T ECHNICAL S ESSION : Agroforestry-based livelihood strategies for smallholders in the Amazon Succession management through fallow enrichment on the Brazilian Amazon: the effect of canopy opening and plant dominance on the establishment and growth of native plant species Jakovac, A.C.C. 1 , Mesquita, R.C.G. 3 , Bentos, T.V. 2 1,2,3
Instituto Nacional de Pesquisas da Amaz么nia. Manaus, Brazil. 1catacj@gmail.com
Traditional Amazonian agroforestry systems comprise many forms of management of secondary succession, including the enrichment of fallows through planting of selected forest species. In a participatory project with smallholders of the Brazilian Amazon, we studied the growth responses of eight Amazonian forest species planted on fallows with different ages (ranging from 2 to 25 years), land-use history and light incidence. The selected species were three fruit species (bacaba Oenocarpus bacaba, cacau Theobroma cacao, castanha Bertholletia excelsa), four oleaginous species (cumaru Dipteryx odorata, andiroba Carapa guianensis, pau-rosa Aniba roseodora, copaiba Copaifera multijuga) and one wood specie (mogno Swietenia macrophyla ). In 11 small properties fallows, we established two 20 x 20 m plots (with 40 seedlings planted in each), being one control and one treatment plot, where around 40% of the basal area was removed in order to increase light incidence. Five of these experimental fallows were heavily used in the past (resulting in a Vismia spp. dominated fallow), and the other six had a less-intensive use and were dominated by Cecropia spp. One year after planting, the mortality rate of the seedlings was 8% and was not different between treatment plots neither between fallow types. All species have shown a higher height relative growth rate (HRGR) on the treatment plots, but this difference was significant only for species with faster growth: Carapa guianensis, Dipteryx odorata, Swietenia macrophylla and Aniba roseodora. Considering only the control plots, we observed a significant interaction between age and type of fallow on the HRGR. In Cecropiadominated fallows the HRGR of most seedlings has diminished as fallows got older, while on Vismia -dominated fallows no effect was observed. These results show that the success of fallow enrichment planting can be highly influenced by the management of the canopy and by the type of the fallow. Key-words: second-growth management, relative growth rate, agroforestry, smallholders, Amazon.