Population structure and nut yield of a Bertholletia excelsa stand in Southwestern Amazonia

LHO Wadt, KA Kainer, DAP Gomes-Silva - Forest Ecology and Management, 2005 - Elsevier
LHO Wadt, KA Kainer, DAP Gomes-Silva
Forest Ecology and Management, 2005Elsevier
Although Brazil nut (B. excelsa) is often touted as one of the most economically successful
NTFPs, little is known about the population structure of this species within its natural range in
Southwestern Amazonia or ecological factors that affect fruit production. Since these are
considered fundamental for sustainable resource management, we examined a natural
Brazil nut stand in an extractive reserve in Acre, Brazil, posing the following questions:(1)
What is the spatial distribution, species density, and size–class structure of B. excelsa? and …
Although Brazil nut (B. excelsa) is often touted as one of the most economically successful NTFPs, little is known about the population structure of this species within its natural range in Southwestern Amazonia or ecological factors that affect fruit production. Since these are considered fundamental for sustainable resource management, we examined a natural Brazil nut stand in an extractive reserve in Acre, Brazil, posing the following questions: (1) What is the spatial distribution, species density, and size–class structure of B. excelsa? and (2) What tree-level factors influence Brazil nut production? In a 420ha census, 568 trees ≥10cm diameter at breast height (dbh) were counted, resulting in a density of 1.35 trees ha−1. Based on the nearest-neighbor method, an index of aggregation (R) of 0.77 indicated a rejection of the null hypothesis of a strictly random distribution pattern. Yet, this value suggests a much greater tendency toward randomness than either clumping or uniformity. Our data do not show the commonly reported existence of groves, referring to clearly defined clusters of 50 to several hundred trees separated from similar clusters by great distances. Almost 1/4 of the population (23%) was composed of non-reproductive juveniles. Maximum R2 improvement analysis applied to four distinct diameter classes provided insight into the dynamics of production-related variables over the species life cycle. While dbh explained 1/3 of production variance (R2=0.3360) in the smallest diameter class (10cm≤dbh<50cm), which included those in the process of reaching reproductive maturity, crown form best explained production variance of very large trees (dbh≥100cm). Results also demonstrated a significant negative correlation between crown vine load and production of trees≥50cm dbh (r=−0.13, P=0.008), suggesting the need for further study on vine cutting as a possible silvicultural treatment for enhancing nut yields.
Elsevier