Efeitos do manejo florestal sustentável nos atributos e estoque de carbono do solo de florestas na Amazônia Brasileira

Abstract

The impacts of human activities are leading to climate change on the planet. Recent studies have shown that some of these effects are already irreversible, requiring a sharp reduction in greenhouse gas emissions and the replacement of polluting activities with sustainable ones. Due to the carbon stored, the soil of tropical forests is an important tool for maintaining climate balance. However, the degradation of forest environments can result in a greater release of carbon, driving adverse effects on climate regulation. Sustainable forest management is emerging as a way to adjust forest resource exploitation activities to sustainable development. In this context, selective logging of reduced-impact timber can combine the economic benefits of logging with the conservation of tropical forests, and is of particular interest to the Amazon region. The objective of this study was to estimate the effects of selective logging of reduced-impact timber on the attributes and carbon stocks in the soil of forests in the Brazilian Amazon. For this purpose, five areas with different ages since logging (two, three, twelve, seventeen and twenty-seven years) and one unlogged area were sampled for organic carbon concentrations, carbon stock and soil density, in addition to 20 other attributes. In total, 300 samples were collected at 150 sampling points with two depth layers (0 to 15 cm, and 15 to 30 cm). Undisturbed samples were obtained from volumetric rings for soil density estimation, and disturbed samples were used for organic carbon concentration estimation, using the wet oxidation method. Soil organic carbon stock was estimated from organic carbon and soil density values. The dimensionality of soil attributes was reduced using Principal Component Analysis, and the number of interpreted components was selected using the broken stick method. The effects of time since logging on soil carbon concentrations were tested using ANOVA models and Spearman correlation tests, while the local-scale effects of distance from harvested trees on soil characteristics were tested using the Wilcoxon test. The results suggest that soil carbon stocks in sites close to and far from harvested trees are similar. Although there are differences in soil attributes between study areas, these differences do not reflect environmental gradients possibly generated by the impacts of logging activities.