United States

Department of

Agriculture

Forest 

Service

Pacific Northwest

Research Station

Resource Bulletin

PNW-RB-252

January 2007

Palau’s Forest Resources, 

2003

Joseph A. Donnegan, Sarah L. Butler, 

Olaf Kuegler, Brent J. Stroud, 

Bruce A. Hiserote, and Kashgar Rengulbai
Authors

Joseph A. Donnegan is an ecologist, Sarah L. Butler is an ecologist, Olaf 

Kuegler is a statistician, and Bruce A. Hiserote is an information management 

specialist, Forestry Sciences Laboratory, 620 SW Main Street, Suite 400, Portland, 

OR 97205-3028. Brent J. Stroud was the quality assurance technician for the 

Portland Forestry Sciences Laboratory, but now works for Interior West Forest 

Inventory and Analysis. Kashgar Rengulbai was a forester on Palau.

The Forest Service of the U.S. Department of Agriculture is dedicated to the principle of 

multiple use management of the Nation’s forest resources for sustained yields of wood, 

water, forage, wildlife, and recreation. Through forestry research, cooperation with the 

States and private forest owners, and management of the National Forests and National 

Grasslands, it strives—as directed by Congress—to provide increasingly greater service 

to a growing Nation.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and 

activities on the basis of race, color, national origin, age, disability, and where applicable, 

sex, marital status, familial status, parental status, religion, sexual orientation, genetic 

information, political beliefs, reprisal, or because all or part of an individual’s income 

is derived from any public assistance program. (Not all prohibited bases apply to all 

programs.) Persons with disabilities who require alternative means for communication of 

program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET 

Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write 

USDA, Director, Office of Civil Rights, 1400 Independence Avenue, SW, Washington, DC 

20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal 

opportunity provider and employer.
Abstract

Donnegan, Joseph A.; Butler, Sarah L.; Kuegler, Olaf; Stroud, Brent J.; 

Hiserote, Bruce A.; Rengulbai, Kashgar. 2007. Palau’s forest resources, 2003. 

Resour. Bull. PNW-RB-252. Portland, OR: U.S. Department of Agriculture, 

Forest Service, Pacific Northwest Research Station. 52 p.

The Forest Inventory and Analysis Program collected, analyzed, and summarized 

field data on 54 forested plots on the islands in the Republic of Palau. Estimates 

of forest area, tree stem volume and biomass, the numbers of trees, tree damages, 

and the distribution of tree sizes were summarized for this statistical sample. 

Detailed tables and graphical highlights provide a summary of Palau’s forest 

resources and a comparison to 1987 data.

Keywords: Palau, biomass, damage, FIA, forest inventory, volume, land cover.
Summary 

The Forest Inventory and Analysis (FIA) Program conducted a systematic inventory of the forests of Palau in 2003 to estimate forest area, tree stem volume, 

biomass, carbon storage, tree damages, and the percentage cover of understory 

vegetation species. Fifty-four permanent field plots were installed, 11 in limestone 

forest and 43 in volcanic forest. Land cover was mapped into five broad classes, 

forest, nonforest vegetation, urban, barren, and inland water, by using recently 

acquired high-resolution satellite imagery. Soil survey information was used to 

classify forest into limestone and volcanic types. Our estimates for this inventory 

are derived from a sample based on 110,028 acres in Palau, with about 16 percent 

of the land classified as limestone forest and 67 percent classified as volcanic forest. 

About 2 percent of the landscape was classified as urban land, the majority on 

Koror and Babeldaob. We estimated gross tree stem volume to be about 302 million 

cubic feet for all size classes including seedlings and saplings. Aboveground dry 

biomass for tree stems 5 inches and greater was estimated to be 4.7 million tons. 

Approximately 13 percent of the trees sampled in the inventory had some form of 

damage. The growth of damaging vines in the crowns of trees was the most prevalent damage type, with conks and lost apical dominance following in prevalence. 

The most frequently identified damaging agents were other vegetation, disease, and 

weather. Palau’s forests are relatively dense and have high species diversity. A total 

of 128 tree species and 132 understory species were measured on FIA plots. The 

average number of tree species per sixth-acre plot was 12 in volcanic forest and 10 

in limestone forest. Palauan foresters and ecologists were especially helpful with 

species identification in the field.
Palau’s Forest Resources, 2003

Introduction

This summary of forest resources on the islands of Palau (fig. 1) was based on a 

forest inventory conducted in 2003 by the USDA Forest Service, Pacific Northwest 

Forest Inventory and Analysis (FIA) Program in cooperation with Pacific Island 

foresters. The inventory is a subset of the national FIA effort and was designed 

to help answer local and national questions about the status and trends in tropical forested ecosystems and to share forestry skills among cultures and agencies. 

The fieldwork for this inventory was conducted by a multinational crew including 

foresters from Palau, American Samoa, and mainland U.S. foresters and ecologists.

This systematic, sample-based field inventory on Palau is an update to prior 

inventory work (Cole et al. 1987, MacLean et al. 1988) estimating forest type area, 

tree size distribution, and stem volume. New information is included for all forests 

on biomass, and damages for living and dead trees. The inventory was designed 

to provide resource managers with information about the current situation so they 

can better manage their forested and nonforested lands, and manage or mitigate 

any changes in the resource. Empirically based knowledge of the status and trends 

in forest vegetation can help managers plan sustainable land use practices, plan 

sustainable supplies of wood, control invasive species, control erosion, and manage 

disturbances such as fire and animal damage.

Objectives

• Estimate the current area of forest land by forest type group and stand size 

class.

• Estimate the volume, biomass, and carbon storage for tree species by diameter class.

• Estimate the numbers of trees affected by damaging agents, such as insects 

and diseases, and estimate the numbers of dead trees.

• Share measurement and analysis techniques among groups involved in the 

inventory.

Methods

Site Description

Palau is well known for its tremendous diversity and concentration of both terrestrial and marine life along the network of coral reefs and the chain of more than 300 

raised limestone and volcanic islands. The chain of islands runs from the northeast 

to southwest for a distance of about 125 miles, approximately 470 miles east of 

the Philippines. The islands range in size from the relatively large, volcanic island 
RESOURCE BULLETIN PNW-RB-252

Figure 1—The Republic of Palau is in the North Pacific Ocean approximately 470 miles east of the Phillipines. Land cover was 

mapped from 2005 QuickBird satellite data.
Palau’s Forest Resources, 2003

of Babeldaob, at about 92,000 acres, to coral rocks topped with trees, only a few 

yards across. The tremendous marine diversity is supported by the convergence of 

oceanic currents and the filtering and nutrient effects of the dense terrestrial forests. 

The topography of the four volcanic islands is marked by steep slopes and rolling 

hills, with mangroves often found on coastal flats. The limestone coral islands or 

“Rock Islands” support a diversity of tree species on often surprisingly shallow 

soils deposited in the recesses of the rugged karstic topography. The highest point 

in Palau is the approximately 700-foot-tall Mount Ngerchelchuus on Babeldaob 

(Palau Conservation Society).

The climate of Palau is hot and humid with little annual variation in the mean 

maximum temperature of 87.9 °F and the mean minimum of 75.6 °F (fig. 2). Total 

annual precipitation averages 147.3 inches. In the wettest months, June and July, 

monthly precipitation averages 17.04 inches, whereas during the driest months, 

February, March, and April, monthly precipitation averages 8.84 inches (data from 

Western Regional Climate Center 2004). During an El Niño year (warm phase of 

the Southern Oscillation), rainfall tends to be above average for that summer and 

below average in the following autumn and winter months (Climate Prediction 

Center 2005).

Palau borders the typhoon belt in the western tropical Pacific and is subject to 

occasional typhoon damage. Prior to European contact, extensive terracing was 

practiced on Babeldaob in upland areas. Paleoenvironmental evidence suggests 

terracing may have contributed to landcover change from forest to savanna and 

fernland, and accelerated erosion as much as 2,500 years before present (Athens 

and Ward 2002). Additional recent disturbances have included mining of bauxite, 

military action during World War II (which denuded much of Peleliu and Angaur), 

and conversion of forest for agriculture. Forest was cleared during the recent 

construction of a new capitol on Babeldaob and a road to encircle the island. Barren 

volcanic soils pose high risk of erosion with frequent, intense rainfall and are often 

a corridor for colonization by invasive species.

Vegetation Types

The flora of Palau shares many common elements with that of east-Asian and 

Indo-Malesian floras (Mueller-Dombois and Fosberg 1998). Species composition in 

Palau is distinctive depending on the parent material the soil is derived from, with 

volcanic soils found in the north (Babeldaob, Arakabesang, Malakal, and Oreor), 

and limestone soils on Peleliu, Angaur, and the Rock Islands to the south. Where 

volcanic soils are deposited along coastal flats, mangrove and freshwater swamps 

are common. The volcanic islands also support a shrubby, strand vegetation, a 
RESOURCE BULLETIN PNW-RB-252

Figure 2—(A) The annual maximum and minimum temperatures in Palau do not fluctuate markedly. However, (B) precipitation is 

highly variable throughout the year with a distinct summer wet season and a dry early spring (Western Regional Climate Center 2004).
Palau’s Forest Resources, 2003

closed-canopy interior volcanic forest, ravine and riparian forest, and savanna and 

fernland on degraded soils (Mueller-Dombois and Fosberg 1998). The southern, 

raised limestone islands support evergreen, closed-canopy forest that is generally 

quite species rich and variable from island to island (Cole et al. 1987). Note that the 

current report does not describe the vegetation of the Southwest Islands of Palau, 

approximately 400 miles southwest of Babeldaob. Additionally, the FIA inventory 

does not provide sufficient plot density to reliably classify vegetation types in these 

highly diverse tropical forests, but provides plot-level data to help refine remotely 

sensed estimates of forest type acreage and developmental stage. Some of the 

species named in the following vegetation descriptions (from Cole et al. 1987, and 

Mueller-Dombois and Fosberg 1998) were not identified on the 2003 sample of FIA 

field plots, either owing to their absence, their understory cover not meeting the 3 

percent threshold, or possible misidentification. The FIA and local island staff were 

trained by regional botanical experts, and when species could not be identified in 

the field, they were sent for expert identification. However, misidentification in the 

field remains a possibility.

Volcanic Forest Types

Mangrove—

Mangroves play a vital role in buffering the effects of storms and waves along 

coastal areas. They also provide habitat for marine life and filter runoff exiting 

terrestrial ecosystems. The filtration that mangroves provide helps to sustain 

coral reef and fish habitat by trapping sediment. The mangroves of Palau are a 

particularly species-rich mangrove type that extends along a narrow strip of the 

tidal zone. The species found here include Rhizophora mucronata, Rhizophora 

apiculata, Bruguiera gymnorrhiza, Ceriops tagal, Sonneratia alba, Avicennia 

marina, Lumnitzera littorea, Xylocarpus granatum, Scyphiphora hydrophyllacea, 

Dalbergia candenatensis, Derris trifoliata, Nypa fruticans, Acrostichum aureum,

and Nephrolepis acutifolia (see table 1 for common and scientific names with 

authorities). Mangroves are very dense forest types where left undisturbed.

Swamp forest—

This forest type tends to occur slightly inland of mangrove in areas of fresh or 

slightly brackish water. Horsfieldia amklaal, Cynometra ramiflora, Barringtonia 

racemosa, Campnosperma brevipetiolata, and Heritiera littoralis are often found 

in the intact freshwater swamps, whereas Hibiscus tiliaceus is found in disturbed 

areas.
Scientific name Common name Number measured Estimated number (≥1 inch diameter) Standard error for estimated number (±) Gross volume (≥5 inches diameter) Aglaia palauensis Kaneh. meseoes 23 847,803 431,384 1,783,505 Allophylus ternatus (Forst.) Radlk. chebeludes 3 36,989 37,027 206,199 Allophylus timorensis (DC.) Bl. ebeludes, chebeludes 1 12,330 12,342 29,280 Alphitonia carolinensis Hosok. elebiob, elebiong 50 1,531,290 803,629 4,434,129 Annona reticulata L. ngel ra ngebard 1 12,330 12,342 62,771 Areca catechu L. buuch, betel nut 6 73,977 74,055 292,165 Artocarpus mariannensis Trec. ebiei, wild breadfuit 4 48,518 35,710 5,140,163 Astronidium palauense (Kaneh.) Mgf. meskui 32 1,641,189 590,773 1,169,439 Avicennia marina (Bl.) Bakh. dadaiit 2 24,659 24,685 1,422,693 Badusa palauensis Valeton ralm 29 897,973 582,173 3,048,028 Barringtonia racemosa (L.) Spreng. koranges 51 3,407,461 2,020,608 2,986,606 Bruguiera gymnorrhiza (L.) Lam. kadeges, denges, adeges 43 1,095,193 671,454 5,542,897 Buchanania palawensis Lauterb. geloagl 10 405,607 253,723 1,308,999 Calophyllum inophyllum L. laurel 34 1,184,578 579,030 5,436,901 Calophyllum pelewense P. F. Stevens chesemoroch 20 608,511 363,048 1,040,719 Calophyllum soulattri Burm. f. olebtaches, chesemoroch 6 356,489 332,521 480,790 Calophyllum sp. L. 6 61,247 45,601 1,910,972 Campnosperma brevipetiolata Volk. kelela charm, kiu 72 1,133,048 372,006 22,836,047 Canarium hirsutum Willd. mesechaues 11 553,209 439,687 1,072,970 Casearia cauliflora Volk. kevert 1 12,330 12,342 157,802 Casearia sp. Jacq. 7 84,906 93,158 626,648 Casuarina equisetifolia L. ngas, ironwood 6 24,259 17,855 1,436,905 Cerbera floribunda K. Schum. emeridech 2 24,659 17,251 281,010 Cerbera manghas L. emeridech 19 362,987 187,580 2,378,467 Cocos nucifera L. lius, coconut 26 318,967 175,394 8,416,588 Commersonia bartramia (L.) Merr. aspitan, eremallueang 7 165,915 153,955 29,882 Cordia micronesica Kaneh. & Hatus. 1 12,330 12,342 312,315 Cyathea lunulata (Forst. f.) Copel. eluu, tree fern 46 634,436 212,213 1,985,641 Diospyros ferrea (Willd.) Bakh. 10 393,478 357,921 384,300 Diospyros sp. L. 10 544,171 302,309 717,026 Dodonaea viscosa (L.) Jacq. 6 73,177 34,397 1,642,371 Dracaena multiflora L. 14 878,093 397,272 459,125 Drypetes nitida Kaneh. keuelt 4 187,882 180,779 373,021 Dysoxylum sp. Blume 13 1,572,844 901,519 64,752 

Table 1—Scientific names, common names, estimated number and gross volume, and standard errors for estimated totals measured as trees on Palau
Table 1—Scientific names, common names, estimated number and gross volume, and standard errors for estimated totals measured as trees on Palau (continued)

Scientific name Common name

Number 

measured

Estimated 

number

(≥1 inch 

diameter)

Standard 

error for 

estimated 

number (±)

Gross 

volume

(≥5 inches 

diameter)

Elaeocarpus graeffei Seem. 1 12,330 12,342 64,508 Elaeocarpus joga Merr. dekemerír 49 1,419,038 530,051 6,648,512 Erythrina fusca Lour. roro 1 12,129 13,308 600,183 Eugenia cumini (L.) Druce mesekerrak, java plum 23 974,799 753,514 1,960,664 Eugenia javanica Lam. rebotel 20 381,553 251,122 4,324,582 Eugenia reinwardtiana (Bl.) DC. kesiil 65 3,017,755 1,068,888 6,011,868 Eugenia sp. L. 7 648,639 313,824 130,011 Evodia sp. 1 153,586 153,747 — Fagraea ksid Gilg and Bened. ksid 19 172,613 76,502 2,248,390 Ficus sp. L. 2 165,915 153,955 409,933 Ficus tinctoria Forst. f. oseked 9 1,096,866 936,957 3,187,214 Flacourtia rukam Zoll. & Moritzi 21 1,388,568 780,722 751,255 Garcinia matudai Kaneh. tilol 12 995,490 741,721 725,013 Garcinia rumiyo Fosb. tilol 40 2,457,435 969,319 2,520,347 Garcinia sp. L. 30 650,797 298,347 2,603,796 Gironniera celtidifolia Gaudich. 3 36,989 37,027 261,379 Glochidion ramiflorum Forst. 26 1,565,282 776,102 1,201,069 Glochidion sp. J.R. & G. Forst. 3 178,245 166,261 93,117 Gmelina elliptica Sm. kalngebard ra belau 22 825,997 495,311 4,368,123 Gmelina palawensis H. J. Lam. blancheos 49 1,027,314 537,789 4,916,499 Gmelina sp. L. 6 73,977 51,752 1,315,262 Guettarda speciosa L. belau 3 460,757 461,240 — Gulubia palauensis (Becc.) Moore & Fosb. chebouch, akaboek 9 97,036 106,466 518,759 Hernandia sonora L. dokou 3 36,388 39,925 360,357 Hernandia sp. L. 5 60,647 66,541 1,714,517 Heterospathe elata (Becc.) Becc. demailei, ebouch 11 700,649 641,212 404,770 Hibiscus tiliaceus L. cheramal 25 2,709,590 2,248,657 375,843 Horsfieldia amklaal Kaneh. emeklachel, eumail 25 1,003,150 563,395 5,112,032 Horsfieldia novo-guineensis Warb. ersachel 24 1,002,188 567,747 10,735,352 Horsfieldia palauensis Kaneh. ersachel 101 3,852,198 1,132,578 13,722,763 Horsfieldia sp. Wild. 5 626,672 614,824 42,993 Inocarpus fagifer (Park.) Fosb. keam, boui 1 12,330 12,342 29,390 Intsia bijuga (Colebr.) O. Ktze. dort 20 381,553 267,583 8,903,896 Lumnitzera littorea (Jack) Voigt ngemoel, mekekad 1 12,330 12,342 127,232 
Scientific name Common name Number measured Estimated number (≥1 inch diameter) Standard error for estimated number (±) Gross volume (≥5 inches diameter) Macaranga carolinensis Volk. bedel 49 5,074,421 1,760,927 671,260 Manilkara udoido Kaneh. udeuid 29 283,579 173,439 2,085,556 Manilkara zapota (L.) P. v. Roy. sapodilla 6 73,977 62,652 1,296,562 Morinda citrifolia L. ngel 8 946,172 352,952 132,139 Morinda latibracteata Val. kesengelengel, ngel 5 61,648 50,610 211,608 Morinda pedunculata Val. kesengelengel 1 12,330 12,342 81,626 Morinda sp. L. 3 36,989 37,027 127,267 Mussaenda frondosa L. 1 153,586 153,747 — Neonauclea forsteri Merrill 3 460,757 461,240 — Nephelium lappaceum L. rambutan, rambotang 1 12,330 12,342 100,828 Osmoxylon oliveri Fosberg & Sachet 3 178,245 155,148 65,896 Osmoxylon sp. 9 675,990 639,395 145,875 Pandanus aimiriikensis Mart. ertochet 25 3,130,866 1,232,969 272,360 Pandanus dubius Spr. beku, ongor 21 810,575 608,016 897,251 Pandanus kanehirae Mart. buuk 6 202,904 190,886 332,031 Pandanus palawensis Mart. ongor 1 153,586 153,747 — Pandanus tectorius Park. ongor 13 559,393 274,312 463,602 Pandanus utiyamai Kaneh. 1 12,330 12,342 1,050,209 Pangium edule Reinw. ex Bl. riamel 2 24,659 24,685 237,335 Parinari corymbosum (Bl.) Miq. bkau, apgau 63 2,008,183 672,025 21,934,439 Parinari laurina Gray eritem, gritin 56 2,086,261 1,251,377 5,980,513 Parinari sp. 4 331,830 223,617 66,714 Pinanga insignis Becc. ebouch, demailei 240 11,655,307 2,337,956 8,329,960 Pithecellobium dulce (Roxb.) Benth. kamatsiri, opiuma 4 465,410 510,641 80,161 Pongamia pinnata (L.) Merr. kisaks 1 151,094 165,778 — Pouteria calcarea (Hosok.) Fosb. elangel 3 36,989 37,027 160,981 Pouteria obovata (R. Br.) Baehni elangel 37 855,954 637,145 4,146,921 Pouteria sp. Aubl. 1 12,330 12,342 59,315 Premna obtusifolia R. Br. osem 9 381,148 309,108 246,764 Pterocarpus indicus Willd. las 2 24,659 24,685 917,560 Ptychosperma palauensis (Kaneh.) Moore & Fosb. esbuuch 8 239,892 240,144 329,740 Rhizophora apiculata Bl. bngaol 129 3,657,133 2,280,225 8,538,981 Rhizophora mucronata Lam. tebechel 31 365,084 327,871 2,265,232 Rhus taitensis Guill. eues 40 714,045 251,240 5,850,777 Table 1—Scientific names, common names, estimated number and gross volume, and standard errors for estimated totals measured as trees on Palau (continued)
Scientific name Common name

Number 

measured

Estimated 

number

(≥1 inch 

diameter)

Standard 

error for 

estimated 

number (±)

Gross 

volume

(≥5 inches 

diameter)

Rinorea carolinensis Kaneh. 1 12,129 13,308 44,758 Semecarpus venenosus Volk. tonget 58 2,266,927 689,153 6,877,953 Sonneratia alba J. E. Sm. urur 52 5,959,545 3,934,040 11,503,833 Stemonurus ammui (Kaneh.) Sleumer ngmui 5 61,648 61,712 3,215,714 Swietenia macrophylla King honduras mahogany 5 202,904 179,561 327,606 Swietenia mahagoni (L.) Jacq. mahogany 8 381,148 345,648 414,720 Symplocos racemosa Roxb. 19 829,575 509,114 224,606 Tecoma stans (L.) Juss. ex HBK. 1 153,586 153,747 — Terminalia catappa L. beach almond, miich 4 49,318 38,757 805,001 Theobroma cacao L. suklatei, cocoa 5 61,648 61,712 617,845 Timonius subauritus Fosberg & Sachet 19 1,595,842 1,090,534 925,779 Tournefortia argentea L. f. rirs, tree heliotrope 4 48,918 36,301 327,509 Trichospermum ledermannii Burret elsau 11 252,222 167,347 1,067,694 Vitex cofassus Reinw. ex Bl. bars, beokel 9 110,966 111,082 5,134,682 Xylocarpus granatum Koen. meduulokebong 16 338,528 292,559 1,399,499 Unknown 0 13 188,082 168,017 120,479 Unknown 1 6 331,630 215,243 37,791 Unknown 2 2 307,171 307,493 — Unknown 3 4 24,659 17,251 228,639 Unknown 5 7 85,906 67,207 513,431 Unknown 11 1 12,330 12,342 126,165 Unknown, other 7 36,989 20,875 1,657,879  Total 2,248 96,594,950 6,639,026 268,511,801 Table 1—Scientific names, common names, estimated number and gross volume, and standard errors for estimated totals measured as trees on Palau (continued)
10

RESOURCE BULLETIN PNW-RB-252

Interior volcanic forest—

Occurring primarily on volcanic substrates, interior volcanic forest encompasses 

distinct subtypes of forest in undisturbed ecosystems. Moving inland from the 

mangroves and swamps, the dominant species include Casuarina equisetifolia and

Pandanus tectorius. Farther inland, the forest grades into a mixed-forest canopy 

that includes Campnosperma brevipetiolata, Horsfieldia amklaal, H. palauensis, 

H. novo-guineensis, Myristica insularis, Parinari laurina, Parinari corymbosum, 

Serianthes kanehirae, Glochidion macrosepalum, G. ramiflorum, Alphitonia 

carolinensis, Calophyllum inophyllum var. wakamatsui, C. soulattri, C. pelewense, 

Symplocos racemosa var. palauensis, Cerbera floribunda, Manilkara udoido, and 

Fagraea ksid. The forest is dense, multilayered, and structurally complex here.

Ravine and riparian forest—

In the complex terrain of Palau’s savannas, ravines often break up the open forest 

and grassland with narrow strips and sheltered hillsides of more dense and diverse 

forest vegetation occurring in relatively moist areas. Barringtonia racemosa and the 

poison tree (causes a severe skin rash) Semecarpus venenosus are common components of the ravine and riparian type.

Limestone forest type

On the limestone substrate of Peleliu, Angaur, and the Rock Islands, organic 

matter from the vegetation forms a thin layer in places over the coral rock. The 

limestone substrate is often steep, porous, and extremely rugged. Rock that borders 

the ocean is often undercut by waves and bioerosion, making access difficult. A 

species-rich and structurally diverse forest forms here with the dominant species 

Intsia bijuga, Psychotria spp., Clerodendron inerme, Eugenia reinwardtiana, 

Morinda latibracteata, Garcinia matudai, G. rumiyo var. clacicola, Rinorea sp.,

Cycas circinalis, Flacourtia rukam var. micronesica, Aidia cochinchinensis, 

Meryta senfftiana, Polyscias grandifolia, Geniostoma sessile, Premna serratifolia, 

Cyrtandra todaiensis, Guettarda speciosa, Badusa palauensis, Psychotria 

hombroniana, Ixora casei, and Tarenna sambucina.

Field Methods

The Palau inventory was based on the FIA inventory design that was implemented 

across the mainland United States beginning in 2000. Adaptations were made 

to the national design to include additional branching and rooting forms, using 

topography to define site productivity or drought resilience (in perhumid climates), 

additional tree crown measurements, and including special-interest species ranging 

from invasive plants to pathogens to culturally or economically important species 
11

Palau’s Forest Resources, 2003

of various life forms. In the mainland FIA Program, plots are spaced within forest 

land on a 3.3-mile grid. With the assistance of the Government of Palau, Bureau of 

Agriculture, plots were spaced across all vegetation types at approximately 1.9-mile 

intervals, yielding a triple intensification of the mainland inventory plot grid.

The FIA plot-cluster is composed of four 24-foot-radius subplots (fig. 3). Three 

of those subplots are equally spaced, as if on spokes of a wheel, around the central 

subplot. The distance from the middle of the central subplot to the middle of each 

subplot on the three spokes was 120 feet.

Forest Inventory and Analysis

Pacific Islands Plot Design

N

Overall plot footprint: ~1.5 acres

Distance between subplot centers: 120 feet

Distance from subplot center to microplot center: 12 feet

1

2

4 3

Plot

Subplot Microplot

6.8-foot-radius microplot: 

 seedlings + saplings

Key

24-foot-radius subplot: 

 all trees (5 inches 

 diameter at breast height)

Figure 3—Forest Inventory and Analysis Pacific Islands plot design.
12

RESOURCE BULLETIN PNW-RB-252

A variety of information was collected at the plot, subplot, and tree levels 

(USDA Forest Service 2003). Differences in forest-type conditions are also mapped. 

For example, roads that intersect subplots are mapped, as are clear boundaries in 

forest tree size classes. The primary variables collected include plot location, slope, 

aspect, elevation, subplot slope position and shape, tree species, diameters, heights, 

damages, branching and rooting forms, decay, epiphytic loadings, crown characteristics, tree locations, and regeneration information. The fieldwork for this inventory 

was performed February to April 2003.

Analysis Methods

The FIA estimates of forest land are based on a system that uses aerial photography 

or satellite imagery to define different types of land (strata) across the landscape. 

The simplest stratification is separating land into forest and nonforest strata. 

However, stratifications can be assisted or refined by using ancillary data such as 

topography, soil information, life zone or climatically based information, and prior 

inventories of vegetation groups.

The Palau stratification for estimating numbers of trees, volume, biomass, 

and carbon was conducted via a classification of 2003 IKONOS satellite data. The 

initial land-cover classification divided the landscape into forest, urban, nonforest 

vegetation, barren, and water cover types. At least 10 percent cover of trees was 

used as the basis for the forest-land classification, and includes both agroforests and 

mangrove forests. Nonforest vegetation includes other vegetation types with less 

than 10 percent cover of trees. A geographic information system (GIS) was used to 

sum acreage for each type. Forest was further classified into volcanic and limestone 

forest types by overlaying a soils layer (USDA Natural Resources Conservation 

Service 1983) on the land-cover-classification layer in a GIS. We used the GIS to 

individually sum the acreage of limestone and volcanic forest types. From this 

limestone/volcanic stratification, field plot condition types were expanded to the 

landscape level. The acreage each field plot represents was derived by dividing 

the total acreage of forest in each of the limestone and volcanic soil types by the 

number of field plots that fell within the geographic bounds of that specific type. 

Average stand size was expanded from the plots to the landscape level by using the 

same expansion factors.

Land cover was further refined into more detailed classes through an ongoing cooperative project with the USDA Forest Service, Pacific Southwest Region, 

Remote Sensing Laboratory. Both the 2003 IKONOS and 2005 QuickBird satellite 

imagery were used for the detailed mapping and served as the basis for land cover 

estimates.
13

Palau’s Forest Resources, 2003

Wood volume was estimated for individual trees by using tree height and two 

stem diameter measurements. These measurements are expanded to tree-level 

volume estimates by using equations for sections of a cone. Both gross stem volume 

and net stem volume estimates were calculated. Net stem volume subtracts damage 

and rotten defects from gross stem volume. Biomass for individual tree stems was 

estimated by using the specific gravity for known species (30 out of 129 species 

measured on Palau have known specific gravities). For species where specific gravity was not known, an average specific gravity, according to forest type, was used. 

These estimates of aboveground tree biomass are derived from bole volume and 

include only biomass for the main stem, excluding branches, roots, and foliage.

An additive combination of relative density and relative basal area (importance 

value) was used to classify forest types and assess the species dominance in a stand. 

Traditional site productivity estimates require forest stand age, derived from the 

annual rings of forest trees. Because tropical trees do not produce consistent annual 

rings, a modified topographic relative moisture index (TRMI) (Parker 1982) was 

examined as a proxy for site productivity. The TRMI used a weighted, additive 

combination of slope steepness, slope shape, and slope position to assess the potential moisture retention in a forested stand. Remeasurement data from these plots at 

the next inventory cycle will provide a better estimate of productivity than TRMI. 

In very wet environments like Palau, TRMI may be best considered a drought 

resilience proxy, predicting where soil and water accumulates, owing to topography, 

across a landscape. We also recognize moisture is not likely to be the only factor 

limiting tree growth and that a prolonged excess of moisture can be detrimental to 

the growth of many tree species.

Reliability of FIA Data

The area of forested land cover types classified from the IKONOS satellite imagery 

was assumed to be accurate and was used as the basis for the expansion of the 

numbers of trees, tree volume, and tree biomass from the plot scale to the foresttype scale. Possible sources of error not accounted for in our estimates include 

errors in the land cover map owing to incorrect interpretation of the image, errors 

from rounding when working with pixel-based imagery, and measurement errors on 

field plots. Standard errors for the expansion of our estimates from field plots to the 

forested landscape were calculated according to the proportion of area occupied by 

either volcanic or limestone forest types. Volcanic and limestone forest areas were 

treated as known rather than estimated, and variance was calculated by using methods in Cochran (1977). Using one standard error as our basis for evaluation gives a 

68 percent chance that the true total gross tree stem volume on Palau lies between 
14

RESOURCE BULLETIN PNW-RB-252

275,061,708 and 329,711,230 cubic feet. There is a 68-percent chance that the true 

number of trees (>1 inch diameter) on Palau lies within the range of 89,955,926 to 

103,233,978. Readers are cautioned to examine the standard errors associated with 

species-level estimates for the number of individuals and volume by tree species in 

table 1.

Resource Highlights

Land Cover

Palau is currently about 82 percent forested, which includes agroforest and secondary forest vegetation (table 2). About 2 percent of the landscape was classified as 

urban land and about 14 percent was classified as nonforest vegetation including 

savanna and agricultural lands. The area for land cover estimates totaled 110,028 

acres.

A prior vegetation survey (Cole et al. 1987) delineated vegetation types by 

using 1976 aerial photography, and estimated forest cover to be 80 percent of total 

land, including secondary vegetation and agroforest (table 2). Nonforest vegetation 

was estimated to be about 20 percent of the total land cover. Total acreage calculated from the Cole et al. (1987) maps that FIA recently scanned and digitized was 

101,851 acres.

The methodology and the area sampled for land cover estimates differ from 

those used for prior estimates. The Cole et al. (1987) work surveyed and mapped 

less limestone forest and defined forested lands on the basis of a canopy cover of 

approximately ≥ 30 percent. The recent effort used a forest-land canopy threshold 

of ≥ 10 percent to remain consistent with national FIA standards and the recent FIA 

work in American Samoa and Guam. In the current survey we mapped roads as 

urban land.

To compare similar sample areas on Palau, we summarized land cover area 

on an island-by-island basis for Babeldaob, Peleliu, Angaur, and Koror (fig. 4). 

Although the difference in canopy cover thresholds between 1987 and 2005 still 

exists, trends suggest there may be some areas of Babeldaob where nonforest 

vegetation has reverted to forest. On Peleliu and Koror, it appears that forest land 

is being converted to urban and nonforest vegetation uses. These observations are 

tentative pending a thorough analysis of land cover change for Palau.
15

Palau’s Forest Resources, 2003

Table 2—Estimated area by land cover, 1976a and 2005

Land cover 1976 2005

Acres

Limestone forestb 9,626 17,316

Volcanic forest 71,948 73,369

 Total forest landc 81,574 90,685

Nonforest and other areas:

Nonforest urban 1,550 2,433

Nonforest vegetation 18,250 15,329

Barren lands 339 1,103

Unclassified 64

Water 139 414

 Total nonforest and other land 20,277 19,343

Total area in survey 101,851 110,028

a

Figures for maps derived from 1976 aerial photography differ slightly from 

those published by Cole et al. (1987). Figures here were derived by scanning the 

historical maps and aggregating area totals with a geographic information system.

b

The sample area for forest cover, especially limestone types, was increased 

between the 1976 and 2005 remotely sensed imagery.

c

Forest land includes agroforest and secondary forest vegetation.

Babeldaob Koror

Forest

Nonforest 

 vegetation

Barren

Urban

Water

Unknown

Total

Land cover

Acres

Peleliu Angaur

100,000

80,000

60,000

40,000

20,000

0

Forest

Nonforest 

 vegetation

Barren

Urban

Water

Unknown

Total

Land cover

Acres

3,000

2,500

2,000

1,500

1,000

500

0

Forest

Nonforest 

 vegetation

Barren

Urban

Water

Unknown

Total

Land cover

Acres

5,000

4,000

3,000

2,000

1,000

0

Forest

Nonforest 

 vegetation

Barren

Urban

Water

Unknown

Total

Land cover

Acres

2,500

2,000

1,500

1,000

500

0

1988

2005

1988

2005

1988

2005

1988

2005

Figure 4—Forest land on Babeldaob is maturing and may be encroaching slightly on nonforest vegetation. On Peleliu, Koror, and 

Angaur, forest land is being lost to urban and nonforest vegetation land uses. Conversion of forest to urban land use is also expected 

on Babeldaob upon completion of the circumnavigating “Compact Road” in 2006, that will open areas previously inaccessible.
16

Productivity and Drought Resilience

Site productivity estimates are difficult to obtain in tropical environments owing 

to a lack of consistent annual tree rings. The standard premise for site productivity 

hinges on determining how height or diameter changes with respect to tree age 

under particular site conditions. Remeasurement of individual trees at the next 

inventory cycle will provide better estimates of site productivity by using growth 

over the specific period. For the present work, we attempted to estimate productivity as an additive index based on a site’s potential moisture accumulation owing 

to local topography (TRMI) (Parker 1982). However, in a region of such high 

precipitation, as in Palau, the TRMI estimate of productivity may be much less 

reliable than productivity estimates based on detailed soil mapping. For example, 

differences among forest, savanna, and fernland topsoils are dramatic with respect 

to soil organic matter, cation exchange capacity, and potential aluminum toxicity 

for plant growth, with a succession of soil degradation occurring from forest soils 

to savanna and fernland soils through processes of land clearing, repeated burning, 

and subsequent erosion and leaching of topsoil nutrients (Smith and Babik 1988). 

The topographic relative moisture index may have utility in very wet environments 

as a predictor of resilience to occasional drought, because TRMI predicts moisture 

accumulation (and likely sediment/soil accumulation as well) based on topography. 

Using TRMI in this context, we classified approximately 58 percent of the forested 

lands in Palau as medium high to highest drought resilience (fig. 5). This relatively 

high percentage owes to much of the land on Babeldaob being gently sloping 

volcanic soils, and thus drought resilience on these lands is expected to be relatively 

high. Babeldaob represents approximately 80 percent of our inventory area. On the 

limestone and limestone-derived soils of the Rock Islands, resilience to drought 

would be expected to be less based on lower moisture retaining capacities of these 

well-drained, often shallow soils and the complex karst topography. However, 

aluminum toxicity to plants is not expected on limestone-derived soils, whereas 

it is likely to limit plant growth in degraded volcanic-derived soils.

Forest Structure

Forest Inventory and Analysis estimates stand size class on forested field plots 

to capture the predominant diameter of live trees in forest stands. In Palau the 

dominant size class for volcanic forest types tends to be small, in the 5- to 11-inch 

diameter category (table 3, fig. 6). Limestone forest types tend to be dominated by 

slightly larger trees, in the 11- to 20-inch category (fig. 6). No plots were sampled 

on limestone soils that included stands in the smallest diameter category of 1 to 5 

inches.
17

Forest land potential drought resilience

(Percentage of total forest area and acreage)

13%

12,260

23%

21,973

19%

17,915

29%

28,546

6%

5,940

10%

10,055

Low

Medium low

Medium

Medium high

High

Highest

Figure 5—A topographic relative moisture index was used to predict drought resilience 

in the perhumid climate of Palau. On the gentle slopes and relatively deep volcanic soils 

of the largest island, Babeldaob (approximately 80 percent of forested acreage on Palau), 

drought resilience is expected to be higher than in the raised limestone Rock Islands.

The diameter distribution for trees on Palau is heavily weighted toward 

small-diameter trees (fig. 7). This “reverse-J” distribution of tree diameter is 

typical where regeneration is abundant. Through time, many small trees die before 

they grow into the larger diameter classes. For trees at least 5 inches in diameter, 

tree heights are predominantly in the 30- to 50-foot height classes (fig. 8). The 

tallest tree on an FIA plot, a Horsfieldia sp., measured 44 inches in diameter and 

approximately 114 feet tall.

Wood volume (fig. 9, tables 4, 5, and 6), biomass (fig. 10, table 7), and carbon storage (table 8) follow a similar distribution as the “reverse-J” seen for the 

number of trees according to diameter (fig. 7). Most of the volume, biomass, and 

carbon is accounted for in the smaller diameter classes owing to the relatively 

high number of trees in those size classes. (Text continues on page 33.)
18

Species

Diameter class (inches)

≤5.0 5.0–6.9 7.0–8.9

9.0–

10.9

11.0–

12.9

13.0–

14.9

15.0–

16.9

17.0–

18.9

19.0–

20.9

21.0–

22.9

23.0–

24.9

25

2

Number of trees

Aglaia palauensis 614,342 122,495 36,989 49,318 — — 24,659 — — — — — Allophylus ternatus — — 36,989 — — — — — — — — — Allophylus timorensis — 12,330 — — — — — — — — — — Alphitonia carolinensis 1,075,099 197,272 135,625 36,989 61,648 — 24,659 — — — — — Annona reticulata — 12,330 — — — — — — — — — — Areca catechu — 61,648 12,330 — — — — — — — — — Artocarpus mariannensis — — — — — 12,129 — — 12,129 — 12,129 12Astronidium palauense 1,382,270 184,943 36,989 36,989 — — — — — — — — Avicennia marina — — — 12,330 — — — — — — — 12Badusa palauensis 606,866 121,295 24,259 84,906 24,259 24,259 12,129 — — — — — Barringtonia racemosa 3,064,235 135,224 86,106 61,047 48,718 12,129 — — — — — — Bruguiera gymnorrhiza 614,342 135,625 172,613 86,307 24,659 49,318 — — — — — — Buchanania palawensis 307,171 73,777 — 12,330 — — — — — 12,330 — — Calophyllum inophyllum 916,529 36,588 61,247 36,588 48,518 12,129 24,259 — 36,588 — 12,129 — Calophyllum pelewense 460,757 61,447 61,648 — 24,659 — — — — — — — Calophyllum soulattri 307,171 12,330 12,330 — 24,659 — — — — — — — Calophyllum sp. — — 24,459 12,129 — — — 12,330 — 12,330 — — Campnosperma brevipetiolata 307,171 123,095 98,636 86,307 147,954 98,636 86,307 73,977 36,989 36,989 36,989 — Canarium hirsutum 455,773 36,588 24,459 12,129 12,129 — — 12,129 — — — — Casearia cauliflora — — 12,330 — — — — — — — — — Casearia sp. — 60,647 12,129 12,129 — — — — — — — — Casuarina equisetifolia — 12,129 — — — — — — — — — 12Cerbera floribunda — 12,330 — — 12,330 — — — — — — — Cerbera manghas 153,586 61,447 36,989 61,648 24,659 12,330 12,330 — — — — — Cocos nucifera — — — 85,706 171,813 49,118 — 12,330 — — — — Commersonia bartramia 153,586 12,330 — — — — — — — — — — Cordia micronesica — — — — — 12,330 — — — — — — Cyathea lunulata 153,586 258,920 147,954 49,318 24,659 — — — — — — — Diospyros ferrea 307,171 49,318 36,989 — — — — — — — — — Diospyros sp. 458,265 49,118 24,459 — 12,330 — — — — — — — Dodonaea viscosa — 12,330 12,129 12,129 — — 24,259 — — 12,330 — — Dracaena multiflora 767,928 73,377 24,459 — 12,330 — — — — — — — Drypetes nitida 151,094 12,330 12,129 — — 12,330 — — — — — — Dysoxylum sp. 1,535,855 36,989 — — — — — — — — — — Elaeocarpus graeffei — 12,330 — — — — — — — — — — Elaeocarpus joga 916,529 159,083 171,813 12,330 86,106 36,388 36,788 — — — — — Erythrina fusca — — — — — — — 12,129 — — — — Eugenia cumini 755,468 109,765 48,718 12,129 24,459 12,129 12,129 — — — — — Eugenia javanica 151,094 36,388 48,518 60,647 12,129 12,129 24,259 12,129 12,129 — — 12Eugenia reinwardtiana 2,434,941 255,319 145,554 97,036 48,518 12,129 12,129 12,129 — — — — Eugenia sp. 611,850 36,788 — — — — — — — — — — Evodia sp. 153,586 — — — — — — — — — — — 

Table 3—Estimated number of live trees on forest land by species and diameter class
19

Species

Diameter class (inches)

≤5.0 5.0–6.9 7.0–8.9

9.0–

10.9

11.0–

12.9

13.0–

14.9

15.0–

16.9

17.0–

18.9

19.0–

20.9

21.0–

22.9

23.0–

24.9

25

2

Number of trees

Fagraea ksid — 49,318 — 61,648 24,659 12,330 24,659 — — — — — Ficus tinctoria 1,072,607 — 12,129 — — — — — — — — — Flacourtia rukam 1,228,684 110,565 36,989 — 12,330 — — — — — — — Garcinia matudai 921,513 36,989 12,330 12,330 — 12,330 — — — — — — Garcinia rumiyo 2,150,197 135,425 85,706 49,118 36,989 — — — — — — — Garcinia sp. 307,171 221,131 49,118 48,718 24,659 — — — — — — — Gironniera celtidifolia — 24,659 12,330 — — — — — — — — — Glochidion ramiflorum 1,369,810 85,506 85,506 12,129 12,330 — — — — — — — Glochidion sp. 153,586 24,659 — — — — — — — — — — Gmelina elliptica 606,866 60,847 24,259 24,259 24,259 24,259 24,459 12,129 12,330 — — — Gmelina palawensis 460,757 234,261 135,625 86,106 49,118 36,989 — 24,459 — — — — Gmelina sp. — — 24,659 12,330 12,330 12,330 — 12,330 — — — — Guettarda speciosa 460,757 — — — — — — — — — — — Gulubia palauensis — 97,036 — — — — — — — — — — Hernandia sonora — 12,129 12,129 — 12,129 — — — — — — — Hernandia sp. — 24,259 — 12,129 12,129 — — — — — 12,129 — Heterospathe elata 614,342 61,648 24,659 — — — — — — — — — Hibiscus tiliaceus 2,610,954 49,318 49,318 — — — — — — — — — Horsfieldia amklaal 757,960 146,954 36,788 — 12,330 36,788 — — — — — — Horsfieldia novo–guineensis 767,928 86,307 36,989 49,318 — 12,330 12,330 12,330 12,330 — — — Horsfieldia palauensis 2,895,698 478,850 208,201 159,283 48,918 12,129 — — 12,129 — — — Horsfieldia sp. 614,342 12,330 — — — — — — — — — — Inocarpus fagifer — 12,330 — — — — — — — — — — Intsia bijuga 151,094 12,129 48,518 24,259 12,129 24,259 24,259 24,259 12,129 12,129 12,129 — Lumnitzera littorea — — — 12,330 — — — — — — — — Macaranga carolinensis 4,914,737 110,565 36,989 12,129 — — — — — — — — Manilkara udoido — 197,272 36,989 12,330 — 12,330 12,330 12,330 — — — — Manilkara zapota — 24,659 — 12,330 12,330 — — — 12,330 12,330 — — Morinda citrifolia 921,513 — 24,659 — — — — — — — — — Morinda latibracteata — 61,648 — — — — — — — — — — Morinda pedunculata — 12,330 — — — — — — — — — — Morinda sp. — 36,989 — — — — — — — — — — Mussaenda frondosa 153,586 — — — — — — — — — — — Neonauclea forsteri 460,757 — — — — — — — — — — — Nephelium lappaceum — — 12,330 — — — — — — — — — Osmoxylon oliveri 153,586 24,659 — — — — — — — — — — Osmoxylon sp. 614,342 61,648 — — — — — — — — — — Pandanus aimiriikensis 3,069,219 36,989 12,330 12,330 — — — — — — — — Pandanus dubius 604,374 181,942 24,259 — — — — — — — — — Pandanus kanehirae 153,586 — 49,318 — — — — — — — — — Pandanus palawensis 153,586 — — — — — — — — — — — Pandanus tectorius 460,757 73,977 24,659 — — — — — — — — — Pandamus utiyamai — — — — — — — — — — — 12Table 3—Estimated number of live trees on forest land by species and diameter class (continued)
20

Species

Diameter class (inches)

≤5.0 5.0–6.9 7.0–8.9

9.0–

10.9

11.0–

12.9

13.0–

14.9

15.0–

16.9

17.0–

18.9

19.0–

20.9

21.0–

22.9

23.0–

24.9

25.

26

Number of trees

Pangium edule — — 12,330 12,330 — — — — — — — — Parinari corymbosum 1,379,778 184,743 73,777 36,989 61,648 86,307 12,330 12,330 12,330 24,659 12,330 49Parinari laurina 1,520,904 282,778 86,106 98,436 48,918 — 36,989 — — — 12,129 — Parinari sp. 307,171 24,659 — — — — — — — — — — Pinanga insignis 9,522,303 2,083,686 36,989 12,330 — — — — — — — — Pithecellobium dulce 453,281 — 12,129 — — — — — — — — — Pongamia pinnata 151,094 — — — — — — — — — — — Pouteria calcarea — 36,989 — — — — — — — — — — Pouteria obovata 453,281 134,424 134,224 73,177 36,388 — — 12,129 12,330 — — — Pouteria sp. — — 12,330 — — — — — — — — — Premna obtusifolia 307,171 49,318 24,659 — — — — — — — — — Pterocarpus indicus — — — — — — 12,330 — — 12,330 — — Ptychosperma palauensis 153,586 86,307 — — — — — — — — — — Rhizophora apiculata 2,288,831 782,687 401,472 110,565 36,788 36,788 — — — — — — Rhizophora mucronata — 242,589 85,506 12,330 24,659 — — — — — — — Rhus taitensis 307,171 86,307 98,636 61,648 61,648 61,648 24,659 12,330 — — — — Rinorea carolinensis — — 12,129 — — — — — — — — — Semecarpus venenosus 1,689,441 271,049 135,224 73,177 49,118 12,129 12,129 — — — — 12Sonneratia alba 5,836,250 12,330 24,659 — 12,330 — 12,330 — — — — — Stemonurus ammui — — 12,330 — — — 12,330 12,330 24,659 — — — Swietenia macrophylla 153,586 36,989 — 12,330 — — — — — — — — Swietenia mahagoni 307,171 49,318 12,330 12,330 — — — — — — — — Symplocos racemosa 767,928 49,318 12,330 — — — — — — — — — Tecoma stans 153,586 — — — — — — — — — — — Terminalia catappa — — 12,330 24,659 12,330 — — — — — — — Theobroma cacao — 12,330 24,659 — 24,659 — — — — — — — Timonius subauritus 1,510,936 36,388 24,259 12,129 — — 12,129 — — — — — Tournefortia argentea — 12,129 12,129 12,330 — 12,330 — — — — — — Trichospermum ledermannii 153,586 36,989 24,659 24,659 12,330 — — — — — — — Vitex cofassus — — 12,330 — — 12,330 24,659 12,330 — 24,659 12,330 12Xylocarpus granatum 153,586 61,648 24,659 36,989 12,330 36,989 — 12,330 — — — — Unknown 0 151,094 36,989 — — — — — — — — — — Unknown 1 307,171 12,129 12,330 — — — — — — — — — Unknown 2 307,171 — — — — — — — — — — — Unknown 3 — 12,330 — — 12,330 — — — — — — — Unknown 5 — 24,259 36,989 24,659 — — — — — — — — Unknown 11 — — — 12,330 — — — — — — — — Unknown, other — 12,330 — 12,330 — — — — — — — —  Total 76,110,228 10,058,255 4,047,132 2,219,238 1,558,645 822,076 551,827 318,767 220,731 160,084 122,295 135

Table 3—Estimated number of live trees on forest land by species and diameter class (continued)
21

Palau’s Forest Resources, 2003

14,202 12,091

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

Less than 5 5–10.9 11–19.9

Stand size class (inches)

Area (acres)

Volcanic

Limestone

57,612

6,511 6,272

Figure 6—The trees that characterize volcanic forests tend to be somewhat small, in the 5- to 

11-inch category. Forested stands on limestone soils tend to be characterized by larger trees in 

the 11- to 20-inch category.

Figure 7—Small trees are very common in Palau, indicating regeneration is abundant.

Number of trees by size class

Total trees in all classes: 94,598,338 

0

10

20

30

40

50

1.0–2.93.0–4.9

5.0–6.97.0–8.9

9.0–10.9

11.0–12.9

13.0–14.9

15.0–16.9

17.0–18.9

19.0–20.9

21.0–22.923.0–24.9

25.0–26.9

27.0–28.9

29.0+

Diameter (inches)

Trees (millions)

60
22

RESOURCE BULLETIN PNW-RB-252

Figure 8—For trees greater than or equal to 5 inches in diameter, the most common heights attained 

range from 30 to 50 feet tall.

Figure 9—As with numbers of trees, gross volume of wood tends to be concentrated in the smaller 

diameter classes. However, many larger diameter trees contribute to the substantial volume in those 

size classes.

0

1

2

3

4

5

6

7

<10

10–19

20–29

30–39

40–4950–5960–6970–7980–89

90–99

100 +

Height (feet)

Number of trees (millions) 

Number of trees

by height class

(>5 inches diameter)

Volume by size class

Total volume in all classes: 268,020,715

0

10

20

30

40

50

60

70

80

5.0–9.9

10.0–14.9

15.0–19.920.0–24.925.0–29.9

30.0–34.9

35.0–39.9

40+

Diameter (inches)

Gross v

olume (million cubic feet)

90
23

Palau’s Forest Resources, 2003

Table 4—Estimated gross volume of all live trees on forest land by forest-type group and 

diameter class

Diameter class (inches)

Forest-type group Less than 5 5–10.9 11–19.9 20+ All sizes

Cubic feet

Limestone forest 6,248,751 28,309,959 28,665,545 19,013,470 82,237,724

Volcanic/ravine forest 28,116,999 62,596,123 60,913,733 68,521,890 220,148,745

 Total 34,365,749 90,906,081 89,579,278 87,535,360 302,386,469

Table 5—Estimated net volume of all live trees ≥5 inches in diameter on 

forest land by forest-type group and diameter class

Diameter class (inches)

Forest-type group 5–10.9 11–19.9 20+ All sizes

Cubic feet

Limestone forest 28,285,444 28,570,500 18,577,815 75,433,759

Volcanic/ravine forest 62,311,497 60,297,635 67,289,502 189,898,634

 Total 90,596,941 88,868,135 85,867,317 265,332,393

Biomass by size class

Biomass total, all classes: 4,686,793

0

200

400

600

800

1,000

1,200

1,400

Stem

bio

mass (thousand tons)

5.0–9.9

10.0–14.9

15.0–19.920.0–24.925.0–29.9

30.0–34.9

35.0–39.9

40+

Diameter (inches)

Figure 10—Biomass is also concentrated in the smaller size classes.
24

Species

Diameter class (inches)

5.0–6.9 7.0–8.9

9.0–

10.9

11.0–

12.9

13.0–

14.9

15.0–

16.9

17.0–

18.9

19.0–

20.9

21.0–

22.9

23.0–

24.9

25.0

26

Cubic feet

Aglaia palauensis 358,196 217,203 448,937 — — 759,169 — — — — — Allophylus ternatus — 206,199 — — — — — — — — — Allophylus timorensis 29,280 — — — — — — — — — — Alphitonia carolinensis 735,731 1,129,350 467,218 1,269,881 — 834,761 — — — — — Annona reticulata 62,771 — — — — — — — — — — Areca catechu 211,184 80,981 — — — — — — — — — Artocarpus mariannensis — — — — 440,417 — — 635,097 — 1,278,815 2,134,Astronidium palauense 577,119 208,231 364,270 — — — — — — — — Avicennia marina — — 114,276 — — — — — — — 1,308,Badusa palauensis 453,193 211,682 816,673 379,532 578,607 608,341 — — — — — Barringtonia racemosa 452,159 527,080 711,656 1,053,700 229,549 — — — — — — Bruguiera gymnorrhiza 524,400 1,038,683 871,613 397,703 852,655 — — — — — — Buchanania palawensis 243,769 — 140,678 — — — — — 924,553 — — Calophyllum inophyllum 188,139 500,540 392,480 704,449 194,770 748,863 — 1,760,060 — 947,598 — Calophyllum pelewense 204,921 498,086 — 337,712 — — — — — — — Calophyllum soulattri 63,170 79,559 — 338,061 — — — — — — — Calophyllum sp. — 164,982 192,860 — — — 309,745 — 1,243,385 — — Campnosperma brevipetiolata 410,952 750,845 973,757 2,465,508 2,491,979 3,277,299 4,050,260 1,937,832 3,038,783 3,494,230 — Canarium hirsutum 116,651 119,701 142,942 195,799 — — 497,877 — — — — Casearia cauliflora — 157,802 — — — — — — — — — Casearia sp. 300,526 118,182 207,941 — — — — — — — — Casuarina equisetifolia 33,773 — — — — — — — — — 1,403,Cerbera floribunda 50,830 — — 143,752 — — — — — — — Cerbera manghas 261,427 272,907 719,166 529,306 267,966 294,836 — — — — — Cocos nucifera — — 1,364,708 4,923,463 1,481,204 — 647,213 — — — — Commersonia bartramia 29,882 — — — — — — — — — — Cordia micronesica — — — — 312,315 — — — — — — Cyathea lunulata 683,380 708,128 306,007 277,547 — — — — — — — Diospyros ferrea 128,287 256,014 — — — — — — — — — Diospyros sp. 187,930 277,568 — 251,528 — — — — — — — Dodonaea viscosa 34,597 67,158 163,789 — — 846,599 — — 530,228 — — Dracaena multiflora 204,143 115,524 — 147,157 — — — — — — — Drypetes nitida 47,105 74,774 — — 251,142 — — — — — — Dysoxylum sp. 64,752 — — — — — — — — — — Elaeocarpus graeffei 64,508 — — — — — — — — — — Elaeocarpus joga 662,676 1,399,992 95,607 1,623,421 1,376,416 1,568,153 — — — — — Erythrina fusca — — — — — — 600,183 — — — — Eugenia cumini 383,104 338,074 160,248 380,749 298,384 400,104 — — — — — Eugenia javanica 127,922 369,502 677,261 190,441 297,325 740,797 497,380 426,207 — — 1,092,7Eugenia reinwardtiana 1,003,419 1,093,777 1,425,442 930,288 382,084 560,575 616,284 — — — — Eugenia sp. 130,011 — — — — — — — — — — Fagraea ksid 161,826 — 499,547 481,374 277,505 822,261 — — — — — Ficus sp. — — — — — — — 409,933 — — — Ficus tinctoria — 56,385 — — — — — — — — — 

Table 6—Estimated gross volume of all live trees on forest land by species and diameter class
25

Species

Diameter class (inches)

5.0–6.9 7.0–8.9

9.0–

10.9

11.0–

12.9

13.0–

14.9

15.0–

16.9

17.0–

18.9

19.0–

20.9

21.0–

22.9

23.0–

24.9

25.0

26

Cubic feet

Flacourtia rukam 399,756 205,465 — 146,034 — — — — — — — Garcinia matudai 181,521 80,400 155,242 — 307,851 — — — — — — Garcinia rumiyo 547,736 734,850 507,022 730,739 — — — — — — — Garcinia sp. 937,863 459,661 605,835 579,278 — — — — — — — Gironniera celtidifolia 89,179 172,200 — — — — — — — — — Glochidion ramiflorum 296,385 533,580 139,993 231,111 — — — — — — — Glochidion sp. 93,117 — — — — — — — — — — Gmelina elliptica 218,166 159,556 363,533 401,804 534,904 701,063 694,331 513,192 — — — Gmelina palawensis 860,819 888,819 771,909 732,695 1,121,009 — 673,159 — — — — Gmelina sp. — 275,888 190,681 268,382 159,607 — 420,704 — — — — Gulubia palauensis 518,759 — — — — — — — — — — Hernandia sonora 48,678 93,646 — 227,398 — — — — — — — Hernandia sp. 72,835 — 120,735 144,215 — — — — — 1,376,732 — Heterospathe elata 223,139 181,631 — — — — — — — — — Hibiscus tiliaceus 157,229 191,147 — — — — — — — — — Horsfieldia amklaal 604,676 248,982 — 270,510 1,020,728 — — — — — — Horsfieldia novo-guineensis 303,272 254,896 744,724 — 344,493 396,646 806,216 930,642 — — — Horsfieldia palauensis 1,795,603 1,549,305 1,962,502 870,606 242,883 — — 856,766 — — — Horsfieldia sp. 61,419 — — — — — — — — — — Inocarpus fagifer 29,390 — — — — — — — — — — Intsia bijuga 60,415 420,363 256,073 176,722 609,515 1,153,528 1,228,373 633,825 742,335 1,089,139 — Lumnitzera littorea — — 127,232 — — — — — — — — Macaranga carolinensis 328,807 186,047 167,974 — — — — — — — — Manilkara udoido 753,108 207,350 226,930 — 225,960 288,213 383,995 — — — — Manilkara zapota 95,965 — 119,687 177,080 — — — 328,616 575,215 — — Morinda citrifolia — 142,104 — — — — — — — — — Morinda latibracteata 211,608 — — — — — — — — — — Morinda pedunculata 81,626 — — — — — — — — — — Morinda sp. 127,267 — — — — — — — — — — Nephelium lappaceum — 100,828 — — — — — — — — — Osmoxylon oliveri 65,896 — — — — — — — — — — Osmoxylon sp. 145,875 — — — — — — — — — — Pandanus aimiriikensis 136,228 51,506 84,627 — — — — — — — — Pandanus dubius 677,136 220,116 — — — — — — — — — Pandanus kanehirae — 332,031 — — — — — — — — — Pandanus tectorius 261,072 188,207 — — — — — — — — — Pandanus utiyamai — — — — — — — — — — 1,050,2Pangium edule — 73,623 163,712 — — — — — — — — Parinari corymbosum 689,431 506,454 431,678 1,097,576 1,990,397 421,904 852,296 607,489 1,822,127 1,386,894 3,444,6Parinari laurina 1,056,482 521,650 925,184 962,513 — 1,115,534 — — — 1,399,150 — Parinari sp. 66,714 — — — — — — — — — — Pinanga insignis 7,832,438 303,291 133,263 — — — — — — — — Pithecellobium dulce — 80,161 — — — — — — — — — Pouteria calcarea 160,981 — — — — — — — — — — Table 6—Estimated gross volume of all live trees on forest land by species and diameter class (continued)
26

Table 6—Estimated gross volume of all live trees on forest land by species and diameter class (continued)Species

Diameter class (inches)

5.0–6.9 7.0–8.9

9.0–

10.9

11.0–

12.9

13.0–

14.9

15.0–

16.9

17.0–

18.9

19.0–

20.9

21.0–

22.9

23.0–

24.9

25.0

26

Cubic feet

Pouteria obovata 541,147 1,054,853 864,486 712,852 — — 595,227 392,699 — — — Pouteria sp. — 59,315 — — — — — — — — — Premna obtusifolia 127,669 119,095 — — — — — — — — — Pterocarpus indicus — — — — — 229,537 — — 488,213 — — Ptychosperma palauensis 314,678 — — — — — — — — — — Rhizophora apiculata 3,089,759 2,545,438 1,320,834 612,144 882,643 — — — — — — Rhizophora mucronata 815,800 758,392 183,142 507,898 — — — — — — — Rhus taitensis 288,555 725,964 586,929 1,176,660 1,461,139 495,846 560,851 — — — — Rinorea carolinensis — 44,758 — — — — — — — — — Semecarpus venenosus 1,155,137 852,343 954,517 891,534 312,069 526,363 — — — — 1,367,0Sonneratia alba 23,568 169,976 — 149,403 — 538,634 — — — — — Stemonurus ammui — 70,618 — — — 633,032 808,378 1,703,686 — — — Swietenia macrophylla 175,805 — 151,802 — — — — — — — — Swietenia mahagoni 179,811 71,296 163,613 — — — — — — — — Symplocos racemosa 128,478 96,128 — — — — — — — — — Terminalia catappa — 165,490 340,579 298,932 — — — — — — — Theobroma cacao 30,258 187,894 — 399,693 — — — — — — — Timonius subauritus 168,555 187,252 131,543 — — 438,429 — — — — — Tournefortia argentea 22,145 44,889 116,849 — 143,626 — — — — — — Trichospermum ledermannii 129,573 288,139 387,762 262,220 — — — — — — — Vitex cofassus — 91,031 — — 319,190 714,086 435,761 — 1,255,579 1,024,803 924,6Xylocarpus granatum 178,267 113,859 368,179 178,624 554,708 — 239,527 — — — — Unknown 0 120,479 — — — — — — — — — — Unknown 1 35,180 48,232 — — — — — — — — — Unknown 3 44,577 — — 184,062 — — — — — — — Unknown 5 67,712 235,500 210,219 — — — — — — — — Unknown 11 — — 126,165 — — — — — — — — Unknown, other 50,997 — 140,256 — — — — — — — —  Total 37,070,470 28,333,126 25,502,485 29,412,054 19,963,042 19,114,573 14,917,757 11,136,046 10,620,417 11,997,362 12,725,0
27

Table 7—Estimated aboveground dry stem weight of all live trees on forest land by species and diameter classSpecies

Diameter class (inches)

5.0–6.9 7.0–8.9

9.0–

10.9

11.0–

12.9

13.0–

14.9

15.0–

16.9

17.0–

18.9

19.0–

20.9

21.0–

22.9

23.0–

24.9

25

2

Tons

Aglaia palauensis 5,722 3,470 7,172 — — 12,128 — — — — — Allophylus ternatus — 3,294 — — — — — — — — — Allophylus timorensis 468 — — — — — — — — — — Alphitonia carolinensis 11,753 18,041 7,464 20,286 — 13,335 — — — — — Annona reticulata 1,003 — — — — — — — — — — Areca catechu 3,374 1,294 — — — — — — — — — Artocarpus mariannensis — — — — 7,036 — — 10,146 — 20,429 34Astronidium palauense 9,219 3,326 5,819 — — — — — — — — Avicennia marina — — 1,826 — — — — — — — 20Badusa palauensis 7,240 3,382 13,046 6,063 9,243 9,718 — — — — — Barringtonia racemosa 7,223 8,420 11,369 16,833 3,667 — — — — — — Bruguiera gymnorrhiza 8,377 16,593 13,924 6,353 13,621 — — — — — — Buchanania palawensis 3,894 — 2,247 — — — — — 14,770 — — Calophyllum inophyllum 3,426 9,115 7,147 12,828 3,547 13,637 — 32,051 — 17,256 — Calophyllum pelewense 3,274 7,957 — 5,395 — — — — — — — Calophyllum soulattri 1,009 1,271 — 5,401 — — — — — — — Calophyllum sp. — 3,426 4,005 — — — 6,432 — 25,819 — — Campnosperma brevipetiolata 6,565 11,995 15,556 39,386 39,809 52,355 64,703 30,957 48,545 55,820 — Canarium hirsutum 1,491 1,530 1,827 2,502 — — 6,363 — — — — Casearia cauliflora — 2,521 — — — — — — — — — Casearia sp. 5,953 2,341 4,119 — — — — — — — — Casuarina equisetifolia 896 — — — — — — — — — 37Cerbera floribunda 812 — — 2,296 — — — — — — — Cerbera manghas 4,176 4,360 11,489 8,456 4,281 4,710 — — — — — Cocos nucifera — — 21,801 78,652 23,662 — 10,339 — — — — Commersonia bartramia 477 — — — — — — — — — — Cordia micronesica — — — — 5,287 — — — — — — Cyathea lunulata 10,917 11,312 4,888 4,434 — — — — — — — Diospyros ferrea 2,869 5,726 — — — — — — — — — Diospyros sp. 4,203 6,208 — 5,625 — — — — — — — Dodonaea viscosa 553 1,073 2,617 — — 13,524 — — 8,470 — — Dracaena multiflora 3,261 1,845 — 2,351 — — — — — — — Drypetes nitida 753 1,195 — — 4,012 — — — — — — Dysoxylum sp. 1,034 — — — — — — — — — — Elaeocarpus graeffei 1,031 — — — — — — — — — — Elaeocarpus joga 10,586 22,365 1,527 25,934 21,988 25,051 — — — — — Erythrina fusca — — — — — — 4,792 — — — — Eugenia cumini 7,955 7,020 3,328 7,906 6,196 8,308 — — — — — Eugenia javanica 2,656 7,673 14,063 3,955 6,174 15,383 10,328 8,850 — — 22Eugenia reinwardtiana 20,836 22,712 29,599 19,317 7,934 11,640 12,797 — — — — Eugenia sp. 2,700 — — — — — — — — — — Fagraea ksid 3,775 — 11,652 11,228 6,473 19,179 — — — — — Ficus sp. — — — — — — — 4,190 — — — Ficus tinctoria — 703 — — — — — — — — — 
28Table 7—Estimated aboveground dry stem weight of all live trees on forest land by species and diameter class (continued)

Species

Diameter class (inches)

5.0–6.9 7.0–8.9

9.0–

10.9

11.0–

12.9

13.0–

14.9

15.0–

16.9

17.0–

18.9

19.0–

20.9

21.0–

22.9

23.0–

24.9

25

2

Tons

Flacourtia rukam 6,386 3,282 — 2,333 — — — — — — — Garcinia matudai 4,349 1,926 3,720 — 7,376 — — — — — — Garcinia rumiyo 13,124 17,607 12,148 17,509 — — — — — — — Garcinia sp. 22,471 11,013 14,516 13,880 — — — — — — — Gironniera celtidifolia 1,425 2,751 — — — — — — — — — Glochidion ramiflorum 4,735 8,524 2,236 3,692 — — — — — — — Glochidion sp. 1,488 — — — — — — — — — — Gmelina elliptica 3,485 2,549 5,807 6,419 8,545 11,199 11,092 8,198 — — — Gmelina palawensis 13,752 14,199 12,331 11,705 17,908 — 10,754 — — — — Gmelina sp. — 4,407 3,046 4,287 2,550 — 6,721 — — — — Gulubia palauensis 8,287 — — — — — — — — — — Hernandia sonora 451 868 — 2,107 — — — — — — — Hernandia sp. 1,164 — 1,929 2,304 — — — — — 21,993 — Heterospathe elata 3,565 2,902 — — — — — — — — — Hibiscus tiliaceus 2,863 3,481 — — — — — — — — — Horsfieldia amklaal 9,660 3,977 — 4,321 16,306 — — — — — — Horsfieldia novo-guineensis 4,845 4,072 11,897 — 5,503 6,336 12,879 14,867 — — — Horsfieldia palauensis 28,685 24,750 31,351 13,908 3,880 — — 13,687 — — — Horsfieldia sp. 981 — — — — — — — — — — Inocarpus fagifer 470 — — — — — — — — — — Intsia bijuga 1,177 8,193 4,991 3,444 11,879 22,482 23,941 12,353 14,468 21,227 — Lumnitzera littorea — — 2,033 — — — — — — — — Macaranga carolinensis 5,253 2,972 2,683 — — — — — — — — Manilkara udoido 12,031 3,312 3,625 — 3,610 4,604 6,134 — — — — Manilkara zapota 1,533 — 1,912 2,829 — — — 5,250 9,189 — — Morinda citrifolia — 2,270 — — — — — — — — — Morinda latibracteata 3,380 — — — — — — — — — — Morinda pedunculata 1,304 — — — — — — — — — — Morinda sp. 2,033 — — — — — — — — — — Nephelium lappaceum — 1,611 — — — — — — — — — Osmoxylon oliveri 1,053 — — — — — — — — — — Osmoxylon sp. 2,330 — — — — — — — — — — Pandanus aimiriikensis 2,176 823 1,352 — — — — — — — — Pandanus dubius 10,817 3,516 — — — — — — — — — Pandanus kanehirae — 5,304 — — — — — — — — — Pandanus tectorius 4,171 3,007 — — — — — — — — — Pandanus utiyamai — — — — — — — — — — 16Pangium edule — 1,176 2,615 — — — — — — — — Parinari corymbosum 16,739 12,297 10,481 26,649 48,327 10,244 20,694 14,750 44,241 33,674 83Parinari laurina 22,952 11,333 20,100 20,911 — 24,235 — — — 30,397 — Parinari sp. 1,449 — — — — — — — — — — Pinanga insignis 125,123 4,845 2,129 — — — — — — — — Pithecellobium dulce — 1,281 — — — — — — — — — Pouteria calcarea 2,572 — — — — — — — — — — 
29

Species

Diameter class (inches)

5.0–6.9 7.0–8.9

9.0–

10.9

11.0–

12.9

13.0–

14.9

15.0–

16.9

17.0–

18.9

19.0–

20.9

21.0–

22.9

23.0–

24.9

25

2

Tons

Pouteria obovata 8,645 16,851 13,810 11,388 — — 9,509 6,273 — — — Pouteria sp. — 1,384 — — — — — — — — — Premna obtusifolia 2,040 1,903 — — — — — — — — — Pterocarpus indicus — — — — — 3,814 — — 8,112 — — Ptychosperma palauensis 5,027 — — — — — — — — — — Rhizophora apiculata 49,359 40,663 21,100 9,779 14,100 — — — — — — Rhizophora mucronata 13,032 12,115 2,926 8,114 — — — — — — — Rhus taitensis 4,610 11,597 9,376 18,797 23,342 7,921 8,960 — — — — Rinorea carolinensis — 715 — — — — — — — — — Semecarpus venenosus 18,453 13,616 15,248 14,242 4,985 8,409 — — — — 21Sonneratia alba 376 2,715 — 2,387 — 8,605 — — — — — Stemonurus ammui — 1,128 — — — 10,113 12,914 27,216 — — — Swietenia macrophylla 2,358 — 2,036 — — — — — — — — Swietenia mahagoni 3,505 1,390 3,189 — — — — — — — — Symplocos racemosa 2,052 1,536 — — — — — — — — — Terminalia catappa — 3,119 6,420 5,635 — — — — — — — Theobroma cacao 483 3,002 — 6,385 — — — — — — — Timonius subauritus 2,693 2,991 2,101 — — 7,004 — — — — — Tournefortia argentea 354 717 1,867 — 2,294 — — — — — — Trichospermum ledermannii 2,070 4,603 6,195 4,189 — — — — — — — Vitex cofassus — 1,454 — — 5,099 11,408 6,961 — 20,058 16,371 14Xylocarpus granatum 2,848 1,819 5,882 2,854 8,861 — 3,826 — — — — Unknown 0 1,925 — — — — — — — — — — Unknown 1 562 771 — — — — — — — — — Unknown 3 712 — — 2,940 — — — — — — — Unknown 5 1,082 3,762 3,358 — — — — — — — — Unknown 11 — — 2,015 — — — — — — — — Unknown, other 815 — 2,241 — — — — — — — —  Total 630,759 486,266 445,152 508,209 347,497 335,342 250,139 188,788 193,672 217,167 251Table 7—Estimated aboveground dry stem weight of all live trees on forest land by species and diameter class (continued)
30

Species

Diameter class (inches)

5.0–6.9 7.0–8.9

9.0–

10.9

11.0–

12.9

13.0–

14.9

15.0–

16.9

17.0–

18.9

19.0–

20.9

21.0–

22.9

23.0–

24.9

25.0

26

Tons

Aglaia palauensis 2,804 1,700 3,514 — — 5,943 — — — — — Allophylus ternatus — 1,614 — — — — — — — — — Allophylus timorensis 229 — — — — — — — — — — Alphitonia carolinensis 5,759 8,840 3,657 9,940 — 6,534 — — — — — Annona reticulata 491 — — — — — — — — — — Areca catechu 1,653 634 — — — — — — — — — Artocarpus mariannensis — — — — 3,447 — — 4,971 — 10,010 16,7Astronidium palauense 4,518 1,630 2,851 — — — — — — — — Avicennia marina — — 895 — — — — — — — 10,2Badusa palauensis 3,547 1,657 6,393 2,971 4,529 4,762 — — — — — Barringtonia racemosa 3,539 4,126 5,571 8,248 1,797 — — — — — — Bruguiera gymnorrhiza 4,105 8,131 6,823 3,113 6,674 — — — — — — Buchanania palawensis 1,908 — 1,101 — — — — — 7,237 — — Calophyllum inophyllum 1,679 4,466 3,502 6,286 1,738 6,682 — 15,705 — 8,455 — Calophyllum pelewense 1,604 3,899 — 2,644 — — — — — — — Calophyllum soulattri 494 623 — 2,646 — — — — — — — Calophyllum sp. — 1,679 1,962 — — — 3,152 — 12,651 — — Campnosperma brevipetiolata 3,217 5,877 7,622 19,299 19,507 25,654 31,704 15,169 23,787 27,352 — Canarium hirsutum 730 750 895 1,226 — — 3,118 — — — — Casearia cauliflora — 1,235 — — — — — — — — — Casearia sp. 2,917 1,147 2,018 — — — — — — — — Casuarina equisetifolia 439 — — — — — — — — — 18,2Cerbera floribunda 398 — — 1,125 — — — — — — — Cerbera manghas 2,046 2,136 5,629 4,143 2,098 2,308 — — — — — Cocos nucifera — — 10,683 38,540 11,595 — 5,066 — — — — Commersonia bartramia 234 — — — — — — — — — — Cordia micronesica — — — — 2,591 — — — — — — Cyathea lunulata 5,349 5,543 2,395 2,173 — — — — — — — Diospyros ferrea 1,406 2,806 — — — — — — — — — Diospyros sp. 2,060 3,042 — 2,756 — — — — — — — Dodonaea viscosa 271 526 1,282 — — 6,627 — — 4,150 — — Dracaena multiflora 1,598 904 — 1,152 — — — — — — — Drypetes nitida 369 585 — — 1,966 — — — — — — Dysoxylum sp. 507 — — — — — — — — — — Elaeocarpus graeffei 505 — — — — — — — — — — Elaeocarpus joga 5,187 10,959 748 12,708 10,774 12,275 — — — — — Erythrina fusca — — — — — — 2,348 — — — — Eugenia cumini 3,898 3,440 1,631 3,874 3,036 4,071 — — — — — Eugenia javanica 1,302 3,760 6,891 1,938 3,025 7,538 5,061 4,337 — — 11,1Eugenia reinwardtiana 10,210 11,129 14,504 9,466 3,888 5,704 6,271 — — — — Eugenia sp. 1,323 — — — — — — — — — — Fagraea ksid 1,850 — 5,709 5,502 3,172 9,398 — — — — — Ficus sp. — — — — — — — 2,053 — — — Ficus tinctoria — 344 — — — — — — — — — 

Table 8—Estimated carbon mass of all live trees on forest land by species and diameter class
31

Species

Diameter class (inches)

5.0–6.9 7.0–8.9

9.0–

10.9

11.0–

12.9

13.0–

14.9

15.0–

16.9

17.0–

18.9

19.0–

20.9

21.0–

22.9

23.0–

24.9

25.0

26

Tons

Flacourtia rukam 3,129 1,608 — 1,143 — — — — — — — Garcinia matudai 2,131 944 1,823 — 3,614 — — — — — — Garcinia rumiyo 6,431 8,627 5,953 8,579 — — — — — — — Garcinia sp. 11,011 5,397 7,113 6,801 — — — — — — — Gironniera celtidifolia 698 1,348 — — — — — — — — — Glochidion ramiflorum 2,320 4,177 1,096 1,809 — — — — — — — Glochidion sp. 729 — — — — — — — — — — Gmelina elliptica 1,708 1,249 2,846 3,145 4,187 5,488 5,435 4,017 — — — Gmelina palawensis 6,738 6,957 6,042 5,735 8,775 — 5,269 — — — — Gmelina sp. — 2,160 1,493 2,101 1,249 — 3,293 — — — — Gulubia palauensis 4,061 — — — — — — — — — — Hernandia sonora 221 425 — 1,032 — — — — — — — Hernandia sp. 570 — 945 1,129 — — — — — 10,777 — Heterospathe elata 1,747 1,422 — — — — — — — — — Hibiscus tiliaceus 1,403 1,706 — — — — — — — — — Horsfieldia amklaal 4,733 1,949 — 2,117 7,990 — — — — — — Horsfieldia novo-guineensis 2,374 1,995 5,830 — 2,697 3,105 6,311 7,285 — — — Horsfieldia palauensis 14,056 12,128 15,362 6,815 1,901 — — 6,707 — — — Horsfieldia sp. 481 — — — — — — — — — — Inocarpus fagifer 230 — — — — — — — — — — Intsia bijuga 577 4,015 2,446 1,688 5,821 11,016 11,731 6,053 7,089 10,401 — Lumnitzera littorea — — 996 — — — — — — — — Macaranga carolinensis 2,574 1,456 1,315 — — — — — — — — Manilkara udoido 5,895 1,623 1,776 — 1,769 2,256 3,006 — — — — Manilkara zapota 751 — 937 1,386 — — — 2,572 4,503 — — Morinda citrifolia — 1,112 — — — — — — — — — Morinda latibracteata 1,656 — — — — — — — — — — Morinda pedunculata 639 — — — — — — — — — — Morinda sp. 996 — — — — — — — — — — Nephelium lappaceum — 789 — — — — — — — — — Osmoxylon oliveri 516 — — — — — — — — — — Osmoxylon sp. 1,142 — — — — — — — — — — Pandanus aimiriikensis 1,066 403 662 — — — — — — — — Pandanus dubius 5,300 1,723 — — — — — — — — — Pandanus kanehirae — 2,599 — — — — — — — — — Pandanus tectorius 2,044 1,473 — — — — — — — — — Pandanus utiyamai — — — — — — — — — — 8,2Pangium edule — 576 1,282 — — — — — — — — Parinari corymbosum 8,202 6,025 5,136 13,058 23,680 5,019 10,140 7,227 21,678 16,500 40,9Parinari laurina 11,247 5,553 9,849 10,246 — 11,875 — — — 14,894 — Parinari sp. 710 — — — — — — — — — — Pinanga insignis 61,310 2,374 1,043 — — — — — — — — Pithecellobium dulce — 627 — — — — — — — — — Pouteria calcarea 1,260 — — — — — — — — — — Table 8—Estimated carbon mass of all live trees on forest land by species and diameter class (continued)
32

Table 8—Estimated carbon mass of all live trees on forest land by species and diameter class (continued)

Species

Diameter class (inches)

5.0–6.9 7.0–8.9

9.0–

10.9

11.0–

12.9

13.0–

14.9

15.0–

16.9

17.0–

18.9

19.0–

20.9

21.0–

22.9

23.0–

24.9

25.0

26

Tons

Pouteria obovata 4,236 8,257 6,767 5,580 — — 4,659 3,074 — — — Pouteria sp. — 678 — — — — — — — — — Premna obtusifolia 999 932 — — — — — — — — — Pterocarpus indicus — — — — — 1,869 — — 3,975 — — Ptychosperma palauensis 2,463 — — — — — — — — — — Rhizophora apiculata 24,186 19,925 10,339 4,792 6,909 — — — — — — Rhizophora mucronata 6,386 5,937 1,434 3,976 — — — — — — — Rhus taitensis 2,259 5,683 4,594 9,211 11,437 3,881 4,390 — — — — Rinorea carolinensis — 350 — — — — — — — — — Semecarpus venenosus 9,042 6,672 7,472 6,979 2,443 4,120 — — — — 10,7Sonneratia alba 184 1,331 — 1,169 — 4,216 — — — — — Stemonurus ammui — 553 — — — 4,955 6,328 13,336 — — — Swietenia macrophylla 1,156 — 998 — — — — — — — — Swietenia mahagoni 1,717 681 1,563 — — — — — — — — Symplocos racemosa 1,006 752 — — — — — — — — — Terminalia catappa — 1,529 3,146 2,761 — — — — — — — Theobroma cacao 237 1,471 — 3,129 — — — — — — — Timonius subauritus 1,319 1,466 1,030 — — 3,432 — — — — — Tournefortia argentea 173 351 915 — 1,124 — — — — — — Trichospermum ledermannii 1,014 2,255 3,035 2,053 — — — — — — — Vitex cofassus — 713 — — 2,499 5,590 3,411 — 9,828 8,022 7,2Xylocarpus granatum 1,395 891 2,882 1,398 4,342 — 1,875 — — — — Unknown 0 943 — — — — — — — — — — Unknown 1 275 378 — — — — — — — — — Unknown 3 — — 988 — — — — — — — — Unknown 5 349 — — 1,441 — — — — — — — Unknown 11 530 1,843 1,646 — — — — — — — — Unknown, other 399 — 1,098 — — — — — — — —  Total 309,072 238,270 218,124 249,022 170,274 164,318 122,568 92,506 94,899 106,412 123,4
33

Palau’s Forest Resources, 2003

Number of Canopy and Understory Species

In addition to counting and measuring overstory trees, understory vegetation 

cover and layer heights were estimated for shrubs, forbs, vines, and grasses on 

FIA subplots where a species occupied at least 3 percent cover on that subplot 

(table 9). Tree seedlings that are less than or equal to 1 inch in diameter are 

also estimated as understory vegetation cover (table 10). Special interest species 

(e.g., rare, endangered, medicinal, or invasive) identified by island foresters were 

also noted when found. However, if a species covered less than 3 percent of a 

subplot and it was not listed as special interest, it was not enumerated.

Forest type

Volcanic Limestone

Scientific name Cover

Number of 

subplots

Standard 

deviation Cover

Number of 

subplots

Standard 

deviation

Percent Percent

Achyranthes aspera L. 2.0 1 — — — —

Adiantum philippense L. 4.8 4 4.1 — — —

Alpinia carolinensis Koidz. 9.6 14 17.6 — — —

Alpinia pubiflora K.Schum. 5.0 3 4.4 — — —

Alpinia purpurata (Vieill.) K. Schum. 3.3 3 3.2 — — —

Alpinia sp. Roxb. 3.2 13 3.0 — — —

Angiopteris evecta (J.R. Forst.) Hoffman 3.7 3 2.5 — — —

Antrophyum plantagineum (Cav.) Kaulf. — — — 1.0 2 0.0

Asplenium nidus L. 1.6 65 1.02 1.4 23 0.7

Asplenium pellucidum Lam. — — — 2.0 1 —

Asplenium polyodon G. Forst. 1.0 1 — 2.1 10 2.1

Bambusa vulgaris Schrad. ex J.C. Wendl. 2.0 1 — — — —

Blechnum orientale L. 4.6 16 6.1 — — —

Bolbitis sp. Schott. 3.3 3 4.0 — — —

Caesalpinia major (Medik.) Dandy & Exell 1.0 1 — — — —

Caesalpinia sp. L. 2.0 1 — — — —

Calamus sp. L. 1.0 1 — 5.0 2 4.2

Cassytha filiformis L. 6.0 3 7.8 — — —

Centotheca lappacea (L.) Desv. 1.3 3 0.6 — — —

Cheilanthes tenuifolia (Burmann) Swartz 1.0 1 — — — —

Clerodendrum sp. L. 1.0 2 0.0 — — —

Clidemia hirta (L.) D. Don 1.3 4 0.5 — — —

Clidemia sp. D. Don 1.0 1 — — — —

Combined ferns 1.0 2 0.0 — — —

Costus speciosus Smith 2.2 5 1.1 — — —

Cyperus sp. L. 50.0 1 — — — —

Cyrtosperma chamissonis (Schott) Merrill 8.3 3 10.1 — — —

Dalbergia palauensis Hosokawa 3.0 1 — — — —

Davallia solida (Forster fil.) Swartz. Schrad 1.7 3 1.2 1.5 4 0.6

Davallia sp. Sm. 3.0 5 1.9 — — —

Decaspermum raymundii Diels 2.0 1 — — — —

Decaspermum sp. J. R. Forst. & G. Forst. 2.0 2 1.4 — — —

Derris sp. Lour. 35.0 4 12.9 — — —

Derris trifoliata Lour. 19.0 5 13.4 — — —

Table 9—Average nontree understory covera on FIA field subplots by species and forest type
34

RESOURCE BULLETIN PNW-RB-252

Forest type

Volcanic Limestone

Scientific name Cover

Number of 

subplots

Standard 

deviation Cover

Number of 

subplots

Standard 

deviation

Percent Percent

Dianella sp. Lam. 1.7 3 1.2 — — —

Dioscorea alata L. 5.0 4 1.6 — — —

Dioscorea bulbifera L. 1.5 2 0.7 — — —

Dioscorea sp. L. 3.0 1 — — — —

Donax cannaeformis (Forst. f.) K. Schum. 11.0 9 11.9 — — —

Donax sp. Lour. 24.0 3 23.3 — — —

Eriachne pallescens R. Br. 45.0 4 5.8 — — —

Eurya japonica (Korth.) This.-Dyer 7.8 10 9.9 — — —

Eustachys petraea (Sw.) Desv. 4.7 3 0.6 — — —

Ficus sp. L. 1.5 4 1.0 — — —

Ficus tinctoria Forst. f. 6.5 2 2.1 — — —

Flagellaria gigantea Hook f. 1.0 1 — — — —

Freycinetia villalobosii Martelli 23.8 6 29.3 — — —

Gleichenia linearis (Luers.) Fosberg 47.1 20 38.3 — — —

Gliricidia sp. (Blank) 15.0 1 — — — —

Hanguana malayana Merrill 19.0 4 14.5 — — —

Hedyotis cornifolia Kaneh. 2.0 7 1.2 — — —

Hedyotis korrorensis (Valeton) Hosok. 1.0 1 — — — —

Hedyotis sp. L. 3.6 5 3.7 — — —

Heterogonium pinnatum (Copel.) Holtt. 2.0 1 — — — —

Hippobroma longiflora (L.) G. Don 1.0 1 — — — —

Hyptis capitata Jacq. 1.5 2 0.7 — — —

Ipomea sp. L. — — — 1.0 1 —

Ischaemum polystachyum J. S. Presl 17.7 3 19.7 — — —

Ixora casei Hance 4.7 3 2.9 — — —

Ixora sp. L. 2.8 37 3.1 5.0 1 —

Lantana camara L. 2.5 2 0.7 — — —

Lindsaea obtusa J. Sm. Hook. 1.1 14 0.3 2.0 1 —

Lycopodium cernuum L. 10.9 11 9.0 — — —

Lycopodium phlegmaria L. 1.0 1 — — — —

Lygodium auriculatum (Willd.) Alston 1.7 9 0.9 — — —

Lygodium circinnatum (Burm. f.) Sw. 6.6 5 3.2 — — —

Machaerina mariscoides (Gaud.) J. Kern 5.3 19 7.3 — — —

Macrothelypteris torresiana (Gaud.) 2.5 2 0.7 — — —

Medinilla blumeana Mansfeld 1.0 2 0.0 — — —

Melastoma malabathricum L. 1.5 16 0.9 — — —

Merremia peltata (L.) Merrill 25.3 19 28.8 5.0 1 —

Merremia sp. Dennst. Ex Endl. 1.5 2 0.7 — — —

Microsorum scolopendria (Burm. f.) 2.2 5 1.6 2.7 19 3.3

Mimosa pudica L. 2.0 1 — — — —

Mussaenda frondosa L. 2.0 1 — — — —

Nepenthes mirabilis Druce 1.2 25 0.4 — — —

Nephrolepis acutifolia (Desv.) J. Christ 2.0 1 — — — —

Nephrolepis biserrata (Sw.) Schott 2.0 4 0.8 24.7 13 30.2

Nephrolepis hirsutula (J.R. Forst.) K. Presl 9.9 7 15.8 — — —

Pandanus aimiriikensis Martelli 10.7 9 24.2 — — —

Pandanus sp. L. f. 4.6 68 5.9 2.0 1 —

Paspalum conjugatum Berg. 11.4 5 8.3 — — —

Pennisetum polystachyon (L.) J.A. Schultes 1.0 1 — — — —

Phaleria nisidai Kaheh. 2.0 1 — — — —

Phragmites karka (Retz.) Trin. ex Steud. 25.3 3 22.4 — — —

Table 9—Average nontree understory cover

a

 on FIA field subplots by species and forest type (continued)
35

Palau’s Forest Resources, 2003

Forest type

Volcanic Limestone

Scientific name Cover

Number of 

subplots

Standard 

deviation Cover

Number of 

subplots

Standard 

deviation

Percent Percent

Phyllanthus sp. L. 1.3 3 0.6 — — —

Piper fragile Benth. 1.0 1 — — — —

Piper sp. L. 1.0 1 — 5.5 6 5.9

Pityrogramma calomelanos (L.) Link 1.0 2 0.0 — — —

Polypodium punctatum (Raddi) Hook. 1.0 2 0.0 — —

Polyscias grandifolia Volk. 22.5 4 19.4 — — —

Portulaca oleracea L. 25.0 3 13.2 — — —

Pteris ensiformis Burm. f. 2.0 1 — — — —

Pteris plumula Desv auct. Non Retz. 2.0 1 — — — —

Pteris tripartita Sw. 1.6 8 0.7 — — —

Pteris vittata L. 1.0 2 0.0 — — —

Rhaphidophora carolinensis (Volk.) Fosberg 2.0 2 1.4 — — —

Rhaphidophora sp. Hassk. 1.5 4 1.0 — — —

Rhaphidophora versteegii Engl. & K. Krause 2.5 23 2.7 2.5 11 1.3

Rhynchospora sp. Vahl 25.0 1 — — — —

Scaevola sericea Vahl var. taccada (Gaertn.) Thieret 

 & B. Lipscomb 5.0 1 — — — —

Schefflera odorata Merr. & Rolfe 17.3 3 14.2 — — —

Schefflera sp. J.R. & G. Forst. 1.0 2 0.0 2.0 2 0.0

Schizaea dichotoma (L.) Sm. 1.2 20 0.5 — — —

Scleria levis Willd. 3.0 8 2.1 — — —

Spathoglottis carolinensis Schlecht. 1.7 3 0.6 — — —

Thelypteris forsteri Morton 6.0 1 — — — —

Thelypteris parasitica (L.) Reed. 2.0 3 1.0 — — —

Thelypteris sp. Schmidel 3.0 1 — — — —

Thelypteris unita (L.) C.V. Morton 6.2 24 14.2 1.0 1 —

Vernonia sp. Schreb. 2.0 3 1.0 — — —

Vitex sp. L. — — — 5.6 7 10.8

Vitex trifolia L. 25.0 1 — — — —

Wikstroemia elliptica Merr. 2.4 5 1.7 — — —

Unknown annual grass 1 4.3 4 4.3 — — —

Unknown fern 0 1.0 1 — — — —

Unknown fern 1 12.8 6 28.0 1.5 4 0.6

Unknown fern 2 8.0 4 9.1 2.0 2 0.0

Unknown fern 3 1.0 1 — — — —

Unknown fern 4 1.0 2 0.0 — — —

Unknown forb 1 3.6 11 2.7 3.0 1 —

Unknown forb 2 3.3 3 1.5 2.0 2 1.4

Unknown grass 1 1.0 1 — — — —

Unknown orchid 0 2.8 5 4.0 1.0 1 —

Unknown perennial grass 1 13.6 13 18.8 — — —

Unknown perennial grass 1a 1.0 1 — — — —

Unknown perennial grass 2 45.5 2 62.9 — — —

Unknown shrub 0 3.1 7 5.2 1.6 11 0.7

Unknown shrub 2 5.0 1 — — — —

Unknown vine 1 2.8 9 4.6 2.0 5 0.7

Unknown vine 2 3.0 1 — 1.0 1 —

Unknown vine 3 25.0 1 — — — —

a

Percentage cover of “1” indicates cover less than or equal to 1 percent. Cover estimates are averaged among subplots where each 

species was found. A total of 188 subplots was surveyed for vegetation cover. The number of subplots where a species was found and the 

standard deviation for cover estimates provide an idea of spatial variability for each species across the island group.

Table 9—Average nontree understory cover

a

 on FIA field subplots by species and forest type (continued)
36

RESOURCE BULLETIN PNW-RB-252

Forest type

Volcanic Limestone

Scientific name Cover

Number of 

subplots

Standard 

deviation Cover

Number of 

subplots

Standard 

deviation

Percent Percent

Aglaia palauensis Kaneh. 2.4 21 1.6 2.3 4 0.5

Aidia cochinchinensis Lour. — — — 1.5 2 0.7

Allophylus ternatus (Forst.) Radlk. 2.0 1 — — — —

Alphitonia carolinensis Hosok. 3.3 6 2.7 — — —

Alphitonia zizyphoides A. Gray 2.0 1 — — — —

Areca catechu L. 3.0 3 2.0 — — —

Astronidium palauense (Kaneh.) Mgf. 1.4 11 0.7 — — —

Astronidium sp. A. Gray 1.0 1 — — — —

Badusa palauensis Valeton 2.0 1 — 2.8 4 0.5

Barringtonia asiatica (L.) Kurz — — — 1.0 1 —

Barringtonia racemosa (L.) Spreng. 5.9 7 6.5 3.0 1 —

Bruguiera gymnorrhiza (L.) Lam. 1.6 15 1.4 — — —

Buchanania engleriana Volk. 1.0 1 — — — —

Buchanania palawensis Lauterb. 3.0 1 — — — —

Buchanania sp. Spreng. 5.5 2 3.5 — — —

Calophyllum inophyllum L. 1.5 2 0.7 2.2 5 0.8

Calophyllum pelewense P. F. Stevens 2.3 4 1.5 — — —

Campnosperma brevipetiolata Volk. 2.8 9 2.9 — — —

Canarium hirsutum Willd. 7.0 2 1.4 — — —

Casuarina equisetifolia L. — — — 2.0 1 —

Cerbera manghas L. 2.8 4 1.7 — — —

Cerbera sp. L. 1.0 1 — — — —

Cocos nucifera L. 3.8 9 4.3 34.0 3 29.5

Commersonia bartramia (L.) Merr. 1.0 1 — — — —

Cyathea lunulata (Forst. f.) Copel. 4.3 4 3.9 — — —

Diospyros discolor Willd. 2.5 2 0.7 — — —

Diospyros ferrea (Willd.) Bakh. 2.5 2 0.7 — — —

Diospyros sp. L. 2.5 2 0.7 — — —

Dracaena multiflora Tentative — — — 3.0 1 —

Drypetes nitida Kaneh. — — — 3.0 1 —

Dysoxylum sp. Blume 2.4 7 1.0 — — —

Elaeocarpus joga Merr. 2.2 5 1.3 8.0 1 —

Elaeocarpus sp. L. 1.0 1 — — — —

Elattostachys falcata (Seem.) Radik. 1.0 1 — — — —

Eugenia cumini (L.) Druce 2.0 1 — 4.8 4 2.8

Eugenia javanica Lam. — — — 1.8 8 0.7

Eugenia reinwardtiana (Bl.) DC. 6.6 7 8.4 4.3 9 2.8

Eugenia sp. L. 1.9 8 1.0 3.3 3 1.5

Evodia sp. Lam. 2.0 1 — — — —

Fagraea ksid Gilg and Bened. 1.0 1 — — — —

Ficus sp. L. 2.3 3 0.6 — — —

Ficus tinctoria Forst. f. 5.3 19 4.4 2.4 7 1.3

Flacourtia rukam Zoll. & Moritzi 2.8 5 1.5 — — —

Garcinia matudai Kaneh. 6.8 4 9.0 — — —

Garcinia rumiyo Fosb. 8.2 19 12.5 — — —

Table 10—Average understory tree cover

a

 on FIA field subplots by species and forest type
37

Palau’s Forest Resources, 2003

Table 10—Average understory tree cover

a

 on FIA field subplots by species and forest type (continued)

Forest type

Volcanic Limestone

Scientific name Cover

Number of 

subplots

Standard 

deviation Cover

Number of 

subplots

Standard 

deviation

Percent Percent

Garcinia sp. L. 4.3 4 3.9 7.8 5 6.9

Glochidion ramiflorum Forst. 3.0 4 1.4 2.0 2 —

Glochidion sp. J.R. & G. Forst. — — — 1.0 1 —

Gmelina elliptica Sm. — — — 2.0 1 —

Gmelina palawensis H. J. Lam. 1.5 2 0.7 — — —

Gulubia palauensis (Becc.) Moore & Fosb. 9.3 3 5.1 2.0 1 —

Heterospathe elata (Becc.) Becc. 4.2 6 2.0 2.0 1 —

Hibiscus tiliaceus L. 5.0 8 5.1 — — —

Horsfieldia amklaal Kaneh. 3.0 2 — 2.5 2 0.7

Horsfieldia novo-guineensis Warb. 4.5 15 3.1 — — —

Horsfieldia palauensis Kaneh. 4.3 45 10.6 2.2 10 0.8

Horsfieldia sp. Wild. 2.5 2 0.7 — — —

Inocarpus fagifer (Park.) Fosb. 2.0 2 1.4 — — —

Macaranga carolinensis Volk. 3.1 17 3.0 5.5 2 3.5

Manilkara udoido Kaneh. 2.0 5 1.4 — — —

Manilkara zapota (L.) P. v. Roy. 1.7 3 0.6 — — —

Melochia aristata A. Gray 2.0 1 — — — —

Morinda citrifolia L. 1.5 4 0.6 — — —

Morinda pedunculata Val. 21.5 2 26.2 — — —

Myristica sp. Gronov. 2.0 1 — — — —

Neonauclea forsteri Merrill 4.0 1 — — — —

Omalanthus sp. A.Juss. 11.5 4 12.3 — — —

Ormosia calavensis Azaola ex Blanco 2.0 1 — — — —

Osmoxylon oliveri Fosberg & Sachet 5.0 4 5.0 — — —

Osmoxylon pachyphyllum (Kanehira) F.R. Fosberg 

 & M.-H. Sachet 3.0 1 — — — —

Osmoxylon sp. Miq. 3.0 10 3.3 1.0 1 —

Pandanus aimiriikensis Mart. 3.5 10 2.8 27.0 3 37.5

Pandanus dubius Spr. — — — 2.5 6 1.6

Pandanus kanehirae Mart. 1.5 2 0.7 — — —

Pandanus peliliuensis Kaneh. — — — 1.5 2 0.7

Pandanus tectorius Park. 3.1 8 2.4 — — —

Parinari corymbosum (Bl.) Miq. 8.0 4 11.4 — — —

Parinari laurina Gray 30.8 12 27.5 2.0 1 —

Parkia parvifoliola Hosok. 1.0 1 — — — —

Pinanga insignis Becc. 19.9 103 20.6 1.5 4 0.6

Pithecellobium dulce (Roxb.) Benth. — — — 1.8 4 0.5

Polyscias nodosa (Bl.) Seem. — — — 3.0 1 —

Pongamia pinnata (L.) Merr. — — — 2.0 1 —

Pouteria calcarea (Hosok.) Fosb. — — — 1.0 1 —

Pouteria obovata (R. Br.) Baehni 1.5 2 0.7 1.6 7 0.5

Premna obtusifolia R. Br. 5.0 1 — — — —

Rhizophora apiculata Bl. 13.9 15 23.9 1.0 4 —

Rhizophora mucronata Lam. 1.5 2 0.7 — — —

Rhus taitensis Guill. 1.9 8 1.4 2.0 1 —
38

RESOURCE BULLETIN PNW-RB-252

For the 2003 inventory, 128 tree species and 132 understory species were 

measured on FIA plots. The volcanic forest area sampled was about four times the 

area sampled for the limestone forest. Because we expect the number of species 

counted to increase with increasing area, it is not surprising that over twice the 

number of tree species and over four times the number of understory species were 

found in volcanic forest compared to limestone forest (fig. 11). On a per-plot basis 

(approximately one-sixth acre), the mean number of tree species found on volcanic 

plots was 12, with an average of 10 tree species found per limestone plot (fig. 12). 

The one limestone plot where only two species occurred (fig. 12) was a mangrove 

plot where 90 trees (>5 inches) were measured, 65 Rhizophora apiculata and 25 

R. mucronata. The area of mangrove forest could not be accurately delineated from 

limestone forest with this small sample, thus separate expansion factors were not 

calculated for mangrove species. Mangrove species numbers may be falsely high 

owing to this expansion. However, because mangrove species tend to dominate the 

extensive mangroves on Palau, and only five partial plots contained mangrove 

species, the estimate may be reasonable. Additional mapping data are forthcoming 

and will help refine our estimate for mangrove species. The urgent need to better 

understand mangroves as buffers to coastal disturbance (storms, typhoons, and 

tsunami) suggests the need for a separate, detailed mangrove inventory.

Forest type

Volcanic Limestone

Scientific name Cover

Number of 

subplots

Standard 

deviation Cover

Number of 

subplots

Standard 

deviation

Percent Percent

Semecarpus venenosus Volk. 2.2 31 1.6 3.0 1 —

Sonneratia alba J. E. Sm. 2.8 8 3.1 — — —

Stemonurus ammui (Kaneh.) Sleumer 40.0 1 — — — —

Swietenia mahagoni (L.) Jacq. 6.0 2 2.8 — — —

Symplocos racemosa Roxb. 2.3 6 0.8 — — —

Tecoma stans (L.) Juss. ex HBK. 3.0 1 — — — —

Terminalia catappa L. 3.0 1 — — — —

Terminalia sp. L. 20.0 1 — — — —

Timonius subauritus Fosberg & Sachet — — — 8.5 2 9.2

Trichospermum ledermannii Burret 1.0 2 — — — —

Xylocarpus granatum Koen. 1.6 8 1.4 — — —

Unknown 0 1.3 4 0.5 — — —

Unknown 1 2.0 1 — — — —

Unknown 20 2.0 1 — — — —

a

Percentage cover of “1” indicates cover less than or equal to 1 percent. Cover estimates are averaged among subplots where each 

species was found. A total of 188 subplots was surveyed for vegetation cover. The number of subplots where a species was found and

 the standard deviation for cover estimates provide an idea of spatial variability for each species across the island group.

Table 10—Average understory tree cover

a

 on FIA field subplots by species and forest type (continued)
39

Palau’s Forest Resources, 2003

0

20

40

60

80

100

120

140

Tree species Understory species Number of plots

Number of species

Volcanic

Limestone

Figure 11—One hundred and twenty-eight tree species and 132 understory species were measured on 

54 forested plots in Palau.

Figure 12—The average number of tree species found per sixth-acre plot was 12 for volcanic forests 

and 10 for limestone forests.

0

1

2

3

4

5

6

7

8

9

10

1–2 3–4 5–6 7–8 9–10 11–12 13–14 15–16 17–18 19–20

Number of tree species on FIA plots

Number of plots

Volcanic

Limestone
40

RESOURCE BULLETIN PNW-RB-252

Tree Damage and Mortality

Approximately 13 percent of the individual trees on Palau show some sign of damage (table 11). The most prevalent damage types are vines in crowns, conks (shelf 

fungus indicating rot), and lost apical dominance (damage to the primary growing leader) (fig. 13). The prevalence of vines in tree crowns was high, 41 percent. 

Although the vines are common, their effect on their supporting tree hosts was not 

quantified. Effects ranged from some additional weight to rare instances of strangulation. For the identifiable damaging agents, damage by other vegetation, disease, 

and weather ranked as the most prevalent primary damage agents (fig. 14).

Less than 5 percent of the trees sampled during the inventory were dead (fig. 

15). Of those dead, nearly one-fourth could not be identified to species level. The 

most prevalent, identifiable dead trees were Cyathea lunulata (7.3 percent of total 

dead), Calophyllum inophyllum, Calophyllum pelewense, and Pinanga insignis 

(each accounting for 6.1 percent of total dead).

Epiphytes—

In the moist environment of the tropics many plant species are found growing on 

longer lived trees. These epiphytes use the trees primarily for support, but they 

also use space, moisture, and nutrients that might otherwise be used by the tree. 

When the epiphytes accumulate over many years, their weight can be excessive, 

leading to the breakage of branches and occasionally the stems of trees. In Palau we 

rated epiphytic loading on trees as a summation of loading on the bole, branches, 

and canopy. We estimate that about 65 percent of the trees in Palau had few to no 

epiphytes, and 45 percent of the trees had moderate to high amounts of epiphytes 

(table 12).

Forest Dynamics—

Forest structure and species composition change through time as a result of forest 

succession and disturbance dynamics. The forests of Palau have been strongly 

influenced by a long history of disturbance, both human-caused and climatic 

disturbance. Human populations and land use on Palau have changed, resulting in 

differing influences on forest vegetation. Within the last century, the most important land use changes have involved the conversion of forest to agriculture and its 

subsequent abandonment and reversion to grassland, and eventually forest. Endress 

and Chinea (2001) documented the abandonment of agricultural lands and reversion 

to forest by comparing 1947 and 1992 aerial photography for approximately 20,500 

acres in the Ngeremeduu Bay drainage area on Babeldaob. These authors noted the 

most dramatic change occurred during the period 1947 to 1976, using the Cole et al. 

(1987) map as an intermediate comparison point. (Text continues on page 49.)
41

Species

No

damage

Broken 

bole

Broken 

branches

Broken 

roots

Canker/

gall Conks

Cracks/

seams

Discolored 

foliage

Excessive 

branching

Lost apical 

dominance

Open 

wound

Vi

c

Number of trees

Aglaia palauensis 171,813 — — — — — — — — 12,330 — 4Allophylus ternatus 36,989 — — — — — — — — — — Allophylus timorensis 12,330 — — — — — — — — — — Alphitonia carolinensis 456,192 — — — — 12,330 — — — — 12,330 Annona reticulata 12,330 — — — — — — — — — — Areca catechu 73,977 — — — — — — — — — — Artocarpus mariannensis 48,518 — — — — — — — — — — Astronidium palauense 258,920 — — — — 12,330 — — — 12,330 — Avicennia marina 12,330 — — — — 12,330 — — — — — Badusa palauensis 254,719 — 12,129 — — 12,129 — — — 12,129 — Barringtonia racemosa 330,896 — — — — 12,129 — — — — — 3Bruguiera gymnorrhiza 468,521 — — — 12,330 — — — — — — Buchanania palawensis 98,436 — — — — — — — — — — Calophyllum inophyllum 293,308 — 12,129 — — — — — — — 24,259 Calophyllum pelewense 197,072 — — — — 12,330 — — — — — Calophyllum soulattri 49,318 — — — — — — — — — — Calophyllum sp. 36,588 24,659 — — — — — — — — — Campnosperma  brevipetiolata 714,911 — 24,659 12,330 — 24,659 — — — — — 6Canarium hirsutum 72,777 — — — — — — — — — 12,330 Casearia cauliflora 12,330 — — — — — — — — — — Casearia sp. 84,906 — — — — — — — — — — Casuarina equisetifolia 60,647 — 12,129 — — — — — — — — Cerbera floribunda 24,659 — — — — — — — — — — Cerbera manghas 135,425 — — — — — — — — — 12,330 6Cocos nucifera 306,637 — — — — — — — — — — Commersonia bartramia 12,330 — — — — — — — — — — Cordia micronesica 12,330 — — — — — — — — — — Cyathea lunulata 542,498 — 12,330 — — — — — — — — Diospyros ferrea 98,636 — — — — — — — — — — Diospyros sp. 73,577 — — — — — — — — 12,330 — Dodonaea viscosa 73,177 — — — — — — — — — — Dracaena multiflora 98,036 — — — — 12,129 — — — — — Drypetes nitida 36,788 — — — — — — — — — — Dysoxylum sp. 36,989 — — — — — — — — — — Elaeocarpus graeffei — — — — — — — — — — — Elaeocarpus joga 453,391 — — — — 24,659 — — — 12,330 12,330 2Table 11—Number of trees by primary damage type and species for all trees (≥5 inches diameter at breast height; includes 
42

Table 11—Number of trees by primary damage type and species for all trees (≥5 inches diameter at breast height; includes (continued) Species No damage Broken bole Broken branches Broken roots Canker/ gall Conks Cracks/ seams Discolored foliage Excessive branching Lost apical dominance Open wound Vi

c

Number of trees Erythrina fusca 12,129 — — — — — — — — — — 

Eugenia cumini 207,201 — — — — — — — — — — Eugenia javanica 181,942 — — — — 24,259 — — — — 24,259 Eugenia reinwardtiana 570,685 — — — — — — — — — 24,259 Eugenia sp. 36,788 — — — — — — — — — — Fagraea ksid 110,966 — 12,330 — — 12,330 — — — — — 3Ficus sp. 12,330 — — — — — — — — — — Ficus tinctoria 24,259 — — — — — — — — — — Flacourtia rukam 135,425 — — — — — 12,129 12,330 — — — Garcinia matudai 49,318 — — — — — — — — 24,659 — Garcinia rumiyo 294,908 — — — — 12,330 — — — — — Garcinia sp. 343,626 — — — — — — — — — — Gironniera celtidifolia 36,989 — — — — — — — — — — Glochidion ramiflorum 134,224 — 12,129 — — 12,330 — — — — — 3Glochidion sp. — — — — — — — — — 12,330 — Gmelina elliptica 182,342 — 12,129 — — 24,659 — — — — — Gmelina palawensis 431,133 — — — — 61,648 — — — 36,989 36,788 Gmelina sp. 36,989 — — — — — — — — — 12,330 2Gulubia palauensis 109,165 — — — — — — — — — — Hernandia sonora 12,129 — — — — 12,129 — — — — — Hernandia sp. 36,388 — — — — 12,129 — — — — 12,129 Heterospathe elata 73,977 — — — — — — — — — — Hibiscus tiliaceus 49,318 — — — — — — — — 12,330 — 3Horsfieldia amklaal 220,531 — — — — 12,330 — — — 12,330 — Horsfieldia novo-guineensis 221,931 — — — — 12,330 — — — — — Horsfieldia palauensis 845,935 — 24,459 — — 36,588 — — — 24,659 12,330 4Horsfieldia sp. — — — — — 12,330 — — — — — Inocarpus fagifer 12,330 — — — — — — — — — — Intsia bijuga 181,942 — — — — 36,388 — — — — 12,129 Lumnitzera littorea 12,330 — — — — — — — — — — Macaranga carolinensis 122,695 — — — — 12,330 — — — — — 3Manilkara udoido 234,261 — — 12,330 — — — — — — — 3Manilkara zapota 49,318 — — — — — — — — 12,330 — Morinda citrifolia — — — — — 12,330 — — — — — Morinda latibracteata 24,659 — — — — 12,330 — — — — — 2
43

Species

No

damage

Broken 

bole

Broken 

branches

Broken 

roots

Canker/

gall Conks

Cracks/

seams

Discolored 

foliage

Excessive 

branching

Lost apical 

dominance

Open 

wound

Vi

c

Number of trees

Morinda sp. 12,330 — — — — — — — — 12,330 12,330 — Morinda pedunculata 12,330 — — — — — — — — — — Nephelium lappaceum — — — — — — — — — — — Osmoxylon oliveri 24,659 — — — — — — — — — — Osmoxylon sp. 24,659 — — — — — — — — — — 3Pandanus aimiriikensis 61,648 — — — — — — — — — — Pandanus dubius 145,554 — — 48,518 — — — — — 12,129 — Pandanus kanehirae 61,648 — — — — — — — — — — Pandanus tectorius 86,307 — — 12,330 — — — — — — — Pandanus utiyamai 12,330 — — — — — — — — — — Pangium edule 12,330 — — — — — — — — — — Parinari corymbosum 554,428 — 12,330 — — 49,318 — — 12,330 12,330 12,330 Parinari laurina 516,039 — — — — 24,659 — — — — — 2Parinari sp. 24,659 — — — — — — — — — — Pinanga insignis 2,071,357 — — — — — — — — — — 12Pithecellobium dulce 12,129 — — — — — — — — — — Pouteria calcarea 36,989 — — — — — — — — — — Pouteria obovata 353,555 — — — — 24,659 — — — — — 2Pouteria sp. 12,330 — — — — — — — — — — Premna obtusifolia 36,989 — — — — — — — — — — 4Pterocarpus indicus 24,659 — — — — — — — — — — Ptychosperma palauensis 86,307 — — — — — — — — — — Rhizophora apiculata 1,343,843 — 12,129 — — 12,129 — — — 12,129 12,330 Rhizophora mucronata 377,214 — — — — — — — — — — Rhus taitensis 357,556 — 12,330 12,330 — 12,330 — — — 12,330 12,330 Rinorea carolinensis 12,129 — — — — — — — — — — Semecarpus venenosus 528,168 — — — — 12,330 — — — 12,330 — 2Sonneratia alba 172,613 — — — — — — — — — — Stemonurus ammui 61,648 — — — — — — — — — — Swietenia macrophylla 49,318 — — — — — — — — — — Swietenia mahagoni 36,989 — — — — — — — — — — 3Symplocos racemosa 36,989 — 12,330 — — — — — — 12,330 — Terminalia catappa 12,330 — — — — — — — — — — 3Theobroma cacao 24,659 — — — — 24,659 — — — 12,330 — Timonius subauritus 84,906 — — — — — — — — — — 2Table 11—Number of trees by primary damage type and species for all trees (≥5 inches diameter at breast height; includes (continued)
44

Species

No 

damage

Broken 

bole

Broken 

branches

Broken 

roots

Canker/

gall Conks

Cracks/

seams

Discolored 

foliage

Excessive 

branching

Lost apical 

dominance

Open 

wound

Vi

c

Number of trees

Tournefortia argentea 36,588 — — — — 12,330 — — — — — Trichospermum ledermanni 98,636 — — — — — — — — — — Vitex cofassus 61,648 — — — — — — — — — 12,330 3Xylocarpus granatum 147,954 — — — — 24,659 — — — — 12,330 Unknown 12,330 — — — — — — — — — — Unknown 0 134,824 — 12,330 — — — — — — — — Unknown 1 24,659 — — — — 24,459 — — — — — Unknown 3 49,318 — — — — — — — — — — Unknown 5 85,906 — — — — — — — — — — Unknown 10 12,330 — — — — — — — — — — Unknown 11 12,330 — — — — — — — — — — Unknown 30 12,129 — — — — — — — — — — Unknown, other 73,977 — — — — 12,330 — — — — —  Total 18,714,675 24,659 195,872 97,836 12,330 687,652 12,129 12,330 12,330 295,308 281,778 1,14Table 11—Number of trees by primary damage type and species for all trees (≥5 inches diameter at breast height; includes (continued)
45

Palau’s Forest Resources, 2003

Figure 13—Vines in the crowns of trees are very common in Palau. Damage from vines was recorded when 

the vines occupied 20 percent or more of the crown. Rot, indicated by the fruiting shelf fungi (conks) was 

also a common damage.

Figure 14—Disturbance by other vegetation and disease were the most common identifiable damaging 

agents for trees.

Tree damages

11%

10%

7%

41%

25%

4%

1%

<1%

<1%

<1%

<1%

Vines in crown

Conks

Lost apical dominance

Open wound

Broken branches

Broken roots

Broken bole

Canker/gall

Discolored foliage

Excessive branching

Cracks/seams

Primary damage agent

19%

11%

11%

53%

3%

<1%

2%

<1%

Vegetation

Disease

Unknown

Weather

Physical

Insect

Fire

Human
46

RESOURCE BULLETIN PNW-RB-252

Epiphyte loadings

Species None Low Moderate High All loadings

Number of trees

Aglaia palauensis 36,388 123,095 61,648 12,330 197,072

Allophylus ternatus — 12,330 12,330 12,330 36,989

Allophylus timorensis — — 12,330 — 12,330

Alphitonia carolinensis 135,625 160,284 110,966 86,307 357,556

Annona reticulata — — 12,330 — 12,330

Areca catechu — 36,989 12,330 24,659 73,977

Artocarpus mariannensis 24,259 — 24,259 — 24,259

Astronidium palauense 12,330 135,625 73,977 61,648 271,249

Avicennia marina — 12,330 12,330 — 24,659

Badusa palauensis 97,036 145,554 36,388 24,259 206,201

Barringtonia racemosa 97,436 134,624 110,966 36,989 282,578

Bruguiera gymnorrhiza 184,943 234,261 36,989 24,659 295,908

Buchanania palawensis — 49,118 24,659 24,659 98,436

Calophyllum inophyllum 60,647 146,154 73,577 49,318 269,049

Table 12—Estimated number of trees on forest land by epiphyte loading (amounts of 

nontree vegetation in the canopy and branches) and species (includes dead trees)

Figure 15—Identifying dead trees proved to be difficult in Palau. Nearly one-fourth of those dead could not be identified.

0

5

10

15

20

25

All unknown

Cyathea lunulata

Calophyllum inophyllum

Calophyllum pelewense

Pinanga insignis

Sonneratia alba

Casuarina equisetifolia

Alphitonia carolinensis

Parinari corymbosa

Barringtonia racemosa

Horsfieldia palauensis

Astronidium paluaensis

Elaeocarpus joga

Rhus taitensis

Rhizophora apiculata

Timonius subauritus

Campnosperma brevipetiolata

Diospyros ferrea

Garcinia rumiyo

Macaranga carolinensis

Pandanus kanehirae

Premna obtusifolia

Badusa palauensis

Calophyllum sp.

Eugenia reinwardtiana

Gulubia palauensis

Rhizophora mucronata

Dead trees (percent)

Species
47

Palau’s Forest Resources, 2003

Table 12—Estimated number of trees on forest land by epiphyte loading (amounts of 

nontree vegetation in the canopy and branches) and species (includes dead trees) 

(continued)

Epiphyte loadings

Species None Low Moderate High All loadings

Number of trees

Calophyllum pelewense 24,659 86,106 36,989 61,648 184,743

Calophyllum soulattri 36,989 12,330 — — 12,330

Calophyllum sp. — 48,918 24,459 — 73,377

Campnosperma brevipetiolata 61,447 332,897 271,249 172,613 776,759

Canarium hirsutum 36,588 12,129 36,388 12,330 60,847

Casearia cauliflora — 12,330 — — 12,330

Casearia sp. — 84,906 — — 84,906

Casuarina equisetifolia 12,129 — 60,647 — 60,647

Cerbera floribunda — 24,659 — — 24,659

Cerbera manghas 12,330 98,436 61,648 36,989 197,072

Cocos nucifera 12,330 159,083 110,565 36,989 306,637

Commersonia bartramia — 12,330 — — 12,330

Cordia micronesica — — — 12,330 12,330

Cyathea lunulata 49,318 98,636 234,261 172,613 505,510

Diospyros ferrea — 49,318 49,318 — 98,636

Diospyros sp. 36,588 49,318 — — 49,318

Dodonaea viscosa 12,129 48,718 — 12,330 61,047

Dracaena multiflora 73,377 24,459 12,330 — 36,788

Drypetes nitida 24,659 12,129 — — 12,129

Dysoxylum sp. 36,989 — — — —

Elaeocarpus graeffei — — 12,330 — 12,330

Elaeocarpus joga 85,706 269,649 122,695 49,118 441,462

Erythrina fusca 12,129 — — — —

Eugenia cumini 36,388 97,836 72,977 12,129 182,942

Eugenia javanica 24,259 121,295 84,906 — 206,201

Eugenia reinwardtiana 218,330 340,025 36,588 — 376,613

Eugenia sp. — — 24,459 12,330 36,788

Fagraea ksid 24,659 24,659 123,295 — 147,954

Ficus sp. — — 12,330 — 12,330

Ficus tinctoria — 12,129 12,129 — 24,259

Flacourtia rukam — 85,906 49,318 24,659 159,883

Garcinia matudai 12,330 36,989 12,330 12,330 61,648

Garcinia rumiyo 36,989 85,706 122,895 73,977 282,578

Garcinia sp. 48,718 233,260 36,989 24,659 294,908

Gironniera celtidifolia — 24,659 12,330 — 36,989

Glochidion ramiflorum 24,659 85,306 73,377 12,129 170,813

Glochidion sp. 12,330 — — 12,330 12,330

Gmelina elliptica 72,777 72,777 61,247 12,330 146,354

Gmelina palawensis 184,943 221,331 110,966 49,318 381,615

Gmelina sp. — 36,989 12,330 24,659 73,977

Gulubia palauensis 109,165 — — — —

Hernandia sonora — — 36,388 — 36,388

Hernandia sp. — 60,647 — — 60,647

Heterospathe elata — 73,977 12,330 — 86,307
48

RESOURCE BULLETIN PNW-RB-252

Epiphyte loadings

Species None Low Moderate High All loadings

Number of trees

Hibiscus tiliaceus — 49,318 — 49,318 98,636

Horsfieldia amklaal 12,330 159,083 49,118 24,659 232,860

Horsfieldia novo-guineensis — 86,307 98,636 49,318 234,261

Horsfieldia palauensis 182,742 355,755 282,178 172,413 810,347

Horsfieldia sp. — 12,330 — — 12,330

Inocarpus fagifer — 12,330 — — 12,330

Intsia bijuga 145,554 84,906 — — 84,906

Lumnitzera littorea — 12,330 — — 12,330

Macaranga carolinensis 12,330 110,565 36,788 12,330 159,683

Manilkara udoido 98,636 110,966 36,989 36,989 184,943

Manilkara zapota — 36,989 24,659 12,330 73,977

Morinda citrifolia — — 24,659 — 24,659

Morinda latibracteata — — 36,989 24,659 61,648

Morinda pedunculata — — — 12,330 12,330

Morinda sp. 24,659 12,330 — — 12,330

Nephelium lappaceum — — — 12,330 12,330

Osmoxylon oliveri — 24,659 — — 24,659

Osmoxylon sp. — — 24,659 36,989 61,648

Pandanus aimiriikensis — 36,989 24,659 — 61,648

Pandanus dubius 109,165 84,906 12,129 — 97,036

Pandanus kanehirae 12,330 24,659 24,659 — 49,318

Pandanus tectorius 49,318 36,989 12,330 — 49,318

Pandanus utiyamai — — — 12,330 12,330

Pangium edule — — 12,330 12,330 24,659

Parinari corymbosum 73,577 197,272 172,613 221,931 591,816

Parinari laurina 49,118 269,649 123,295 123,295 516,239

Parinari sp. 12,330 12,330 — — 12,330

Pinanga insignis 110,966 1,269,939 505,510 308,238 2,083,686

Pithecellobium dulce 12,129 — — — —

Pouteria calcarea — 24,659 12,330 — 36,989

Pouteria obovata 60,647 134,824 109,365 97,836 342,025

Pouteria sp. — 12,330 — — 12,330

Premna obtusifolia — 12,330 36,989 36,989 86,307

Pterocarpus indicus — — — 24,659 24,659

Ptychosperma palauensis — 24,659 61,648 — 86,307

Rhizophora apiculata 1,145,970 246,590 — — 246,590

Rhizophora mucronata 303,236 24,659 49,318 — 73,977

Rhus taitensis 110,966 234,261 61,648 24,659 320,567

Rinorea carolinensis 12,129 — — — —

Semecarpus venenosus 73,377 294,708 135,425 73,977 504,109

Sonneratia alba 135,625 36,989 — — 36,989

Stemonurus ammui — 12,330 — 49,318 61,648

Swietenia macrophylla 24,659 24,659 — — 24,659

Swietenia mahagoni — 36,989 24,659 12,330 73,977

Table 12—Estimated number of trees on forest land by epiphyte loading (amounts of 

nontree vegetation in the canopy and branches) and species (includes dead trees) 

(continued)
49

Palau’s Forest Resources, 2003

Table 12—Estimated number of trees on forest land by epiphyte loading (amounts of 

nontree vegetation in the canopy and branches) and species (includes dead trees) 

(continued)

Epiphyte loadings

Species None Low Moderate High All loadings

Number of trees

Symplocos racemosa 49,318 12,330 — — 12,330

Terminalia catappa 12,330 12,330 — 24,659 36,989

Theobroma cacao 12,330 12,330 36,989 — 49,318

Timonius subauritus 24,259 36,388 48,518 — 84,906

Tournefortia argentea 24,259 12,330 12,330 — 24,659

Trichospermum ledermannii — 73,977 24,659 — 98,636

Vitex cofassus — 24,659 24,659 61,648 110,966

Xylocarpus granatum 110,966 73,977 — — 73,977

Unknown 12,330 — — — —

Unknown 0 73,177 36,989 12,330 24,659 73,977

Unknown 1 24,459 — 12,330 12,330 24,659

Unknown 3 24,659 12,330 12,330 — 24,659

Unknown 5 24,259 61,648 — — 61,648

Unknown 10 — — 12,330 — 12,330

Unknown 11 — — 12,330 — 12,330

Unknown 30 — 12,129 — — 12,129

Unknown, other 36,989 — 36,989 12,330 49,318

 Total 5,182,700 8,742,199 4,794,504 2,772,138 16,308,841

Comparing the inventory data from the present study to data from the MacLean 

et al. (1988) timber inventory suggests that the trend of forest recovery and maturation continues on Palau. With the exceptions of forest loss owing to roads and urban 

uses, forests appear to be maturing. On average, trees have been getting larger (fig. 

16), and as they increased in size, some trees died during the “thinning phase” 

(Oliver and Larson 1996) of forest succession. We found fewer stems per acre, 

and greater basal area and volume per acre on forested field plots compared to the 

MacLean et al. (1988) data (table 13). The MacLean et al. (1988) work was restricted 

to forested lands on Babeldaob, whereas the current inventory included additional 

forest types in limestone forest and the Rock Islands. Although our current sample 

of plots in limestone forest was relatively small (11 out of 54 plots total), the 2003 

data suggest much higher net wood volume in limestone (4,107 cubic feet per acre) 

than in volcanic forests (2,424 cubic feet per acre). Much of the limestone forest is 

in difficult terrain where access and human populations are limited. The limestone 

forests were probably less impacted by agricultural development and thus are likely 

to be in a later phase of maturity than their volcanic counterparts. Soil fertility may 

also play a role in wood volume differences owing to less aluminum toxicity in 

limestone versus the volcanic-derived soils.
50

RESOURCE BULLETIN PNW-RB-252

Figure 16—The diameter distribution for the percentage of total trees measured on field plots appears to have 

changed between the 1985 and 2003 inventories. Trees measured in the latest inventory were, on average, 

larger than those measured in 1985, contributing to higher basal area and volume per acre values.

Percentage of all trees by diameter class

0

10

20

30

40

50

60

5.0–6.9

7.0–8.9

9.–10.9

11.0–12.9

13–15

15–17

17–19

19–21

21–23

23–25

25–27

27–29

>29

Diameter (inches)

All trees (percent)

1985

2003

70

Table 13—Estimated number of trees per acre, basal area per 

acre, net volume per acre, and standard errors (SE) for 1985 and 

2003

1985 SE 2003 SE

Trees per acre 1,282 102 856 68

Basal area (ft2

 per acre) 136 — 146 —

Volume (ft3 per acre) 1,740 188 2,744 296
51

Palau’s Forest Resources, 2003

Acknowledgments

The FIA Pacific Island inventories are the result of cooperative effort between 

a number of groups and agencies. The USDA Forest Service, State and Private 

Forestry in the Pacific Southwest Region has been a strong supporter of natural 

resource assessments in the Pacific Islands. Many thanks to the Pacific Islands 

Imagery Consortium partners for sharing costs on imagery and interpretation. 

Thanks to Margie Falanruw with the Institute of Pacific Islands Forestry, Lynn 

Raulerson at University of Guam, and Agnes Rinehart for species identification 

and training; Lisa Fischer and Zhafeng Liu (Leo) at the Remote Sensing Lab in the 

Pacific Southwest Region and Julie Anderson with PNW-FIA for imagery interpretation and mapping support; Pua Michael, Larry Mamis, Pamela Skilang, Dale 

Baer, Falaniko Mika, Ritofu Lotovale for field assistance and logistical support. We 

also thank Dale Weyermann, John Chase, Chuck Veneklase, and Ron Wanek with 

FIA for GIS, programming, and technical support. Tom Cole, Robin DeMeo, Bob 

Gavenda, and Tarita Holm offered very helpful comments on prior drafts.

Metric Equivalents

When you know: Multiply by: To find:

Inches 2.54 Centimeters

Feet .305 Meters

Miles 1.609 Kilometers

Acres .405 Hectares

Cubic feet .028 Cubic meters

Tons 907 Kilograms

Tons per acre 2.24 Tonnes or megagrams per hectare

Cubic feet per acre .07 Cubic meters per hectare

Trees per acre 2.471 Trees per hectare

Degrees Fahrenheit (F - 32)/1.8 Degrees Celsius

Literature Cited

Athens, J.S.; Ward, J.V. 2002. Holocene paleoenvironmental investigations on 

Ngerekebesang, Koror, south Babeldaob, and Peleliu islands. Honolulu, HI: 

International Archaeological Research Institute, Inc. 

Climate Prediction Center. 2005. Composite rainfall of ENSO (El Niño/Southern 

Oscillation) for Pacific Island stations. http://www.cpc.ncep.noaa.gov/pacdir/

ENSO11.shtml. (April 1). 

Cochran, W.G. 1977. Sampling techniques. New York: John Wiley & Sons. 428 p.
52

RESOURCE BULLETIN PNW-RB-252

Cole, T.G.; Falanruw, M.C.; MacLean, C.D.; Whitesell, C.D.; Ambacher, A.H. 

1987. Vegetation survey of the Republic of Palau. Resour. Bull. PSW-RB-22. 

Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest 

Research Station. 13 p.

Endress, B.A.; Chinea, J.D. 2001. Landscape patterns of tropical forest recovery 

in the Republic of Palau. Biotropica. 33: 555–565.

MacLean, C.D.; Cole, T.G.; Whitesell, C.D.; McDuffie, K.E. 1988. Timber 

resources of Babelthuap, Republic of Palau. Resour. Bull. PSW-RB-23. Berkeley, 

CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research 

Station. 8 p.

Mueller-Dombois, D.; Fosberg, F.R. 1998. Vegetation of the tropical Pacific 

Islands. New York: Springer-Verlag. 733 p.

Oliver, C.D.; Larson, B.C. 1996. Forest stand dynamics. New York: Wiley. 520 p.

Parker, A.J. 1982. The topographic relative moisture index: an approach to soilmoisture assessment in mountain terrain. Physical Geography. 3: 160-168.

Smith, C.W.; Babik, N.R. 1988. Properties and management considerations of 

some acid soils on the islands of Palau. In: Demeterio, J.L.; DeGuzman, B., 

eds. Management and utilization of acid soils of Oceania. Guam: University of 

Guam: 39–61.

U.S. Department of Agriculture, Forest Service [USDA FS]. 2003. Field 

instructions for the inventory of the Pacific Islands. Portland, OR: Pacific 

Northwest Research Station, Forestry Sciences Laboratory, Forest Inventory 

and Analysis. 256 p.

U.S. Department of Agriculture, Natural Resources Conservation Service. 

1983. Soil survey of Islands of Palau, Republic of Palau. Washington, DC: 

Soil Conservation Service. 120 p., 72 plates.

Western Regional Climate Center. 2004. Koror, Palau, period of record monthly 

climate summary, 1953-2004. http://www.wrcc.dri.edu/cgi-bin/cliMAIN.

pl?pikoro. (September 12).
Pacific Northwest Research Station

Web site http://www.fs.fed.us/pnw/

Telephone (503) 808-2592

Publication requests (503) 808-2138

FAX (503) 808-2130

E-mail pnw_pnwpubs@fs.fed.us

Mailing address Publications Distribution

Pacific Northwest Research Station

P.O. Box 3890

Portland, OR 97208-3890
U.S. Department of Agriculture

Pacific Northwest Research Station

333 SW First Avenue

P.O. Box 3890

Portland, OR 97208-3890

Official Business

Penalty for Private Use, $300