Human influence on the regeneration of the Brazil nut tree (Bertholletia excelsa Bonpl., Lecythidaceae) at Capanã Grande Lake, Manicoré, Amazonas, Brazil

Abstract

This study examines the population structure and regeneration of Brazil nut tree (Bertholletia excelsa) populations at sites subjected to extractive activities in the Capanã Grande Lake Extractive Reserve (Rio Madeira, Amazonas, Brazil). We analyze correlations between three regeneration levels (seedling, sapling and juvenile density) and seven possible explicatory variables related to vegetation structure and human action. The tested vegetation structure variables include adult tree density, crown area, basal area, canopy openness, and fruits opened by agoutis. We also test the time of human use and distance from residences as possible explicatory variables. The density values of the Brazil nut stands in the region are high (12.5 tree/ha), with 60 % of trees having a diameter at breast height (DBH) > 80 cm. The mean potential regeneration (24.8 seedlings/ha), pre-established regeneration (4.4 saplings/ha) and established regeneration (3.2 juveniles/ha) values are high compared to other Brazil nut tree populations and tend to be greater in the "intensively used" stands, defined as sites where human presence during the year is more frequent. The time of human use and the density of adult Brazil nut trees are the variables that best correlate with established regeneration (density of juveniles). The number of juveniles/adult Brazil nut trees is five times higher in intensively used stands than in those moderately used. These results suggest that extractive activities and disturbances in the understory caused by human presence may favor (intentionally or not) regeneration of Brazil nut trees in more-frequently used stands. The data support the concept, frequently suggested in the literature, that aggregations of Brazil nut trees could be a consequence of the activities of Amerindian populations. © 2015 Springer Science+Business Media New York.