Mixed tree plantations and tree-crop combinations with native species of economic value maybe viable alternatives for the preservation of native species and to contribute to soil fertility restoration in degraded areas. This research will be conducted at Pau Brasil Ecological Station in Porto Seguro, Bahia, Brazil (16-23'S, 39-11'W). The station has a 1000 ha reserve of Atlantic rain forest, an endangered ecosystem suffering strong pressure from agricultural expansion; an arboretum with approximately 40 species from the forest, all planted in monospecific stands, with similar age and on the same soils; and other experimental pure and mixed-tree plantations. Preliminary results (June 1989) showed low soil N availability during early establishment of pure and mixed-tree stands, possibly with high competition with the soil microflora. Planning activities will include: a) to examine species/site relationships for the species in the arboretum; b) to study factors controlling N availability in existing pure and mixed- tree plantations; c) based on this information, to design mixed plantations taking into consideration the potential ameliorating effects of trees on soils, and their nutrient requirements for complementary use of nutrient resources. This type of research is broadly important to the field of ecology, and will provide significant information regarding Conservation of tropical forests.
