1

Fine Root Dynamics in Trees

Vikas Kumar2013-27-102Dept. of Silviculture & AgroforestryCollege of Forestry, KAU, ThrissurMo. No.: 9995093698Email ID: vkskumar49@gmail.com

PhD second seminar

Contents

Introduction

Fine Root Production/ Biomass (FRP/FRB)

Method of estimation of FRP

Factors influence FRP

FRP research in various ecosystems

Conclusion

Future line of work

2

Non-woody and having <2 mm diameter (Zobel and Waisel, 2010).

High biological activity and resource cycling.

Short life span and continuous turnover (van Noordwijk et al., 1994).

Aboveground litter and belowground fine roots are the principal components of

nutrient cycling- adding to soil carbon and nutrient pools (Finner et al., 2011).

Introduction

3

• Fine root Production/Biomass:

• Forest ecosystems - the belowground biomass accounts for 13-25% of the total stand

biomass and fine roots represent of 2-15% (Helmisaari et al., 2002).

• FRP >40% of NPP in forest because of their high turnover rate where as 10-30% of NPP

of temperate ecosystems

• Aboveground rate of litter decomposition contributed 19% and belowground litter

decomposition contributed 58% to total soil respiration in coniferous forest (Finer et al.,

2011).

• Lacking of technical and methodological information in tropical woody ecosystems.

4

Fine root biomass and production

Direct method

i. Ingrowth method

ii. Root mesh method

iii. Sequential core method

iv. Minirhizotron method

Indirect method

i. Nitrogen (N) budget approach

ii. Allometric equations

Methodology

5

• It also known as ‘Mesh bag method’.

• Most promising approach in grassland and forestry (Hendricks et al., 2006).

• It determines FRP per unit area and time (Mgha-1yr-1) (Steingrobe et al., 2001).

• It gives the quantitative information on fresh FRP by accessing fine root ingrowth into specific volume of

root free soil in mesh bag.

• Perfolatorated aluminum circular mesh bag of size 30 cm length and 15-20 cm diameter.

Ingrowth Method

Direct method

6

Mesh bag installation

Retrieval of Mesh Bags

Figure 1. Diagrammatic representation of mesh bag installation 7

1. High disturbance to root and rooting environment.

2. Physical properties may change especially BD.

3. Severing of the roots may lead to fine root proliferation and hence may lead to

over estimation.

4. Decomposition is not quantified.

Limitation of Ingrowth method

8

a. Positive increment approach

9

Pa= Fine root production over the whole sampling.

N= Number of days throughout the study period after mesh bag installation.

Pi, j= FRP after i month of regrowth (2,3,4...) during sampling period during j season.

• Mean biomass and necromass in all season.

• Pa= FRP over the whole sampling year.

• P3, j= FRP after 3 months of regrowth during sampling period.

b. Short term cores approach

10

The following procedure as follows:

I. Take a straight stainless steel blade size (10 x 30 x 0.2 cm) and push into the soil surface

up to depth of 20 cm.

II. A nylon mesh size (10 x 10 x 0.1 cm) fit between two thin straight stainless steel sheets

(10 x 30 x 0.1 cm) attach to a single handle.

III. The apparatus containing the mesh insert gradually into the slit, along the inserted blade.

IV. The blade was removed slowly from the slit.

V. The handle of the apparatus made of two thin stainless steel sheets remove and each sheet

individually extracted from the slit, leaving the mess insert vertically in the soil.

Root Mesh Method

11

Fig 2. Root Mesh Method: (A). A straight and sharp stainless steel blade for the making the soil slit, two thinner

stainless steel sheets for placing the mesh, and a nylon mesh sheet; (B). Photos of each step in the procedure; and

(C). Schematic illustration of the procedure

Figure 2. Diagrammatic representation of Root mesh bag installation 12

• Fine root production and necromass over time.

• Carried out repeatedly in the same location to establish inter annual variation.

• Sum of all fine root biomass between growing seasons on a year.

Sequential Coring

13

Figure 3. Diagrammatic representation of the sampled plots for sequential core method

Retrieval of Mesh Bags

• Based on three assumptions of dying of fine root dynamics (Osawa and Aizawa, 2012).

• Fine root production (gij) = Bj − Bi + Nj − Ni + dij

Here, B= Live fine roots; N= Fine root necromass and dij =Decomposition between times i and j

• Mortality (mij) = Nj − Ni + dij

• Decomposition (𝑌𝑖𝑗) = 1 − )(𝑒 −𝑦∆𝑡

a. Compartment Flow approach

15

• Annual fine root production (Pa(MM)) = (Bmax –Bmin)

• Necromass not considered.

b. Maximum-Minimum approach

16

• Annual fine root production (Pa(MM)) = ƸP

• The production (P) between two sampling dates is calculated either by adding the differences in

biomass (ΔB) and necromass (ΔN), or by adding only the differences in biomass (ΔB), or by equaling

P to zero (Fairley and Alexander 1985).

I. P= ΔB + ΔN a) if biomass and necromass have increased; and b) If biomass has decreased and

necromass has increased.

II. P = ΔB if biomass has increased and necromass has decreased

III. P= 0 a) if biomass and necromass have decreased.

c. Decision Matrix approach

17

• Fine root production, longevity, mortality of fine root fractions (<2 mm) through the

minirhizotrons of transparent tubes.

• Video photography has been using to measure root activity.

• Image analysis helps to take several parameters viz., root length, root width, root

thickness, longevity, root density, root formation pattern, root structure, mortality period

(depend on species, climatic and edaphic factor) and other physical appearances such as

colour and colonization.

Minirhizotrons Method

18

Figure 4. Diagrammatic representation of minirhizotron installation 19

Limitations:

I. Difficulty during ascertaining process.

II. Roots are only classified as dead when they disappear, the overall root longevity may be either

overestimated or underestimated.

III. Cost involved is high.

20

• Annual N allocation to FR= Difference between net N mineralization in soil and net N flux into

aboveground tissues.

• FRP = Production of annual N allocation to fine roots and the C:N ratio in fine roots (Aber et., 1985).

• N budget approach to work the following information:

i. N inputs into an ecosystem,

ii. N storage in all plant tissues, and

iii. N mineralization rates in the soil.

• Several assumptions:

i. No N retranslocation from roots,

ii. Steady-state conditions,

iii. Mineralizable N is totally taken up by plants, and

iv. N limits plant growth.

Nitrogen (N) Budget Approach

Indirect method

21

• FRB can also be estimated based on easily measurable aboveground metrics such as basaldiameter, DBH, height and crown foliage (Ammer and Wagner, 2002).

• These models function on the basis of a strong relationship between FRB and abovegroundvariables at both tree and stand-levels, although this may not apply to all sites (Jurasinski etal., 2012).

Allometric equations method

22

Limitations

• Leading to uncertainties in the estimates they produce (Jurasinski et al., 2012).

• Unable to reflect the high temporal and spatial heterogeneity in FRB distribution common in most ecosystems (Zerihun et al., 2007).

• Some of the assumptions used to parameterize models may not hold true for all tree species and ecosystems (Lee et al., 2004).

23

24

Figure 5. Relationships between aboveground biomass and fine root biomass and total root biomass for softwood (A)

and hardwood (B) species (Kurz et al., 1996).

25

Figure 6. Relative fine root biomass (rFRB) of a tree in relation

to the distance (from the stem trunk and diameter a: breast

height (dbh) as assumed by the model) (Ammer and Wagner,

2004).

Figure 7. The relationship between decomposition rates of leaf litter

versus fine root in Pinus massoniana (filled square), Castanopsis hysrix

(open triangles), Michelia macclurei (open circles) and Mytilaria

laosensis (open square) plantations (Wang et al., 2010).

Figure 8. Production of fine root biomass in total root

biomass (Kurz et al., 1996).

Figure 9. Fine root production as a function of fine root biomass.

Symbols indicate the data point for the different species groups:

softwood (A) and hardwood (B) (Kurz et al., 1996).

TBmax = (Pa)/ Bmax

RT unit as yr—1

The influence of fine root turnover, depends on

(i). Soil stratification;

(ii). Soil depth;

(iii). Root diameter;

(iv). Number of samplings per year.

Fine root turnover

26

Factors influencing FRP/FRT

CO2

Soil depth

Stand management

Species composition

Stand age

Season

Soil nutrients

Soil pH

Basal area

27

Figure 10. A conceptual model of deeper rooting distributions under elevated CO2 concentration (Iversen, 2010).

CO2

28

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

FINE ROOT (0-20 CM) FINE ROOT (20-40 CM) FINE ROOT (0-40 CM)

0.3

0.12

0.43

0.77

0.17

0.94

Fin

e ro

ot

bio

mass

kg/m

2

Soil profile

Hill-slope forest Gallery Forest

Figure 11. Fine root biomass in the two forests grove overall profile

Republic of the Congo (Ifo et al., 2015).

Soil depth

29

Figure 12. Fine root biomass and necromass in the four forest use types according to the fine root inventory (50

cm depth) in forest-use type.

University of Göttingen, Germany (Harteveld et al., 2007)

Stand management

30

A: Undisturbed natural

forest (NF)

B: NF with little timber

extraction

C: NF with substantial

timber extraction

D: Cacao plantation under

natural shading trees

Figure 13. Annual fine root production calculated (a). In growth core method and (b). In different soil

layer by sequential coring method in three different stands (n=3) of Larix principis-rupprechtii.

Beijing Forestry University, China Wang et al., 2014

Stand age

31

Figure 14. Distribution of fine roots (< 2 mm) at two soil depths (□ 0 - 15 and ■ 15 - 30 cm) in the three stands.

W- winter, S- spring, R- rainy and A- autumn.

North Eastern Regional Institute of Science & Technology, Arunachal Pradesh (Barbhuiya et al., 2012)

Season

32

Figure 15. Relationship between fine root production and basal area of the stands.

University of Göttingen, Germany (Harteveld et al., 2007)

Basal area

33

A: Undisturbed natural

forest (NF)

B: NF with little timber

extraction

C: NF with substantial

timber extraction

D: Cacao plantation under

natural shading trees

Table 1. Fine root production in various ecosystemEcosystem Fine root production (Mg ha−1yr−1) References

NATURAL FOREST

Tropical moist deciduous forest 8.32-8.9 Kubisch et al., 2016

Tropical broadleaf’s evergreen forest 0.6 to 22.7 Yang et al., 2004

Evergreen broad-leaved forest in SW Japan 6.3 to 9.4 Sato et al., 2015

Dry tropical forest NE India 2.9 to 5.3 Singh et al., 2011

Undisturbed forest stand, Nepal 6.67 Gautam et al., 2016

Disturbed forest stand, Nepal 3.35 Gautam et al., 2016

Subtropical forest 1.1 to 10.6 Yang et al., 2004

Disturbed subtropical humid forest NE India 5.9 – 7.7 Arunachalam et al., 1996

Temperate forest 0.5 to 10 Vogt et al., 1986

Boreal forest 1.51 to 5.28 Yuan and Chen, 2010

Mono and multispecific forest plantations in the Amazon 3.1 to 14.3 Barlow et al., 2007

Regrowth forest 8.64±0.08 Silva et al., 2011

PLANTATION

Teak plantation in dry tropics, Chhattisgarh 4.80 to 9.81 Sahu et al., 2013

Poplar plantations (5 to 8 yrs.) in Central Himalaya 1.0 to 1.2 Lodhiyal et al., 1995

6-yr old Schizolobium-based plantation forests (Monospecific) 5.92±0.15 Silva et al., 2011

6-yr old Schizolobium-based plantation forests (Mixure) 6.08±0.13 Silva et al., 2011

AGROFORESTRY

6-yr old Schizolobium-based plantation forests (Agroforestry) 6.63±0.13 Silva et al., 201134

Forest type Location Methodology Fine root production

(g m-2yr-1)

Source

Amazonian Tropical forest San Carlos,

Venezuela

Ingrowth core (30 cm) 806 Cuevas and Medina (1988)

Amazonian Tropical forest

(sandy soil)

Para, Brazil Ingrowth core (30 cm) 400 Metcalfe et al. (2008)

Amazonian Tropical forest

(clay soil)

Para, Brazil Ingrowth core (30 cm) 400 Metcalfe et al. (2008)

Semi-evergreen forest Barro Colordo

Island, Panama

Ingrowth core (25 cm) 352 Cavelier et al. (1999)

Semi-evergreen forest Kodayar, South

India

Ingrowth core (25 cm) 185.9 Sundarapandian and Swamy

(1996)

Deciduous tropical forest Kodayar, South

India

Ingrowth core (25 cm) 185.9 Sundarapandian and Swamy

(1996)

Tropical dry forest Jalisco, Mexico Sequential core (10 cm) 180.5 Castellanos et al. (2001)

Tropical dry evergreen

forest

Coromandel, India Ingrowth pit (10 cm) 117.1 Visalakshi (1994)

Table 2. Fine root production in tropical forests

35

Conclusions• Fine roots- the below ground litter- important role in nutrient cycling.

• Production of fine roots are influence on CO2, soil depth, stand management, stand age, seasonand basal area.

• Controversy exists in the literature on what are the best methods to use (direct or indirectapproaches) for estimating the biomass and production of fine roots at an ecosystem level.

• Generally estimation of fine root production is through combination of methods such asingrowth method and sequential coring method.

• It suggests that the direct methods should still be utilized when studies are being initiated on anew site.

36

Future lines

• Little information is available about fine root production of different tropical broad leaf

species.

• Nutrient recycling role of fine roots have to be studied in much larger scale i.e. in ecosystem

level.

37

38