Quantifying uncertainty about forest recovery 32-years after selective logging in Suriname

Abstract

The inclusion of managed tropical forests in climate change mitigation has made it important to find the sustainable sweet-spot for timber production, carbon retention, and the quick recovery of both. Here we focus on recovery of aboveground carbon and timber stocks over the first 32years after selective logging with the CELOS Harvest System in Suriname. Our data are from twelve 1-ha permanent sample plots in which growth, survival, and recruitment of trees ≥15cm diameter were monitored between 1978 and 2012. We evaluate plot-level changes in basal area, stem density, aboveground carbon, and timber stock in response to average timber harvests of 15, 23, and 46m3ha−1. We use a linear mixed-effects model in a Bayesian framework to quantify recovery time for aboveground carbon and timber stock, as well as annualized increments for both. Our statistical models accounted for the uncertainty associated with the height and biomass allometries used to estimate aboveground carbon and increased precision of annualized aboveground carbon increments by including data from forty-one plots located elsewhere on the Guiana Shield. The probabilities of aboveground carbon recovery to pre-logging levels 32years after harvests of 15, 23 and 46m3ha−1 were 45%, 40%, and 24%, respectively. Net aboveground carbon increment for logged forests across all harvest intensities was 0.64MgCha−1yr−1, more than twice the rate observed in unlogged forests (0.26MgCha−1yr−1). The probabilities of timber stock recovery at the end of the 32-year period were highest after harvest intensities of 15 and 23m3ha−1 (with 80% probability) and lowest after the harvest of 46m3ha−1 (with 70% probability). Timber stock recovery across all harvest intensities was driven primarily by residual tree growth. Application of the legal cutting limit of 25m3ha−1 will require more than 70 and 40years to recover aboveground carbon and timber stocks, respectively, with 90% probability. Based on the low recruitment rates of the twelve species harvested, the 25year cutting cycle currently implemented in Suriname is too short for long-term timber stock sustainability. We highlight the value of propagating uncertainty from individual tree measurements to statistical predictions of carbon stock recovery. Ultimately, our study reveals the trade-offs that must be made between timber and carbon services as well as the opportunity to use carbon payments to enable longer cutting rotations to capture carbon from forest regrowth.