The Potentials of 20 Indigenous Tree Species for Soil Rehabilitation in the Atlantic Forest Region of Bahia, Brazil

Abstract

1. The goal of this research was to identify indigenous tree species with a positive influence on soil fertility, in order to design mixed-tree and tree/crop systems for the Atlantic forest region of Bahia, Brazil. 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 replication limits the interpretation of the results, the pure tree stands offered a unique opportunity to evaluate the nutrient cycling characteristics of several species which could be useful for their future utilization in land rehabilitation systems. 2. Soils for chemical analysis and bulk density were sampled under a 25-year-old secondary forest, a mixed-species plantation, the native forest and under the 20 species in question. 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. Litter 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 20 species studied, among those Inga affinis, Parapiptadenia pterosperma (N-fixing species) ; Arapatiella psilophylla, Caesalpinia echinata, (leguminous, non-N-fixing) ; Eschweilera ovata, Lecythis pisonis, Licania hypoleuca (of other families). 5. Among the 20 species in the arboretum, the highest dry weights of forest-floor litter were found under Arapatiella psilophylla, Bombax macrophyllum, Inga affinis, Licania hypoleuca and Pithecellobium pedicellare ; positive effects on soils were found under all these species, with P. pedicellare having the least influence. This suggests that forest-floor nutrients were incorporated in the soil via decomposition under these species. 6. Species that contribute to increased C and N, such as Caesalpinia echinata, Inga affinis, Parapiptadenia pterosperma and Plathymenia foliolosa, could be combined with those that increase soil pH, basic cations or both, such as Copaifera luscens, Eschweilera ovata, Lecythis pisonis and Licania hypoleuca. 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 availability, as well as by farmers' preferences, local uses for the species and economic aspects (cost of establishment and market potential).