Manejo de florestas naturais degradadas na Amazônia: estudo de caso sobre critérios de colheita

This paper deals with an innovative experience regarding tree harvesting criteria in degraded natural forest in the Amazon. The research was carried out in 535.6 ha of forest at Fazenda Shet, in Dom Eliseu/PA state, using the database of forest census for trees with DBH ≥ 25 cm. Criteria for tree harvesting considered, as a priority, the following elements: degree of health, shape of stem (2 and 3), maximum diameter to remain in the forest (DBH = 100 cm), smaller diameter trees (25 ≥ DBH ≤ 55 cm), species with higher tree density per unit area, diameter distribution according to the Liocourt coefficient, maintenance of intensively exploited species in the past and tree population ≤ 0.15 arv.ha-1. A total of 46,012 trees belonging to 106 species were inventoried and planned for harvest 23.19% (10,671 trees) at 12 years after the previous harvest. Based on harvest planning and following the criteria, the harvest forecast in relation to the total inventoried population resulted in: 2.16% trees by the criterion of health; 15.45% for the shape of stem; 0.26% by the maximum diameter; 93.93% for the smallest diameter; 57.50% for the tree density; and 5.04% for the maintenance of the species. Harvesting was performed on 98.79% of trees with compromised health; 22.20% with stem 2 and 3; 97.39% with maximum diameter; 95.02% with smaller diameter; and 90.30% with higher tree density. Were kept 98.14% of the species Astronium lecointei, Cordia goeldiana, Copaifera sp., Hymenaea courbaril, Hymenolobium petraeum, Handrohanthus serratifolius and Manilkara elata, intensively exploited in the past, and 98.70% of 53 other species with less abundance (≤ 0.15 arv.ha-1). The exploration planning following the proposed harvesting criteria allowed the extraction of trees in cycles of 10 to 12 years, being a shorter time than the one foreseen by the legislation. The maintenance of tree species diversity and forest conservation, provided for with these technical criteria, may be alternatives to ecologically and economically viable forest management.