Short-term effects of thinning, clear-cutting and stump harvesting on methane exchange in a boreal forest
Forest management practices can alter soil conditions, affecting the consumption and production processes that control soil methane (CH 4) exchange. We studied the short-term effects of thinning, clear-cutting and stump harvesting on the CH 4 exchange between soil and atmosphere at a boreal forest site in central Sweden, using an undisturbed plot as the control. Chambers in combination with a high-precision laser gas analyser were used for continuous measurements. Both the undisturbed plot and the thinned plot were net sinks of CH 4, whereas the clear-cut plot and the stump harvested plot were net CH 4 sources. The CH 4 uptake at the thinned plot was reduced in comparison to the undisturbed plot. The shift from sink to source at the clear-cut and stump harvested plots was probably due to a rise in the water table and an increase in soil moisture, leading to lower gas diffusivity and more reduced conditions, which favour CH 4 production by archea. Reduced evapotranspiration after harvesting leads to wetter soils, decreased CH 4 consumption and increased CH 4 production, and should be accounted for in the CH 4 budget of managed forests.