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 (CH4) exchange. We studied the
short-term effects of thinning, clear-cutting and stump harvesting
on the CH4 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 highprecision
laser gas analyser were used for continuous measurements.
Both the undisturbed plot and the thinned plot
were net sinks of CH4, whereas the clear-cut plot and the
stump harvested plot were net CH4 sources. The CH4 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
CH4 production by archea. Reduced evapotranspiration after
harvesting leads to wetter soils, decreased CH4 consumption
and increased CH4 production, and should be accounted for
in the CH4 budget of managed forests.