Response of a tropical tree to non-timber forest products harvest and reduction in habitat size.

Non-timber forest products (NTFPs) are widely harvested by local people for their livelihood. Harvest often takes place in human disturbed ecosystems. However, our understanding of NTFPs harvesting impacts in fragmented habitats is limited. We assessed the impacts of fruit harvest, and reduction in habitat size on the population structures of Pentadesma butyracea Sabine (Clusiaceae) across two contrasting ecological regions (dry vs. moist) in Benin. In each region, we selected three populations for each of the three fruit harvesting intensities (low, medium and high). Harvesting intensities were estimated as the proportion of fruits harvested per population. Pentadesma butyracea is found in gallery forests along rivers and streams. We used the width of gallery forests as a measure of habitat size. We found negative effects of fruit harvest on seedling and adult density but no significant effect on population size class distribution in both ecological regions. The lack of significant effect of fruit harvest on population structure may be explained by the ability of P. butyracea to compensate for the negative effect of fruit harvesting by increasing clonal reproduction. Our results suggest that using tree density and population structure to assess the ecological impacts of harvesting clonal plants should be done with caution

Data from: Recurrent fruit harvesting reduces seedling density but increases the frequency of clonal reproduction in a tropical tree

Studies on the ecological impacts of non-timber forest products (NTFP) harvest reveal that plants are often more resilient to fruit and seed harvest than to bark and root harvest. Several studies indicate that sustainable fruit harvesting limits can be set very high (>80% fruit harvesting intensity). For species with clonal and sexual reproduction, understanding how fruit harvest affects clonal reproduction can shed light on the genetic risks and sustainability of NTFP harvest. We studied 18 populations of a gallery forest tree, Pentadesma butyracea (Clusiaceae), to test the impact of fruits harvest, climate and habitat size (gallery forest width) on the frequency of sexual or clonal recruitment in Benin, West Africa. We sampled populations in two ecological regions (Sudanian and Sudano-Guinean) and in each region, we selected sites with low, moderate and high fruit harvesting intensities. These populations were selected in gallery forests with varying width to sample the natural variation in P. butyracea habitat size. Heavily harvested populations produced significantly less seedlings but had the highest density and proportion of clonal offspring. Our study suggests that for plant species with dual reproductive strategy (via seeds and clonal), fruit harvesting and associated disturbances that come with it can lead to an increase in the proportion of clonal offspring. This raises the issue that excessive fruit harvest by increasing the proportion of clonal offspring to the detriment of seed originated offspring may lead to a reduction in genetic diversity with consequence on harvested species capability to withstand environmental stochasticity

Data 1: Seedling and adult Density and Basal Area for Pentadesma

Data 1: Population density and basal area data for 18 Pentadesma butyraceae populations in Benin, West Africa This data set includes for each plot in each of the 18 populations of Pentadesma butyraceae in Benin, seedling, clonal and adult densities, and population level fruit harvesting intensity and gallery forest width

Effect of fruit harvest (Harvest: L = low, M = medium, H = high), gallery forest width (FSize) on <i>Pentadesma butyracea</i> seedlings density in two ecological regions of Benin (RegSG vs. RegS).

<p>Regression coefficients, adjusted 1 SE and P-values are estimated from information theoretic model averaging approach following a generalized mixed effect model with negative binomial error structure.</p

Influence des pressions anthropiques sur la structure des populations de Pentadesma butyracea au Bénin

La présente étude examine l’influence des pressions anthropiques sur les caractéristiques structurales des populations de Pentadesma butyracea Sabine (Clusiaceae), une espèce ligneuse vulnérable et à but multiple. Au total 116 placeaux de 500 m² ont été installés de façon aléatoire, dont 68 dans la zone soudanienne et 48 dans la zone soudano-guinéenne, pour réaliser les mesures dendrométriques et inventaires floristiques. Les populations de P. butyracea ont été catégorisées suivant les pressions anthropiques auxquelles elles sont sujettes à l’aide d’une Analyse factorielle des correspondances (AFC). Trois groupes ont été discriminés : le groupe1 (populations de Penessoulou et de Kandi) est caractérisé par une forte pression due aux feux de végétation et aux activités agricoles ; le groupe 2 (populations de Manigri et de Ségbana) est caractérisé par des coupes fréquentes de bois, l’écorçage régulier de P. butyracea, l’élagage de P. butyracea et la pâture des animaux dans les galeries ; et le groupe 3 (populations de Natitingou, Toucountouna et Tchaourou) est caractérisé par un fort niveau de ramassage des fruits de P. butyracea et d’extraction de sable dans les galeries. La répartition par classes de diamètre donne des structures en cloche avec une dissymétrie gauche ou droite selon les types de pressions auxquelles les populations discriminées sont soumises. Pour une conservation des populations de P. butyracea, les forêts galeries très dégradées doivent faire l’objet de reboisement et des mesures de protection doivent être mises en oeuvre dans les populations peu dégradées.The present study examined the influence of human activities on the structural characteristics of the populations of P. butyracea, a vulnerable multipurpose woody species. A total of 116 plots of 500 m² were randomly installed, 68 in the sudanian region and 48 in the sudano-guinean region, for dendrometric and floristic inventories. The populations of P. butyracea were categorized according to human pressures they are exposed to, using a Factorial Analysis of Correspondences. Three groups were discriminated : Group 1 (populations of Penessoulou and Kandi), characterized by a pressure from wild vegetation fires and agricultural activities ; Group 2 (populations of Manigri and Ségbana), characterized by illegal selective logging, abusive barking of P. butyracea, animal grazing ; and Group 3 (populations of Natitingou, Toucountouna and Tchaourou), characterized by excessive seeds collection and sand removal from the stream by humans. The diameter distribution structures were of left or right dissymmetry according to pressures types to which the discriminated groups are subjected. For a conservation of remnant populations of P. butyracea, the most degraded gallery forest stands should be reforested while protecting the least degraded ones

Effect of fruit harvest (Harvest: L = low, M = medium, H = high), gallery forest width (FSize) on <i>Pentadesma butyracea</i> adult density in two ecological regions (RegSG vs. RegS).

<p>Regression coefficients, adjusted 1 standard error (SE) and p-values are estimated from information theoretic model averaging approach following a generalized mixed effect model with negative binomial error structure.</p

Size class distribution for <i>Pentadesma butyracea</i> populations with low, medium and high fruit harvesting rates in two ecological regions.

<p>Size class distribution for <i>Pentadesma butyracea</i> populations with low, medium and high fruit harvesting rates in two ecological regions.</p

Data 2: Individual Demography of Pentadesma butyraceae in Benin

Data 2: This data set includes dbh, total height, trunk height, number of fruits, distance to river bed data for 482 Pentadesma butyraceae trees in 18 populations in Benin, West Africa distributed across two climatic regions. For each of these individual trees, we also added fruit harvesting intensity at the plot level, the gallery forest width and river width