Timber yield of commercial tree species in the eastern Brazilian Amazon based on 33 years of inventory data

Selective logging in neotropical forests has directly affected the dynamics of tree species, compromising species conservation and timber yield. Sustainable use of logged forests requires new tree recruitment and diameter growth in remaining trees to compensate for trees removed between cutting cycles. This long-term study investigated timber yields in four species groups with differing values (lower, intermediate, high, and mixed) in logged and unlogged forests in the plateau region of the Tapajos River in the eastern Brazilian Amazon. Analysis was based on two size classes: medium and large commercial-sized trees. In both forest types (logged and unlogged), we found relevant tree recruitment and changes in size classes for all value groups. Most of the recruited trees observed during the 33 years of monitoring remained in the medium size class, but they also occurred in the large size class in logged forests. Over the same period, a significant loss of timber yield was seen, resulting from high mortality among the remaining trees in both size classes due to natural processes and the aftereffects of logging. Timber yield was also seen to be influenced by species richness within the group of commercial species, and recruitment and tree diameter growth capacity to counterbalance losses from mortality of the remaining trees after logging had become restricted. Forest timber yield was mainly regulated by light-demanding species, and shade-tolerant species contributed little to timber yield during the first cut. Continuous monitoring of the remaining trees and measures to reduce tree mortality during cutting cycles can encourage growth and reduce losses in stocked trees. Additionally, the national rules for forest management in the Brazilian Amazon need to be improved to achieve long-term management sustainability.