Short-term winter snow reduction stimulates soil nutrient leaching without changing the microbial biomass in an alpine fir forest

Abstract

Winter snowpack maintains a relatively warm environment for soil microorganisms and modulates soil biogeochemical cycles in cold ecosystems; however, snowpack reduction induced by climate warming may change soil dissolved nutrient leaching and microbial biomass. Here, we performed a snow depth manipulation experiment in an alpine forest on the eastern Tibetan Plateau. We assessed the following effects of snowpack reduction and removal during the snow formation, coverage and melt periods: the concentrations of dissolved organic carbon, nitrogen, ammonium and nitrate; microbial biomass carbon and nitrogen; and the microbial respiration rate. We found that dissolved organic carbon and nitrogen concentrations decreased after snowpack reduction but significantly increased after snowpack removal and that the soil nitrate concentration significantly increased after snowpack reduction. Microbial biomass carbon and nitrogen were significantly higher during the snow formation period than during the snow coverage and melt periods, although the microbial respiration rate was higher during the snow melt period than during the snow formation and coverage periods. However, the snowpack reduction did not significantly affect the soil microbial biomass carbon and nitrogen concentrations or invertase and urease activities. The effects of snowpack reduction on the soil nitrate concentration and microbial respiration rate were stronger in the organic soil than in the mineral soil. These results suggest that short-term snowpack reduction over the first winter of manipulation stimulated the leaching of soil available nutrient but did not change the microbial biomass. Overall, our study indicates that soil microbes have rapid adaptability to the negative effects of snowpack reduction. Although microbial activity and biomass are decoupled, a comprehensive interaction occurs with available nitrogen and enzyme activities at different soil horizons, which may represent a special ecological function in the underground decomposition mediated by the freeze-thaw cycle during a warmer winter.