United States

Department of

Agriculture

Forest Service

Southern Forest

Experiment Station

Research Note

SO-358

December 1989

The Luquillo Experimental Forest Arboretum

John K. Francis

SUMMARY

Since 1960, various tree species, mostly exotics with

productive potential, have been planted in small blocks

within a tract of subsistence farmland. The site, located

on the lower western slope of the Luquillo Experimental

Forest in Puerto Rico, has become a unique arboretum.

The plantings were weeded and maintained for several

years, but later were neglected. A complete inventory

and measurements have been made now that some of

the species have reached harvest size. Sixty-eight species, some represented by multiple subspecies or provenances, still survive. Fourteen species have died out

completely. Promising species are identified for timber

production or for ornamental use in high rainfall areas of

Puerto Rico. Statistics given for plots of each species

are: average height and diameter for trees on the plot,

height and diameter of the tallest tree, percent survival,

and seed and seedling production.

INTRODUCTION AND METHODS

Many native Puerto Rican trees, while producing wood

of superior quality, often grow slowly. Some species lack

sufficient populations to justify development of markets

and management methods. For these reasons, many

useful exotic species have been imported and tested for

adaptability and growth potential. A number of adaptability tests were established in Puerto Rico. One site of

such tests is the Luquillo Experimental Forest arboretum, which is the source of the data in this study. In

addition to comparing a large number of species in a

single area, the arboretum is used for ecological research, seed collection, demonstration, and instruction.

The arboretum is about 625 m above sea level and lies

on the western flank of El Toro Peak. Rainfall is approximately 3000 mm per year. Of 10 soil samples removed

from the upper 10 cm of mineral soil, all were clays with

a mean pH of 4.7 and an organic matter content of 8.6

percent. The area was cleared for subsistence farming in

the 1920’s and later was partially replanted with trees

and allowed to grow up in brush. In the pristine state, the

area probably straddled the transition between the

Tabonuco (Dacryodes excelsa) Forest and Palo Colorado (Cyri//a racemiflora) Forest.

Although a small test plantation established in 1959

was incorporated into the arboretum, the main planting

project commenced in 1960 and continued through

1963. Since then, several plots have been planted with

seeds from novel species. Incomplete records have not

permitted the sources (provenances) of the seeds to be

identified in all cases. The seeds were germinated in

trays, and the resulting seedlings were transplanted into

plastic nursery bags where they grew until large enough

for planting in the field. Sites were prepared by slashing

trees and brush, and “coronas” (areas 1 meter in diameter that were scalped and tilled) were prepared at the

plantation spacing of 3 by 3 m. Plots consisted of 49

trees (7 by 7 trees) when sufficient seedlings were available. After seedlings were planted in the coronas, weeds

were controlled by a combination of hoeing, chemical

spraying, and lopping until the seedlings grew above the

competition, 2 to 6 years later. Replacements for the

seedlings that failed were planted during the first year for

a few of the plots when extra seedlings were available.

A map of the area with the plot positions indicated is

presented in figure 1. Early measurements were performed on some of the plots, but no complete inventory

and measurement work was done until 1987. At that

Southern Forest Experiment Station/l-10210 U.S. Postal Services Bldg., 701 Loyola Avenue, New Orleans, La. 70113

Forest Service, U.S. Department of Agriculture.

Serving Alabama, Arkansas, Louisiana, Mississippi, E. Oklahoma, Tennessee, E. Texas, Puerto Rico, U.S. Virgin Islands

1
Figure l.- Map of plot locations in the Luquillo Experimental Forest arboretum, Cianaga Alta, Puerto Rico.

John K. Francis is research forester at the Institute of Tropical Forestry, Southern Forest Experiment Station, USDA Forest Service, Rio Piedras,

Puerto Rico, in cooperation with the University of Puerto Rico, Rio Piedras, PR.

2
time, tree height was measured with an altimeter and

diameter at breast height (d.b.h.) was measured with a

diameter tape. Clear bole length (the distance between

the groundline and the first branch) was also measured.

Survival, seed production, and presence of natural reproduction in the understory were noted.

RESULTS AND DISCUSSION

The surviving species with their respective provenances are listed in alphabetical order in table 1, which

also shows age, height, d. b. h., survival, and presence

of reproduction for each species. Some results tended to

support planting preferences already evident in Puerto

Rico. One of the best performers, Pinus caribaea var.

hondurensis, is also one of the most widely used species

for forest plantations. Swietenia macrophyla and Hibiscus elafus performed reasonably well in the arboretum

and are both widely planted in Puerto Rican forests.

Agathis robusta, a valuable softwood planted to a limited

extent in Puerto Rican forests, has shown steady diameter growth.

Several other species have shown enough promise to

be recommended for planting or further testing. Two

African species that are recommended for pilot plantations are Maesopsis eminii and Terminalia ivorensis.

Both species grow rapidly, are self-pruning, and reproduce naturally both in the arboretum and on other test

sites across Puerto Rico. In fact, one individual that regenerated naturally from the Maesopsis plot is now approaching a 40-cm d.b.h. Both species produce a

medium-density wood suitable for construction, paneling, furniture parts, and pulp. The wood of Maesopsis is

light brown and that of Terminalia is a lustrous yellow.

Pinus caribaea var. caribaea is not presently used in

planting operations in Puerto Rico, but could be used as

a substitute for P. caribaea var. hondurensis, especially

on dry and alkaline soils. It has better form and wood

quality than P. caribaea var. hondurensis. Pinus oocarpa

performed well in the arboretum and in other tests and

compares favorably with P. caribaea var. hondurensis.

So far this species has not been consistently better and

probably will not replace P. caribaea var. hondurensis.

The low altitude seed source of P. chiapensis grew well

in the arboretum, but has not performed well at lower

elevations. It might find limited use as a windbreak or

shade tree at higher elevations in Puerto Rico.

All three of the Khaya (African mahogany) species

compared well with Swiefenia macrophyla. Khaya grandifolia grew the fastest, had the best form, and has

produced seeds. Seeds from both K. nyasica and K.

senegalensis are available from other Puerto Rican

sources. Cordia alliodora is a widely occurring native

species that performed fairly well in the arboretum plot.

Although widely planted in Central America, this Cordia

has not been used to any great extent in Puerto Rican

plantations. Fraxinus uhdei has shown respectable

growth in the arboretum plot, although the commercial

bole section in somewhat short. Seeds can be obtained

from other Puerto Rican sites. Fraxinus wood is valuable

for furniture, trim, and tool handles.

Eucalyptus grandis and E. saligna in these plots are

the tallest trees currently known in Puerto Rico. These

species and E. robusta have great wood-producing potential. Unfortunately, except for limited use as treated

posts, building poles, and rough lumber, the wood of

Eucalyptus is little used in Puerto Rico. If future markets

for fuel or other biomass develop, one or more of these

species would be an excellent choice for planting on

mountain sites. Three fast-growing ,species with lowdensity wood are Anthocephalus chinensis, Aleurifis

moluccana (fig. 2), and Hemandia Sonora. All produce

seeds, but conditions have favored reproduction of only

the latter two. None of the three are currently marketable

in Puerto Rico. The 22 timber species mentioned so far

are compared in box plots (fig. 3) using the index: d.b.h.

squared multiplied by height-which normally is highly

correlated with tree volume.

Several of the planted species demonstrated potential

as ornamentals and shade trees. Pterocarpus indicus

forma echinatus (fig. 4) grows faster than both

P. macrocarpus and P. indicus, which are currently popular shade trees in urban areas. It has the same deep

green foliage and pleasing form. Abundant reproduction

was observed nearby. Clitoris racimosa is a small- to

medium-sized tree with pleasing form, color, and attractive violet blossoms; it has also produced many

seedlings. Callitris glauca and C. intertropica are similar

conifers with blue-green foliage; these trees both have

potential as ornamentals.

Fourteen species suffered loo-percent mortality.

They are listed in table 2. The specific causes of mortality were not known or recorded. Because the plots were

weeded for up to 6 years, it seems reasonable to assume that the primary cause of failure was poor adaptation to the soil or local climate and not competition. It

should not be concluded that plantings of the same seed

sources on different sites in Puerto Rico would also fail.

Eucalyptus deglupta, Swietenia mahagoni and Tectona

grandis are growing successfully on other (drier) sites in

Puerto Rico. One additional species, Cecropia peltata,

was planted but not evaluated. This short-lived species

is ubiquitous in openings and low-basal area plots in the

area. It could not be determined whether the few Cecropia peltata trees present were the original planted

trees or volunteers.

Since the measurements for this document were

made, a thinning to remove suppressed, deseased, and

malformed trees was conducted, and the entire area was

weeded. Seven new species have been planted recently

(table 3) and others will be established as time and resources permit. One of those recently planted, Goetzia

elegous, is endangered and has disappeared entirely

from the Luquillo Mountains. The arboretum should be

considered as an excellent site to plant rare species that

need preservation and protection.

3
Table 1 .--Species survival, growth, and reproduction in the Luquillo Experimental Forest arboretum, located in Puerto Rico

Plot average + standard error’ Tallest tree

Plot

no. Species (seed source) Age Height D.b.h. CBL Height D.b.h Survival

Seeds and

reproduction

present

8 5

258

1 6

22A

2 3

8 2

7 0

2 6

1 4

1 1

34A

348

7 1

75A

3 1

35D

21A

1 5

25A

3 2

3 8

6 0

4 6

5 9

5

6 1

1 7

8 1

8 3

Agathis robusta

(Queensland, Australia)

Aleurites moluccana

(Queensland, Australia)

Anthocephalus chinensis

(. . y

Araucaria angustifolia

(Comanducaia, Mines Gerais, Brazil)

Araucaria angustifolia

(Misiones, Argentina)

Araucaria angustifolia

Argentina

Araucaria cunninghamii

(Papua, New Guinea)

Callitris glauca

(New South Wales, Australia)

Callitris intrakopica

(Northern Territory, Australia)

Carapa guianensis

(Coastal Plain, Surinam)

Casuarina equisetifolia

(locally collected)

Cedrela ioona

(Umtali, Rhodesia)

Cedrela toona

(Umtali, Rhodesia)

Crickrassia tabularis

(Colombo, Ceylon)

Clitoris racemosa

(Belen, Brazil)

Cordia alliodora

(Turrialba, Costa Rica)

Cryptomera japonica

(Ali-san, Taiwan)

Cunninghamia laceolata

(Dehra Dun, India)

Cupressus lusitanica

(Tecpamo, Guatemala)

Entandophragma angolensis

(Sapoba Forest, Nigeria)

Eucalyptus grandis

(. . . .)

Eucalyptus citriodora

(. . . .)

Eucalyptus maidenii

(. . . . . . . . . . . .)

Eucalyptus x mysore-bangalore

(India)

Eucalyptus crebra

(. . . .)

EucalypUs robusta

(. . .)

Eucalyptus robusta

(. .)

Eucalyptus saligna

(. . . . .)

Fraxinus uhdei

(Oaxaca, Mexico)

Gmelina arborea

(. . . . . . .)

Y r m c m m m

2 9 13.8a1.g2 21.621.2 5.220.4 22.5

2 3 23.320.5 43.6kO.8 11.820.8 24.0

2 6 17.220.8 27.8a2.3 11.5kO.7 29.0

2 5 11.2k1.7 23.5k5.4 4.4kl.O 17.0

2 5 12.3208 19.620.6 3.021 .o 13.0

2 5 9.5a1.3 17.4k3.4 3.8kO.4 14.0

5 3.350.2 3.6-cO.3 c.5 5.5

2 3 13.8+1.8 26.5k3.4 2.950.3 23.5

2 3 9.8kO.9 26.222.1 1.3kO.l 13.0

2 6 18.1k1.2 24.7k2.6 3.6a0.3 22.0

2 6 11.621.5 13.8k2.4 3.OkO.5 17.5

2 3 15.821.8 18.8k2.6 3.5kO.5 17.5

2 3 11.5t1.5 20.726.0 3.OkO.4 13.0

2 3 8.2kO.7 9.320.9 2.220.6 9.5

1 7 11.3*1.9 15.3k4.0 0.5*0.1 18.0

2 4 14.7k1.2 19.822.6 9.5kO.5 22.5

2 3 8.0 15.7 0.5 8.0

2 5 12.5kO.6 18.721.3 1.2kO.l 17.5

2 6 16.0 37.0 2.5 16.0

2 3 11.7k1.5 13.2-cl.3 9.121.2 16.0

2 4 30.9k1.8 41.7k4.3 13.6k1.7 46.5

2 3 29.4k2.2 38.3k4.2 17.121.5 39.0

2 4 11.9t1.7 16.522.3 7.Ok1.5 14.5

2 5 21.3kO.9 29.3k2.3 7.820.5 29.0

2 4 13.6’1.4 19.653.1 4.2kO.8 20.0

2 6 20.720.8 34.0k1.8 8.5kO.5 31 .o

2 4 18.7+1.4 37.623.5 6.OkO.8 31.3

2 5 28.5-c 1.5 38.623.8 13.321.1 43.0

2 3 16.1 -CO.9 21.521.6 4.5-co.4 23.5

1 4 13.520.6 19.5k1.4 4.5rto.4 24.0

c m No./percent Yes / No

36.9 55 I 75 No No

51.7 13 I 93 Yes Yes

58.0 35 / 71 Yes No

40.7 5 I 20 No No

20.2 217 No No

33.5 10 / 18 No No

7.5 39 I -* No No

39.3 9 I 18 Yes No

27.2 14 I 29 No No

38.7 9 I 18 No No

18.8 9 I 18 No No

16.2 21 6 No No

32.5 3 I 21 No No

10.2 31 6 No No

30.2 9 I 82 Yes Yes

32.5 13 I26 Yes Yes

15.7 1 I 50 No No

25.8 29 I - Yes No

37.0 11 2 No No

14.8 8 I 27 No No

75.2 25 I 51 Yes No

50.4 9 I 26 Yes No

15.6 4 I 20 No No

48.9 26 I 53 Yes No

33.4 9 I 20 Yes No

58.8 41 I 84 Yes No

71.0 22 I 79 Yes No

58.0 32 I 56 Yes No

41.9 42 I 86 No No

47.0 46 I 94 Yes No
Table 1 .-Species survival, growth, and reproduction in the Luquillo Experimental Forest arboretum, located in Puerto Rico-Continued

Plot average f standard error’ Tallest tree Seeds and

Plot reproduction

no. Species (seed source) Age Height D.b.h. CBL Height D.b.h Survival present

1 2

2

2 9

45A

9

5 0

4 0

a 4

7 7

1 0

1

5 8

2 8

7 6

7 5

5 1

3

5 2

6 9

7

5 6

6 8

5 5

3 0

42A

4 8

1 3

4 4

7 9

748

Hernandia Sonora

(locally collected)

Hibiscus elatus

(Jamaica)

lnga Vera

(locally collected)

Khaya grandifoliola

(Ife Forest, Nigeria)

Khaya nyasica

(. . . . . . . .)

Khaya senegalensis

(Wad Medani, Sudan)

Maesopsis eminii

(Uganda)

Oiea sp.

(. . . .)

Pinus bahamensis

(

. . . . . . . . . . . . 1

Pinus caribaea var. caribaea

(Cuba)

Pinus caribaea var. hondurensis

(Belize)

Pinus caribaea var. hondurensis

(Honduras)

Pinus chiapensis (Solistahuacan,

Chiapas, Mexico, 540 m elevation)

Pinus chiapensis (Oaxaca, Mexico,

820 m elevation)

Pinus chiapensis (Oaxaca, Mexico,

1,340 m elevation)

Pinus echinata

(Florida, USA)

Pinus elliotti var. densa

(Florida, USA)

Pinus elliotti var. elliotti

(Florida, USA)

Pinus insularis

(Baguio, Mt. Province, Philippines)

Pinus massoniana

(Nanking, Huansi, China)

Pinus michoacana

(Uruapan, Michoacan, Mexico)

Pinus montezuma

(Chimaltenango, Guatemala)

Pinus oocarpa

(Guatemala)

Pinus oocarpa

(Mexico)

Pinus patula

(

. . . . . . . . . . . . )

Pinus pseudostrobus

(Puebla, Mexico)

Pinus taeda

(Florida, USA)

Pinus taeda

(Mississippi, USA)

Pterocarpus indicus

(Philippines)

Pterocarpus indicus forma echinatus

(Philippines)

Y r

2 6

2 6

2 4

2 3

2 6

2 5

2 4

?

2 3

2 6

2 6

2 4

2 4

2 3

2 3

2 5

2 6

2 5

2 3

2 6

2 5

2 3

2 5

2 5

2 3

2 5

2 5

2 6

2 3

2 3

m

18.320.6

20.420.5

14.0*0.9

2O.lkO.6

16.OkO.8

19.5kO.6

19.1+0.6

10.8-cO.9

19.6kO.8

21.6r0.7

23.8kO.9

25.6+1 .O

19.821.3

19.OkO.5

11.0

7.2+1 .O

18.OkO.5

10.220.5

20.2kl.l

12.820.5

11.6k1.8

16.620.6

23.8k1.3

17.522.0

14.OkO.9

16.8kO.8

11.8?0.3

12.2kO.4

10.4k1.5

17.9k1.5

c m

25.7k1.4

31.2-cl.5

11.2&0.6

22.9-co.9

23.5k1.3

25.0? 1.4

28.6&l .9

12.5k1.3

25.5? 1.8

29.32 1.4

35.221.8

45.5k2.5

32.723.6

43.6k1.5

23.3

15.Okl.6

25.3? 1.3

13.820.8

35.0~2.2

22.4k1.3

22.924.0

39.5k2.8

36522.7

26.5k5.0

30.6k2.5

32.8k4.3

18.8?0.8

18.3-cO.6

11.422.2

31.3k4.2

m

7.5kO.5

3.9kO.5

4.1 kO.4

12.OkO.6

5.9kO.4

8.120.5

8.620.7

2.120.4

12.120.5

10.2kO.5

11.6kO.7

10.2rtrO.6

3.1 kO.4

3.2-cO.2

4.5

3.2kO.3

1 O.OkO.5

3.9kO.3

5.5kO.7

4.lkO.3

2.9kO.9

2.4kO.8

9.1 kO.9

4.5kO.5

2.2kO.4

1.7kO.4

2.9kO.2

3.6a0.4

4.050.6

2.9kO.3

m

24.0

26.0

16.0

24.5

25.0

27.0

26.0

13.8

27.0

29.5

31 .o

33.0

27.0

19.5

11.0

9.5

24.0

15.0

26.5

17.6

16.5

17.5

33.0

19.5

17.5

19.5

14.0

16.5

13.5

26.0

c m No/percent Yes / No

47.0 46 I 94 Yes Yes

34.5 43 I 88 Yes Yes

20.3 38 I 78 Yes Yes

24.1 28 I 80 Yes No

37.7 49 I100 No No

48.8 44 I 90 No No

56.8 28 I 57 Yes Yes

16.6 7/- No No

23.3 29 I 59 Yes No

49.3 41 I 64 Yes No

45.6 39 I80 Yes No

51.1 24 I 53 Yes No

34.8 18 I36 Yes No

42.1 21 4 No No

23.3 II 2 No No

18.9 5 I 10 No No

29.7 41 I a4 Yes No

19.7 33 I Si No No

44.1 22 I45 Yes No

38.0 22 I45 No No

37.2 71 9 No No

37.1 31 6 No No

50.2 22 I 45 Yes No

31.5 21 4 No No

43.3 8 I 42 No No

38.6 8 I 16 No No

21.8 18 I37 No No

20.4 27 I 56 No No

16.4 4 I 11 No No

52.2 20 I 95 Yes Yes

5
Table 1 .--Species survival, growth, and reproduction in the Luquillo Experimental forest arboretum, located in Puerto Rico-Continued

Plot average f standard error* Tallest tree Seeds and

Plot reproduction

no. Species (seed source) Age Height D.b.h. CBL Height D.b.h Survival present

3 3

6

1 9

7 3

7 2

8 0

1 8

8

3 9

7 8

5 3

8 4

35A

Pterocarpus macrocarpus

(locally collected)

Schizolobium parahybum

(Guatemala)

Swietenia macrophyla

(locally collected)

Swietenia macrophyla

(Quintana Roo, Mexico)

Swietenia macrophylla

(Belize)

Swietenia macrophylla

(Quintana Roo, Mexico)

Tababuia donnell-smithii

(Mexico)

Tabebuia heterophylla

(St. Croix, U.S. Virgin Islands)

Taxodium mucronatum

(Guatemala)

Terminalia catappa

(Manokwari, Iran Jira)

Terminalia ivorensis

(Nigeria)

Toona ciliata

(India)

Toona surenia

(Monokawave, Iran Jira)

Yr m c m m

2 5 l4.4+-1.1 19.122.0 4.2a0.3

2 5 17.3kl.O 31 .l k2.8 9.9a0.8

2 6 17.1 kO.9 23.8k1.9 8.31rO.5

2 3 17.6kO.8 21.821.5 7.820.5

2 3 16.6-cO.8 22.521.6 6.6kO.4

2 3 17.2kO.9 21.6k2.0 6.9kO.5

2 6 9.5kO.5 8.9kO.9 7.2~0.2

2 6 12.020.8 18.6k1.9 5.1 kO.3

2 6 4.450.5 15.522.4 1.820.2

2 3 17.521.9 21.5k1.2 5.3kO.7

2 3 22.620.7 31.5k1.7 13.220.7

2 3 15.4-r-0.7 25.721.8 3.7kO.5

2 3 16.5kl.O 26.2k2.4 7.8~0.8

m c m

24.0 36.9

24.0. 47.9

26.0 35.5

20.5 34.3

22.5 34.9

22.0 31 .o

9.5 9.8

20.0 37.4

9.0 34.1

28.1 25.9

27.0 54.0

19.0 27.2

21.0 32.4

No/percent Yes / No

22 I 45 Yes No

19 I 39 Yes Yes

29 I 59 Yes Yes

23 I 82 No No

24 I 69 No No

18 I 51 No No

2 I 49 No No

15 I 31 Yes No

18 I 37 No No

8 I 17 Yes No

25 I 62 Yes Yes

121 - No No

13 I 62 No No

‘Abbreviations: d.b.h.=diameter at breast height; CBL=clear bole length.

Tlnformation on source is not available.

*Percent cannot be calculated because number planted is not known.

Table 2. -Species suffering loo-percent mortality on old farmland

in the Luquillo Experimental Forest arboretum, located in

Puerto Rico

Species Seed source

Acacia koa Hawaii

Acrocarpus fraxinifolius Kenya

Afromosa elata Nigeria

Cedrela odorata Mexico, Guatemala

Chlorophora excelsa Ghana

Eucalyptus deglupta New Guinea

Entandophragma utile Nigeria

Pinus ayacahuite Puebla, Mexico

Sequoia sempervirens California, USA

Simaruba amara Grenada

Swietenia humilis Guatemala

Swietenia mahagoni Unknown

Terminalia superba Nigeria

Tectona grandis India

Widdringtonia whytei Malawi

Number

planted

1 6

1 0

4 9

140

1 0

Unknown

3

2

1 7

8

Unknown

2 8

3 1

2 1

4 9

Table 3. -Species recently planted in the Luquillo Forest Arboretum

in Puerto Rico’

Species (seed source)

Number

planted Year

Alstonia macrophylla (Unknown) 4 9

Annona squamosa (Local) 3

Castanospermum australe

(Queensland, Australia) 4 9

Goetzia elegans (Local) 2

Gyranthera caribensis (Venezuela) 4 9

Myroxylon balsamum (El Salvador) 4 4

Parkia timoriana (Unknown) 4 4

*These plots do not appear in the map (fig. 1).

1989

1987

1988

1987

1989

1988

1988
Figure 2.-Arboretum plot of Aleurites moluccana.

AGATHIS ROBUSTA

AL EURf TES MOL UCCANA

AN rHOCEPHAL US CHJNENSIS

CORD/A ALL IODORA

EUCA L Y P TUS GRANDIS

EUCALYPTUS x PArENrINERVlS

EUCALYPTUS ROBUSrA

EUCALYPTUS SAL IGNA

FRAXfNUS UtfDEl

HERNANDIA SONORA

HlBlSCUS El ArUS

KHAYA GRAND/f OL IOL A

KHAYA NYAS/CA

KHAYA SENEGAL ENS/S

MAESOPSIS EM/N//

PINUS CARIBAEA CARIBAEA

PINUS CARIBAEA HONDURENSIS (BELIZE)

PINUS CARIBAEA HONDURENSIS IHONDURA:

PINUS COCARPA

SW/E TENIA MACROPH YL L A (PUERTO RICO)

SWIE TENlA MACROPHYL L A (BEL l.?El

TERMINAL IA I VORENSIS

0 5 IO I5 2 0 25

(D.B.H.)2 X HEIGHT

Figure 3.-Box plot of volume index [(d.b.h.)2 x height]. Extremes of horizontal bars are low and high values; vertical

bars indicate 25th percentile, median, and 75th percentile.

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Figure 4.-Arboretum plot of Pterocarpus indicus forma echinatus.

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