Logging intensity affects growth and lifespan trajectories for pioneer species in Central Amazonia

Management of tropical forest in the form of timber harvesting is a viable alternative to deforestation in Ama-zonia. Nevertheless, a significant challenge for timber management in the Amazon is the maintenance or establishment of commercial timber species, after logging operations are completed. This is because fast-growing non-commercial pioneer species outcompete the slower growing timber species. To determine the challenges posed to commercial species in the context of the cutting cycle in the Brazilian Amazon of 25-35 years, growth and cumulative survival rates of six abundant pioneer species were assessed. This was accomplished with 30 years of growth data from permanent plots established in the Central Amazon in the 1980 ' s and logged in 1987 and 1988 at various intensities. In terms of relative growth rates, pioneer species dominated the post-logging site by 2 to 5 times, when compared to commercial species, throughout the evaluation period. This was regardless of the various logging intensities of 5, 8 or 16 trees harvested per hectare. Two commercial pioneer species, Jacaranda copaia and Simarouba amara, presented rapid growth rates similar to non-commercial pioneer species. Three pioneer species survived beyond 30 years to continue into a potential 2nd cutting cycle. Therefore, to maintain or establish commercial timber species while there is a continued and expanding site occupancy of non-commercial pioneer species after logging presents numerous challenges for sustainable forest management.

Automated summary

Management of tropical forests through timber harvesting is a viable alternative to deforestation in the Amazon. However, the maintenance or establishment of commercial timber species is a significant challenge due to competition from fast-growing non-commercial pioneer species. A study in the Brazilian Amazon evaluated the growth and survival rates of six pioneer species over 30 years, and found that the pioneer species outcompeted commercial species throughout the evaluation period, regardless of logging intensity. Two commercial pioneer species showed rapid growth rates similar to non-commercial pioneer species, and three pioneer species were able to survive beyond 30 years. This poses challenges for sustainable forest management in maintaining or establishing commercial timber species while dealing with expanding non-commercial pioneer species after logging.