Snow removal alters soil microbial biomass and enzyme activity in a Tibetan alpine forest

Abstract

Projected future decreases in snow cover associated with global warming in alpine ecosystems could affect soil biochemical cycling. To address the objectives how an altered snow removal could affect soil microbial biomass and enzyme activity related to soil carbon and nitrogen cycling and pools, plastic film coverage and returning of melt snow water were applied to simulate the absence of snow cover in a Tibetan alpine forest of western China. Soil temperature and moisture, nutrient availability, microbial biomass and enzyme activity were measured at different periods (before snow cover, early snow cover, deep snow cover, snow cover melting and early growing season) over the entire 2009/2010 winter. Snow removal increased the daily variation of soil temperature, frequency of freeze–thaw cycle, soil frost depth, and advanced the dates of soil freezing and melting, and the peak release of inorganic N. Snow removal significantly decreased soil gravimetric water, ammonium and inorganic N, and activity of soil invertase and urease, but increased soil nitrate, dissolve organic C (DOC) and N (DON), and soil microbial biomass C (MBC) and N (MBN). Our results suggest that a decreased snow cover associated with global warming may advance the timing of soil freezing and thawing as well as the peak of releases of nutrients, leading to an enhanced nutrient leaching before plant become active. These results demonstrate that an absence of snow cover under global warming scenarios will alter soil microbial activities and hence element biogeochemical cycling in alpine forest ecosystems.