Improving tree selection for felling and retention in natural forest in Amazonia through spatial control and targeted seed tree retention : a case study of a forest management project in Amazonas State, Brazil
An important aspect of forest management is the promotion of natural regeneration of commercial timber species. To explore the potential of tree selection processes that consider species requirements for regeneration, I developed an approach to select trees to be retained as seed trees and to be felled alternative to a conventional system. The commercial species were characterised for attributes relevant to tree selection. The alternative approach developed to retain seed trees consisted in to retain 10-30% regarding to seven ecological attributes. The conventional consisted of 10% retention regardless species characteristics. I compared the % of retention per species of conventional and alternative approaches in blocks of 100 ha. The two methods selected a similar proportion of seed trees (17%), yet the alternative approach retained relatively more seed trees for species with more limitations for regeneration. Shade bearing species were responsible for 87% of commercial species group basal area, suggesting that gap reduction and damage control on advanced regeneration as a silvicultural strategy. The alternative approach to select trees for felling included a harvest map designed to facilitate the protection of seed trees and potential crop trees. A field rule was introduced to control the spatial variation in harvest intensity. I compared impacts of treatments on residual stand conditions and timber production. The area in logging gaps was reduced from 28% to 15% with the introduction of the alternative approach, the impacts on ground level, from 52% to 32% and on damage on potential crop trees from 13% to 6%. Timber production from the conventional approach was on average 45.5 m3 ha-1 and from the alternative was 24.4 m3 ha-1. However, the proportion of volume of high valued species increased from 57.5% to 72.7% with the alternative approach. This study suggests that a compromise between timber production and impact reduction is required to achieve sustainable forest management.