Pterocarpus ofﬁcinalis forested wetlands of Puerto Rico...

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Species composition and differences in diversity among the

Pterocarpus officinalis forested wetlands of Puerto Rico

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CaribbeanNaturalist

No. 4 2013

Species Composition and Differences in Diversity Among

the Pterocarpus officinalis Forested Wetlands of Puerto Rico

Rusty A. Feagin, Frances Toledo-Rodríguez, Ricardo J. Colón-Rivera, Fred Smeins, and Roel Lopez

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Cover Photograph: Traversing a tidal creek in the secondary Pterocarpus officinalis forest in la Reserva Natural de Humacao, Puerto Rico.. Photograph © Doel Delgado.

CARIBBEAN NATURALIST

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USAKeith Goldfarb, Eagle Hill Institute, Steuben, ME, USA ... Editor-in-ChiefGrizelle González, International Institute of Tropical Forestry, San Juan, Puerto Rico, USAGary R. Graves, Department of Vertebrate Zoology, Smithsonian Institution, Washington, DC, USAS. Blair Hedges, Department of Biology, Pennsylvania State University, University Park, PA, USAJulia A. Horrocks, Dept. of Biological and Chemical Sciences, Univ. of the West Indies, Cave Hill

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Píedras, USA

1

R.A. Feagin, F. Toledo-Rodríguez, R.J. Colón-Rivera, F. Smeins, and R. Lopez2013 Caribbean Naturalist No. 4CARIBBEAN NATURALIST2013 No. 4:1–25

Species Composition and Differences in Diversity Among the Pterocarpus officinalis Forested Wetlands of Puerto Rico

Rusty A. Feagin1,*, Frances Toledo-Rodríguez2, Ricardo J. Colón-Rivera1, Fred Smeins1, and Roel Lopez3

Abstract - Pterocarpus officinalis (Dragonsblood Tree, known as Palo de Pollo in Puerto Rico)-dominated forests are a rare ecosystem, found only in fifteen locations in Puerto Rico, most of which are adjacent to the coast and are at risk from sea level rise, nutrient pollution, upstream hydrological modifications, and deforestation. Prior to this study, there was little information on the diversity of organisms inhabiting these forests. The central objectives of our study were to examine the diversity and species composition of three Pterocarpus forests in Puerto Rico located in Humacao, Patillas, and Dorado; compare and contrast diversity among the three forests; and identify possible differences caused by human influences or natural factors. Visual surveys, vegetation plots, pitfall traps, insect traps and nets, and audio recordings were carried out to collect records of birds, mammals, amphibians and reptiles, invertebrates (insects, crustaceans, mollusks), plants, and fungi. The Dorado Pterocarpus forest is only 2.4 ha in extent, but is the rich-est and most diverse; Humacao, the largest tract sampled at 150 ha (63% of the total Pterocarpus coverage in Puerto Rico), is the least rich and diverse. The most obvious factor influencing richness and diversity among the forests is the adjacent land cover and history of the sites. Saltwater intrusion (Humacao), freshwater inflow from watersheds (Humacao, Dorado), and emerging spring water sources (Patillas) may also be factors that alter richness and diversity. Our results will be useful to those planning the appropriate management of this ecosystem in the context of ongoing sea-level rise, climate change, nutrient pollution, upstream hydrological modifications, and deforestation.

Introduction

Tropical wetlands are considered among the most valuable (Costanza et al. 1989) and important ecosystems in the world because of the ecosystem services they provide (e.g., flood protection, wildlife habitat; Mitsch and Gosselink 2007). Forested wetlands, in particular, are a feature of low-lying coastal areas in the Ca-ribbean region (Bacon 1990). Rhizophora mangle L. (Red Mangrove) dominates most of these wetlands except for forested areas influenced by freshwater, where the leguminous tree Pterocarpus officinalis Jacq. (Dragonsblood Tree, known as Palo de Pollo in Puerto Rico) is the dominant species (Fig. 1; Weaver 1997). Adapted to flooded ecosystems, P. officinalis inhabits river floodplains, coastal basins, and subtropical rainforests (Alvarez-Lopez 1990). Due to human disturbance and land clearing, Pterocarpus wetlands are now limited to small, genetically isolated

1Department of Ecosystem Science and Management, Texas A&M University, College Station, TX , USA 77845. 2US Fish and Wildlife Service, Parker River National Wildlife Refuge, Newburyport, MA, USA 01950. 3Institute of Renewable Natural Resources, Texas A&M University, College Station, TX, USA 77843. *Corresponding author - [email protected].

R.A. Feagin, F. Toledo-Rodríguez, R.J. Colón-Rivera, F. Smeins, and R. Lopez2013 Caribbean Naturalist No. 4

2

Figure 1. A Pterocarpus officinalis tree during the dry season in the secondary re-growth section of the Humacao Natural Reserve forest (H2 section of forest), in Humacao, PR, USA. Photograph © Doel Delgado.

3


patches scattered throughout the Caribbean region (Muller et al. 2009, Rivera-Oca-sio et al. 2006). Although the floristic composition of these wetlands has been well described by Alvarez-Lopez (1990) and Imbert et al. (2000), these ecosystems have not received the same research attention as mangrove swamps or upland rainforests (Imbert et al. 2000). In the last century, Puerto Rico lost nearly all of its Pterocarpus forested wetland cover (Helmer 2004), due largely to clearing of the coastal plain for agricultural purposes, often to establish sugarcane plantations. Today, the total area of Ptero-carpus is estimated to cover only 261 ha in approximately 15 locations (Gould 2007). Furthermore, remnant Pterocarpus wetlands in Puerto Rico are restricted to the coast, abutting mangrove ecosystems (Cintrón 1983); the remaining stands now occur near their ecological limits in terms of salinity (Rivera-Ocasio et al. 2007). Though work has also been done on drought tolerance (Lopez and Kursar 2007) and nutrient depletion (Medina et al. 2008), sea-level rise and associated saltwater intrusion appear to be the most serious threats affecting the Pterocarpus ecosystem. Salinities above approximately 12% can kill populations of these trees (Rivera-Ocasio et al. 2007). Pterocarpus wetland forests sustain a unique set of fauna, mainly composed of reptiles, water birds, amphibians, crustaceans, and mollusks (Quiñones-Ramos et al. 1992). This wetland forest type is recognized as rare and limited in extent on the island by the Puerto Rico National Heritage Program (Schwartz 2004). The importance of Pterocarpus wetland forests rests on their rarity, high level of bio-logical productivity, and floral composition. These ecosystems are also of interest to science, and they have intrinsic social value (Figueroa et al. 1984) in terms of recreational and spiritual purposes. The biodiversity of these Puerto Rican wetlands is one factor that has resulted in their designation as a protected ecological resource (Commonwealth of Puerto Rico 2008). However, little is known about the differences in species composition among these forests in Puerto Rico, and the potential causes for these differences. Is there any variance in composition among sites? Is diversity highest in relatively natural areas, or in areas altered by humans? What are the most likely causes for any po-tential differences: temperature, precipitation, salinity, proximity to the coast, soil parameters, or land-use history? The central objective of this work was to examine the diversity and species com-position of three Pterocarpus forests in Puerto Rico (Humacao Natural Reserve, Dorado Pterocarpus Forest Natural Protected Area, and Punta Viento Wetland Natu-ral Reserve). We chose these three forests based on their relative sizes, locations, level of community interest in their preservation, and our ability to gain access to them (Fig. 2). The specific objectives of this project were to sample and list a wide range of plant and animal species, and then to compare and contrast the diversity among the three forests, and determine if differences are caused by human influ-ences or natural factors.


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Field Site Description

Humacao Natural Reserve The Humacao Natural Reserve (HNR), in Puerto Rico, contains the largest and best preserved Pterocarpus forest in the United States, yet the forested stand is only 150 ha in size (representing over half of Pterocarpus forest cover in the US; Alvarez-Lopez, 1990). Much of the original forest acreage was converted for sug-arcane production, and eventually into flooded lagoons (Fig. 2b, c). The reserve is currently managed by the Departamento de Recursos Naturales y Ambientales (DRNA). The community of Punta Santiago sits immediately adjacent to the forest, between the lagoons and the ocean. This low-income residential area flooded repeatedly after the 1970s, in part because there was reduced forest cover to absorb and reduce runoff. Subsequently, in 2000, the US Army Corps of Engineers modi-fied the Antón Ruiz River and several other drainages to open a connection between the lagoons and the ocean to allow floodwaters to flow into the ocean (Schwartz 2004). Unfortunately, this has also increased saltwater intrusion into the lagoons and the adjacent Pterocarpus forest (Ferrer 2007). The remnant Pterocarpus wet-lands are now threatened by saltwater intrusion due to rising global sea levels, a problem that may be exacerbated by climate change over the next decades.

Dorado Pterocarpus Forest Natural Protected Area (DPFNPA) The DPFNPA forest was donated to the Puerto Rico Conservation Trust in 1995 by the developers of a housing project, as required by the Planning Board (Junta de Planificación), and it is managed by the Fideicomiso de Conservación de Puerto Rico. The forest is located within the property of the Dorado Beach Hotel Corpo-ration, a luxury resort community (Fig. 2d, e). The forest is considered to be the best remaining example of a Pterocarpus forest community on the north coast of the island. The DPFNPA forest covers 2.4 ha. Endangered species like Peltophryne lemur Cope (Puerto Rican Crested Toad), Eleutherodactylus karlschmidti Grant (Web-Footed Coqui), Sabicea cinerea Aubl. (Largeflower Woodvine), and Epi-crates inornatus Reinhardt (Puerto Rican Boa) are known to occur in this forest (Figueroa et al. 1984, Quiñones-Ramos et al. 1992). In 1984, the USDA repeated a 1926 study (Gleason and Cook 1926) and found no change in composition of the climax swamp forest formed by Pterocarpus officinalis and six other tree species in the 54 years between studies (1926–1984). However, to-tal forested area was reduced by 30 percent over this time period. The primary cause of the forest cover loss was anthropogenic tree-cutting and hydrological modifica-tion. Construction of a golf course west of the study area altered drainage patterns, resulting in declines of both Pterocarpus and other secondary forest.

Punta Viento Wetland Natural Reserve in Patillas The Patillas forest is located on the south coast of Puerto Rico in El Bajo sector of the Municipality of Patillas (Fig. 2f, g). The forest covers an area of 4.6 ha and is enclosed within the Patillas Punta Viento Wetland Natural Reserve. The reserve

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Figure 2. (a) Pterocarpus forest study site locations across Puerto Rico; Humacao, (b) in 1977 and (c) 2006; Dorado, (d) in 1962 and (e) 2006; Patillas, (f) in 1967 and (g) 2006. Stars represent sampled forest sections in (b-g). Imagery courtesy of USGS (2013).


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contains more than 500 acres of wetlands. In 2008, a community-based organiza-tion, Frente Ambiental Amigos de la Naturaleza, Patillas, urged legislators to pass Act No. 92 (Commonwealth of Puerto Rico 2008), designating the wetlands of Punta Viento as an ecological reserve to be managed by the DRNA.

Methods

Sampling and identification of organisms We sampled a wide range of plant and animal species at the 3 different Ptero-carpus forests in Puerto Rico (Humacao, Patillas, and Dorado). The second author (F. Toledo-Rodríguez) identified organisms to the lowest taxonomic level possible in two sections of each forest. Taxonomy can be referenced in several databases by authority (Bird Life International 2013, Encylopedia of Life 2013, USDA 2013). The Dorado and Patillas forests were relatively small, and the sampled sec-tions were close together (approximately 67 m and 141 m between the sampled sections, respectively) and, thus, we assumed them to be similar. Subsequently, we grouped the section-level data to present a single list for each forest. In con-trast, the Humacao forest was relatively large and contained 2 different sections (approximately 1755 m apart). The Humacao 1 (H1) section was composed of primary forest that had not been cut since Pre-Columbian times, and had exclu-sively freshwater inputs, whereas the Humacao 2 (H2) section was composed of secondary re-growth following a tree harvest in the 1920s; it has both saltwater and freshwater inputs. We present the lists for each section of Humacao separately where applicable. We established two 100 m-long parallel transects in each section of forest. Each transect line had five points spaced 20 m apart (Fig. 3a). The first transect was used to survey birds, amphibians, reptiles, invertebrates, vegetation, and fun-gi, and the second was used to identify birds only. We chose this sampling scheme based on rapid-assessment techniques commonly used by US federal agencies. We collected or recorded all organisms during four 2–4 day sample sessions over a 2-year period, with at least 2 sessions in the rainy season and two in the dry season (Table 1). The driest months in Puerto Rico are December–April and the wettest months are May–November.

Table 1. Sampling dates for the forests, 2011–2012.

Session I Session II Session III Session IV

Humacao Natural Reserve 13, 17 Nov 15, 16 March 23, 24 Dec 1, 2 May 11, 12 Jan 6, 7 May

Dorado Pterocarpus Forest 28, 29 Nov 22, 23 March 20 Dec 15, 16 April Natural Protected Area 19, 20 Jan 17, 18 April 8, 9 Jan

Punta Viento Wetland Natural 18, 19 Nov 20, 21 March 17, 18 Jan 11, 12 AprilReserve, Patillas 13, 14 April

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We conducted bird surveys from 7:00–7:30 AM (UTC-4). We recorded all birds seen and heard during a 5-minute period, within a 5-m radius around each point on the transect (Bibby et al. 1998, Hill et al. 2005). We placed audio recording equip-ment (Olympus, Olympus Linear Recorder, LS-11) in the deepest part of the forest (last point on the transect lines) and left it overnight to record both amphibian and bird vocalizations. We identified organisms to the lowest taxonomic level pos-sible by listening to the audio recording for 10 minutes at intervals of every hour throughout the duration of the recording. Additionally, we surveyed for reptiles and amphibians from 9:00–9:30 AM through visual observation and traps. We placed pitfall traps (1.5 gallons) with an opening of 27.75 cm at each transect point and recovered them 24 hours later (Corn and Bury 1990, Hill et al. 2005, Lambert 2002). The overnight recordings described above were particularly useful for our identifications of the endemic coquís. To collect insects, we placed 16-ounce pitfall traps at each transect point and recovered them 24 hours later (Grootaert et al. 2010, Raghavendra et al. 1990). Additionally, we placed baited hanging traps and ground-level traps at the deepest part of the forest transect for a 24-hour period, after which we retrieved them and identified trapped organisms. We sampled vegetation at each point along all transects (Fig. 3b). To estimate the understory cover, we established a 10-m transect perpendicular to the primary transect at each point and recorded the percent cover by species within ten 1-m2 quadrats (Fidelibus and MacAller 1993, Hill et al. 2005). We defined understory

Figure 3. Within each forest section, (a) sampling points and traps were placed along two parallel transects, (b) with vegetation sampling centered on a transect point.


8

as the vegetation at the lower level in the forest, below 1.3 m in height. We also recorded the percentage of the ground that was covered by woody Pterocarpus of-ficinalis roots in these quadrats. For tree samples, we used circular plots with a 5-m radius centered around each point and divided the plots into four quadrants. For each quadrant, we identified all tree species present and measured the diameter at breast height (dbh) of the 5 largest trees. We measured dbh 1.3 m from the ground and included the buttress root width, which can be relatively large on Pterocarpus trees. We quantified the percent cover of the upper forest canopy using a spherical crown densiometer and recorded canopy cover for the largest single tree at every quadrant, for a total of 4 trees per point. We measured canopy cover for each tree at the 4 cardinal directions (north, east, south, and west) and recorded the average of these values as the canopy cover for each tree. We then averaged the single-tree canopy cover values to estimate the canopy cover in the transect area. For reference, we used LIDAR data from another unpublished study (William Gould, International Institute of Tropical Forestry, US Forest Service, San Juan, Puerto Rico, USA, unpubl. data) (in H1) to estimate the canopy height, which was ≈30 m for the largest trees, though height varies greatly by forest location and section. Fungi and fishes were also surveyed when we encountered them along the tran-sects (Backiel 1980, BCME 1997, Hill et al. 2005, Schieck and Stambaugh 2006). We then compared species composition and variety among the different forests, and we categorized each species as endemic, native, common resident, visitor, or in-troduced. We calculated Shannon’s diversity index as the total of all species within an organismal group, and for all species together, for a particular forest. Shannon’s diversity index (H') was calculated for each forest using the following formula: s H' = ∑ -(Pi * ln Pi), i = 1where S is the species count and Pi is the relative abundance of each species (i.e., the to-tal number of observations of the species divided by the total number of observations).

Soil, land cover, and environmental factors We sought to identify the environmental differences among the three forests that were related to human influences or natural factors. We used NOAA-NCDC (2013) temperature and precipitation records from 1980–2010 recorded at nearby stations. The station name is Dorado 2 WnW PR for the Dorado Forest data, Patillas PR US and Guayama 2E, PR US for the Patillas forest, and Roosevelt Roads for the forest in Humacao. We collected soil samples from each forest, beginning at the surface and taking samples at every 10 cm to a depth of 40 cm. We immediately placed samples in bags and sent them to Servi-Tech Laboratories to determine percent nitrate-nitrogen, phosphorus, potassium, sulfur, calcium, magnesium, sodium, organic matter, soil pH, buffer pH, soluble salts, cation exchange capacity, and base saturation. We used GIS to digitize and map the land cover that surrounded each forest. Land cover classes included Pterocarpus forest, agricultural or human-managed,

9


non-Pterocarpus forest, pasture, forest and pasture mix, mangrove forest, marsh, open water, palm forest, and urban. We then measured the distance from each for-est to the following closest features: house, street, ocean, agricultural land, and human-managed area. We used cover classes and distances to determine the pos-sible human influence on the forest.

Results

Sampling and identification of organisms Among all Pterocarpus officinalis forests, we found 39 species of birds (Table 2). Dorado, Patillas, and Humacao had 33, 23, and 21 species, respectively. The primary section of forest in Humacao (H1) had 11 bird species and the sec-ondary section (H2) had 19 species. After visiting each forest 6 times, the number of newly-identified organisms slowed for nearly all organisms except for birds (Fig. 4). It appeared that the sampling effort had not yet detected all birds at Do-rado or Patillas, though the numbers at Humacao had begun to level out (Fig. 4c). These species sampling-effort curves demonstrate that, because we generally did not detect new species beyond the fifth visit, our sampling effort proved adequate for most organisms. Among all forests, we found 17 species of amphibians and reptiles. Dorado, Pa-tillas, and Humacao had 15, 10, and 11 species, respectively (Table 3). The primary section of forest in Humacao (H1) had 10 species, while the secondary section (H2) had 11.

Figure 4. Species-sampling effort curves for birds, amphibians and reptiles, and inverte-brates for Dorado (a), Patillas (b), and Humacao (c).


10

Tabl

e 2.

Bird

s su

rvey

ed in

the

fore

sts.

D =

Dor

ado

fore

st, P

= P

atill

as fo

rest

. H1

= H

umac

ao p

rimar

y fo

rest

, H2

= H

umac

ao s

econ

dary

fore

st.

Scie

ntifi

c na

me

Sp

anis

h co

mm

on n

ame

Engl

ish

com

mon

nam

e St

atus

D

P

H1

H2

Amm

odra

mus

sav

anna

rum

Gm

elin

G

orrió

n C

hich

ara

Gra

ssho

pper

Spa

rrow

C

omm

on re

side

nt

√

Anth

raco

thor

ax d

omin

icus

L.

Zum

bado

r Dor

ado

A

ntill

ean

Man

go

Com

mon

resi

dent

√

√

√An

thra

coth

orax

vir

idis

Aud

eber

t & V

ieill

ot

Zum

bado

r Ver

de d

e Pu

erto

Ric

o G

reen

Man

go

Ende

mic

√

Ar

dea

alba

L.

Gar

za R

eal

Gre

at E

gret

C

omm

on re

side

nt

√ √

√

Arde

a H

erod

ias

L.

Gar

zon

Cen

izo

G

reat

Blu

e H

eron

V

isito

r

√ √

√Br

otog

eris

ver

sico

luru

s M

ülle

r Pe

rico

Ali-

Am

arill

o W

hite

-win

ged

Para

keet

In

trodu

ced,

191

2 √

Bu

teo

jam

aice

nsis

. Gm

elin

G

uara

guao

R

ed-ta

iled

Haw

k C

omm

on re

side

nt

√ √

Buto

ride

s vi

resc

ens

L.

Mar

tinet

e G

reen

Her

on

Nat

ive

√ √

√

Coc

cyzu

s m

inor

Gm

elin

B

obo

Men

or

Man

grov

e C

ucko

o C

omm

on re

side

nt

√ √

√ √

Coe

reba

flav

eola

L.

Rei

nita

B

anan

aqui

t C

omm

on re

side

nt

√ √

√ √

Cro

toph

aga

ani L

. Ju

dío

Gar

rapa

tero

Sm

ooth

-bill

ed A

ni

Com

mon

resi

dent

√

√D

endr

oica

ade

laid

ae B

aird

R

eini

ta M

arip

oser

a A

dela

ide'

s W

arbl

er

Ende

mic

√

√

D

endr

oica

dis

colo

r V

ieill

ot

Rei

nita

Gal

ana

Prai

rie W

arbl

er

Vis

itor

√

Gal

linul

a ch

loro

pus

L.

Gal

lare

ta C

omún

C

omm

on M

oorh

en

Perm

anen

t res

iden

t √

Ic

teru

s do

min

icen

sis

L.

Cal

andr

ia

Puer

to R

ican

Orio

le

Com

mon

resi

dent

√

M

arga

rops

fusc

atus

Vie

illot

Zo

rzal

Par

do

Pear

ly-e

yed

Thra

sher

C

omm

on re

side

nt

√ √

Meg

asco

ps n

udip

es D

audi

n M

ucar

o C

omún

/ M

ucar

ito

Puer

to R

ican

Scr

eech

-Ow

l En

dem

ic

√ √

Mel

aner

pes

port

oric

enci

s D

audi

n C

arpi

nter

o de

Pue

rto R

ico

Pu

erto

Ric

an W

oodp

ecke

r En

dem

ic

√ √

√ √

Mim

us p

olyg

lotto

s L.

R

uise

ñor

Nor

ther

n M

ocki

ngbi

rd

Com

mon

resi

dent

√

√M

olot

hrus

bon

arie

nsis

To

rdo

Lust

roso

Sh

iny

Cow

bird

In

vasi

ve, 1

955

√

√

M

yair

chus

ant

illar

um G

mel

in

Juí J

uí d

e Pu

erto

Ric

o

Puer

to R

ican

Fly

catc

her

Ende

mic

√

√ √

√M

yiop

sitta

mon

achu

s B

odda

ert

Peric

o M

onje

M

onk

Para

keet

In

trodu

ced,

197

0 √

N

ycta

nass

a vi

olac

ea L

. Ya

boa

Com

ún

Yello

w-c

row

ned

Nig

ht-H

eron

C

omm

on re

side

nt

√ √

√ √

Oxy

ura

jam

aice

nsis

Gm

elin

Pa

to C

horiz

o

Rud

dy D

uck

Rar

e vi

sito

r

√

Pa

rula

am

eric

ana

L.

Rei

nita

Pec

hido

rada

N

orth

ern

Paru

la

Vis

itor

√

Pata

gioe

nas

leuc

ocep

hala

L.

Palo

ma

Cab

ecib

lanc

a W

hite

-cro

wne

d Pi

geon

C

omm

on re

side

nt,

√ √

n

ear t

hrea

tene

dPa

ndio

n ha

liaet

us L

. Á

guila

de

Mar

O

spre

y M

igra

nt

√

Pata

gioe

nas

squa

mos

al B

onna

terr

e Pa

lom

a Tu

rca

Scal

y-na

ped

Pige

on

Com

mon

resi

dent

√

√ √

√Pr

ogne

dom

inic

ensi

s G

mel

in

Gol

ondr

ina

Car

ibeñ

a C

arib

bean

Mar

tin

Nat

ive

√

Qui

scal

us n

iger

Bod

daer

t M

ozam

biqu

e, C

hang

o

Gre

ater

Ant

illea

n G

rack

le

Nat

ive

√

√

11


Tabl

e 3.

Am

phib

ians

and

rept

iles

surv

eyed

in th

e fo

rest

s. D

= D

orad

o fo

rest

, P =

Pat

illas

fore

st. H

1 =

Hum

acao

prim

ary

fore

st, H

2 =

Hum

acao

sec

onda

ry

fore

st.

Scie

ntifi

c na

me

Sp

anis

h co

mm

on n

ame

Engl

ish

com

mon

nam

e St

atus

D

P

H1

H2

Amei

va e

xsul

Cop

e Si

guan

a C

omún

C

omm

on S

igua

na

Nat

ive

√

Anol

is c

rist

atel

lus

Dum

éril

& B

ibro

n La

garti

jo C

omún

Pu

erto

Ric

an C

rest

ed A

nole

En

dem

ic

√ √

√ √

Anol

is e

verm

anni

Ste

jneg

er

Laga

rtijo

Ver

de

Emer

ald

Ano

le

Ende

mic

√

An

olis

gun

ladc

hi P

eter

s La

garti

jo B

arba

Am

arill

a Ye

llow

-Bea

rded

Ano

le

Ende

mic

√

An

olis

pul

chel

lus

Dum

éril

& B

ibro

n La

garti

jo J

ardi

nero

C

omm

on G

rass

Ano

le

Ende

mic

√

√

√An

nolis

str

atul

us C

ope

Laga

rtijo

Man

chad

o B

arre

d A

nole

En

dem

ic

√ √

Bufo

mar

inus

L.

Sapo

Mar

ino

Can

e To

ad

Intro

duce

d, 1

920

√ √

√ √

Eleu

ther

odac

tylu

s an

tille

nsis

Rei

nhar

dt &

Lüt

ken

Coq

uí C

hurr

í Fi

eld

Coq

ui

Ende

mic

√

√ √

√El

euth

erod

acty

lus

britt

oni S

chm

idt

Coq

uí d

e la

s H

ierb

as

Gra

ss C

oqui

En

dem

ic

√ √

√ √

Eleu

ther

odac

tylu

s co

chra

nae

Gra

nt

Coq

uí P

itito

W

hist

ling

Frog

En

dem

ic

√ √

√ √

Eleu

ther

odac

tylu

s co

qui T

hom

as

Coq

uí C

omún

C

oqui

En

dem

ic

√ √

√ √

Igua

na ig

uana

L.

Gal

lina

de P

alo

Gre

en Ig

uana

In

trodu

ced,

197

0

√

√Le

ptod

acty

lus

albi

labr

is G

ünth

er

Ran

ita d

e La

bio

Bla

nco

Whi

te-li

pped

Fro

g N

ativ

e √

√ √

√Ra

na c

ates

beia

na S

haw

R

ana

Toro

A

mer

ican

Bul

lfrog

In

trodu

ced

√

√ √

Rana

gry

lio S

tejn

eger

R

ana

Cer

do

Pig

Frog

In

trodu

ced,

199

8

√

√Sp

haer

odac

tylu

s m

acr o

lepi

s G

ünth

er

Sala

man

quita

Com

ún

Com

mon

Dw

arf G

ecko

N

ativ

e √

√

Tabl

e 2,

con

tinue

d.

Scie

ntifi

c na

me

Sp

anis

h co

mm

on n

ame

Engl

ish

com

mon

nam

e St

atus

D

P

H1

H2

Seiu

rus

mot

acill

a G

mel

in

Pizp

ita d

e M

angl

e

Nor

ther

n W

ater

thru

sh

Com

mon

resi

dent

√

√ √

√Sp

inda

lis p

orto

rice

nsis

Bry

ant

Rei

na M

ora

Puer

to R

ican

Spi

ndal

is

Ende

mic

√

√ √

Ti

aris

bic

olor

L.

Gor

rión

Neg

ro

Bla

ck-f

aced

Gra

ssqu

it C

omm

on re

side

nt

√

Tur d

us p

lum

beus

L.

Zors

al d

e Pa

tas

Col

orad

as

Red

-legg

ed T

hrus

h C

omm

on re

side

nt

√ √

Tyra

nnus

cau

difa

scia

tus

d’O

rbig

ny

Clé

rigo

Logg

erhe

ad K

ingb

ird

Com

mon

resi

dent

√Ty

rann

us d

omin

icen

sis

Gm

elin

Pi

tirre

G

ray

Kin

gbird

C

omm

on re

side

nt

√

√

Vire

o al

tiloq

uus

Vie

illot

Ju

lian

Chi

ví

Bla

ck-w

hisk

ered

Vire

o C

omm

on re

side

nt

√ √

Vire

o la

timer

i Bai

rd

Bie

n-te

-veo

Pu

erto

Ric

an v

ireo

En

dem

ic

√ √

√

Zena

ida

auri

ta T

emm

inck

Tó

rtola

Car

dosa

nter

a Ze

naid

a D

ove

Com

mon

resi

dent

√

√

√


12

We found relatively few invertebrates overall. Our sampling methods were re-stricted to two types of hanging traps and a single type of land trap, and thus the survey did not capture the full range of insect niche habitats; for example we did not sample habitats within decaying plant materials. Moreover, both flying and crawl-ing insects were subject to frequent precipitation events and flooding of the forest floor. On one of our sampling dates, our results were affected by flooding of the traps themselves, though that effort was repeated on a subsequent date. For these reasons, we present here the list of organisms found in our surveys but we did not include them into our calculations of Shannon’s diversity index, nor in our further discussion of the forests. We found 15 species of insects, 6 species of arachnids, 2 species of myriapods, 2 species of mollusks, 3 species of crustaceans, and 2 additional animals (Table 4). All forests had nearly the same number of insect species—Dorado had 8, Patillas had 6, H1 had 8, and H2 had 7. We detected mollusks only at Dorado and Patil-las. Patillas had the most crustaceans, and H2 had the least. In terms of additional animals, only H1 had fish, probably because this section of forest receives direct freshwater inflow from a nearby creek. Among all forests, we found 56 species of plants and 6 species of fungi (Table 5). Dorado had 47 plant species, Patillas had 16, and Humacao had only 6. H1 had the largest trees, followed by Patillas; Dorado and H2 had much smaller trees (Fig. 5a). The canopy cover percentage was similar among all forests, except

Figure 5. (a) Average DBH, (b) canopy coverage percentage, (c) understory coverage per-centage and coverage of Pterocarpus officinalis roots for Dorado, Patillas, Humacao 1 and Humacao 2.

13


Tabl

e 4.

Inv

erte

brat

es a

nd o

ther

ani

mal

s su

rvey

ed in

the

fore

sts.

D =

Dor

ado

fore

st, P

= P

atill

as f

ores

t. H

1 =

Hum

acao

prim

ary

fore

st, H

2 =

Hum

acao

se

cond

ary

fore

st.

Scie

ntifi

c na

me

Sp

anis

h co

mm

on n

ame

Engl

ish

com

mon

nam

e D

P

H1

H2

Inse

cts

Odo

ntom

achu

s ha

emat

odus

L.

Ber

raco

/ H

orm

iga

Fier

cely

Biti

ng B

lack

Ant

/ Tr

ap-J

aw A

nt

√ √

√ √

Sub

fam

ily E

mes

inae

sp.

C

hinc

he D

epre

dado

r Th

read

-legg

ed A

ssas

sin

Bug

√

S

capt

eris

cus

bore

llii G

iglio

-Tos

G

rillo

Top

o So

uthe

rn M

ole

Cric

ket

√ √

√ √

Oro

char

is s

p.

Gril

lo d

e A

rbus

to

Loud

-sin

ging

Bus

h C

ricke

t √

√ √

√ S

uper

fam

ily F

ulgo

roid

ea

Salta

Hoj

as /

Salta

Pla

ntas

Pl

anth

oppe

r √

F

amily

Ter

mito

idae

sp.

C

omej

én

Dry

Woo

d Te

rmite

√

√ √

√ D

oldi

na in

terj

unge

ns B

ergr

oth

Chi

nche

Dep

reda

dor

Ass

assi

n B

ug

√

Api

s sp

. A

beja

Dom

éstic

a, A

veja

Afr

ican

izad

a D

omes

tic H

oney

bee,

Afr

ican

ized

Hon

ey B

ee

√

Dys

derc

us a

ndre

ae L

. B

ombe

ritos

Lo

ve B

ug, P

yrrh

ocor

id B

ug

√

√

Bat

tus

poly

dam

as L

. O

ruga

de

Mar

ipos

a Pa

pilio

C

ater

pilla

r of G

old

Rim

Sw

allo

wta

il

√

O

rder

Hem

ipte

ra

Inse

cto,

no

iden

tifica

dos

mas

Tr

ue B

ug, n

ot id

entifi

ed fu

rther

√

O

rder

Hem

ipte

ra

Inse

cto,

no

iden

tifica

dos

mas

Tr

ue B

ug, n

ot id

entifi

ed fu

rther

√

O

rder

Hem

ipte

ra

Esca

raba

jo R

ojo

True

Bug

, not

iden

tified

furth

er

√ √

Tet

ragn

atha

sp.

A

raña

Ext

ensa

St

retc

h Sp

ider

√

Mol

lusk

s P

olyd

onte

s lim

a Fé

russ

ac

Car

acol

Ásp

ero

o R

aspa

do

Ras

ping

Nip

ple

Snai

l √

C

arac

ullu

s m

argi

nella

C

arac

ol d

e B

anda

s B

ande

d C

arac

ol

√ √

Cru

stac

eans

Uca

lept

odac

tyla

Rat

hbun

C

angr

ejo

Vio

linis

ta

Fidd

ler C

rab

√ √

√ √

Car

diso

ma

guan

hum

i Lat

reill

e Ju

ey C

omún

B

lue

Land

Cra

b √

√

U

cide

s co

rdat

us L

. Ju

ey P

elú

Zam

buco

M

angr

ove

Land

Cra

b

√ √


14

Tabl

e 4,

con

tinue

d.

Scie

ntifi

c na

me

Sp

anis

h co

mm

on n

ame

Engl

ish

com

mon

nam

e D

P

H1

H2

Ara

chni

ds F

amily

Pho

lcid

ae s

p.

Ara

ña d

e Pa

tas

Larg

as

Dad

dy-lo

ngle

gs /

Cel

lar s

pide

r √

√

F

amily

Lyc

osid

ae s

p.

Ara

ña L

obo

Wol

f Spi

der

√ √

√

Ord

er O

pilio

nes

sp.

Opi

lión

Har

vest

men

√

C

oryt

halia

ban

ski R

oew

er

Ara

ña S

alta

dora

Ju

mpi

ng S

pide

r √

√ S

elen

ops

insu

lari

s K

eyse

rling

A

raña

Pla

na

Flat

Spi

der

√

Leu

caug

e re

gnyi

Sim

on

Ara

ña T

ejed

ora

Orc

hard

Spi

der

√ √

√ √

Fam

ily B

uthi

dae

sp.

Esco

rpió

n Sc

orpi

on

√ √

Myr

iapo

ds S

colo

pend

ra a

ltern

ans

Leac

h C

ienp

iés

Cen

tiped

e

√ √

F

amily

Jul

idae

sp.

M

ilpié

s M

illip

ede

√

Oth

er a

nim

als

pres

ent

Cla

ss A

ctin

opte

rygi

i sp.

Pe

z, n

o id

entifi

cado

Fi

sh, n

ot id

entifi

ed fu

rther

√

Est

here

lla s

p.

Lom

briz

de

Tier

ra

Earth

wor

m

√ √

√ √

15


Tabl

e 5.

Pla

nts

and

fung

i sur

veye

d in

the

fore

sts.

D =

Dor

ado

fore

st, P

= P

atill

as fo

rest

. H =

Hum

acao

fore

st.

Scie

ntifi

c na

me

Sp

anis

h co

mm

on n

ame

Engl

ish

com

mon

nam

e St

atus

D

P

H

Plan

ts A

cros

tichu

m a

ureu

m L

. H

elec

ho d

e M

angl

e

Gol

den

Leat

her F

ern

Nat

ive

√ √

√ A

ndir

a in

erm

is W

right

M

oca

Cab

bage

-bar

k Tr

ee

Nat

ive

√

A

nnon

a gl

abra

L.

Cay

ur

Pond

App

le

Nat

ive

√ √

A

nona

cea

sp.

Ann

onac

eae

Cus

tard

App

le F

amily

√

D

esco

noci

da

Ant

huri

um c

rena

tum

Kun

th

Leng

ua d

e Va

ca

Scal

lope

d La

ce L

eaf

Nat

ive

√ √

√ A

rdic

ea s

p.

Ard

icia

spp

A

rdic

ea

√

Ard

isia

elli

ptic

a Th

unb.

M

amey

uelo

Sh

oe B

utto

n A

rdis

ia

Intro

duce

d √

Buc

ida

buce

ras

(L.)

Wrig

ht

Uca

r G

rego

ry W

ood

Nat

ive

√

B

urse

ra s

imar

uba

(L.)

Sarg

. A

lmac

igo

Gum

bo L

imbo

N

ativ

e √

Cal

ophy

llum

cal

aba

Brit

ton

Mar

ía

Sant

a-M

aria

N

ativ

e √

√

Cas

eari

a gu

iane

nsis

(Aub

l.) U

rb.

Palo

Bla

nco

G

uyan

ese

Wild

Cof

fee

Nat

ive

√

C

asea

ria

sylv

estr

is S

w.

Laur

el E

spad

a C

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n N

ativ

e √

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sia

rose

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cq.

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ey

Wild

-mam

ee

Nat

ive

√

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q.

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ra

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Tong

ue

Nat

ive

√

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idym

opan

ax m

orot

oton

i (A

ubl.)

Mag

uire

, Ste

yerm

. & F

rodi

n Ya

grum

o M

acho

M

atch

woo

d N

ativ

e √

Eug

enia

jam

bos

(L.)

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ton

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arro

sa

Mal

abar

Plu

m

Intro

duce

d √

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enia

pse

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sidi

um J

acq.

G

uaya

ba S

ilves

tre

Chr

istm

as C

herr

y N

ativ

e √

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acea

e sp

. # 1

Fa

bace

ae

Faba

ceae

√

P

elto

phor

um p

tero

carp

um (D

C.)

Bac

ker e

x K

. Hey

ne

Flam

boya

n A

mar

illo

Gol

den

Flam

boya

nt

√

Far

amea

occ

iden

talis

(L.)

A. R

ich.

C

afec

illo

Fals

e C

offe

e N

ativ

e √

Fic

us c

itrifo

lia M

ill.

Jagü

ey B

lanc

o W

ild B

anya

n Tr

ee

Nat

ive

√

F

icus

sp.

Fi

cus

Fic

us

√

G

enip

a am

eric

ana

L.

Jagu

a Ja

gua

Nat

ive

√

G

uapi

ra fr

agra

ns (D

um. C

ours

.) Li

ttle

Cor

cho

Bla

ck M

ampo

o N

ativ

e √

Hoh

enbe

rgia

ant

illan

a M

ez

Bro

mel

ia

Ant

illes

Lac

ebar

k N

ativ

e √

Hyl

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eus

trig

onus

(Haw

.) Sa

ff.

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tus

Pita

haya

W

ild S

traw

berr

y N

ativ

e √

√

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enae

a co

urba

ril L

. A

lgar

robo

St

inki

ng T

oe

Nat

ive

√

I

nga

laur

ina

(Sw

.) W

illd.

G

uam

a Sa

cky

Sac

Bea

n N

ativ

e √

Lau

race

a sp

. La

urac

ea

Laur

acea

√


16

Tabl

e 5,

con

tinue

d.

Scie

ntifi

c na

me

Sp

anis

h co

mm

on n

ame

Engl

ish

com

mon

nam

e St

atus

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P

H

Lic

aria

par

vifo

lia (L

am.)

Kos

term

. C

anel

illa

Puer

to R

ico

Cin

nam

on

Nat

ive

√

M

anilk

ara

bide

ntat

a (A

.DC

.) A

. Che

v A

usub

o B

ulle

t Woo

d N

ativ

e √

√

Mas

ticho

dend

ron

foet

idis

sim

um J

acq.

To

rtugo

Am

arill

o

Fals

e M

astic

N

ativ

e √

Mor

inda

citr

ifolia

L.

Non

i In

dian

Mul

berr

y In

trodu

ced

√

M

orus

nig

ra L

. M

oral

B

lack

Mul

berr

y In

trodu

ced

√

O

rmos

ia k

rugi

i Urb

. Pa

lo d

e M

atos

Pe

roni

a N

ativ

e √

Pau

llini

a pi

nnat

a L.

B

ejuc

o de

Cos

tilla

B

read

and

Che

ese

Nat

ive

√

√ P

hleb

odiu

m a

ureu

m (L

.) J.

Sm

. H

elec

ho E

spad

a G

olde

n Se

rpen

t Fer

n N

ativ

e √

√

Pip

er a

mal

ago

L.

Hig

uillo

de

Lim

ón

Rou

gh-le

aved

Pep

per

Nat

ive

√

P

runu

s du

lcis

(Mill

.) D

.A. W

ebb

Alm

endr

o

Swee

t Alm

ond

Nat

ive

√

P

silo

tum

nud

um (L

.) P.

Bea

uv.

Hel

echo

Esc

oba

Whi

sk F

ern

Nat

ive

√ √

P

sych

otri

a br

achi

ate

Sw.

Palo

de

Cac

him

bo

Palo

de

Cac

him

bo

Nat

ive

√

P

tero

carp

us o

ffici

nalis

Jac

q.

Palo

de

Pollo

D

rago

n B

lood

woo

d T r

ee

Nat

ive

√ √

√ R

andi

a ac

ulea

te L

. Ti

ntill

o W

hite

Indi

go B

erry

N

ativ

e √

Roy

ston

ea b

orin

quen

a O

.F. C

ook

Pa

lma

Rea

l R

oyal

Pal

m

Nat

ive

√ √

√ T

abeb

uia

hete

roph

ylla

(DC

.) B

ritto

n R

oble

Bla

nco

Whi

te C

edar

N

ativ

e √

Till

ands

ia fa

scic

ulat

e Sw

. B

rom

elia

G

iant

Airp

lant

N

ativ

e √

Unk

now

n #

1

√

U

nkno

wn

# 2

√

√

Unk

now

n #

3

√

U

nkno

wn

# 4

√

Van

illa

clav

icul

ata

(W.W

right

) Sw

. O

rqui

dea

Vain

illa

Gre

en W

ithe

Nat

ive

√

Fung

i C

hlor

ophy

llum

mol

ybdi

tes

(G. M

ey.)

Mas

see

Hon

go S

ombr

illa

Verd

e G

reen

Par

asol

√

C

ooke

ina

tric

holo

ma

(Mon

t.) K

ount

ze

Cop

itas

Red

Cup

Fun

gus

√

Gan

oder

ma

appl

anat

um (P

ers.

) Pat

. O

reja

de

Palo

A

rtist

's C

onk

√

√ P

helli

nus

igni

ariu

s (L

.) Q

uél.

Yesc

a Ph

ellin

us F

ungu

s

√

P

silo

cybe

sp

Hon

gos

Mág

icos

M

agic

Mus

hroo

ms

√

Tra

met

es g

ibbo

sa

Yesq

uero

Bla

nco

Lum

py B

rack

et

17


H2, where cover values were lower (Fig. 5b). Understory cover was highest at Do-rado and lowest at H2. Patillas had the most visible root coverage on the ground surface (Fig. 5c). In summary, Dorado had the highest faunal abundance (48 organisms, excluding invertebrates) and the highest faunal Shannon’s diversity value (H' = 3.40 [exclud-ing invertebrates]; Table 6). Dorado had the greatest number of native or endemic species—birds, 7; amphibians/reptiles, 12; and plants, 43. However, Dorado also had the most invasive or exotic bird and plant species, 3 and 4, respectively. For plants and fungi, Dorado had the highest plant and fungal diversity (H' = 2.87). Patillas was second in richness for both fauna (H' = 2.89) and plants/fungi (H' = 1.27). H2 was the least rich in fauna (11 organisms, excluding invertebrates) and least diverse (H' = 1.56). Humacao had the most invasive amphibian/reptile spe-cies, 4. All of the plants in both Patillas and Humacao were native or endemic.

Soil, land cover, and environmental factors The Dorado area has an average temperature of 25.1 °C (77.2 °F), a mean an-nual maximum temperature of 28.3 °C (83.0 °F), and a mean annual minimum

Table 6. Shannon’s diversity index values for each forest. H1 = Humacao primary forest, H2 = Hu-macao secondary forest.

Dorado Patillas H 1 H 2

Birds 3.08 2.40 1.94 2.21Amphibians and reptiles 2.14 2.00 1.85 1.89Fauna (excluding invertebrates) 3.40 2.89 2.59 1.56Plants and fungi 2.88 1.27 0.73

Table 7. Temperature and precipitation averages for the forests from 1980 to 2010.

Rainfall Avg min temp Average temp Avg max tempForest (station)/period mm (in) °C (°F) °C (°F) °C (°F)

Dorado (Dorado 2 WnW PR US) Annual 1637.0 (64.5) 21.3 (70.4) 25.1 (77.2) 28.3 (83.9) Winter (DJF) 388.4 (15.3) 19.4 (67) 24.1 (73.5) 26.6 (80) Spring (MAM) 349.8 (13.8) 20.7 (69.4) 24.7 (76.6) 28.7 (83.7) Summer (JJA) 404.9 (15.9) 22.8 (73.1) 26.6 (79.9) 30.4 (86.8) Fall (SON) 494.0 (19.5) 22.2 (71.9) 25.8 (78.6) 29.5 (85.2)Patillas (Guayama 2 E PR US) Annual 1386.1 (54.6) 23.5 (74.4) 27.1 (80.9) 30.7 (87.4) Winter (DJF) 182.9 (7.2) 22.2 (72) 25.9 (78.7) 29.6 (85.4) Spring (MAM) 247.9 (9.7) 23.1 (73.5) 26.7 (80.1) 30.3 (86.6) Summer (JJA) 421.1(16.6) 24.8 (76.7) 28.3 (83) 31.7 (89.2) Fall (SON) 534.2 (21.0) 24.1 (75.3) 27.7 (81.9) 31.3 (88.4)Humacao (Roosevelt Roads) Annual 1329.4 (52.3) 23.8 (75) 27.1 (80.8) 30.2 (86.5) Winter (DJF) 242.1 (9.5) 22.3 (72.2) 25.5 (78) 28.7 (83.7) Spring (MAM) 281.4 (11.1) 23.4 (74.1) 26.6 (79.9) 29.7 (85.6) Summer (JJA) 333.0 (13.1) 25.4 (77.8) 28.5 (83.3) 31.5 (88.8) Fall (SON) 472.9 (18.6) 24.4 (75.9) 27.6 (81.8) 31.0 (87.8)


18

temperature of 21.3 °C (70.4 °F) (Table 7). The average annual precipitation is 1637.0 mm (64.5 in). At Patillas, the average temperature is 27.1 °C (80.9 °F), the mean annual maximum temperature is 30.7 °C (87.3 °F), and the mean annual mini-mum temperature is 23.5 °C (74.3 °F). On average, Patillas receives 1386.1 mm (54.6 in) of precipitation annually. The average temperature for the Humacao area is 27.1 °C (80.8°F), with a mean annual maximum temperature of 30.2 °C (86.4 °F) and a mean annual minimum temperature of 23.8 °C (74.3 °F); Average annual precipitation is 1329.4 mm (52.3 in). For the soil samples, we present here only nitrate, percent organic matter, soluble salts, sulfur, and calcium. Nitrate was highest in the Dorado samples, but

Figure 6. Soil components for Dorado, Patillas, Humacao 1 and Humacao 2 forest: (a) ni-trate, (b) organic matter %, (c) soluble salts, (d) sulfur, and (e) calcium.

19


was low in those from Patillas, H1, and H2 (Fig. 6a). Organic matter values were lowest in samples from H1 followed by H2; higher values were recorded for the Patillas and Dorado soils (Fig. 6b). Soluble salts were highest at H2, but low in H1 and Dorado (Fig. 6c). Sulfur values were highest in H2 soils; Dorado and H1 had the lowest values (Fig. 6d). Calcium was the lowest in Dorado, H1, and H2; the highest value was recorded at Patillas (Fig. 6e). The Dorado forest (Fig. 7a) is located within lands owned by the Dorado Beach Hotel Corporation, which is a luxury resort community. To the north of the Ptero-carpus forest, there is an additional non-Pterocarpus forested area that is managed by the Puerto Rico Conservation Trust. To the east, the Dorado forest is separated from a large area of urban development by only a small patch of trees. A remain-ing small patch of forest adjacent to another well-developed urban area lies to the south, and there is a large golf course to the west. The Patillas forest (Fig. 7b) occurs within the Punta Viento Natural Reserve. A large pasture abuts the forest on the north and mangrove forests occur to the east, south, and west. The Humacao forest (Fig. 7c) is the only one of the forests we sampled that has direct connections to open water through channels or lagoons connected to the ocean. Agricultural lands are adjacent to the northern part of the forest. Urban areas are immediately across the lagoon, to the southwest. The Dorado forest was the closest to roads, houses, human-managed ecosys-tems, and the ocean (Table 8). In contrast, H1 had the greatest distances to roads,

Figure 7. Land-use/land-cover maps, for (a) Dorado, (b), Patillas, and (c) Humacao.


20

houses, and the ocean. Patillas was the closest to an agricultural area, and H2 was the farthest from an agricultural area.

Discussion

Richness and diversity among the forests, and possible causes for differences Of the forests we sampled, the Dorado Pterocarpus forest is the most rich and diverse in terms of organisms and has the greatest number of native and endemic species, while the Humacao Pterocarpus forest is the least rich and diverse. How-ever, Dorado is the smallest forest, covering only 2.4 ha, while Humacao is the largest, with an area of 150 ha, which comprises 63% of the total Pterocarpus cov-erage in Puerto Rico. The temperature and precipitation differences among the forests do not likely explain the difference in richness or diversity. The average annual precipitation is 1637.0 mm (64.5 in) in Dorado Forest and 1329.4 mm (52.3 in) in Humacoa, a dif-ference of only ≈1/5 the total (NOAA 2013). The average temperatures are 25.1 °C (77.1 °F) and 27.1 °C (80.8 °F) for Dorado and Humacao, respectively, a difference of only 2 °C (3.7 °F) (Table 7; NOAA 2013). One potential explanation for the differences in species richness and diversity can be found in results of our soil sampling. Dorado soil samples were high in ni-trate, a component of many commercial fertilizers. It is also produced by fixation of nitrogen by soil bacteria as part of the nitrogen cycle, as well as through the decay of organic matter in the soil. The relatively high level of nitrate may be due, in part, to inputs from human activity: Dorado is surrounded by human-managed areas, including a golf course and urban areas. Dorado soils also had the highest organic matter percentage, likely because of the large amount of plant material deposited due to high understory cover and low overstory canopy cover. In contrast, H1 has soils with nitrate below detectable limits, and low impact from human disturbance. The mature trees in H1 have the largest average dbh and, due to the large dense canopy, there is low understory coverage and a low amount of organic matter. Ad-ditionally, the low organic matter in H1 forest soils could be explained by inflow that washes the material downstream during frequent rain events. Inflow and water sources may also be factors that alter richness and diversity. The amount of soluble salts and sulfur in the forests’ soils are likely related to saltwater intrusion, as they were highest at the H2 forest, followed by the Patillas forest. Hydrogen sulfide often results from anaerobic digestion or reduction, the

Table 8. Distance of forest to selected features.

Distance (m)

Features Dorado Patillas H 1 H 2

Road 173.43 542.19 1455.42 734.58House 107.57 640.61 1253.19 723.00Agricultural area 1764.99 620.92 1443.95 2509.16Ocean 477.77 495.61 2514.75 1106.54Human managed 118.62 578.52 1170.34 1326.03

21


bacterial breakdown of organic matter in the absence of oxygen, which commonly occurs in swamps. The subsequent oxidation of hydrogen sulfide produces sulfur. Interestingly, Patillas soils had the highest calcium levels, reaching almost 4000 ppm. Patillas differs from the other sites because spring water enters the forested wetland’s surface waters from underlying karst limestone through the Pozo Encan-tado or Enchanted Well. The most evident factor influencing richness and diversity among the forests is the adjacent land-use history of the sites. As mentioned earlier, the Dorado forest is the smallest as well as the most fragmented one, in terms of its interspersion with other land-cover types. Dorado also has the highest number of endemic and native plant species, as well as invasive plant species. Increased plant diversity provides increased animal habitat, and explains, in part, the higher richness of fauna. The forest’s perimeter-to-area ratio is high and it is surrounded by urban homes, infra-structure, and a golf course. Patillas is the second smallest forest, but it is entirely enclosed within a natural reserve. It consistently ranks in the middle of the three forests sampled, in terms of richness and diversity, proximity to human disturbance, and average dbh. It also has the highest Pterocarpus root-cover percentage, likely because it is drier than Huma-cao, though it is still influenced to a small degree by salt, rain, and spring water. H1 is the best example of a large, mature, historically undisturbed, primary Ptero-carpus forest in Puerto Rico. Its trees have a large dbh and canopy coverage, and its soils are low in nutrients, organic matter, and have limited saltwater influence. H2 is the youngest forest of the sites we sampled, and is composed of second-ary re-growth established in the 1950s. It has the lowest dbh and overstory canopy cover among all of our study sites. It is strongly affected by saltwater intrusion, with channels crossing it that connect directly to the ocean. It is also necessary to mention that our methodology excluded some habitats where we likely would have recorded additional species. For example, we would undoubtedly have detected additional invertebrates utilizing habitat niches such as dead wood, live tree interiors, and the upper canopy of the forest.

Primary versus secondary Pterocarpus forests At Humacao, the primary and secondary forests have been exposed to different human disturbances. Humans have altered the water flowing into the forests in both sections of forest, though the primary forest has been more affected by altered up-stream inflow through digging of irrigation channels for sugarcane production. The secondary forest, while also affected by changes in water flow, was cut and cleared in the 1950s. Subsequently, abandonment of this section resulted in re-growth. In 2000, the US Army Corps of Engineers attempted to reduce flooding in the nearby urban community of Punta Santiago, and their creation of a canal introduced saltwater to the Humacao secondary forest. The number of bird, amphibian and reptile species is lower in the primary forest (total 21) than the secondary forest (total 30). Moreover, the soil in the primary forest had the lowest organic matter values and low nutrient values, including nitrate, while also showing signs of saltwater inundation.


22

Our results suggest that mature Pterocarpus officinalis-dominated forests are largely vegetatively monospecific (as also found by Alvarez-López 1990), low in number of dependent species, and have nutrient-poor soils. The fragmentation of these forests, alteration of hydrology, and conversion of adjacent environments has only increased their floristic and faunal diversity.

Conclusion Human influences on these forests have been significant across Puerto Rico and the Caribbean region. Our analysis points out that fragmentation and changes in the surrounding land used by humans increased both richness and diversity in these for-ests. This increase in the diversity of species comes from both native and endemic Puerto Rican species that have become established in the fragmented forest and small remnants, but also from exotic and invasive species. Still, all Pterocarpus forests provide a natural environment to sustain organisms, and there are likely organisms that thrive particularly in conjunction with Pterocar-pus. For example, although we did not identify any species endemic to Pterocarpus forests, we did find small, as yet unidentified fish in only the most undisturbed por-tions of the primary forest in Humacao. Because the remaining areas covered by the Pterocarpus forest are so limited in extent, protection and management of this forest type are necessary. Ptero-carpus forests are known to support a number of native and endemic species (Cintrón 1983), specifically amphibians, which are reported to be imperiled worldwide. Our results should be useful to those who manage areas that support Pterocarpus forests, not only in a broad sense, but also more specifically to the managers of the forests included in this research. This work will assist those who manage this limited resource in the context of ongoing sea level rise, climate change, nutrient pollution, human interaction, upstream hydrological modifica-tions, and deforestation. We suggest that future management should focus on two distinct preservation efforts. Maintenance of high diversity and use of beneficial habitat should be the goals for Dorado and Patillas, the smaller forests. One problem with this strategy is that Pterocarpus trees may not be able to replace themselves over multiple genera-tions, as other flora may be able to outcompete Pterocarpus seedlings in areas with lower amounts of upper canopy cover and higher sun exposure, particularly con-sidering the low number of trees from which to recruit propagules. If management is undertaken to favor Pterocarpus growth, this might negatively affect several species of concern present at the site. Whether these forests will eventually lose their Pterocarpus trees or revert back to a forest with more complete Pterocarpus dominance is unknown, but future studies on tree age structure and recruitment suc-cess could help to answer this question. Conversely, for the remaining large forest (Humacao), the maintenance of low diversity as a semblance of the Pre-Columbian state should be the goal because this forest is the remaining exemplar of the natural state of the Pterocarpus forest ecosystem in Puerto Rico.

23


Acknowledgments

This research was funded in part by the Hispanic Leaders in Agriculture and the Envi-ronment Fellowship Program, and the College of Agriculture and Life Sciences at Texas A&M University. We would like to thank Dr. Manuel Piña and Dr. Dave Reed for mentor-ship and support. We would like to thank Doel Delgado for his photography skills. This research would not have been possible without the assistance of Ana Pagan, Luis Baergas, Maño Corbet, Cynthia Morales Otero, Omar Monzon Carmona, Frank Cosme Arroyo, Ray Rodriguez Colon, Noel Rivera Gómez, Carlos Zayas, Alejandro Maldonado, Natalia López-Figueroa, and Denny Fernández del Viso.

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