THE POTENTIALS OF 20 INDIGENOUS TREE SPECIES FOR SOIL REHABILITATION IN THE ATLANTIC FOREST REGION OF BAHIA, BRAZIL

1. The goal of this research was to identify indigenous tree species w ith a positive influence on soil fertility in order to design mixed-tr ee and tree/crop systems for the Atlantic forest region of Bahia, Braz il. The study focused on 20 native tree species growing in 14-15-year- old stands in an arboretum at Pau Brasil Ecological Station. Although the small size of the areas sampled and the lack of adequate replicati on limits the interpretation of the results, the pure tree stands offe red a unique opportunity to evaluate the nutrient cycling characterist ics of several species which could be useful for their future utilizat ion in land rehabilitation systems. 2. Soils for chemical analysis and bulk density were sampled under a 25-year-old secondary forest, a mix ed-species plantation, the native forest and under the 20 species in q uestion. Forest-floor litter and live leaf samples were analysed for N , P, K, Ca, Mg and Al. 3. Soil fertility was higher in secondary than in primary forest. The mixed plantation had similar soil pH, C, N and Mg, slightly higher P, and lower K and Ca than the primary forest. Lit ter accumulation on the floor was larger in secondary than in primary forest. Litter nutrients were also higher in secondary than in primary forest. 4. Positive effects on soils were noted under 15 out of the 2 0 species studied, among those Inga affinis, Parapiptadenia pterosperm a (N-fixing species); Arapatiella psilophylla, Caesalpinia echinata, ( leguminous, non-N-fixing); Eschweilera ovata, Lecythis pisonis, Licani a hypoleuca (of other families). 5. Among the 20 species in the arbore tum, the highest dry weights of forest-floor litter were found under A rapatiella psilophylla, Bombax macrophyllum, Inga affinis, Licania hyp oleuca and Pithecellobium pedicellare; positive effects on soils were found under all these species, with P. pedicellare having the least in fluence. This suggests that forest-floor nutrients were incorporated i n the soil via decomposition under these species. 6. Species that cont ribute to increased C and N, such as Caesalpinia echinaia, Inga affini s, Parapiptadenia pterosperma and Plathymenia foliolosa, could be comb ined with those that increase soil pH, basic cations or both, such as Copaifera luscens, Eschweilera ovata, Lecythis pisonis and Licania hyp oleuca. The inclusion of Arapatiella psilophylla, Bombax macrophyllum, Buchenavia grandis, Caesalpinia echinata, Cassia spp., Hymenaea aurea and Inga affinis could contribute to increased levels of extractable P in the surface soils. In addition to their potential effects on soil fertility, species choices must be guided by seed and seedling availa bility, as well as by farmers' preferences, local uses for the species and economic aspects (cost of establishment and market potential).