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The Brazil nut tree (Bertholletia excelsa) is a frequent component of agroforestry systems in the Amazon because of its adaptation to nutrient-poor upland soils and multiple uses. We investigated the aboveground biomass production (kg dry weight), nutrient uptake and requirements (N, P, Ca, Mg, K) of Brazil nut trees of different sizes grown under agroforestry conditions and fertilized at different levels. Eight of 70 experimental trees with different size were harvested and stem, branches and leaves were separated. Nutrient contents were determined for three trees of varying size. Average tree growth was fast, but variability was high, suggesting considerable potential for the improvement of this economically important species. The trees responded to increased levels of fertilizer and lime with significantly increased foliar nutrient contents and growth, probably because of the improved availability of Mg and Ca for which the species seems to have a relatively high demand. In contrast to Brazil nut trees grown in forest or dense plantations, the agroforestry trees invested a substantial part of their biomass and nutrients in large branches and developed spreading crowns. To improve stem form, reduce competition with associated crops for light and recycle nutrients, regular pruning of lower branches or planting arrangements that favor self-pruning are recommended. These measures would also increase the recycling of Ca and Mg, large quantities of which are contained in the branches.

Tropical forest countries are struggling with the partially conflicting policy objectives of socioeconomic development, forest conservation, and safeguarding the livelihoods of local forest-dependent people. We worked with communities in the lower Tapajós region of the central Brazilian Amazon for over 10 years to understand their traditional and present land use practices, the constraints, and decision making processes imposed by their biophysical, socioeconomic, and political environment, and to facilitate development trajectories to improve the livelihoods of forest communities while conserving the forest on the farms and in the larger landscape. The work focused on riverine communities initially in the Tapajós National Forest and then in the Tapajós-Arapiuns Extractive Reserve. These communities have a century-old tradition of planting rubber agroforests which despite their abandonment during the 1990s still widely characterize the vegetation of the river banks, especially in the two protected areas where they are safe from the recent expansion of mechanized rice and soybean agriculture. The project evolved from the capacity-building of communities in techniques to increase the productivity of the rubber agroforests without breaking their low-input and low-risk logic, to the establishment of a community enterprise that allowed reserve inhabitants to reforest their own land with tree species of their choice and sell reforestation (not carbon) credits to local timber companies while retaining the ownership of the trees. By making land use practices economically more viable and ecologically more appropriate for protected areas, the project shows ways to strengthen the system of extractive and sustainable development reserves that protects millions of hectares of Amazon forest with the consent of the communities that inhabit them.

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