Recovering ecosystem functions through the management of regenerating community in agroforestry and plantations with Khaya spp. in the Atlantic Forest, Brazil

Abstract

Our aims were to describe the role of the selective management of regenerating community (RC) on the recovery of ecosystem functions in production areas of African mahoganies under mixed stands and agroforestry systems, established on abandoned farmland. A randomized block experiment was set up with the following treatments: (T1) mixed-plantation of African mahogany under conventional system (including herbicide application); (T2) mixed-plantation of African mahogany with selective conduction of RC; (T3) agroforestry system with African mahogany; (T4) agroforestry system with African mahogany with selective conduction of RC. The parameters of horizontal structure, diversity and ecological attributes of species of the regenerating community were studied. In addition, the production of aboveground biomass and nutrient stocks, soil fertility, and soil microbial activity were assessed. In T1, herbicide application (glyphosate) affected the floristic composition of the regenerating community by reducing the dominance of monocots and Pteridium arachnoideum, allowing the regeneration of other taxonomic groups of herbaceous species. In response, there was a reduction in the litter biomass stock comparing to the other treatments. The treatments with selective management of the RC (T2 and T4) produced more biomass and accumulated higher amounts of C and nutrients than the conventional treatments (T1 and T3). These treatments also allowed other shrub and tree species to overcome the ecological filter imposed by grasses and colonize the experimental area. Baccharis dracunculifolia, Vismia guianensis, Cecropia pachystachya and Inga sp. were the most important regenerating species that contributed most to the stocks of all nutrients in living aboveground biomass. Pruning and selective management in T4 increased the soil effective cation exchange, while in the T1 treatment there was a lower activity of the β-glucosidase enzyme. The selective management of RC in agroforestry systems through the manipulation of competitive relationships allowed the colonization of native tree and shrubby species that provide several additional ecosystem services, including pollination, fauna attraction, food production, pest control and environmental regulation for the agroecosystem.