Biomass and demographic dynamics of the Brazil nut family (Lecythidaceae) in a mature Central Amazon rain forest

Abstract

In this study, we analyze the demographic rates and biomass dynamics of Lecythidaceae in a 100-ha permanent forest plot in the Central Amazon. We characterize habitats in the plot, analyze the effect of habitat on tree density, species richness, and biomass and demographic dynamics, and quantify significant species habitat associations. The plot experienced a 13.2 % net loss of Lecythidaceae individuals (n = 1023) but aboveground biomass (AGB; Mg ha−1) did not differ between the two censuses. Growth rates averaged 1.2 mm year−1 with high intraspecific variation and differed significantly among species height classes. Stem density and species richness decreased in all six terra firme habitats and were significantly lower in both years in the flood disturbed habitat. Only the flood disturbed areas experienced a significant loss in AGB, along with the highest annual mortality, recruitment, and growth rates across the plot. The lower-lying habitats experienced higher mortality rates than the slopes and plateaus, suggesting too much moisture is a higher risk to Lecythidaceae individuals than drought in this plot. There were no overlapping habitat associations among sister species, or among the seven most abundant species, which suggests that terra firme habitat association provides a niche partitioning mechanism for closely related Lecythidaceae species. As intended with its establishment, this plot continues to provide integral baseline data for one of the most ecologically dominant and culturally significant tree families in the Amazon region.