Mudanças na regeneração natural em uma floresta manejada na Amazônia Central

Abstract

The use of natural resources through sustainable forest management in tropical forests should incorporate a vision that focuses not only on wood production but also on the potential for biodiversity conservation in these environments. Monitoring growth and natural regeneration in managed tropical forests is a valuable tool for planning forest utilization. There is a very large gap in remnant stands, and little is known about the impact of managed logging on remnant forests in diameters below 30 or 40 cm. The objective of this study was to evaluate the medium-term impacts of forest management on remnant vegetation classified as natural regeneration in a central Amazon forest, to verify whether conducting commercial management interferes with the composition and diversity of natural regeneration. The data are from the forest monitoring carried out by Embrapa in 03 Annual Production Unit of the company Mil Madeiras Precious in Itacoatiara / AM, explored from 1996 to 1998. Measurements were made before and after logging in 1996, 1997, 1998, 2001 and 2014, in 820 subplots of 100 m² belonging to 41 permanent 1-hectare plots installed in UPAS B, C and D, 5cm trees were recorded. ≤ DBH <15 cm. After updating the scientific nomenclature of the species, the richness and temporal diversity in the UPAS were analyzed, and it was verified by the Student's t test if there was a negative change in the diversity. The similarity was analyzed using the Jaccard and Morisita-Horn indices. Subsequently, cluster analysis was performed using the UPGMA method. In the 03 UPAS, 8090 individuals distributed in 48 families and 244 species were registered, of which 91 occur in the 03 UPAs, 32 occur in two UPAs and 121 occur in at least one of the units analyzed. The diversity analyzed by Shannon index is considered high, and there was variation of values. Only in UPA C, there was no statistical difference in this variation. In Upas B and D, diversity increased over the years following exploitation, but no difference was found in diversity in mediations in the years immediately following exploitation (1997, 1998 and 2001). Analyzing temporal similarity by Jaccard and Morisita indices, it was found that after the intervention, as in similar studies in Tapajós Forest, there is a change in the composition of vegetation in natural regeneration, the similarity, although high, decreased over the years. Two groups were formed by the UPGMA analysis method, the vegetation recorded in 2014 in all UPAS differs from the initial state recorded. Factors such as mortality and species inflow, sample size and distribution of floristic diversity may influence this result. Thus, the analyzed natural regenerating vegetation undergoes changes due to logging over time, it is necessary for forest management for logging purposes to increase knowledge about the remaining forest to assess whether logging will cause a very drastic change in the forest and whether imminent need for forestry interventions in naturally regenerating vegetation. Consideration should be given to the tendency that for a second cycle, the forest will present itself as a second or third environment and it is inevitable to review the list of species to be managed.