Too rare for non-timber resource harvest? Meso-scale composition and distribution of arborescent palms in an Amazonian sustainable-use forest

Arborescent palms can provide an important source of non-timber forest products (NTFPs) within tropical forest REDD+ frameworks. To identify the NTFP potential of arborescent palms, we examined meso-scale patterns of abundance and distribution within a sustainable-use protected area in the eastern Brazilian Amazon. To understand the environmental correlates of observed patterns we evaluated the effects of topography, hydrography and geographic space on the presence, density and biomass of adult arborescent palms. Adult palms were sampled in 30 (250 × 20 m) plots systematically distributed within a 25-km² grid. Topographic and hydrographic variables were derived from a remotely sensed digital elevation model. Spatial correlations in the explanatory and response variables were examined using Mantel tests and GLMs. To test for evidence of dispersal limitation, semi-variograms were used to examine spatial patterns in GLM residuals. Adult arborescent palms were rare occurring in only 12 of the 30 plots. In total, we recorded 118 individuals from six species (Bactris maraja, Euterpe oleracea, Iriartella setigera, Oenocarpus bacaba, Oenocarpus bataua and Oenocarpus minor). This corresponded to a mean live aboveground biomass per plot of 0.85 Mg ha⁻¹ (range: 0–28.1 Mg ha⁻¹). Hydrographic and topographic variables suggest that environmental conditions are suitable for E. oleracea, an economically important species. The presence, biomass, and density of palms were uncorrelated with geographic distances among plots. The hydrographic model significantly explained variation in palm presence and biomass, whereas density was only explained by the topographic model. Our findings indicate that arborescent palms are currently too rare to be efficiently harvested as NTFPs in the study area. Yet, comparisons with published estimates suggest that there is significant potential for agroforestry to facilitate the commercialization of palm NTFPs for community based extractive activities.