Effects of changes in the soil environment associated with heavy precipitation on soil greenhouse gas fluxes in a Siberian larch forest near Yakutsk(Environment)

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A future increase in heavy precipitation events is predicted in boreal regions. An irrigation experiment was conducted in Taiga forest in eastern Siberia to evaluate the effect of heavy precipitation on greenhouse gas ([GHG] CO_2, CH_4, and N_2O) fluxes in the soil. The GHG fluxes on the soil surface were measured using a closed-chamber method and GHG production rates in the mineral soil were estimated using the concentration-gradient method based on Fick's law. Irrigation water (20mm day^<-1>) was applied continuously for 6 days (120mm in total; the same amount as summer precipitation in this region). Greenhouse gas production rates in the organic layer (O-layer) were defined as the difference between the GHG fluxes and the GHG production rates in the mineral soil. Carbon dioxide flux was measured both in root-intact (R_s) and trenched plots (R_<mw>). The root respiration rate (R_r) was calculated as the difference between R_s and R_<mw>. Considering the root distribution in the soil, we regarded the CO_2 production rate in the mineral soil to be the microbial respiration rate in the mineral soil (R_<mm>) and microbial respiration rate in the O-layer (R_<mo>) as the difference between R_<mw> and R_<mm>. Irrigation increased both soil temperature and moisture in the irrigated plot. The R_s, CH_4 flux and N_2O flux during the irrigation period were higher in the irrigated plot than that in the non-irrigated plot (P<0.05; mean R_s±standard deviation [SD] (mg C m^<-2> h^<-1>) were 171±20 and 109±11, mean CH_4 flux±SD (μg C m^<-2> h^<-1>) were -5.4±4.1 and -14.0±6.5, and mean N_2O flux±SD (μg N m^<-2> h^<-1>) were 1.6±1.6 and 0.2±1.1, respectively). Soil moisture had a positive effect on R_<mm> and CH_4 production rate in the O-layer, a negative effect on R_r, and did not affect R_<mo>, the CH_4 production rate in the mineral soil or the N_2O production rates in both the O-layer and the mineral soil. Soil temperature had a positive effect on R_r and R_<mo>. The increment of global warming potential of the soil mainly resulted from an increase in microbial respiration rates. Future changes in precipitation patterns in this region would accelerate decomposition of the soil organic matter.

Effects of changes in the soil environment associated with heavy precipitation on soil greenhouse gas fluxes in a Siberian larch forest near Yakutsk(Environment)

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