Efeito do manejo florestal sustentável sobre a deposição de serapilheira em uma floresta de terra firme na Amazônia brasileira

Abstract

Tropical forests have been drastically altered by anthropic action, with deforestation, forest fires and logging as the main threats to this ecosystem. In order to reduce the impacts caused by logging, sustainable forest management emerges as a rational logging model, reducing impacts on the environment, contributing to the conservation of natural resources and promoting the sustainable use of timber resources. However, sustainable forest management still causes changes in forest structure and important ecosystem processes such as nutrient cycling. Considering the importance of nutrient cycling in maintaining soil fertility in tropical forests through litter deposition and decomposition, the aim of this study was to evaluate the effects of sustainable forest management on litter deposition in a dryland forest in the Amazon. Brazilian For this purpose, litter production was evaluated in 11 areas with different years of exploitation and in an untapped control area. To collect the litter produced by the forest, 240 collectors were installed during the dry season and 240 collectors during the rainy season, being 20 collectors per sampled area. The material deposited in the collectors was removed monthly during four months of sampling in each season, and the litter deposition estimated from the dry weight of the collected material. To evaluate the difference between the areas in the amount of litter stored was collected the accumulated litter on the soil. The relationship between litter deposition and canopy cover, shear intensity and monthly precipitation was also evaluated. The average deposition rate of litter found was 6,060 Mg.ha-1, with the leaves fraction presenting the largest contribution in the deposition (> 80%). For the two sampled seasons, the areas subjected to forest exploitation showed no significant difference in litter deposition between the exploited areas and the unexplored area. On the other hand, there was a difference in deposition between dry season (higher deposition) and rainy season (lower deposition), with strong negative correlation between deposition and precipitation. The average litter stock for the study areas was 18.908 Mg.ha-1, with no significant difference in stock between explored and unexplored areas. There was no correlation between litter deposition and canopy cover, cutting intensity and litter stock. The absence of difference in litter deposition and stockpiling between logged and unexplored areas suggests that logging at intensities ranging from 12 to 16.8 m³ / ha does not significantly reduce forest productivity. The maintenance of forest productivity after logging can be explained by the rapid growth of pioneer species and remnant tree individuals, stimulated by increased light input after logging. Thus, sustainable forest management, with low exploitation intensity and using techniques to reduce environmental impacts, has no measurable effects on litter deposition and contributes to the compatibility of the use of timber forest resources with the maintenance of ecosystem processes. in the forest environment.