number of species unique to the

second quadrat

To compare flora species composition between

land use types, One-way analysis of variance was

used. And where the result was significant Turkey

was used to separate the means.

RESULTS

Flora Composition Across Land Use Types

A total of 1,175 plant species with 102,825

individuals in 556 genera and 120 families were

recorded in all. Out of this number, 329 (28%)

with 14,736 individuals were trees species, 273

(23%) with 20,797 individuals were shrub species;

335 (29%) with 54, 835 individuals were herb

species while 238 (20%) with 12,467 individuals

were climber species (Tables 1and 2). Table 2

indicates that composition of trees, shrubs and

climbers decreased from the core of the park to the

plantation.

Tree species decreased from 285 to 128 in the core

of the park to plantation, shrubs species decreased

from 211 in the core to 92 species in the

plantation, while climbers decreased from 155 to

56. Herb species composition increased from 88 in

the core to 270 in the farm fallow. The highest

numbers of individuals for all the life forms were

recorded in the farm fallow; 4, 628, 6,426 28,431

and 4,060 for trees, shrubs, herbs and climbers,

respectively. Similarly, the highest density of

individuals per hectare for all the life forms were

recorded in the farm fallow: 462.8, 1,785, 789,750

and 1,079.7 for trees, shrubs, herbs and climbers,

respectively (Table 2). Analysis of variance

revealed significant differences in plant species

composition across the various land use types.

Tukey's pair wise comparisons also revealed that

life forms differed in composition between

plantation and other land use types (Table 3 and

4).

Table1: Flora species distribution according to four life forms in the Oban Division of the Cross River

National Park, Nigeria.

Life Form FI IG IF UD total Genus Families

Tree 309 14 0 6 329 213 59

Shrub 225 26 0 22 273 136 43

Herb 283 24 8 20 335 175 51

Climber 202 13 0 23 238 123 45

Total 1033 76 8 71 1175

Note: FI = Fully Identified, IG = Identified to only genus, IF = Identified to only family, UD = Unidentified.



Table 2: Distribution of flora life forms and individual species occurrence across land use types in the

Oban Division of the Cross River National Park, Nigeria.

Life form Core Buffer Farm

fallow

Plantation Total

Tree Number of species 285 271 129 128

Individuals 3,260 3,012 4,628 3,826 14, 726

Family 52 50 39 41

Density (per hectare) 336 301 462.8 382.6

Shrub Number of species 211 172 112 92

Individuals 6,240 5410 6426 3,721 20,797

Family 40 38 27 27

Density(No/ha) 1,733.30 1,502.80 1,785 1,033

Herb Number of species 88 139 270 190

Individual 5141 5901 28431 15362 54,835

Family 18 30 46 40

Density(no/ha) 142,805.

6

162,916.70 789, 750 426, 722.2

Climber Number of species 155 116 111 56

Individual 3604 3269 4060 1534 12, 467

Family 38 36 32 24

Density(no/ha) 1,000.30 888.6 1,079.70 384.2

Table 3: One-way analyses of variance for floral species composition across land use types in the Oban

Division of the Cross River National Park, Nigeria.

Life form SS Df MS F P

Trees Between groups: 68.2333 3 22.7444 123 3.165E-70**

Within groups: 242.511 1312 0.18484

Total: 310.744 1315

Shrubs Between groups: 32.8599 3 10.9533 49.95 3.033E-30**

Within groups: 238.601 1088 0.219302

Total: 271.461 1091

Herbs Between groups: 53.9485 3 17.9828 85.55 1.24E-50**

Within groups: 280.836 1336 0.210206

Total: 334.784 1339

Climbers Between groups: 19.0719 3 6.35729 27.88 2.64E-17**

Within groups: 224.405 984 0.228054

Total: 243.477 987

Note **= significant; ns = not significant



Table 4: Tukey's pair wise comparisons for flora species composition: (p > 0.05)

Life form Core Buffer Farm fallow Plantation

Core 0.5825 ns 7.721E-06** 7.721E-06**

Trees Buffer 7.721E-06** 7.721E-06**

Farm fallow 0.9997ns

Plantation

Shrubs Core 0.002082** 7.721E-06** 7.721E-06**

Buffer 7.923E-06** 7.721E-06**

Farm fallow 0.2602ns

Plantation

Core 0.0001073** 7.721E-06** 7.721E-06**

Herbs Buffer 7.721E-06** 0.0001073**

Farm fallow 7.721E-06**

Plantation

Core 0.001038** 0.000143** 7.721E-06**

Climbers Buffer 0.9634ns 7.756E-06**

Farm fallow 8.359E-06**

Plantation

Note **= significant; ns = not significant

Family Composition

Trees were represented by 56 families (44.7%),

shrubs 43 families (35.8%), herbs 51 families

(42.5%) and climbers represented by 45 families

(37.5%) (Tables 1 and 5). The highest number of

families for trees, shrubs and climbers were

recorded in the core, 52, 40, and 38 respectively.

The highest number of families for herbs was

recorded in the farm fallow. The core recorded the

least number of families for herbs; farm fallow

recorded the least number of families for trees. For

shrubs both farm fallow and plantation recorded

the least number of 27 families each, while the

least number of families for climbers were

recorded in plantation

The dominant family was Rubiaceae with 140

species representing (11.91%) of the total species

recorded. This was followed by Papilionoideae, 50

(4.26%), Orchidaceae 48 (4.09%) and

Euphorbiaceae 48 (4.09%). Only seven families

(Rubiaceae, Euphorbiaceae, Papilionoideae,

Caesalpinioideae, Malvaceae, Melastomataceae

and Verbenaceae) were represented across all the

life forms (tree, shrub, herb and climber).

Caesalpinioideae had the highest number of

species of trees, Rubiaceae had the highest

number of shrubs, Orchidaceae had the highest

number of herbs, while Apocynaceae had the

highest number of species of climbers (Table 5).

Thirty two families, constituting 26.67% of the

families were represented by only one species

each.

Flora Species Diversity

Species richness (D) for trees, shrubs and climbers

decreased from core to plantation (D = 35.11-15-

17), (D = 24.03-11.07), (D = 18.8-7.50) and (D =

4.138-2.583), respectively. Similarly, species

diversity (H') for trees, shrubs, and climbers

decreased from core to plantation (H '= 4.896-

3.013), (H '= 4.659-2.797) and (H'= 3.711-2.606)

respectively.



Table 5: Twenty families with the highest number of species for the four life forms in Oban Division of

the Cross River National Park, Nigeria.

S/N Family Trees Shrubs Herbs Climbers Total

1 Rubiaceae 14 97 18 11 140

2 Papilionoideae 10 18 9 14 51

3 Euphorbiaceae 24 14 7 0 49

4 Orchidaceae 0 0 48 0 48

5 Apocynaceae 13 1 0 28 42

6 Caesalpinioideae 35 4 1 1 41

7 Acanthaceae 0 6 28 3 37

8 Araceae 0 0 21 10 31

9 Asteraceae 1 2 28 0 31

10 Annonaceae 24 0 0 2 26

11 Moraceae 17 4 5 0 26

12 Sapindaceae 9 7 0 4 20

13 Sterculiaceae 14 4 2 0 20

14 Verbenaceae 7 6 2 3 18

15 Marantaceae 0 0 17 0 17

16 Mimosoideae 12 0 4 0 16

17 Melastomataceae 2 4 9 1 16

18 Amaranthanceae 0 0 15 0 15

19 Icacinaceae 0 7 0 8 15

20 Malvaceae 3 1 10 1 15

For herbs, species richness and diversity increased

from core to farm fallow (D=10.18-26.23) and

(H'=3.469-4.577).Species evenness (J) did not

show any definite pattern among the various land

use types (Table 6). For trees, shrubs and herbs,

the values were high in the buffer zone but lower

in the plantation (J´=0.48-0.16), (J´=0.51-0.18),

(J´= 0.37-0.32).

Similarity Index

Result for similarity index shows high similarity

for trees between core and buffer (0.84); the

lowest similarity value for trees was recorded

between the core and farm fallow (0.29). Shrubs,

farm fallow and plantation were more similar,

with index value of 0.60. The least value of

similarity was recorded between core and



plantation (0.24). For herbs, the Jaccard Similarity

Index shows farm fallow and plantation to be

more similar with index value of 0.57; the least

index value of 0.13 was recorded between core

and plantation. Farm fallow and plantation were

more similar in terms of climbers with index value

of 0.40, while the least index value of 0.10 was

recorded between core and plantation (Table 7).

Table 6: Flora species diversity indices across land use types in the Oban Division of the Cross River

National Park, Nigeria.

Life Form Core Buffer Farm fallow Plantation

H´ J´ D H´ J´ D H´ J´ D H´ J´ D

Trees 4.896 0.47 35.11 4.87 0.48 33.7 3.31 0.22 15.17 3.01 0.16 15.39

Shrubs 4.659 0.5 24.03 4.48 0.51 19.9 3.02 0.18 12.66 2.8 0.18 11.07

Herbs 3.469 0.365 10.18 3.85 0.34 15.9 4.58 0.36 26.23 4.11 0.32 19.61

Climbers 3.991 0.349 18.8 3.71 0.35 14.2 3.84 0.42 13.24 2.61 0.24 7.5

Table 7: Similarity indices for flora species across the various land use types in the Oban Division of the

Cross River National Park, Nigeria.

Land Use Types Trees Shrubs Herbs Climbers

Core versus Buffer 0.84 0.57 0.36 0.37

Core versus Farm Fallow 0.29 0.29 0.17 0.23

Core versus Plantation 0.29 0.24 0.13 0.1

Buffer versus Farm Fallow 0.36 0.35 0.32 0.35

Buffer versus Plantation 0.36 0.3 0.34 0.19

Farm Fallow versus Plantation 0.54 0.6 0.57 0.39

DISCUSSION

Flora Species Composition

One of the most astonishing features of tropical

rain forest is its high diversity of plant and animal

species. The record of good number of species in

other life forms apart from tree is a confirmation

that the Oban Division of the Cross River National

Park (CRNP) like other tropical rain forests is not

just rich in tree species but it is also rich in other

plant life forms (Gentry and Dodson, 1987).

It is clear from this study that Oban Division of

CRNP still harbours a high number of vascular

plants, although the present study recorded lower



numbers compared to the work of Schmitt (1996).

This may be due to the effects of human activities

in the area. However, the present study recorded

more climbers and herb species compared to the

work of Schmitt (1996). The high number of herbs

and climbers could be linked to increased

conversion of forest to agricultural land which

allows pioneer species of weedy characteristics to

invade the area, as a result of opening up of the

forest canopy (Fujisaka et al., 1998). For instance,

Chromolaena odorata which was not recorded in

previous studies (Reid, 1989; Schmitt, 1996) was

the dominant shrub species in the farm fallow and

plantation. A similar observation was made in

Korup (Bobo et al., 2006). Chromolaena odorata

is a light demanding invasive weed species.

The 329 tree species recorded in this study is less

than the 444 recorded by Schmitt (1996) in this

region. It is, however, higher than the values

recorded in other rainforests in different parts of

the world. For example, Fujisaka et al. (1998)

recorded 144 species in an Amazon forest

ecosystem Bobo et al. (2006) recorded 239 species

in Korup, Cameroon; while Duran et al. (2006)

recorded 148 tree species in a Mexican deciduous

forest at Chamela, Mexico. Rajkumar and

Parhtasarathy (2008) recorded 105 tree species in

Andaman Giant Evergreen forest in India; Ihenyen

et al. (2009) recorded 99 tree species in Ehor

Forest Reserve, Edo State, Nigeria; Lu et al.

(2010) recorded 207 species in China, and

Adekunle et al. (2013) recorded 94 tree species in

a strict nature reserve in the rainforest of south

western Nigeria.

This variation in the number of tree species

recorded could be due to sampling intensity which

Richards (1996) reported could affect the number

of species encountered. However, the fact that the

value here is less than the 444 tree species

recorded by Schmitt (1996) in this location may

reflect the impact of human activities such as

logging and oil palm/ cocoa plantation

development which are currently very rampant in

the area (Oates et al.,2004, Bisong and Mfon,

2006; Macdonald et al.,2012 ). This agrees with

the submission by Sagar et al. (2003) that human

disturbance could usually cause an immediate

decline in biodiversity. The high number of herbs

recorded in the farm fallow and plantation is in

agreement with findings from similar studies

(Metlen and Fiedler, 2006; Ares et al., 2010;

Odiwe et al., 2012). This shows that

anthropogenic disturbances cause increase in

herbaceous layer.

This decrease in flora species composition and

diversity in the Oban region is a serious cause for

concern about the impact of land use on the forest

biodiversity. This is more particularly so when

Jimoh et al. (2012) had earlier reported a similar

depletion in large mammals population in this

area.

Tree species composition or richness decreased

from core to plantation by 47.72% and to farm

fallow by 47.42%. This value is lower than the

62.1% and 79.5% respectively, obtained by Bobo

et al. (2006) in the Korup National Park, but

higher than the 19% obtained by Turner et al.

(1994) in Singapore.

The observation is a further indication of decrease

in tree species diversity with increasing human

disturbance. There was a 30.45% increase in the

herb species richness from core to plantation and

54.33% increase from core to farm fallow. These

figures are lower than the 57% recorded by Bobo

et al. (2006) between primary forest and farm land

around the Korup National Park in Cameroon. The

higher herb species richness in the plantation

confirms the poor nature of plantation in terms of

support for higher plant life forms (Bobo et al.,

2006; Fitzherbert et al., 2008; Bruhl and Eltz,

2009; Danielsen et al., 2009).

The fewer species of herbs (88) recorded in the

core of the park compared to 270 species in farm

fallow is typical of a tropical rainforest (Costa and

Magnusson, 2002). This is due to the suppression



by tree canopy which could only permit shade-

loving species to thrive under closed canopy

(LaFrankie et al., 2006). The number of herb

species recorded in the core of the park was

similar to what is obtainable in other tropical

rainforests. For instance, Poulsen and Balslev

(1991) recorded 96 herbs species in Ecuador,

Poulsen and Balslev (1996) listed 87 herb species

in Borneo.

Family Composition

The dominance of the families such as Rubiaceae,

Euphorbiaceae, Fabaceae (Papilionoideae,

Caesalpinioideae, Mimosoideae), Apocynaceae,

Acanthaceae, Asteraceae and Moraceae in this

study is comparable with the results of other

studies in other rain forest regions ( Kessler et al.,

2005; Ihenyen et al., 2009; Mbue et al., 2009;

Rasingam and Parathasarathy, 2009; Adekunle et

al., 2013). The poor representation of most of the

families is typical of the African rain forest (Plana,

2004).

Five out of the nine plant families endemic to the

Guineo-Congolian Region are found in Oban Hills

Region (Schmitt, 1996). Four of the families

(Lepidobotryaceae, Octoknemaceae, Pandaceae,

and Scytopetalaceae) were recorded in this study.

All of them were recorded in the core and buffer

zones of the park. This implies that one of them,

Medusandraceae, might have become locally

extinct as it was with Yellow-backed and Bay

duikers in the area (Jimoh et al., 2012). Also most

of the families recorded in this study, especially

those in the herbaceous and shrubby life forms,

like Acanthaceae, Amaranthaceae, Aracaceae,

Asteraceae, Commelinaceae are strongly

associated with land use pressures (Houlahan et

al., 2006).

Species Diversity

The H' index range of 3.02-4.66 in shrub layer and

3.47-4.58 in the herb layer, suggests less variation

in species diversity in the herb layer than in the

shrub layer in the four land use types. As

suggested by Lu et al. (2011), high H' index and

low J´ index of the understory in the four land use

types indicate that the species diversity of the

understory in this the area may be constituted by

rare species or dominated by few species. In all

the four land use types, the evenness of shrubs was

relatively low (0.18-0.51) indicating that only few

species like; Olax gambecola and Chromolaena

odorata, clearly dominate core and buffer; farm

fallow and plantation respectively. For instance,

the evenness index was lower in farm fallow

(0.18) which was dominated by Chromolaena

odorata.

A Similar pattern was observed for herbs. The

evenness index was higher in the core (0.3648)

with 88 species compared with the plantation

(0.32) with 190 species. This shows that plantation

was dominated by few species like Commelina

benghalensis, Ageratum conyzoides, Celosia

leptostachya, Asystasia gangetica, and Acanthus

montanus. This higher dominance is attributable to

continued anthropogenic disturbances which

favoured herbaceous layer (Ares et al., 2010; Lu et

al., 2011).

The lower values of species evenness recorded in

the study may also be an indication of poor

representation of some genera and families, most

of which were represented by only one species,

even though they contribute greatly to the

diversity indices. This poor representation was

also recorded by Rasingam and Parathasarathy

(2009) in India and Adekunle et al. (2013) in a

strict nature reserve in the rainforest of south

western Nigeria. It also indicates that most of the

families in the area have species that are not

evenly distributed; giving rise to fragile nature of

most of the families, genera and species. The

ecological implication of this is that continued

disturbance of this ecosystem may cause local

extinction of some of the species or genera or even

some families. The decrease in plant species

diversity from core to plantation indicates that



land use has an impact on plants diversity in the

study area (Bobo et al., 2006). Other studies also

show similar pattern (Fusjisaka et al., 1997; Sagar

et al., 2003; Gradstein et al., 2007; Mbue et al.,

2009).

However, there was an exception with herbs, as

the composition and diversity increased from core

to plantation and was highest in the farm fallow,

suggesting that herbs are favoured by land use

change as competition from trees for light and

below-ground resources is reduced (Ares et al.,

2010). This is in line with the observation by

Schulze et al. (2004) that, diversity indices may

not always decrease with human disturbances, but

in some instances it may stimulate increase in

occurrences of other species.

The decreased diversity values of the other life

forms (trees, shrubs and climbers) from core to

plantation, according to Norris et al. (2010), could

be as a result of land preparation method for the

establishment of such plantation. This view was

expressed by Bobo et al. (2006) in a different way

which links it to poor farm management methods.

This study however, agrees with the view of

Norris et al. (2010), which ascribed the

observation to poor land preparation in which the

land is bulldozed or slashed and burned.

Similarity Index

Not much variation was observed between buffer

and the core in terms of floristic composition,

richness and diversity in the study area. There was

no discernible pattern of flora species occurrence

as one moved from buffer to the core of the park.

The species richness and diversity values are

similar. A similar pattern was reported in the

Korup National Park (Zapfack et al., 2002; Bobo

et al., 2006; Mbue et al., 2009). This similarity is

an indication that the buffer and core are the same

forest with minimal human impacts. Another

possible reason for the similarity could be an

indication of recovery of buffer areas after human

disturbance especially logging activities, which

allows for the re-establishment of species which

are usually considered old growth forest

specialists in the buffer (Fujisaka et al., 1998;

Laidlaw et al., 2007; Chazdon et al., 2009).

Chazdon et al. (2009), opined that this similarity

could be age-dependent., even though the present

study did not assess the age of the secondary

forest but the similarity was more pronounced in

Aking, Ekuri, Obung / Old Netim Erokut and

Ifumkpa where human activities especially

farming, in the buffer, was minimal.

CONCLUSION

There is significant impact of land use on plant

species diversity in the study area. Tree species

composition decreased from 444 in 1996 to 329 in

2013 implying a loss of about 26%. Herbs were

favoured by forest conversion to other land uses

especially agriculture (farm fallow and plantation).

Vascular plant species especially trees, shrubs and

climbers are more reactive to the land-use change

as they exhibit a decrease in species richness and

diversity from core to plantation. Even though the

area is highly diverse, especially the core of the

park, where the vegetation is near primary forest

the biotic community appears to be ecologically

fragile, as there is a high number of rare flora

species with many species and families

represented by only one individual or species.

Some of the species and families are endemic and

have specialized habitats which make them more

vulnerable to extinction. Medusandraceae, one of

the five endemic families in Oban Hills was not

recorded during this study, and it appears the

family has become locally extinct. Therefore

continued conversion of their particular habitat by

human activities is a threat to their continued

existence in the area.

It is recommended that, good land use planning be

put in place and implemented. Also conservation

efforts in the area should extend beyond the core

and buffer zones to include support zone

communities if the future of this remnant of the



biologically diverse Gulf of Guinea forest in

Nigeria is to be saved.

ACKNOWLEDGEMENTS

We thank the Volkswagen Foundation, Hanover,

Germany, for providing the grant to the University

of Ibadan, Nigeria, within its ‘Africa Initiative’ –

‘Knowledge for Tomorrow – Cooperative

Research Projects in sub-Saharan Africa’ which

made this study possible. We are grateful to the

Federal Board for National Park Service, Abuja,

the Conservator of Cross River National Park,

Chief J. Keffa, for permitting us to carry out the

study within the Park, and other members of staff

of the Cross River National Park, for their kind

assistance in planning and logistics. We must

appreciate the contributions of Mr. Adamu Usman

Afikpo of blessed memory; he was indeed a friend

and a helper. We also appreciate the assistance of

local community members in the Oban Sector of

CRNP for their enthusiastic support during field

work. We acknowledged the contributions of Dr.

Matthias Waltert and our other colleagues on the

project.

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