Influence of forest disturbance on CO2, CH4 and N2O fluxes from larch forest soil in the permafrost taiga region of eastern Siberia

To evaluate the effect of increasing forest disturbances on greenhouse gas budgets in a taiga forest in eastern Siberia, CO2, CH4 and N2O fluxes from the soils were measured during the growing season in intact, burnt and clear-felled larch forests (4-5 years after the disturbance). Soil temperature and moisture were higher at the two disturbed sites than at the forest site. A 64-72% decrease in the Q(10) value of soil CO2 flux from the disturbed sites compared with the forest site (5.92) suggested a reduction in root respiration and a dominance of organic matter decomposition at the disturbed sites. However, the cumulative CO2 emissions (May-August) were not significantly different among the sites (2.81-2.90 Mg C ha(-1) per 3 months). This might be because decreased larch root respiration was compensated for by increased organic matter decomposition resulting from an increase in the temperature and root respiration of invading vegetation at the disturbed sites. The CH4 uptake (kg C ha(-1) per 4 months [May-September]) at the burnt site was significantly higher (-0.15) than the uptake at the forest (-0.045) and clear-felled sites (0.0027). Although there were no significant differences among the sites, N2O emission (kg N ha(-1) per 4 months) was slightly lower at the burnt site (0.013) and higher at the clear-felled site (0.068) than at the forest site (0.038). This different influence of burning and tree felling on CH4 and N2O fluxes might result from changes in the physical and chemical properties of the soil with respect to forest fire.