U.S. Department of Agriculture

Forest Service

Research Paper SO-152

TREE GROWTH IN SEVERAL TROPICAL FORESTS

OF PUERTO RICO

PETER L. WEAVER

d

soutkb

F

station
SUMMARY

About 2400 individual stems > 4.1 cm

d.b.h., and representing about 100 species, from

six plots in three Life Zones, some with edaphic

variation and/or silvicultural treatment,

scattered throughout Puerto Rico, were studied

for varying periods, usually ranging from 24

through 30 years but in one instance for only 2

years. Also, more than 11,000 mangrove stems

> 1 cm at ground level were followed after

clearcutting on 3 plots consisting of two separate

treatments and a control.

The periodic annual increment for all stems

> 4.1 cm, regardless of species or crown class,

ranged from about 0.05 cm/yr in the Guanica dry

limestone forest of the southwest (Subtropical

Dry Life Zone) to about 0.45 cm/yr in the Piiiones

mangrove and early secondary rainforest at Saint

Just, both in Subtropical Moist Life Zone.

The species diversity of forests in Puerto Rico

is intermediate between those of continental

temperate forests of the United States and

continental tropical forests. Ten species accounted for 70 to 95 percent of the stems on all

sites, exclusive of Pinones mangrove and

Guanica.

RESUMEN

Alrededor de 2400 tallos individuales > 4.1

cm d.a.p., localizados en 6 parcelas en 3 Zonas de

Vida, y representando unas 100 especies, algunos

de ellos en parcelas con una variaci& edafica y/o

tratamiento silvicola, fueron estudiados por

periodos variables fluctuando entre 24 a 30 aiios,

aunque en unit ocasion por solo 2 aiios. Ademas,

despues de limpiar 3 rodales consistentes de 2

tratamientos diferentes y un control, se estudiaron la regeneration de 11,000 tallos de

mangle > 1 cm a nivel de1 suelo.

El increment0 periodic0 anual de1 d.a.p.

(IPA) para todos 10s tallos > 4.1 cm, hacienda

case omiso de la especie y clase de copa, fluctuo

desde 0.05 cm/aiio en el bosque seco de piedra

caliza de Guanica en el sudoeste de Puerto Rico

(Zona de Vida Seca Subtropical) hasta 0.45

cm/aiio en el manglar de Piiiones y el bosque

pluvial secundario en St. Just, ambos en Zona de

Vida Humeda Subtropical.

La diversidad de especies en Puerto Rico

intermedia entre las de 10s bosques templados

continentales de 10s Estados Unidos y 10s bosques

tropicales continentales. Diez especies respondieron por el 70 al 95 por ciento de 10s tallos en

todos 10s sitios, sin contar el mangle de Pinones y

el bosque de Guanica.

ACKNOWLEDGMENTS

I am indebted to Carl Jordan, Ariel Lugo, and Peter Murphy for their

critical review of the manuscript.

1979
Tree Growth in Several Tropical

Forests of Puerto Rico

PETER L. WEAVER

INTRODUCTION

From 1943 to 1951, the staff of the Institute of

Tropical Forestry established plots in several

forests throughout Puerto Rico to determine

periodic annual d.b.h. increment (PAI) and to

evaluate the potential of different species and

forest types for timber production. Initial results

disclosed that d.b.h. growth was comparable to

that of temperate forests. Subsequently, many of

the studies were discontinued after 5 or 10 years.

Since little is known about long-term PAI,

stand changes over time, or stand diversity in

tropical forests, and since this information isvital

to forest planning and management, the plots

were remeasured during the mid-70’s.

The principal purpose of this paper is to

summarize PAI’s by species and crown class for

several modified or natural stands in Puerto Rico.

Also, baseline data on rates of ingrowth, mortality, and stand diversity are provided. Such

information will serve as a standard for comparison with other tropical and temperate zone

forest types, and with the results of future

research in secondary forests of Puerto Rico.

THE STUDY AREA

AND RESEARCH PLOTS

Puerto Rico is located at 18”N latitude and

66”W longitude in the West Indies archipelago. It

is about 165 km long by 55 km wide and has a

highly diverse physical environment (Pica 1950).

The island comprises a central mountain

range that isoriented east to west andvaries from

600 m to over 1200 m in elevation. The northern

foothills and northern coastal lowlands encompass a large region of limestone origin in which

karst hills are the dominant land form. Limestone

is also found in the southwestern coastal region.

The island receives an average of 1900

mm/yr of rainfall, mostly orographic, with

marked differences in amount over short distances. The southwest, or leeward coastal areas,

receive about 800 mm/yr; the northeast, east and

southeast, or windward coastal areas, about 1500

to 2000 mm/yr. In the mountains, rainfall varies

with location, gradually increasing with elevation to over 5000 mm/yr.

Surrounding ocean temperatures vary from

25.5”C to 27.8”C seasonally, and as a result, mean

air temperatures have a small range between the

warmest and coldest months. Potential evapotranspiration is estimated at 2000 mm/yr in the

coastal areas and 1000 mm/yr or less in the

interior mountains (Calvesbert 1970). February,

March, and April are drier than the other

months.

Mangrove, dry, deciduous, rain, lower montane, upper montane, palm, and elfin forest are

terms that indicate the variability of the island’s

vegetation types. Several authors have described

them according to their preferred classification

schemes (Gleason and Cook 1927, Beard 1944,

Stehle 1945, Dansereau 1966, Ewe1 and Whitmore 1973). The last classification recognized six

Life Zones (Holdridge 1947, 1967) of which the

Subtropical Dry, Subtropical Moist, and Subtropical Wet Life Zones comprised 98.6 percent of

the island’s land area (fig. 1).

Nine research plots were selected within

three Life Zones (fig. 1): one in Subtropical Dry at

Guanica on azonal limestone soil; six in Subtropical Moist, two at Cambalache on azonal

limestone soil with different exposures, three at

Pinones mangrove, and one on zonal soil at St.

Just; and two in the Lower Montane Wet Colorado

association, one at Toro Negro on zonal soils, and

one at Maricao on serpentine. Mean monthly and

mean annual rainfalls and temperatures for each

plot are provided in figure 2.

Peter Weaver is Research Forester at the Institute of Tropical Forestry, Southern Forest Experiment Station, Forest Service

-USDA, Rio Piedras, Puerto Rico.
%ARE& LIFE ZONE

, , .e a SUBTROPICAL DRY FOREST

58. .+ a SUBTROPICAL MOIST FOREST

22 6 m SUBTROPICAL WET FOREST

0.1 # SUBTROPICAL RAIN FOREST

l,Li ‘=I: “I ::,“:,” ::I:,“,“: R:::I”,: 1

Figure l.-Ecological Life Zones of Puerto Rico and location of study sites indicated by asterisk

(adapted fro& Ewe1 and Whitmore. l!173).

METHODS

On each plot, all trees were measured with a

steel tape at diameter at breast height and

permanently marked with sequentially

numbered tags at 15 cm below diameter at breast

height to avert errors due to swelling. Crown

classes were also recorded. In some instances,

thinnings or clearcuts were made. Periodically

thereafter, the plots were revisited, and the

surviving trees measured again. Simultaneously,

mortality was observed, and during the final

measurement, both ingrowth and mortality were

tallied.

Details about plot sizes, number of stems, soil

types (U.S. Dep. Agric. 1972), and silvicultural

treatments are compiled in table 1. The Life Zone

system is used as a framework for analysis

because results are often applicable in corresponding Life Zones elsewhere.

Statistical testing of PAI’s by crown classes

was done with Tukey’s Omega Procedure (Steel

and Torrie 1960). Statistical testing of PAI’s

among species, however, was considered inappropriate because of possible confounding due to

unequal replication, grouping without respect to

crown class, and differential effects of previous

silvicultural treatments.

The Shannon-Weiner Index, which is influenced by both the variety and equitability of

2

the species sampled (Krebs 1972), was used to

determine species diversity. All species names

were derived from Common Trees of Puerto Rico

and the Virgin Islands (Little and Wadsworth

1964, Little and others 1974).

RESULTS

Subtropical Dry Life Zone

Subtropical Dry Forest on limestone occupies 210 km2 or 13 percent of the Life Zone,

which in turn occupies 1650 km2 or 18 percent of

Puerto Rico.

In 1944, 66 stems of Bucida buceras were

measured in secondary forest; by 1975, only 34

stems remained. Mortality was highest in the

small diameter classes, and in the suppressed and

intermediate crown classes. Since the plot was

dimensionless, ingrowth was impossible to determine.

The PA1 for the 34 surviving stems is only

0.06 cm/yr, with dominants averaging 0.11

cm/yr, codominants 0.08, intermediates 0.04, and

suppressed stems 0.02 cm/yr (table 2). Previous

measurements of PA1 on the same plot showed

that the “thriftiest and most vigorous” trees

averaged only 0.13 cm/yr during the first 17

years of measurement (Briscoe 1962).
(MM) (“Cl

6 0 3 0

4 0 2 0

JFMAMJJASOND

I

I I I I I I I I I I’

JFMAMJJASOND

(MM) (“C) (MM) 1°C)

.30

.20

. IO

I I

1 I I I, 1 I I I1

JFMAMJJASOND

“Cl

2oj, , ,:a:‘,““, , , , , i_

JFMAMJJASOND

(MM) (“Cl

I I

6 0

4 0 CAMBALACHE

2 0 1411 MM

25.3 “c

3 0

2 0

IO

200

100

8 0

6 0

1501 MM

25.8 Oc

(MM) (“Cl

r

200

100

80

6 0 30

4 0 2 0

1915 MM

2 0 25.8 Oc

t

IO

Figure Z.-Climatic diagrams for six plots in natural forests of Puerto Rico.
Table l.- Selected sites for comparative ecosystem growth study in Puerto Rico

Holdridge Life

Zone (association)

Subtropical Dry

(Limestone)

Subtropical Moist

(Rain forest)

Subtropical Moist

(Limestone)

Subtropical Moist

(Mangrove)

Lower Montane Wet

(Colorado)

Number

Name of public of Plot size in ha Plot Data: Seral stage: soils; elevation;

forest and plots trees (mX m) silviculture

G&ica 65 None Secondary; shallow dry limestone; 150 m; none

St. Just 1018 0.40 Early secondary; shallow, humid volcanic; 60

(40 x 100) m; selective thinning before study

Cambalache 0.10 Secondary: lower slopes and ridges of “pepino

1. slope 402 (20 x 50) hills.” wet limestone soils; 30 m and 60 m;

2. ridge 463 abandoned agricultural land in mid 1930s

PiGones 0.10 Mangrove reproduction; deep organic

1. Plot A 3789 (31.6 X 31.6) (mangrove) soils; sea level; plot A and plot C

2. Plot c 4098 basal area reduced by 50 percent in 1937-38

3. Plot E 3317 and again in 1949; Plot A thinned to basal area

of 20 mY/ha in 1951, and Plot C to 14 m”/ha; Plot

E kept as control

Toro Negro 245 0.10 Late secondary colorado transition; deep, red,

(20 x 50) acid clay: 930 m; selective thinning in 1947 and

1957

Lower Montane Wet

(Colorado)

Maricao 228 0.10

(20 x 50)

Climax: deep, red, acid clay, 670 m; selective

thinning in 1951

Table 2.- Periodic annual diameter increment (PAI) by crown class for Bucida buceras from

19&+ through 1975 in Gu&ica Forest (Subtropical Dry Forest) on all trees that

survived the entire period

Crown Class 1944-54 1954-75

1944-1975 statistics’ D.b.h. range

Mean CV Stems 1944

____________________cm/yr-______________-----

Dominant 0.20 0.06 0.11

Codominant 0.15 0.04 0.08

Intermediate 0.08 0.02 0.04

Suppressed 0.04 0.02 0.02

Total 0.12 0.04 0.06

*CV = Coefficient of variation.

(%) (No.) (cm)

24 4 8-11

30 15 6-10

63 13 4- 9

94 2 5

53 34 4-11

Subtropical Moist Life Zone

Subtropical Moist Forest occupies 5400 km”

or 58 percent of the island.

St. Just. The St. Just forest is an early

secondary stand that was selectively thinned

before the first measurement. During 2 years of

observation, the number of stems decreased from

2460fha to 1845/ha, and basal area decreased

from 12.2 m2/ha to 10.3 m2/ha (table 3). In both

years, 10 species accounted for 90 percent of the

stems and basal area. Ingrowth and mortality did

not appreciably change species composition.

The PA1 for all 685 stems during the brief 2-

year period of measurement was 0.47 cm/yr, and

ranged from a low of 0.15 cm/yr to a high of 0.91

cm/yr for Buchenavia capitata, a fast growing

species (table 3). The codominant crown class

averaged 0.66 cmfyr, followed by intermediates

at 0.56, dominants at 0.48, and suppressed stems

at 0.40 cm/yr.

The Cambalache Forest. The Cambalache

stand is secondary forest on limestone, which

occupies 800 km2 or 14 percent of the Subtropical

Moist Life Zone. Measurements spanned 26

years.

1. The Lower Slope Forest - In 1950, the 10

most common species accounted for nearly 90

percent of the stems and basal area, and by 1976,

about 80 percent of each (table 4). During the

same period, stems decreased by nearly half

while the basal area increased only slightly.

4
Table 3.- Ranking of species by density and basal area (HA) dominance in St. Jwt Forest (Subtropical Moist Forrat) from 1952 to 19.54

Species 1952 1954

Ingrowth’ Mortality by d.b.h. class,

1952-54 1952-54’ 1952-54 statistics2 D.b.h. range

Stems BA Stems BA Stems BA 5 II) 20 Total Mean CV

(No./ha) (m’/ha) (No./ha) (m2/ha) (No./ha) (m’/ha) _______._... No./ha ________ (cm/yr) (%>)

Inga laurina

Ocotea leucoxylim

Nectandra coriacea

Byrsonima coriacea

Tetragastris balsamifera

Casearia arborea

Miconia prasina

Manilkara bidentata

Hymenaea courbaril

Casearia guianensis

Chrysophyllum argenteum

Andira inermis

u1 Symplocos martinicensis

Zanthoxylum martinicense

Buchrnaria capitata

Pouteria multiflora

Tabebuia heterophylla

Citharexylum fruticosum

Ficus citrifolia

10 remaining species

765 3.70 654 3.91 42

355 1.80 213 0.96 13

245 1.30 176 0.74 13

205 1.40 148 1.01 2

198 0.57 172 0.76 28

125 0.30 64 0.18 11

90 0.19 48 0.11 7

85 0.27 80 0.35

82 1.14 81 1.28 7

48 0.09 42 0.01 2

45 0.12 29 0.10 2

39 0.12 35 0.14 3

38 0.29 20 0.15

22 0.15 12 0.05

18 0.24 15 0.27

15 0.10 13 0.11

13 0.05 8 0.03 -

12 0.06 5 0.01 -

10 0.08 5 0.01

49 0.24 26 0.14 2

62 83

58 84

41 23

17 27

43 11

51 21

46 3

5 -

5 3

8 -

16 2

7 -

2 11

3 5

3

2 -

2 3

2 5

3

12 11

8

13

18

15

-

-

:

2

2

153 0.63 51

155 .38 80

82 .20 105

59 .35 76

54 .58 42

72 .40 82

49 .20 85

_

:

.58 35

.53 78

8 .25 73

18 .40 52

7 .28 99

18 .28 96

10 .15 77

3 .90 38

2 .38 62

5 .25 100

7 .12 0

5 .12 0

25 .40 72

Stems 1952

(No.) (cm)

242 4-16

80 4-19

64 4-22

56 4-20

66 4-20

23 4-10

16 4-10

31 4-13

29 4-45

15 4- 8

11 4-12

13 4-12

8 4-12

4 4-16

6 8-22

5 4-17

3 5- 8

2 4- 7

2 4- 5

9 4-18

Total 2459 12.21 1846 10.32 132 0.26 382 298 65 745 0.47 69 685 4-45

‘Ingrowth refers to stems present in final survey but absent in initial survey; mortality, stems recorded initially but absent in the final survey. Mortality d.b.h. classes increase geometrically from the 5 cm through 20 cm class: 5 cm (4.1-6.5) 10 cm (6614.1) 20 cm (14.2-26.8). Stems which entered the lowest d.b.h. class (i.e. 4.1 cm)

after the initial survey, but died before the final survey, were not tallied.

CV = coefficient of variation.

... -.. .I
Table 4.- Ranking of species by density and basal area (BA) dominance in the Cambalache Slope Forest (Subtropical Moist

Forest)from 1950 to 197’6’

Species 1950 1976

Ingrowth Mortality by d.b.h. class,

1950-76 1950-76

Tetrazygia elaeagnoides

Sabinea florida

Ardisia obovata

Phyllanthus nobilis

Thouinia striata

Coccoloba diversifolia

Cuettarda scabra

Andira inermis

Bursera simaruba

Dipholis salicifolia

Eugenia rhombea

Terebraria resinosa

Cupania americana

Plumeria alba

Montezuma speciosissima

Citharexylum fruticosum

Cordia nitida

Eupatorium portoricense

Clusia rosea

Maytenus elliptica

Xylosma buxifolium

Picramnia pentandra

Allophyllus racemosus

Comocladia glabra

Exothea paniculata

Dendropanax arboreus

11 remaining species

Stems

(No./ha)

760

620

580

430

280

200

190

160

140

130

60

40

40

40

30

30

30

30

20

20

20

20

20

20

20

20

BA Stems BA 5

(my/ha) (i$‘& (m2/ha) (No./ha)(mz/ha)

10 20 Total

___--_-______No,/ha__ . .

3.64

1.43

1.94

1.30

0.63

0.56

0.40

0.49

0.47

0.76

0.14

0.15

0.08

0.07

0.13

0.12

0.06

0.06

0.42

0.12

0.04

0.04

0.03

0.03

0.03

0.03

0.17

20 0.12

490 3.16

40 0.10

300 2.06

270 2.28

100 0.39

190 0.58

110 0.56

30 0.29

100 1.65

30 0.08

80 1.06

40 0.25

10 0.05

10 0.13

10 0.06

20 0.08

120 0.23

30 0.07

110 0.46

50 0.22

30 0.05

50 0.13

-

30 0.07

50 0.24

20 0.03

- -

- -

10

20

30

20

160

20

10

40

120

-

0.02

0.24

0.13

0.18

0.34

0.04

0.02

0.18

10 0.02

10 0.02

140 0.28

20 0.04

-

20 0.03

70 0.78 120 0.37

240

140

250

140

50

100

40

10

90

-

30

20

30

10

30

-

20

10

60

490

110

320

100

10

30

10

40

20

30

30

10

-

-

20

10

10

10

-

-

-

-

-

-

-

10

-

-

--

740

250

570

240

60

130

50

50

110

30

60

10

20

30

20

20

10

30

10

10

-

20

10

-

70

Total 4020 13.34 2280 14.83 810 2.26 1270 1260 20 2550

‘Ingrowth refers to stems present in final survey but absent in initial survey; mortality, stems recorded initially but absent in the

final survey. Mortality d.b.h. classes increase geometrically from the 5 cm through 20 cm class: 5 cm(4.1.6.5) 1Ocm (6.6-14.1),

20 cm (14.2-26.8). Stems which entered the lowest d.b.h. class (i.e. 4.1 cm) after the initial survey, but died before the final

survey, were not tallied.

Ingrowth and mortality resulted in changes in

the dominance ranking: Tetraxygia elaeagnoides,

Ardisia obovata, and Bursera simaruba, all

secondary species, nearly disappeared from the

stand. Sabinea florida, Phyllanthus nobilis, both

present in the original stand, regenerated well.

The PA1 for all stems that survived the short

term from 1950 to 1956 was 0.16 cm/yr.

Dominants grew fastest at 0.26 cm/yr followed by

codominants at 0.22, intermediates at 0.14, and

suppressed stems at 0.08 cm/yr. The PA1 for the

150 stems that survived the entire period of

measurement was 0.14 cm/yr, and ranged from

0.02 to 0.39 cm/yr (table 5).

2. The Ridge Forest - From 1950 to 1976,

the number of stems increased by 10 percent and

the basal area by over 50 percent (table 6). In both

years, the 10 most common species accounted for

over 95 percent of the stems and basal area.

Ingrowth and mortality, however, changed

the dominance ranking: Ardisia obovata, a

previously abundant secondary species, disappeared entirely from the stand, while Coccoloba diversifolia, Dipholis salicifolia,

Terebraria resinosa, Eugenia rhombea, Sabinea

florida, and Cuettarda scabra, major constituents

of the wet limestone forest type, and all present in

the original stand, regenerated well. Bursera

simaruba, Andira inermis, and Tabebuia

heterophylla, generally recognized as secondary

species, regenerated within the stand.

The PA1 for all stems that survived the

1950-56 period was 0.09 cm/yr, with dominants

growing the fastest at 0.17 cm/yr followed by

codominants at 0.11, intermediates at 0.08, and

suppressed stems at 0.03 cm/yr. The PA1 for the

237 trees that survived the entire period of

6
Table 5.- Periodic annual diameter increment (PAI) by species from 1950 to 1976 i n

Cambalache Slope Forest (Subtropical Moist Forest) on all trees that survived the

entire period

Species PAI 1950-76 statistics’ D.b.h. range

1950-56 1956-67 1967-75 Mean C V Stems 1950

_______-----cm/yr_______________---___-___._._. (%) (No.) (cm)

Tetrazygia elaeagnoides 0.20 0.16 0.02 0.12 40 2 7-14

Sabinea florida .18 .14 .09 .13 55 37 4-18

Ardisia obovata .08 .12 .08 .09 - 1 6

Phyllanthus nobilis .19 .12 .14 .14 62 19 4-17

Thouinia striata .22 .19 .16 .19 57 22 5-18

Coccoloba diversifolia .05 .05 .06 .06 108 7 4-11

Guettarda scabra .05 .08 .02 .05 78 14 4- 8

Andira inermis .14 .05 .04 .07 75 11 4-12

Bursera simaruba .oo .12 .I5 .09 50 3 9-11

Dipholis salicifolia .31 .17 .ll .19 58 10 8-20

Terebraria resinosa .24 .47 .40 .39 79 3 5-24

Cupania americana .29 .22 .19 .23 69 2 8-14

Pluvneria alba .13 .15 .05 .12 1 8

Montezuma speciosissima .51 .05 .05 .14 - 1 12

Citharexylum fruticosum .15 .oo .oo .04 1 8

Cordia nitida .lO .lO .oo .07 21 2 6- 7

Clusia rosea .05 .oo .02 .02 - 1 4

Maytenus elliptica .83 .oo .oo .22 1 16

Xylosma buxifolium .ll .ll .ll .ll 69 2 4- 9

Picramnia pentandra .25 .23 .14 .20 52 2 8

Allophyllus racemosus .08 .06 .02 .05 30 2 6

Exothea paniculata .05 .02 .02 .03 1 5

Dendropanax arboreus .22 .19 .09 .16 9 2 9

Ilex nitida .12 .33 .20 .24 - 1 10

Phylanthus nobilia .36 .25 .18 .25 1 12

Zanthoxylum martinicense .28 .20 .12 .20 1 10

Total .18 .13 .lO .14 76 150 4-24

XV = coefficient of variation.

Table 6.- Ranking of species by density and basal area (BA) dominance in Cambalache Ridge Forest (Subtropical Moist

Forest) from 1950 to 1976’

Ingrowth Mortality by d.b.h.

Species 1950 1976 1950-76 class, 1950-76

Stems BA Stems BA

(No./ha) (m:ka) (k$$(m’/ha)

5 10 20 Total

(No./ha) m”/ha) -____________No,/ha ___....______

Coccoloba diversifolia 1040 4.12 1580 7.27 910 2.49 100 260 10 370

Ardisia obovata 950 2.56 - - - - 650 300 - 950

Dipholis salicifolia 710 2.50 810 4.94 230 0.91 90 40 - 130

Terebraria resinosa 680 2.02 810 3.93 250 0.68 70 50 - 120

Eugenia rhornbea 380 0.65 970 2.34 740 1.53 130 20 - 150

Bursera simaruba 190 0.56 140 0.79 60 0.15 70 40 - 110

Sabinea florida 160 0.31 220 0.62 140 0.28 50 30 - 80

Andira inermis 110 0.52 60 0.33 20 0.04 50 20 - 70

Tabebuia heterophylla 100 0.41 50 0.31 10 0.02 40 10 10 60

Citharexylum fruticosum 90 0.15 40 0.08 20 0.04 60 10 - 70

Guettarda scabra 80 0.13 190 0.40 130 0.27 20 - - 20

Tetrazigia elaegnoides 30 0.10 - 10 20 - 30

14 remaining species 50 0.11 250 0.66 220 0.53 - 20 - 20

Total 4570 14.14 5120 21.67 2730 6.94 1340 820 20 2180

‘Ingrowth refers to stems present in final survey but absent in initial survey; mortality, stems recorded initially but absent in the

final survey. Mortality d.b.h. classes increase geometrically from the 5 cm through 20 cm class: 5 cm (4.1-6.5) 1Ocm (6.6-14.1)

20 cm (14.2-26.8). Stems which entered the lowest d.b.h. class (i.e. 4.1 cm) after the initial survey, but died before the final

survey, were not tallied.

7
Table 7.- Periodic annual diameter increment (PAI) by species from 1950 to 1976 in

Cambalache Ridge Forest (Subtropical Moist Forest) on all trees that survived the

entire period

D.b.h.

Species PA1 1950-X statistics’ range

1950-56 195667 1967-75 Mean CV Stems 1950

_______ cm/yr________-____________ (%) (No.) ..... ......_.. (cm)

Coccoloba dirersifolia 0.16 0.09 0.07 0.10 72 67 4-13

Dipholis salicijolia .ll .ll .07 .lO 74 58 4-14

Terebraria resinosa .09 .09 .06 .08 71 56 4-12

Eugenia rhombeu .06 .09 .05 .07 45 23 4- 6

Rursera simaruba .07 .14 .12 .12 69 8 4-10

Sabinea florida .13 .09 .07 .09 46 8 4- 6

Andira inermis .02 .Ol .oo .Ol 148 4 5-15

Tabebuia heterophylla .08 .14 .14 .13 84 4 5- 8

Citharexylum fruticosum .oo .05 .02 .03 52 2 4- 5

Guettarda scabra .05 .05 .oo .03 100 6 4- 5

Myrcia leptoclada .13 .15 .lO .12 - 1 6

Picramnia pentandra .08 .20 .18 .17 1 5

Adelia ricinclla .05 .oo .oo .Ol 1 5

Total .ll .lO .07 .09 74 237 4-15

CV = the coefficient of variation.

Table 8.- Ranking ofspecies bydensityand basal area (BA) dominancrforall treesfrom 193x through 1975on plotsA, C. and E

in PiEorws Ebrrst

Plot Species 1938 1945 1949’ 1951’ 1955 1975

Stems BA Stems BA Stems BA Stems BA Stems BA Stems BA

(No/ha) (n?/ha) (No/ha) (n?/ha) (No/ha) (d/ha) (No./ha) (d/ha) (No./ha) (m2/ha) (No./ha) (mYha)

A Laguncularia racemosa - 26458 18.55 23125 29.73 72 0.61 445 3.67 1285 17.12

Aricennia nitida - 1300 2.43 1198 4.18 322 2.80 438 5.13 395 6.76

Total 38920 19.72 27758 20.98 24322 33.91 394 3.41 882 8.80 1680 23.88

C Laguncularia racrmosa - 39450 20.13 26460 28.79 52 0.38 585 3.21 1448 22.01

Aricennia nit ida - 1720 3.42 958 4.91 292 2.96 320 4.20 322 6.68

Total 42096 15.15 40720 23.55 27418 33.70 344 3.34 905 7.41 1770 28.69

E Laguncularia racencosa - 31615 26.38 22178 30.07 178 1.32 458 3.85 1235 18.04

ATicennia nitida - - 698 2.73 435 3.88 395 4.65 405 6.57 260 5.83

Total 34092 18.78 32313 29.11 22613 33.95 573 5.97 863 10.42 1495 23.87

‘The apparent discrepancy between the 1949 and 1951 entries is due to a change in sampling procedure. In 1949, all stems were

measured: in 1951, only stems > 9.1 cm.

measurement was also 0.09 cm/yr, and ranged

from 0.01 to 0.17 cm/yr (table 7).

The PA1 for all surviving stems on the slope

exceeded that on the ridge. Also, the PAI’s of each

crown class were higher on the slope than the

ridge, and in general, individual species grew

faster on the slope. The exceptions were Coccoloba

diversifolia and Bursera simaruba (tables 5 and

7).

Previously reported PAI’s also varied by site.

Two hundred codominant trees of several species,

selected at random, on both lower slope and

summit, averaged 0.30 and 0.15 cm/yr respectively, (U.S. Dep. Agric. For. Serv. 1954).

Pinones Mangrove Forest. Originally,

mangroves covered about 27,000 ha in the

Subtropical Moist and Subtropical Dry Life

Zones of which slightly over 3000 ha remain

today.

In 1937, three plots in the Piiiones Forest

were cleared (table 1). Regeneration after clearing yielded about 40,000 stems/ha (table 8). In

1945 and 1949, less than 5 percent of the stems

were Avicennia although the basal area ranged

from 10 to 15 percent of the stand. In 1951, after a

change in sampling procedure (table 8), 70

percent or more of the total stems > 9.1 cm, as

well as 80 percent or more of the basal area,

8
belonged to A’vicennia. By 1975, Laguncularia

once again dominated the stand in stem numbers

and basal area, although Avicennia was well

represented among the larger stems.

The PA1 of Avicennia exceeded that of

Laguncularia from 1938 to 1955 (table 9) but this

trend was reversed from 1955 through 1975. An

overall estimate of PAI for both species on all

three plots over the 37-year duration of the study

is 0.45 cm/yr.

Previously reported mean annual d.b.h.

increments (MAI) at Pinones are high. In a

sapling stand, dominants averaged 0.82 cmfyr,

codominants 0.49, intermediates 0.32, and suppressed stems 0.16 cm/yr during 4 years; in a pole

stand these averages were 0.46, 0.40, 0.24, and

0.17, respectively, during 3 years (Wadsworth

1959).

Table 9.- Mrn~ crz~unl diamrtrr increment by species from

193X through 1975 in PiEones Forest on trees thut

surl,ic*ed the entire period

Plot Species

Mean annual diameter Trees’

increment (No.1

1938 1951 1955 1938

-51 -55 -65 -75

.__.__.. _ __._. cm/y~________-___--

A La,q~~c&-icr rewmosu 0.77 0.42 0.30 0.48 6

A c?cwznia nitida 0.79 0.63 0.13 0.42 1 4

Subtotal 0.78 0.57 0.18 0.44 2 0

C Laguncularia racemosa 0.74 0.62 0.38 0.54 5

A~~icennia nifidw 0.85 0.69 0.14 0.46 17

Subtotal 0.82 0.67 0.19 0.48 22

E Laguncularia racemosa 0.71 0.36 0.33 0.47 8

A ricennia nitida 0.97 0.55 0.20 0.51 4

Subtotal 0.80 0.42 0.28 0.48 12

Total 0.80 0.58 0.21 0.46 54

‘More trees survived, but only those trees that could be

positively identified by tags were used.

Lower Montane Wet Life Zone

This Life Zone, scattered in the summits of

the Cordillera Central and Luquillo Mountains,

occupies 110 km2 or about 1 percent of the island.

Toro Negro. The late secondary colorado forest at Toro Negro was harvested for fence posts in

1947, and had all stems 6 12 cm removed in

1957.

During the 24-year period of measurement,

the number of stems decreased by about 10

percent while the basal area increased by over 35

percent (table 12). In 1951 and 1975, the 10 most

common species accounted for over 70 percent of

the stems and 75 percent of the basal area.

Ingrowth, mortality, and the effects of selective

thinning had an effect on composition: Drypetes

alba, a persistent understory climax species,

reproduced well. Pseudolmedia spuria, Eugenia

jumbos, Cecropia peltata, Rapanea ferruginea

and Casearia sylvestris, all secondary species, as

well as nine additional species, regenerated

within the stand in limited numbers.

The PA1 for all stems that survived the 1951-

56 interval was 0.10 cm/yr, with only slight

differences among crown classes. Codominants

grew the fastest at 0.15 cm/yr followed by

dominants at 0.11, suppressed at 0.09, and

intermediate stems at 0.08 cm/yr.

During the 24-year period of measurement,

the number of stems decreased by 30 percent

The PA1 for those stems that survived the

while basal area increased only slightly (tabie 10).

entire period of measurement was 0.12 cm/yr and

In 1951 and 1975, over 90 percent of the stems and

ranged from 0.03 cm/yr for Ocotea leucoxylon to

over 85 percent of the basal area belonged to only

0.58 cm/yr for Ficus citrifolia, the strangler fig

(table 13).

10 species. During that same period, ingrowth,

mortality, and selective thinning resulted in

compositional changes: Solanum rugosum,

Cecropia peltata, Policourea riparia, and

Miconia prasina, secondary species that invaded

the plot after thinning, largely disappeared;

Myrcia splendens, Byrsonima wadsworthii,

Cuatteria blanii, and Ocotea leucoxylon, all

climax species common in the understory, were

probably removed in the 1957 thinning of small

stems; and, Micropholis garciniaefolia,,

Dacryodes excelsa, both climax overstory species,

and Casearia arborea, a common understory tree

in both secondary and climax forests, reproduced

well within the stand.

The PA1 for all stems that survived the 1951-

56 interval was 0.24 cm/yr with codominants

growing the fastest at 0.32 cm/yr followed by the

intermediates at 0.29, the dominants at 0.25, and

the suppressed stems at 0.11 cm/yr. The PAI for

the 109 stems that survived the entire period of

measurement was 0.15 cm/yr, and ranged from

0.05 to 0.50 cm/yr (table 11).

Maricao Serpen,tine Forest. Serpentine soils

occupy 65 km2 on the island, a small part of which

is in the Lower Montane Wet Life Zone. In 1951,

suppressed stems were removed on the Maricao

plot to provide growing space for remaining

trees.

9
Table lO.-Ranking of species by density and basal area (BA) dominance in Toro Negro Forest frm 1951 to 1976’

Species

Ingrowth

1951 1975 1951-75

Stems BA Stems BA Stems BA

(No./ha)(m2/ha)(No./ha) (mz/ha) (No./ha) (m2/ha)

Mortality by d.b.h. class, 1951-75

5 10 20 40 Total

______________________No./ha___________________

Micropholis garciniaefolia

Solanum rugosum

Cecropia peltata

Eugenia stahlii

Dacryodes excelsa

Myrcia splendens

Matayba dominguensis

Rapanea ferruginea

Calycogonium squamulosum

Byrsonima wadsworthii

Guatteria blanii

Casearia arborea

Didymopanax mortoton i

Ocotea leucoxylon

Cordia sulcata

Palicourea riparia

Miconia prasina

Cedrela odorata

Buchenavia capitata

1050 6.32 1010 10.41 250

390 1.06 10 0.15 10

260 2.25 20 0.28 -

170 1.26 90 1.44 10

120 5.32 110 5.99 -

100 0.50 - - -

40 2.14 30 1.63 -

40 0.11 20 0.49 -

30 0.89 - -

30 0.56 - -

30 0.31 - -

30 0.05 180 0.68 170

20 0.26 20 0.46 10

20 0.07 - -

20 0.05 10 0.10 -

20 0.03 - -

20 0.03 50 0.33 50

20 0.03 10 0.13 -

10 2.06 10 2.47 -

0.48

0.15

0.01

-

-

-

-

-

-

-

0.58

0.20

-

0.57

160

170

40

50

10

30

-

-

10

-

-

-

-

10

-

20

10

10

-

10

120 10 290

220 - - 390

110 90 - 240

40 - - 90

- 10

70 - 100

-

- 10 10

20 - - 20

20 - - 30

20 10 - 30

30 - - 30

20 - - 20

- 10 - 10

10 - - 20

10 - - 10

- 20

10 - - 20

- 10

-

8 remaining species 30 0.10 120 1.01 100 - 10

Total 2450 23.40 1690 25.57 600 2.32 530 700 120 10 1360

‘Ingrowth refers to stems present in final survey but absent in initial survey; mortality, stems recorded initially but absent in the

final survey. Mortality d.b.h. classes increase geometrically from the 5 cm through 40cm class: 5 cm (4.1-6.5) 10 cm (6.6.14.1),

20 cm (14.2-26.8),40cm(26.9-54.6). Stems which entered the lowest d.b.h. class (i.e. 4.1 cm) after the initial survey, but died

before the final survey, were not tallied.

Table 1 l.- Periodic annual diameter increment (PAI) by species from 1951 through 1976 in Toro

Negro Forest on all trees that survived the entire period

Species PA1 1951-76 statistics’ D.b.h. range

1951-56 1956-62 1962-67 1967-75 Mean C V Stems 1951

_......_______ _______cm/yr_______________----------_- (%) (No.) (cm)

Micropholis garciniaefolia 0.19 0.18 0.11 0.08 0.14 51 76 5-23

Cecropia peltata .30 .24 .04 .I4 .I9 48 2 5-10

Eugenia stahlii .24 .17 .02 .ll .12 79 8 5-23

Dacryodes excelsa, .12 .08 .lO .09 .09 126 11 10-48

Matayba dominguensis .32 .28 .22 .16 .25 76 3 lo-36

Rapanea femuginea 82 .57 .28 .26 .50 18 2 5

Casearia arborea .55 .40 .22 .04 .27 - 1 5

Didymopanax morototoni .80 .57 .31 .38 .50 - 1 5

Cordia sulcata .70 .31 .04 .oo .23 - 1 5

Cedrela odorata .65 .44 .09 .34 .37 - 1 5

Buchenavia capitata .lO .18 .31 .20 .20 - 1 51

&area ramiflora .oo .40 .oo .04 .11 - 1 8

Ocotea moschata .05 .09 .04 .04 .05 - 1 8

Total .21 .19 .11 .09 .15 71 109 5-51

CV = coefficient of variation.

10
Table 12.-Ranking of species by density and basal area (BA) dominance in Maricao Forest from 1951 to 1975

Species

Ingrowth Mortality by d.b.h.

1951 1975 1951-75 class, 1951-75

Stems BA Stems BA Stems BA 5 10 Total

(No./ha) (m2/ha) (No./ha) (m2/ha) (No./ha) (m2/ha) _____----___No./ha__-______________

Microphoiis chrysophylloides 280

Terebraria resinosa 230

Linociera dorninguensis 230

Homalium racemosum 190

Tabebuia schumanniana 180

Eugenia stahlii 130

Myrcia splendens 120

Matayba dominguensis 120

Cordia borinquensis 50

Pluvneria alba 40

Guettarda ovalifolia 40

Myrtaceae 30

Guatteria blainii 30

Ocotea leucoxylon 30

Myrcia deflexa 30

Micropholis garciniaefolia 20

Coccoloba swartzii 20

Lauraceae 20

Urypetes glauca 20

Ficus citrifolia 10

Drypetes alba 10

24 remaining species 120

2.72

1.62

1.31

0.70

0.74

1.10

0.68

0.47

0.15

0.16

0.14

0.17

0.13

0.07

0.06

0.27

0.12

0.05

0.04

0.34

0.06

200

140

110

170

130

100

80

90

20

40

40

30

10

50

40

20

20

10

10

130

3.00 30 0.05 40 70 110

1.78 10 0.03 30 70 100

1.50 - 30 90 120

1.29 30 0.06 20 30 50

0.71 10 0.02 20 40 60

1.40 - 10 20 30

0.93 20 0.08 40 20 60

0.76 10 0.03 20 20 40

0.11 - 20 10 30

0.35 - - -

0.08 40 0.08 30 10 40

0.39 - - -

0.04 - 20 20

0.12 20 0.03 - -

0.18 20 0.03 10 10

0.38 - - -

0.27 - - -

0.02 10 - 10

-

-

20 20

0.95 - - -

0.34 130 0.34 - 10 10

0.39 280 1.06 230 0.59 60 10 70

Total 1950 11.49 1720 15.66 550 1.34 380 400 780

‘Ingrowth refers to stems present in final survey but absent in initial survey; mortality, stems recorded initially but absent in the

final survey. Mortality d.b.h. classes increase geometrically from the 5 cm to 10 cm class: 5 cm (4.1-6.5) 10 cm (6.6-14.1). Stems

which entered the lowest d.b.h. class (i.e. 4.1 cm) after the initial survey, but died before the final survey, were not tallied.

Both plots in the Lower Montane Wet Forest

share species, but Maricao contains some that are

also found in the drier coastal forests: Terebraria

resinosa, Tabebuia schumanniana, Guettarda

ovalifolia, Ocotea cuneata, Coccoloba sintenisii,

Eugenia monticola, and Cassipourea elliptica.

Species Diversity on Plots

The number of species per plot ranged from a

low of two in the Piiiones mangrove forest to a

high of 39 at the end of the study in the Maricao

serpentine forest (table 14). In the mangrove

forest, the Shannon-Weiner species diversity

index was below 1.0 and in the Maricao serpentine forest, above 4.0; other forests were intermediate in both species numbers and diversity

(table 14).

Increment

DISCUSSION

The reported PAI’s corroborate previous

studies in Puerto Rico and are similar to those of

11

the temperate zone. For example, Acer

saccharum, Quercus rubra, Pinus strobes, and P.

taeda, common species in the United States,

average from 0.15 too.50 cm/yr (U.S. Dep. Agric.

For. Serv. 1965), even though the growing season

ranges from under 200 to 300 daysjyr. Furthermore, Jordan (1971) suggests that the rate of

woody production in intermediate age stands on

mesic sites, regardless of latitude, is similar.

The fastest PAI’s for all measured stems

were found in St. Just and Piiiones forests. St.

Just is a selectively thinned early secondary stand

measured over 2 years. As the stand develops,

competition among stems will probably reduce

PA1 considerably. The Piiiones stands are

mangrove regeneration plots that were measured

after clearing. An earlier study that summarized

the development of the stands from 1938 to 1953

found that the control plot grew rapidly with

stems equal in form and quality to the crop trees

of the thinned plots (U.S. Dep, Agric. For. Serv.

1954). In 1975, plot C had from 5 to 18 percent

more stems, and about 20 percent more basal area
Table 13.- Periodic annual diameter increment (PAI) by species from 1951 through 197'5 in

Maricao Forest on all trees that survived the entire period

Species PAI 1951-75 statistics’ D.b.h. range

1951-56 1956-67 1967-75 Mean CV Stems 1951

---------_-______-_cm/yr-_-----___---___ (%I (No.1 (cm)

Micropholis chrysophylloides 0.09 0.10 0.12 0.11

Terebraria reainosa .13 .09 .09 .lO

Linocirra dominguensis .17 .16 .16 .16

Homalium racemosum .12 .12 ..20 .15

Tabebuia schumanniana .05 .08 .lO .08

Eugenia stahlii .12 .09 .08 .09

Myrcia splendrns .lO .lO .ll .lO

Matayba dominguensis .12 .13 .12 .12

Cordza borinyuensis .08 .06 .02 .05

Plunwria alba .06 .07 .23 .15

Myrtacear .16 .18 .17 .17

Guattrria blainii .oo .15 .09 .09

Ocotea leucoxylon .03 .02 .05 .03

Myrcio deflexa .38 .20 .15 .22

Micropholis garciniaefolia .07 .ll .ll .lO

Coccoloba war&ii .lO .Ot( .ll .lO

Laumceae .05 .02 .06 .04

Ficus citrifolia .50 .64 .55 .58

Buchenal>ia capitata .43 .39 .31 .38

Hrlicterrs jamaicrnsis .24 .24 .25 .24

Guapira fragans .05 .05 .03 .04

Ardisia oboeata .oo .05 .18 .07

54

63

56

57

85

43

45

92

42

33

61

-

115

23

17

-

17 5-25

13 5-18

11 5-12

14 5-10

12 5-12

10 5-18

6 5-18

8 5-10

2 5- 8

4 5-10

3 8-10

1 5

3 5

1 5

2 13

2 12

1 4

1 20

1 8

1 8

1 5

1 8

Total .ll .ll .13 .12 75 115 5-25

‘CV = coefficient of variation.

than either A or E, which are remarkably similar Table 14.- Total numbers of species and Shannon-Weiner

(table 8). The effects of selective thinning have not diversity indices (H) for several forests in Puerto

been fully tested in this experiment. Rico

The Guanica plot has the lowest rate of PAI.

Since only one species was measured, generalities

about the forest are difficult. It may be

hypothesized, however, that since Bucida is one of

the largest stems in the Guanica Forest, its PA1

probably exceeds the average for all species. The

remaining plots, Cambalache slope and ridge,

Toro Negro, and Maricao, are uniform in size, of

nearly equal duration of measurement, and have

PAI’s intermediate between those of St. Just and

Guanica.

Public forests No. of Species H’

and plots Beginning End Beginning End

St. Just 29 25 3.42 3.28

Cambalache

1. slope 34 33 3.80 3.96

2. ridge 17 22 3.05 2.91

Pihones 2 2 0.15 0.67

Toro Negro 22 20 2.93 2.38

Mariacao 31 39 4.06 4.32 c

‘H = -i (pi) (log2 pi).

i=l

Comparisons among stands are difficult

because of confounding due to many factors

(species, soils, seral stages, age of stems,

silviculture, and different durations of measurement), yet certain trends seem apparent. Early

secondary forests represented by St. Just and

Pinones, are comparatively fast growing. The

PA1 on surviving stems in secondary forests that

have been measured over a long period shows a

gradual decline probably due to closing of the

stand and/or senescence. On Cambalache slope,

for example, suppressed stems increased in

relative abundance from 20 to 50 percent, on

Cambalache ridge from 10 to 20 percent, and at

Maricao from 5 to 15 percent: at Toro Negro, 25

percent of the stems were suppressed throughout

the period of measurement.

In the wet limestone hills represented by

Cambalache, exposed summits have lower PAI’s

than the slopes, probably because of moisture

stress. With ascent of the mountains, PAI’s

decrease. Saturated soils and reduced solar

radiation have been suggested as causes

12
(Wadsworth 1952). In the dry limestone forest,

lack of moisture again hinders tree growth (Lug0

et al. 1979).

Crown classes appear useful as indicators of

growth potential. On limestone soils, PA1 by

crown class for all stems, regardless of species

exhibits the pattern D > CD > I > S, probably

reflecting the competitive advantage of larger

stems in an environment where water is limiting.

On mesic sites, the pattern CD = D = I > S

prevails. This pattern does not corroborate

previous work in the Subtropical Wet Forest of

Luquillo (Crow and Weaver 1977) where D > CD

>I > S was most common. The Luquillo study,

however, dealt with thinned “crop trees” by

species, whereas this study considered all stems

by plot.

Although exceptional rates of growth have

been reported for many plantations of exotics in

the tropics, PAI’s in excess of 1 cm/yr are rare in

undisturbed tropical forests (Fernando 1962,

Keay 1961, Crow and Weaver 1977). These

modest growth rates have been attributed to the

energetic costs of plant maintenance necessary

for trees to survive in a highly competitive

environment (Odum and Jordan 1970, Kira 1969).

Because controls were missing, the selective

thinnings-practiced in St. Just, Toro Negro, and

Maricao do not lead to any firm conclusions about

their effect on the residual stands. Nor do the

PAI’s reported herein reflect the growth potential of the stands under continuous management.

First, the thinnings in Toro Negro and Maricao

were conducted in stands that were late secondary or climax. Crown growth must be encouraged early in stand development since “big

trees are unable to respond to silvicultural

treatment much if at all” (Whitmore 1975).

Second, as mentioned previously, from 15 to 50

percent of the stems in Cambalache and both

montane forests were overtopped. Increment in

the suppressed crown class, regardless of environment, is slow in comparison to dominant,

codominant, and most intermediate stems.

Species Diversity

In Puerto Rico, four species dominate

mangrove soils: Rhixophora mangle, largely

climited to the seaward or estuarine fringe;

Conorcarpus erecta, at the landward edge; and

Laguncularia racemosa and Avicennia nitida, in

the central portion, or basin (Wadsworth 1959,

Lugo and Snedaker 1974). The latter two species

probably constitute 95 percent of the stems in the

Piiiones Forest.

In the Cambalache Forest, species numbers

and diversity indices are greater on slopes than on

ridges. This reflects the severe stress caused by

well-drained limestone soils on the exposed

hilltops (table 14). The comparatively low values

for St. Just and Toro Negro are probably due to

the selective removal of certain species during the

improvement cuttings.

In the colorado type, which corresponds to

the mature vegetation of the zonal association

within the Subtropical Wet Life Zone, 57 species

have been identified (Wadsworth 1951). The high

number of species and high species diversity

index on the Maricao plot (table 14) could reflect

the well-drained and well-aerated nature of these

serpentine soils (Tschirley et al. 1970). The

sharing of species between the Cambalache and

Maricao forests supports this hypothesis.

Investigations of species diversity within the

southern mixed hardwoods and mixed

mesophytic forest of the United States yielded

indices from 2.0 through 3.4, with most values

below 3.0 (Monk 1967). Within the tropics, Jin-,

Bee (1960) reported that the mangrove forests of

the Malay peninsula contained 17 principal

species, and that a typical 0.4 ha patch of lowland

rain forest would contain about 200 treesof about

100 species. Although direct comparisons are

difficult to make, the forests of Puerto Rico

apparently are intermediate in diversity between

continental temperate and continental tropical

forests.

LITERATURE CITED

Beard, J.S.

1944. Climax vegetation in tropical America.

Ecology 25:127-158.

Briscoe, C.B.

1962. Tree diameter growth in the dry

limestone hills. Trop. For. Notes No. 12, 2p.

U. S. Dep. Agric. For. Serv., Inst. Trop. For.,

Rio Piedras, Puerto Rico.

Calvesbert, R.J.

1970. Climate of Puerto Rico and U. S. Virgin

Islands. Publ. No. 52. U. S. Dep. Comm.,

Washington, D.C. 29p.

Crow, T.R., and P.L. Weaver.

1977. Tree growth in a moist tropical forest of

Puerto Rico. U.S. Dep. Agric. For. Serv. Res.

Pap. ITF-22, 17~. Inst. Trop. For., Rio

Piedras, Puerto Rico.

13
Dansereau, P.

1966. Studies on the vegetation of Puerto

Rico, 1. Description and integration of the

plant-communities. Spec. Publ. No. 1 Univ.

Puerto Rico, Inst. Caribb. Sci., Mayaguez,

Puerto Rico. 287~.

Ewel, J.J., and J.L. Whitmore.

1973. The ecological life zones of Puerto Rico

and the U.S. Virgin Islands. U.S. Dep. Agric.

For. Serv. Res. Pap. ITF-18, 72~. Inst. Trop.

For., Rio Piedras, Puerto Rico.

Fernando, D.F.S.

1962. Computation of girth increment rates

for dry zone species-satin, ebony, mila and

palu. Ceylon For. 5:191-192.

Gleason, H.A., and M.T. Cook.

1927. Plant ecology of Porto Rico. In:

Scientific survey of Puerto Rico and the

Virgin Islands 7(1-2):1-173. N.Y. Acad. Sci.,

New York.

Holdridge, L.R.

1947. Determination of world plant formations from simple climatic data. Science

105:367-368.

Holdridge, L.R.

1967. Life Zone ecology. Rev. ed. 206~. Trop.

Sci. Cent., San Jose, Costa Rica.

Jin-bee, Oi.

1960. The nature and distribution of the

natural vegetation of Malaya. Pac. Viewpoint 1(2):183-204.

Jordan, C.F.

1971. Productivity of a tropical forest and its

relation to a world pattern of energy storage.

J. Ecol. 59:127-142.

Keay, R.W.J.

1961. Increment in the Okomu Forest

Reserve, Benin. Nigerian For. Inf. Bull., No.

11. 34p.

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14
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15

Library Card

WEAVER, PETER L.

1979. Tree growth in several tropical forests of Puerto Rico.

U.S. Dep. Agric. For. Serv. Res. Pap. SO-152 15~. South.

For. Exp. Stn. New Orleans, La.

Presents periodic annual diameter increment for about 2400

stems > 4.1 cm d.b.h., which were studied for periods ranging

from 2 to 30 years. Over 100 tree species and three Life Zones

on the island are represented.

Additional keywords: diameter increment, species composition, basal area, ingrowth, mortality, species diversity.