Tree population studies in low-diversity forests,Guyana. II. Assessments on the distributionand abundance of non-timber forest products

MARK JOHNSTONDepartment of Environmental Health & Science, University of the West of England (UWE)

Coldharbour Lane, Bristol, BS16 IQY, UK

Received 12 September 1994; revised and accepted 1 May 1997

Comparisons between two forest localities were undertaken to assess the potential availability of

non-timber forest products (NTFPs) within the low-diversity forests of Guyana. Information on theabundance and distribution of tree species, and local and national ethnobotanical surveys were usedclassifying species into ®ve categories (timber, construction, technological, edible and medicinal). Atotal of 152 species were recorded from the two localities; covering 236 di�erent uses, 33 known

commercial timber species and 106 species with potential non-timber product utilization. The mostimportant plant families with the highest number of uses at both localities were Leguminosae (sub-families Caesalpinioideae and Mimosoideae), Arecaceae, Bombacaceae and Chrysobalanaceae, al-

though these families were not the most abundant families at both localities. At both forest localitieseight tree species represented over 50% of all the trees. At Kurupukari three species, each with morethan three identi®ed NTFPs, represented over 20% of the trees.

Potential utilization of NTFPs are discussed in accordance with species richness, tree density, thenumber of di�erent uses per species, and the percentage of trees represented by each utilizable species.Considering the constraints on the future potential commercialization of NTFPs, two scenarios for theextraction of NTFPs are discussed. Within relatively species-rich forest types the high diversity ofproducts provides potentially viable multiple-species extractionism. In contrast, in low-diversity foresttypes, typical of the Guiana Shield, one or two NTFP species frequently represent over 50% of the canopytrees, and therefore substantially increase the potential sustainable extraction for single-species harvesting.It is suggested that these low-diversity types of forest are prioritized for conservation on the basis ofensuring future utilization, refuge, of non-timber forest products.

Keywords: non-timber forest products; low-diversity forests; species dominance; tropical forest

conservation; Iwokrama; Guyana.

Introduction

The value and importance of non-timber forest products in the future conservation oftropical forests has become well recognized (Balick and Mendelsohn, 1992; Phillips et al.,1994). However, relatively few studies critically assess the relative value of non-timberproducts in terms of the actual abundance and distribution of species/resources. Suchquantitative ecological studies of non-timber products are essential for accurate assess-ments (Hall and Bawa, 1993; Salafsky et al., 1993; Boot and Gullison, 1995).

Controversy continues over the actual utilization potential of forest products (Peterset al., 1989a; Allegretti, 1990; Browder, 1990; Phillips, 1993; Tremaine, 1993; Phillips et al.,1994) whereby the main disadvantages associated with utilization of non-timber forestproducts are high extraction costs (exacerbated by the large variation in tree density), adiscontinuous supply of products, and unknown ecological sustainability (Richards,

0960-3115 Ó 1998 Chapman & Hall

Biodiversity and Conservation 7, 73±86 (1998)

1993). The potential utilization (whether within local markets or on a national basis) offorest products has been primarily assessed from relatively `species-rich' forest types, withtypically over 120 tree species per hectare (diameter of greater than 10 cm), with up to65% of the species represented by a single tree (Gentry, 1988, 1990). While the extractionof products in relatively species-rich forest types may be costly, extraction from relativelylow-diversity or species-poor forest types may act as an alternative viable option. Theselow-diversity forests have been de®ned by Connell and Lowman (1989) as a forest in whicha single tree species may represent between 50 and 80% of the canopy trees. Here,quantitative assessments are made on the distribution and abundance of non-timber forestproducts within low-diversity forest types at two forest localities in Guyana.

Methodology

The relative abundance of potentially useful tree species was assessed from two localities,both within lowland tropical forests of Guyana, South America. Tree population datawere taken from studies by Davis and Richards (1934) at Moraballi Creek, and byJohnston and Gillman (1995) at Kurupukari, using tree data at 10.0 cm diameter atbreast height (dbh). The utilization potential for each species was then assessed usingethnobotanical surveys undertaken by Fanshawe (1947) and by Johnston and Col-quhoun (1996). Comparisons between the two localities and between di�erent types offorest could then be made in relation to the relative abundance and distribution ofdi�erent tree species and their utilization categorization (Prance et al., 1987; Phillips andGentry, 1993a).

The utilization potential of each tree species was then assessed in accordance to one ormore of ®ve utilization categories (timber, construction, technology medicinal and edible),in accordance with Prance et al. (1987), except with the inclusion of commercial timberspecies (Pinedo-Vasquez et al., 1990), and the exclusion of the commerce category as noproducts at Kurupukari were sold on a commercial basis.

Comparisons between forest types

Davis and Richards (1934) undertook detailed tree population surveys in ®ve 1.2-ha forestplots, each within di�erent forest types of a region south of Bartica on the Essequibo River(Fig. 1; 70 km from the coast), surveying all trees greater than 10 cm dbh. Each of thedi�erent study plots was characterized by particular canopy species dominant or co-dominant.InplotsIandIIsinglespeciesdominated,withMoraexcelsa(Caesalpinioideae) andMora gonggrijpii representing 23.5 and 25.8% of the trees in these two plots respectively.Two plots (III and IV) were considered mixed-species forest types with species of Chlor-ocardium rodiaei (Lauraceae), Eschweilera sp. (Lecythidaceae), Licania alba (Chrysoba-lanaceae), Licania heteromorpha and Pentaclethra macroloba (Mimosoideae) commonthroughout both plots. Plot V is classi®ed as white-sand forest with three dominantcanopy species, Eperua falcata (Caesalpinioideae), Catostemma fragrans (Bombacaceae)and Licania buxifolia (Chrysobalanaceae).

In 1992/93 for 1-hectare study plots (labelled Mora, TA2, TA12 and TA19) weresurveyed within the four main forest types at Kurupukari on the Essequibo (280 km fromthe coast), and within the study area of the International Iwokrama Rain Forest Pro-

74 Johnston

Figure 1. Map of Guyana, showing the position of (I) Moraballi Creek near Bartica on the Esse-quibo River, and (II), Kurupukari within the study area of the Iwokrama International Rain Forest

Programme (http://www.idrc.ca/iwokrama).

Tree populations in Guyana 75

gramme. Full details regarding the methodology, species identi®cation and ¯oristiccomposition of these plots are given in Johnston and Gillman (1995).

In brief, at Kurupukari the species composition and species dominants of the Mora plotresembled those of plot I, with Mora excelsa the main canopy species, and TA2 plotresembled plot V. Similar species composition was also recorded in the TA12 and TA19plots at Kurupukari, with canopy in these two plots dominated by Chlorocardium rodiaei,Catostemma fragrans, Sclerolobium guianensis (Caesalpinioideae), Swartzia sp. (Leg.Papilionoideae), Licania alba, Licania heteromorpha and Pentaclethra macroloba (John-ston and Gillman, 1995).

Statistical analysis

The number of species and trees within each of these categories was used to assess theutilization of the di�erent forest types at the two localities. A Generalized Linear Inter-active Model (GLIM) was used for a two-way analysis of variance to examine the sta-tistical di�erence between the utilization categories �n � 5� and localities �n � 2� with thestudy plot acting as replicates. For data transformation in the model a Poisson errordistribution was assumed for the number of species and binomial for the percentage oftrees and species within each category (Crawley, 1993).

Results

A total of 152 species covering 31 families were recorded from the nine study plots. Ofthese, 112 species were found to have some form of utilization potential in accordance withlocal knowledge and published literature (Fanshawe, 1948; Johnston and Colquhoun,1995): 33 species were utilized for timber; 47 for construction; 46 for technology; 52 hadmedicinal properties, and 28 species provided edible products. At Kurupukari a total of112 species from the four 1-ha plots were recorded (Table 1), 70.8% of the species wereclassed into at least one of the ®ve utilization categories (Table 2) and represented 1793trees (87.3% of the total number of trees). At Moraballi Creek, 115 species were recordedfrom the ®ve 1.2 ha plots (Table 1), with 59.1% of the species within the utilization

Table 1. Species composition summary data for the two Guyana localities,Kurupukari (Johnston and Gillman, 1995) and Moraballi Creek (Davis andRichards, 1934). *Species dominance is given as the number of species

represented by 25, 50 and 95% of the total number of trees per plot. Standarderrors are given in parenthesis.

Kurupukari Moraballi Creek

Total no. of species 112 115Mean no. of species/ha 63.0 (4.6) 68.2 (4.1)Mean no. of trees/ha 508.7 (82.1) 651.6 (89.1)

Mean no. of families/ha 23.2 (0.25) 27.8 (1.9)Species dominance*25% 1±3 1±450% 2±7 4±8

95% 32±42 28±56

76 Johnston

categories; representing 2422 trees (74.3% of the total number of trees, Table 2). A total of236 di�erent uses were identi®ed, with a mean of 1.65 and 1.53 uses per species forKurupukari and Moraballi Creek, respectively (Fig. 2).

Locality di�erences by use category

There were no signi®cant di�erences in the number of trees or the number of speciesbetween the two localities (F[1,7] = 1.37 and F[1,7] = 0.03 respectively). However, signi-®cant di�erences were detected between categories and between localities (F[4,40] = 8.28and F[1,43] = 4.54 respectively) for the percentage of species used, but only between cat-egories for the percentage of trees used (F[4,40] = 26.32) and not between localities(F[1,43] = 1.31). Signi®cant di�erences between localities for each use category weredetected for timber and medicinal products only, both signi®cantly higher at Kurupukarithan at Moraballi Creek (Table 2). Regarding di�erences in the percentage of usablespecies between categories, at Kurupukari both construction and medicinal categoriesshowed similar percentage of usable species (32.9 and 32.6%, with no signi®cant di�erencebetween the two categories, LSD = 1.08). Timber and technological products weresigni®cantly lower at 26.9 and 27.8% of the species, and edible products were lower still

Table 2. Summary of species and tree utilization potentials between Kurupukari andMoraballi Creek, Guyana, with percentage for species and trees within each of ®ve

utilization categories.

Kurupukari Moraballi Creek

Total no. of sp. with use (%) 70.8* 59.1Total no. of trees with use (%) 87.3 74.3Total no. of di�erent uses 172 136

Mean no. of uses per sp. (SE) 1.65 (0.16) 1.53 (0.16)

TimberMean % of species (SE) 26.9 (1.9)* 18.2 (1.7)Mean % of trees (SE) 52.7 (4.5)* 33.8 (3.9)

Construction

Mean % of species (SE) 32.9 (1.5) 28.5 (2.9)Mean % of trees (SE) 53.8 (6.3) 51.2 (3.9)

Technology

Mean % of species (SE) 27.8 (2.0) 25.3 (2.5)Mean % of trees (SE) 37.0 (7.3) 36.3 (7.7)

Medicinal

Mean % of species (SE) 32.6 (1.7)* 25.3 (2.8)Mean % of trees (SE) 62.9 (3.2)* 40.7 (6.1)

EdibleMean % of species (SE) 17.2 (1.4) 14.2 (1.0)

Mean % of trees (SE) 6.2 (0.7) 5.7 (0.8)

*Signi®cant di�erence between localities at p < 0.05 (n = 4 for Kurupukari, n = 5for Moraballi Creek). SE=standard errors.

Tree populations in Guyana 77

with 17.2% of the species (F[4,15] = 4.28, LSD = 1.08). Similarly, at Moraballi Creek,species used for construction exhibited the highest percentage of species (Table 2), al-though both technological and medicinal categories showed signi®cantly lower percentageof usage species, followed by timber and edible products (F[4,20] = 5.44, LSD = 1.07).

For the percentage of trees, a slightly di�erent pattern emerged. Trees used formedicinal products represented the highest percentage of trees (62.9% at Kurupukari,compared to 40.7% at Moraballi Creek), then timber and construction categories atKurupukari with 53.8% and 52.7% (these two categories not being signi®cantly di�erent,LSD = 5.24), followed by technological and edible products. At Moraballi Creekconstruction represented the most important category, with 51.2% of the trees, followedby medicinal, technological, timber and edible products (all signi®cantly di�erent,F[4,20] = 11.76, LSD = 1.18, Table 2).

Potential utilization by plant families

When considering the number of di�erent uses per plant family, the Mimosoideaerepresented the most important, with family use value ranging from 2.25 to 6.50 The nextmost important family being the Arecaceae, with a range of 2.33 to 6.00 uses per speciesper plot (Appendix 1), followed by the Ceasalpinioideae, Bombacaceae and Chrysobala-naceae. Other plant families with high-use values, but with limited distribution between

Figure 2. Frequency distribution for the number of di�erent uses per species, with a maximum ofeight uses for one species at both localities.

78 Johnston

the nine plots were Caryocaraceae, Anacardiaceae, and Humiriaceae, all with use valuesgreater than three.

While the Arecaceae presented high-use values, the Arecaceae represented less than 2%of the total number of trees for any one use category (Table 3). Species of Caesalpinio-ideae represented the highest number of utilizable trees for timber and construction inboth forest localities, followed by Bombacaceae (also commonly used for both timber andconstruction) and Lauraceae. In addition, Lecythidaceae was particularly important forconstruction material, with 8.90 and 10.96% of the trees. For technological utilization,Chrysobalanaceae was the most important family at Kurupukari, and Lecythidaceae atMoraballi Creek, and the sub-family Mimosoideae the third most important with 4.03 and6.59% of the trees at Kurupukari and Moraballi Creek respectively.

For medicinal uses at Kurupukari Bombacaceae, Chrysobalanaceae, and Ca-esalpinioideae were the most important families (with 12.05 to 6.54% of the trees). AtMoraballi Creek Caesalpinioideae, Mimosoideae and Bombacaceae were the mostimportant, although the percentage of trees for medicinal uses were generally lower than atKurupukari. The number of species and trees with edible products remained lowthroughout, Rubiaceae dominated at Kurupukari with 1.92% of the trees, and Sapotaceaeat Moraballi Creek with 1.38% of the trees.

Ten species between both localities were found at mean densities of greater than ®vetrees per hectare and more than three uses per species (Table 4), and three species atdensities of greater than ®ve trees per hectare but less than three uses. A further 19 specieswere recorded with more than three uses, but they occurred at densities less then ®ve treesper hectare. The species with the largest number of uses was Pentaclethra macroloba, witheight documented uses, followed by Mora excelsa, Eschweilera sagotiana and Eperuafalcata (all with ®ve or more uses). Although tree densities were relatively high for theseten species, the variation in tree density (given as the coe�cient of variation, CV) was alsohigh, where in only six out of a possible 22 occurrences was the CV value less than 100%(Table 4).

Table 3. Percentage of trees with potential utilization for 10 of the most abundant plant families; forTimber, Construction, Technology, Medicinal and Edible categories.

Kurupukari Moraballi Creek

T C Te M E T C Te M E

Annonaceae 0.09 1.08 0.39 0.74 0.64 ± 1.84 1.65 0.24 0.06

Lauraceae 7.11 ± ± 2.80 ± 4.63 ± ± 3.92 ±Bombacaceae 12.12 12.69 0.59 12.05 ± 6.66 6.78 0.21 4.39 ±Moraceae ± 0.24 ± 0.98 ± ± ± ± ± ±

Lecythidaceae 6.93 8.90 ± 6.78 0.19 0.21 10.96 8.01 ± 0.21Sapotaceae ± 0.15 ± ± 0.19 ± 0.93 ± ± 1.38Chrysobalanaceae 4.23 ± 9.09 10.72 0.09 3.72 ± 6.57 6.62 ±Leg. Caesalpinioideae 19.13 19.13 6.24 6.54 ± 14.28 14.36 3.71 10.56 ±

Leg. Papilionoideae 2.06 2.06 2.06 3.78 ± 0.10 ± 0.31 4.11 ±Leg. Mimosoideae ± 4.47 4.03 4.47 0.44 ± 6.87 6.59 6.97 0.37Rubiaceae ± ± ± ± 1.92 ± ± ± ± 0.39

Arecaceae ± 0.34 1.47 ± 0.78 ± 0.55 1.31 ± 0.61

Tree populations in Guyana 79

Species dominance and key species for utilization

Of the thirteen species identi®ed in Table 4, nine represented more than 5% of the trees inat least one of the nine hectare plots, six species over 10%, and two species with more than20% (Mora excelsa and Eperua falcata) of the trees (Table 5). The four species with morethan ®ve uses represented 26.9% of the total number of trees at Kurupukari and 16.7% at

Table 4. Species use values (taken as the total number of di�erent uses), tree densities (number oftrees/ha) and the coe�cient of variations (percentage standard deviation of the density mean), for

the tree species with a mean density of more than ®ve trees per hectare

NumberKurupukari Moraballi Creek

Species of uses Tree density CV(%) Tree density CV(%)

Pentaclethra macroloba 8 20.5 122.1 42.4 74.8Mora excelsa 6 21.0 163.2 22.6 213.8

Eschweilera sagotiana 5 33.2 107.2 ± ±Eperua falcata 5 65.5 153.5 44.6 187.3Catostemma fragrans 4 61.2 153.3 28.6 215.9Licania alba 4 21.5 111.5 30.3 88.8

Ormosia coutinhoi 4 10.5 127.6 2.0 223.6Chlorocardium rodiaei 3 14.2 156.7 25.6 108.8Licania heteromorpha 3 24.7 90.6 18.6 112.9

Clathrotropis brachypetala 3 2.5 200.0 5.6 100.7Catostemma commune 2 ± ± 14.4 61.2Unonopis glaucopetala 1 ± ± 9.8 97.2

Eschweilera subglandulosa 1 ± ± 28.4 83.0

Table 5. Percentage of trees (species dominance) at 10.0 cm dbh represented by the ten mostimportant tree species for each of the nine study plots at Kurupukari and Moraballi Creek.

Kurupukari Moraballi Creek

Species Mora TA12 TA19 TA2 I II* III IV V

Pentaclethra macroloba 8.7 11.1 ± ± 10.2 4.5 11.3 9.2 ±

Mora excelsa 20.2 2.1 0.4 ± 23.6 ± ± 0.6 ±Eschweilera sagotiana 1.7 15.0 13.2 ± ± ± ± ± ±Eperua falcata 3.6 7.2 0.2 28.9 1.9 1.9 1.0 0.5 21.1

Catostemma fragrans 2.8 3.9 3.0 27.2 ± ± ± 0.5 15.1Licania alba 1.7 5.9 11.1 ± ± 3.4 9.5 5.6 0.1Ormosia coutinhoi ± 1.7 0.9 4.0 ± ± ± ± 1.0Chlorocardium rodiaei ± 2.2 9.8 ± 1.5 2.8 4.3 9.4 0.7

Licania heteromorpha 2.8 5.0 11.9 1.2 ± 1.0 9.1 5.3 0.5Clathrotropis brachypetala 2.8 ± ± ± 3.6 1.0 0.5 0.6 ±Catostemma commune ± ± ± ± 3.6 5.0 2.0 2.4 ±

Unonopis glaucopetala ± ± ± ± 1.1 0.6 3.4 2.3 0.1Eschweilera subglandulosa ± ± ± ± 2.2 7.4 5.0 7.6 ±

*Plot dominated by Mora gonggripii with 25.9% of the trees (no documented use)

80 Johnston

Moraballi Creek. In only two of the 9-hectare plots did no one species represent more than10% of the trees, and in four of the plots (two forest types) at least one species representedover 20% of the trees. The highest species dominance was found within the white-sandforests dominated by Eperua falcata and Catostemma fragrans, both species representingover 50% of the trees in TA2 plot at Kurupukari and over 36% in plot V at MoraballiCreek.

Discussion

Non-timber forest products are being promoted as a possible means of increasing themonetary value of tropical forests (Peters et al., 1989b; Salick et al., 1995), but numerousaccounts have speci®ed the problems of NTFP utilization and extraction, and the estab-lishment of large-scale NTFP extraction reserves may fall short of initial expectations as amechanism for conserving tropical forests (Salafsky et al., 1993; LaFrankie, 1994).However, due to high species dominance within these low-diversity forest types at bothKurupukari and Moraballi Creek, the utilization potential of NTFPs may be signi®cantlyincreased. Within the two forest localities, three species occurred at densities which rep-resent over 20% of the trees at all size-classes, and up to 80% of the canopy trees. AtKurupukari in TA2 plot and plot V at Moraballi Creek, Eperua falcata Caesalpinioideaeand Catostemma fragrans Bombacaceae represented over 55 and 36% of the trees, with®ve and four NTFP uses respectively. In the Mora plot at Kurupukari, and plot I atMoraballi Creek, 20.2 and 23.6% of the trees belonged to Mora excelsa Caesalpinioideaewith ®ve known uses (Fanshawe, 1947; Table 5).

Comparisons between species-rich and species-poor forests

High percentage of utilizable species does not necessarily mean high extraction potentials.Within these low-diversity types of forest large variation in the distribution of tree specieswithin relatively small distances still occurs (Table 4), and may represent the maindisadvantage to any potential economic extraction of a product (with an increase inextraction cost with increasing spatial variation in resource abundance). Salafsky et al.(1993) concluded that relatively species-poor forests (between 50 and 100 species perhectare, Connell and Lowman, 1989) may represent a viable option for extractive reserves,but may be sustained only under speci®c conditions covering both ecological and social-economic conditions. Similarly, Peters et al. (1989b) concluded that species-poor forestsmay represent an important resource for speci®c forest products; in the case of Peters et al.(1989b) species yielding edible products dominated.

On reviewing published material from di�erent neotropical forest localities the per-centage of locally utilized species typically ranged from 33.4 to 91.2%, and the percentageof utilized trees from 55.3 to 96% (Table 6). However, baseline ethnobotanical informa-tion on the utilization of species within di�erent use categories is noticeably lacking, butwhere information is available, between-locality di�erences in species use by use categoryis also just as variable. For instance, the percentage of species at Panare, Venezuela, isnoticeably low, as is the percentage of species yielding edible products in the low-diversityforest of Guyana, although edible products represent a high percentage of local Amer-indian knowledge (Johnston and Colquhoun, 1996). While this is only a preliminaryreview of the ethnobotanical information available, it is worth noting that the percentage

Tree populations in Guyana 81

Table

6.Speciescompositionsandpercentageutilizationofspeciesfrom

nineneotropicalforest

localities

coveringtwenty

studyplots.Where

obtainable,thepercentageofspecieswithin

sixutilizationcategories

isalsopresented.

Kurupukari

Guyana

Kurupukari

Guyana

Kurupukari

Guyana

Kurupukari

Guyana

Moraballi

Guyana

Moraballi

Guyana

Moraballi

Guyana

Moraballi

Guyana

Moraballi

Guyana

Panare

Locality

Mora

TA12

TA19

TA2

III

III

IVV

Venezuela1

No.ofsp.

64

71

67

50

55

69

80

66

71

70

No.oftrees

357

459

477

742

462

460

644

773

919

Usefultrees(%

)90.1

96.1

91.6

89.2

82.0

94.5

69.1

73.7

55.3

Usefulsp.(%

)84.4

83.1

75.6

70.0

63.6

63.7

56.0

69.7

33.4

48.6

Timber

25.0

32.3

28.3

22.0

21.8

28.8

15.0

22.7

12.7

Construction

35.9

35.2

32.8

28.0

29.1

27.5

32.5

36.4

16.9

2.9

Technology

32.8

29.6

26.8

22.0

27.3

28.9

27.5

28.7

14.1

4.3

Medicinal

34.4

35.2

26.8

34.0

34.5

23.1

20.0

30.3

18.3

7.1

Edible

18.7

21.1

14.9

14.0

12.7

15.9

17.5

13.6

11.3

34.3

Commerce

±±

±±

±±

±±

±4.3

Ka'apor

Tem

be

Chacobo

Loreto

Waimiri

Tambopata

Peru4

Tambopata

Peru4

Tambopata

Peru4

Tambopata

Peru4

Tambopata

Peru4

Locality

Brazil1

Brazil1

Bolivia1

Peru2

Brazil3

TFSandITFSandIIUpper

Flood.Old

Flood.ClayFlood.

No.ofsp.

99

119

94

(218)

200

178

164

181

182

186

No.oftrees

(3,780)

550

56.8

530

560

561

Usefultrees(%

)66.4

95.2

91.2

88.8

96.0

96.0

Usefulsp.(%

)76.8

61.3

78.7

60.1

79.0

89.3

85.7

91.0

91.2

90.2

Timber

±±

±24.4

±Construction

20.2

30.3

17.0

31.3

32.0

Technology

19.2

21.0

18.1

22.1

31.0

Medicinal

21.2

10.9

35.1

9.9

15.0

Edible

34.3

21.8

40.4

28.2

27.0

Commerce

2.0

2.0

1.1

4.6

0

Inform

ationsources:1Prance

etal.(1987);

2Pinedo-Vasquez

etal.(1990);

3Milliken

etal.(1992);

4Phillipset

al.(1994)

82 Johnston

of species used for construction and technology products is highest within these low-diversity forests of Guyana. Edible products are noticeably high in the Cha cobo forests ofBolivia at 40.4% (Prance et al., 1987), while medicinal products are more variable betweenlocalities.

Di�erences in the abundance of NTFPs is a function of the distribution and dominanceof particular utilizable plant families, with some plant families containing signi®cantlymore useful species than other plant families (Phillips and Gentry, 1993b). From infor-mation on the known distribution of particular plant families, it should be possible topredict NTFP availability within di�erent forest types. However, even small di�erences inthe abundance or dominance of plant families in di�erent forest types can make a signi-®cant di�erence in the availability of NTFPs. This is re¯ected in the percentage of speciesand trees according to the plant families between the two Guyana localities, with species ofCaesalpinioideae, Bombacaceae and Annonaceae being `useful families' for non-timberproducts and predominantly Lauraceae and Caesalpinioideae for timber products (Ta-ble 2). These are similar to the ®ndings of Phillips and Gentry (1993a) who concluded thateight plant families contained more useful species than expected for non-indigenous peoplein south-eastern Peru; these were Clusiaceae (considered here as Guttiferae), Burseraceae,Caesalpinioideae, Meliaceae, Myristaceae, Lauraceae, Annonaceae and Arecaceae. Me-liaceae was absent from two Guyana localities, while Myristaceae was only found atMoraballi where two species represented ®ve non-timber uses. The remaining six familiesidenti®ed by Phillips and Gentry (1993a) as being of exceptional signi®cance were alsoimportant at Kurupukari and Moraballi Creek.

Within relatively species-rich forest types (perhaps those forests with typically morethan 250 species per hectare), potential NTFP utilization may occur only if a large pro-portion of the species render a harvestable product (Peters et al., 1989b). Such circum-stances may be relatively limited, whereby only a small proportion of the species mayrender a suitable product, and the inherent low density of any one species in high speciesrichness forest may mean uneconomical extraction. For instance, studies by LaFrankie(1994) on Aquilaria malaccensis (Thymelaeceae) and Cinnamomum mollissimum (Laura-ceae), found that the natural densities of these species at two and three trees over 1 cm dbhper hectare would prevent economic exploitation. In contrast, within low-diversity forests,the density of a particular species may represent 50 to 80% of the canopy trees, andtherefore likely to render the possibility of economically sustainable NTFP extraction(provided that the dominant species does indeed yield a useful NTFP).

Conservation and utilization of forest resources

The utilization and possible extraction of NTFPs within neotropical forests may be rep-resented by two extremes of contrasting approaches to the utilization of products. Amajority of forest types in South America are not low-diversity nor particularly highspecies richness forests. Within such forests the densities of any one given species may stillremain de®ciently low for viable single species harvesting, nor may there be su�cientlyhigh numbers of utilizable species for a multiple species harvesting scheme. In summary, itmay be suggested that NTFP extraction may be economically viable only when either theproduct being extracted is in high abundance (the case of many low-diversity forests), orwhen there are su�ciently high numbers of di�erent species which may be harvested fromany given forest type, such as the species-rich and fertile soils of Peru due to the large

Tree populations in Guyana 83

diversity of high yielding species (Peters et al., 1989a). Likewise, the combinations ofmultiple product extraction under a `High Diversity Forestry' scheme (LaFrankie, 1994),in comparison to the low-diversity forests of Guyana where extraction potential may behigh only if the dominant species yields useful products.

Utilizable NTFP extraction forest types, however, are likely to represent less than 10%of the neotropics, the remaining forests represented by the species-rich poor soil terra ®rmawith signi®cantly lower NTFP yields (Phillips, 1993). While both the mature ¯oodplainand terra ®rma forests may need to be prioritized for conservation (Prance et al., 1989;Phillips et al., 1994), it is equally important to consider future rates of deforestation withinareas currently considered relatively `undisturbed'; these include an estimated 350 000 km2

of the low-diversity forest types of the Guiana Shield (Berry et al., 1995; Harcourt andSayer, 1996). Myers (1988) stated that the forests of the Guiana Shield may represent oneof the last blocks of lowland forest by the end of the century. However, recent commercialdevelopments within Guyana impose a major threat (Colchester, 1994), with less than0.4% of Guyanese forests currently protected (Harcourt and Sayer, 1996).

While future deforestation of Guyanese forests is pending, these low-diversity forestsmay produce relatively high yields of extractable non-timber forest products, and couldrepresent an important development in the establishment of non-timber extractionreserves. Those forest types with a high number of uses and /or relatively high speciesdominance are likely to be key forests for future economic utilization for the sustainableharvesting of non-timber forest products. While there is an obvious need to undertakelong-term manipulation experiments to assess extraction size-thresholds and potentialutilization of NTFPs (Hall and Bawa, 1993), it is also essential that studies take intoconsideration both the percentage of useful species/trees, and the species dominancewithin each forest type investigated; only then may such information be used for inte-grated NTFP extractionism and conservation of tropical forest systems.

Acknowledgement

I am indebted to the Amerindians of Kurupukari for their invaluable knowledge ofethnobotany. I also wish to thank Sir Ghillean Prance, Dr Mike Gillman, the anonymousreferees for comments, and Araminta Colquhoun for assistance with data collection.These studies were supported by an Open University fellowship.

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Tree populations in Guyana 85

Appendix 1. Family use values, given as the mean number of uses per species for all plant families atboth Guyanese localities (equivalent to the Familial use value used by Prance et al., 1990, except that

no distinction is made between minor and major products).

Kurupukari Moraballi Creek

Mora TA12 TA19 TA2 I II III IV V

Annonaceae 2.00 2.00 1.80 1.33 1.00 1.00 1.75 1.75 1.00Myristicaceae ± ± ± ± 3.00 2.00 2.00 2.00 ±

Lauraceae 1.30 1.30 1.42 1.00 2.00 1.67 1.25 1.17 1.33Caryocaraceae ± 4.00 ± ± 0.00 ± 4.00 4.00 ±Guttiferae 0.00 0.00 0.00 0.75 1.00 0.67 0.67 1.00 2.00Quiinaceae ± ± ± ± 2.00 1.00 1.00 1.00 2.00

Elaeocarpiaceae ± ± ± ± 0.00 0.00 ± 0.00 ±Tiliaceae ± ± ± ± ± ± 0.00 0.00 0.00Sterculiaceae ± ± 1.00 1.00 1.00 1.00 0.50 0.50 ±

Bombacaceae 3.00 3.00 4.00 3.00 2.00 2.00 2.00 2.00 2.00Moraceae 2.75 2.25 2.00 0.75 ± ± 5.00 ± ±Lecythidaceae 1.75 2.00 1.50 1.00 1.50 0.67 1.75 1.50 1.00

Violaceae 0.00 0.00 0.00 ± ± ± ± ± ±Flacourtiaceae ± ± ± ± ± 0.00 0.00 0.00 0.00Sapotaceae ± 3.00 1.00 1.00 0.33 0.80 0.80 0.80 0.33

Lissocarpaceae ± ± ± ± ± ± 0.00 0.00 0.00Chrysobalanaceae 1.80 2.00 3.50 1.00 0.00 2.33 2.33 1.33 2.33Leg. Caesalpinioideae 3.25 4.33 4.33 5.00 4.00 3.00 3.25 4.50 3.00Leg. Papilionoideae 1.33 1.75 1.75 1.25 1.50 1.33 2.00 2.00 1.67

Leg. Mimosoideae 4.33 4.33 ± 5.00 6.50 2.25 4.00 3.00 2.00Myrtaceae 0.75 1.00 0.66 0.00 1.00 0.50 0.50 0.50 1.00Melastomataceae ± ± ± 0.00 0.00 ± ± 0.00 ±

Combretaceae ± ± ± ± 0.00 0.00 0.00 ± ±Sapindaceae 0.50 1.00 1.00 0.50 ± 2.00 ± ± 1.00Goupiaceae 2.00 2.00 2.00 ± ± 2.00 ± 2.00 ±

Icacinaceae ± ± ± 2.00 ± ± ± ± ±Dichapetalaceae 2.00 2.00 2.00 2.00 ± ± ± ± ±Euphorbiaceae ± ± ± ± 0.33 0.00 0.00 0.00 0.00Burseraceae 2.00 2.00 1.00 1.00 2.00 2.00 2.00 3.00 2.00

Anacardiaceae 2.00 3.00 ± 2.00 3.00 1.50 3.00 ± 3.00Simaroubiaceae 1.50 1.00 1.50 2.00 ± ± ± ± ±Meliaceae ± ± ± ± ± 0.00 0.00 ± ±

Rutaceae ± ± ± ± ± ± ± 1.00 1.00Humiriaceae ± ± ± 5.00 ± ± 0.00 ± ±Malpighiaceae ± ± ± ± ± 1.00 1.00 1.00 ±

Araliaceae 0.00 0.00 ± ± 1.00 1.00 1.00 1.00 ±Apocynaceae 2.00 2.00 2.00 1.50 2.00 2.50 2.00 2.00 1.00Boraginaceae 1.00 2.00 ± ± ± 1.00 1.00 1.00 ±

Bignoniaceae 1.00 1.00 1.00 ± ± 1.00 1.00 1.00 ±Rubiaceae 1.00 1.00 1.00 1.00 1.00 1.00 ± 1.00Arecaceae 2.33 4.00 3.00 6.00 5.50 3.25 3.25 ± ±

86 Johnston