What explains the low production of fruits by Bertholletia excelsa tree in pasture areas?

Abstract

In several regions of the Amazon is common to observe isolated populations of Brazil nut trees (Bertholletia excelsa Bonpl.) in pastures, some of which are dead. In these altered environments, the literature indicates that fruit production of the remaining Brazil nut trees is lower than those of adjacent forest with a significant occurrence of B. excelsa (Brazil nut groves). The objective of this study was to explore which factors better explain the low fruit production of Brazil nut trees in deforested areas. We studied dendrometric variables, soil physical parameters, litter and microclimatic variables. The results showed that pasture areas presented higher values of soil density, lower values of soil moisture and litter, as well as drier and warmer microclimatic conditions than in the forested areas. The average distance between the trees was significantly greater in the pasture area than in the Brazil nut groves, in contrast, the canopy area of B. excelsa trees was on average significantly smaller than in the Brazil nut groves, thus reducing the possibilities of pollination of the trees. In summary, more unfavorable environmental conditions in pasture areas (soil, microclimate, physical isolation) could partially explain the low fruit production of Brazil nut trees compared to observed production in adjacent forests.