Silvicultural strategies for the management and conservation of secondary tropical forests: subsidies for the recovery of altered areas in Amazonas

Abstract

Secondary growth forests are forest formations established after the degradation of mature forest communities. In the Legal Amazon, about 23% of land use and land cover classes in deforested areas are secondary vegetation at different stages of regeneration. Although they occupy extensive areas of the Amazon rainforest and are considered potential phytophysiognomies for the conservation and sustainable use of forest resources, the management and conservation of these areas has been little explored and not included in the current public policies in Brazil. The lack of knowledge about the most appropriate management of native forest species constitutes one of the main barriers to the adoption of silvicultural experiences in the Amazon. Silvicultural Systems based on Enrichment Plantations and Conducting Natural Regeneration of species of economic interest are important management strategies in secondary forests. In parallel, the application of silvicultural treatments that promote favorable conditions for the growth of species in secondary forests is crucial to enable forest production in these sites. Thus, looking for silvicultural strategies for forest conservation and production in secondary forest areas in the Amazon, our objective is to investigate whether silvicultural treatments influence the growth and quality of wood of economically important forest species introduced via enrichment plantations and present in natural regeneration secondary forests. The proposal is divided into two experiments: 1) enrichment plantations - installed in March 2017 at the Experimental Farm of the Federal University of Amazonas (FAEXP-UFAM) in 17 hectares of secondary forest. 1,800 seedlings of six forest species of recognized economic value were planted. The species are growing under different light conditions promoted by the application in October 2016 of thinning at different intensities to reduce the basal area of natural vegetation (0%, 20%, 40%, 60%, 80% and 100%). Survival and growth have been monitored for three years and are expected to continue for two years more, including destructive analyzes, after four years, of biomass partition and wood characteristics; 2) conducting natural regeneration - it will be installed in another area of secondary forest also at FAEXP-UFAM, with about 35 hectares. Natural regeneration is dominated by individuals from Goupia glabra Aubl., a forest species of great economic interest. Part of the individuals of this species will undergo release thinning and part will not. The release will be made through the direct cut of individuals of natural regeneration present throughout the projection area of the canopy of individuals of G. glabra. The past growth history of individuals of G. glabra will be estimated from dendrochronological analyzes, using the growth rings as bioindicators of the inferences and temporal and spatial processes to which the trees have been exposed throughout their lives. By adding a long-term perspective, the growth rings complement the temporal limitations of forest inventories, providing new opportunities and perspectives on silvicultural practices. The responses of growth and quality of the wood will be measured during two years after the application of the release treatment. The results achieved will be fundamental to elucidate mechanisms of response of tropical tree species to the availability of light, in addition to recommending silvicultural species and treatments more suitable for the implementation of silvicultural systems in the sustainable management of secondary tropical forests. The information generated should subsidize public policies through silvicultural protocols for recovering alterations in the Amazon region, secondary forests in particular, in the expectation of reintroducing them to ecological and productive processes. (AU)