Shifting cultivation effects on Brazil nut (Bertholletia excelsa) regeneration
2008
Cotta, Jamie N. | Kainer, Karen A. | Wadt, Lúcia H.O. | Staudhammer, Christina L.
Brazil nut (Bertholletia excelsa), has emerged as the cornerstone of the extractive economy in much of the Amazon, but the debate continues as to whether or not current harvest levels have a detrimental effect on Brazil nut seedling recruitment. While regeneration studies to date have been conducted solely within mature forest, our study provides further insight into current Brazil nut regeneration dynamics, with a unique first look at regeneration in swidden fallows within two multiple-use areas in Acre, Brazil. Recruitment of individuals <=10cm diameter at breast height (dbh) was evaluated within three 9ha mature forest plots and six fallows of 0.5-1.0ha each. Higher mean densities of B. excelsa seedlings (individuals <1.5m in height) were observed in fallow than in mature forest (12.7 and 5.3individualsha⁻¹, respectively). A generalized linear mixed model analysis revealed that in addition to forest type, proximity to seed sources also explained seedling densities. Height and diameter growth of young B. excelsa individuals was positively related to light availability. Photosynthetic photon flux density levels were over three times higher in fallows versus mature forest during peak sunlight hours. Results suggest that fallow environments may provide favorable conditions for B. excelsa regeneration. Not only can anthropogenic disturbance in the form of shifting cultivation play a positive role in B. excelsa regeneration, its historic presence on the landscape could explain current Brazil nut densities and distributions. Finally, swidden fallows could potentially be managed for enhanced Brazil nut densities, which may provide an opportunity for greater income for extractive families while contributing to the sustainability of Brazil nut extraction and forest conservation in the long term.
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