Forest biomass recovery twenty-four years after conventional and reduced-impact logging in Eastern Amazon

Abstract

Given the mounting global concerns about mitigating climate change and curbing greenhouse gas emissions, it becomes increasingly crucial to comprehend the effects of logging techniques on biomass dynamics in tropical forests. This understanding is essential for fostering greater carbon retention and sequestration, aligning with the objectives of initiatives like REDD+ (Reducing Emissions from Deforestation and forest Degradation plus sustainable forest management and the conservation and enhancement of forest carbon stocks) and other conservation goals. In this context, this study investigated the effects of two wood harvesting methods, reduced-impact logging (RIL) and conventional logging (CL), on above-ground biomass (AGB) recovery rates 24 years after harvesting. The experimental design was based on three treatments: RIL, CL, and an unlogged control plot, situated in the municipality of Paragominas, State of Pará, in the Eastern Amazon region of Brazil. All trees with diameter at breast height (DBH) ≥25 cm, as well as all trees of commercial species with a DBH ≥10 cm, were monitored in a 24.5 ha plot within each treatment. Additionally, a 5.25 ha subplot within each treatment was designated for the monitoring of all trees with DBH ≥10 cm. The biomass data were generated from 11 measurements carried out from 1993 to 2017 (24-year period). Pre-logging AGB stocks were estimated at 181 Mg ha^-1 in the RIL plot, 187 Mg ha^-1 in the CL plot, and 174 Mg ha^-1 in the control plot. One year after logging, AGB decreased by 19 % under RIL and 30 % under CL, while the control forest remained unchanged. By 13 years after harvest, the RIL plot achieved 102 % AGB recovery, while the CL plot recovered 86 % of the original pre-harvest stock. Over the 24-year post-logging period, AGB stocks recovered to 128 % in the RIL plot compared to only 90 % in the CL plot, while the control forest maintained 93 % of its original stock. The average annual ABG increment rates were 3.56 Mg ha^-1 year^-1 after RIL and 2.33 Mg ha^-1 year^-1 after CL. Our findings demonstrate that implementing RIL is a more effective strategy for maintaining post-logging AGB stocks and accelerating AGB recovery rates, serving as a significant mitigation measure against climate change.