Intensification of açaí palm management largely impoverishes tree assemblages in the Amazon estuarine forest.

The exploitation of non-timber forest products has been encouraged in order to reconcile economic uses, biodiversity conservation and the provision of ecosystem services. In this paper we investigate how increments on the açaí palm density (Euterpe oleracea) via forest management change tree assemblages across 47 plots in the Amazon estuarine forest (Brazil). Assemblage attributes were confronted to açai clump density, soil fertility, canopy openness and elevation. Both tree species density and richness were negatively affected by acai, but species richness was also affected by tree abundance. Species-accumulation curves also indicated higher alpha and beta diversity across low-intensity forest patches with high-intensity patches lacking half of the tree species. A small set of species dominated forest patches, but açaí density did not correlate with the abundance of valuable species. Explanatory variables, including açai density, explained a small fraction of the variation on the functional profile of tree assemblages, but functional richness was reduced by a half across forest stands exceeding 600 açaí clumps per ha. Our results suggest that açaí intensification alters the structure of woody plant assemblages in estuarine forest. Tree abundance and species richness consistently declines as açaí clump density increases, with some forest stands being dominated by açaí and almost lacking any tree species. Accordingly, landscapes dominated by high-intensity forest stands are largely impoverished in terms of understory, canopy and emergent tree species. These findings question the current legal regulations and thresholds adopted for açai management, while alert for potential disasters caused by poorly-regulated extractions of NTFPs. • Açaí intensification for enhancing fruit yield represents a complete reorganization of the estuarine forest. • Landscapes dominated by high-intensity forest stands are largely impoverished in terms of understory, canopy and emergent tree species. • Current legal regulations on açaí intensification fail to protect forest integrity and biodiversity. • Açaí represents a key economic opportunity for locals but a real threat for the estuarine forest. [ABSTRACT FROM AUTHOR]