Effects of management treatments on the carbon cycle of a cool-temperate broad-leaved deciduous forest and its potential as a bioenergy source

The ecological effects of management treatments on the carbon cycles of secondary forests remain poorly understood. Here, we compared carbon cycles at three sites, a managed understory harvesting site (UH), a managed understory harvesting and litter raking site (LR), and an unmanaged site that served as a control (U_m). We considered the harvests of understory and litter biomass as bioenergy sources, and made compartment models for the carbon cycle in units of carbon. Management increased the net primary production from 6.7 tC ha⁻¹ year⁻¹ for the U_m site to 7.2 tC ha⁻¹ year⁻¹ for the UH site and 7.8 tC ha⁻¹ year⁻¹ for the LR site. Concurrently, management reduced the decomposition rate from 5.1 tC ha⁻¹ year⁻¹ for the U_m site to 3.7 tC ha⁻¹ year⁻¹ for the UH site and 3.8 tC ha⁻¹ year⁻¹ for the LR site. Management also reduced fossil fuel use by 0.7 tC ha⁻¹ year⁻¹ for the UH site and 3.5 tC ha⁻¹ year⁻¹ for the LR site. These values suggest that harvesting had positive effects on net ecosystem production (NEP). In contrast, bioenergy use released 1.3 tC ha⁻¹ year⁻¹ into the atmosphere (in the form of carbon dioxide) for the UH site and 6.9 tC ha⁻¹ year⁻¹ for the LR site. These values suggest that harvesting had negative effects on NEP. We conclude that understory harvesting without litter raking (UH) maximized NEP at 2.9 tC ha⁻¹ year⁻¹. Our findings underscore the importance of a balanced ecological approach to forest management.