Effects of harvest treatments on forest carbon pools in eastern North America: A meta-analysis

Understanding carbon dynamics in managed forest ecosystems is increasingly crucial for formulating informed recommendations in the context of climate change. Silviculture significantly impacts forest carbon pools, though these effects can vary depending on the type of treatment applied. In recent decades, partial cuttings have been proposed as an alternative to more intensive treatments like clearcutting to mitigate negative impacts on forest function and enhance carbon sequestration. In this study, we conducted a meta-analysis comparing the effects of clearcutting and partial cuttings across North America on six forest carbon pools: live trees, snags, understory vegetation, coarse woody debris, forest floor, and soil mineral horizons. The analysis was based on a database of 558 carbon observations from temperate and boreal forests in eastern North America. Our findings indicate a -30% difference in total carbon post-harvesting, predominantly influenced by changes in the overstory carbon pool. Only the live tree carbon pool was significantly affected by cutting intensity, with clearcutting resulting in lower total carbon values (-78% relative to the reference) compared to partial cuttings (-45%). However, after 30-40 years, live tree carbon levels were similar between clearcutting and partial cuttings. The primary factor influencing differences in deadwood carbon pools was the time since treatment, while soil carbon pools showed minimal variation with no significant differences compared to unmanaged forests. This meta-analysis suggests that using partial cuttings instead of clearcutting to mitigate the effects of forest management on carbon pools may be more complex than previously thought and will depend on site conditions and allowing sufficient time for the forest to recover. Further studies are needed to identify suitable forest stands for partial cuttings and evaluate tree selection strategies that optimize forest productivity and carbon sequestration.