Effect of tree harvesting on heterotrophic soil respiration in boreal drained peatland forests

In drained peatland forests, a key environmental challenge is controlling CO 2 emissions deriving from decomposition of peat as heterotrophic soil respiration (R HS ). However, the effects of harvesting – a central management operation – on R HS remain poorly understood. We compiled R HS data from eight drained peatland forests in Finland to quantify how harvest method (clearcut, selective harvest, strip or gap harvest), harvest intensity (removed basal area), soil water-table level (WTL), soil temperature and site type jointly regulate momentary and annual R HS . Both nutrient-rich (herb-rich, blueberry) and nutrient-poor (lingonberry, dwarf-shrub) site types were included. R HS was measured using manual chambers from root exclusion plots 1–8 years after harvests, in several cases also before harvests. Nonlinear statistical model was used to quantify the controls of momentary R HS and to reconstruct annual R HS . Momentary R HS was more sensitive to harvest intensity, soil temperature, and WTL in nutrient-rich than poor sites, which was reflected in annual fluxes. Harvested treatments generally had higher WTL than controls, which resulted in some post-harvest reductions in annual R HS of nutrient-rich sites: selectively harvested herb-rich sites had 14% lower annual R HS than controls, and clearcut blueberry sites had 26% lower values. In contrast, poor sites showed no reduction or even increased annual R HS after harvest; in clearcut lingonberry sites, annual R HS was 17% higher than in controls. No changes in annual R HS were detected after gap or strip harvests. Overall, the results indicate a non-uniform R HS response to harvest, with site type acting as a key modifier.