Recovery of species richness and conservation of native Atlantic forest trees in the cacao plantations of southern Bahia in Brazil

摘要

The Atlantic forests of southern Bahia in Brazil present great species richness and a high degree of endemism. A large part of these native forests were transformed into cacao plantations in an agroforestry system known locally as cabrucas, where native trees were culled and cacao was planted under the shade of remaining trees. The present study analyzed the influence of time of implantation (age) and time of abandonment of management practices on tree species diversity of cabruca plantations to evaluate the capacity for conservation and recovery of species richness of native Atlantic Forest trees in cabrucas. Phytosociological surveys were conducted in five cabrucas with different conditions of age and state of abandonment. All trees, including hemiepiphytes and excluding the cacao plants, with a minimum stem diameter of 10 cm at breast height, were surveyed within a 3-ha sampling area in each plantation. A total of 2514 individual trees belonging to 293 species and 52 families were recorded in the five cabrucas. The Shannon diversity index varied from 3.31 to 4.22 among the cabrucas and was positively correlated with the time of abandonment (r = 0.97). The new cabrucas showed the highest values of estimated total richness (Chao) and the highest proportion of late successional species than the old ones. All areas preserved a very high proportion of native forest species while the three old cabrucas showed a higher proportion of exotic species than the two new ones. Thus the exotic species seem to replace more of the native species in the long run because of management practices and local preferences. The cabrucas presented also a high capacity for the regeneration of tree species richness after abandonment. Simple alterations in management practices could improve the recruitment of late successional species in these areas. Economic incentives may be necessary for the farmers to adopt management practices to retain native species which bring no economic returns.