Seasonal effects of snow cover on soil soluble carbon and nitrogen content and microbial activity

Global warming is becoming increasingly serious, and the complicated climate change situation has led to obvious changes in global snow cover patterns. Therefore, we explored the effects of future climate warming on the physical and chemical properties of black soil in Northeast China. This study adopted the method of artificial snow depth control from November 2020 to May 2022 and divided the plots in the test area into three treatment groups: snow increase (TS), snow removal (TR), and control (C). Soil environmental factors, available carbon and nitrogen contents, microbial biomass, urease activity, and sucrase activity were determined. The seasonal dynamic change process of each index was analyzed. Long-term field experiments showed that snow removal significantly reduced soil temperature and humidity. In addition, lower soil temperature and humidity accelerated the release of soil nutrients, and significantly increased the contents of soil nitrate nitrogen and ammonium nitrogen in early winter, while the opposite was true with snow increase treatment. However, from the beginning of the deep snow period, the snow removal treatment caused a loss of soil inorganic nitrogen to a certain extent while increased contents of soluble organic carbon and nitrogen. The snow removal treatment maintained soil microbial activity at a high level for most of the winter. However, at the end of winter, owing to the rapid release of soluble organic matter under snow treatment, soil microorganisms under snow treatment absorbed a large amount of nutrients and exist in a more suitable soil environment, which significantly increases the soil microbial activity under the snow treatment. However, owing to the loss of heat insulation from snow cover, a large number of microorganisms decomposed and died at this time, which significantly reduced soil microbial activity. Before and after the test period, snow treatment significantly increased the soil microbial activity by 23.07 mg∙kg⁻¹, and snow removal treatment significantly increased the soil microbial activity by 11.92 mg∙kg⁻¹, with a difference of 93.5%. The decrease in snow cover significantly decreased the activities of soil urease and sucrase during most of the winter, and the activities of soil urease and sucrase were significantly increased by snow treatment. These results show that the activities of these two enzymes increased significantly by more than 10.5%. In summary, this study demonstrated that changes in snow cover in the future will lead to changes in the dynamic change characteristics of soil available carbon and nitrogen and microbial activity, and the influence of snow cover change on soil enzyme activity will also indirectly affect the soil nutrient cycling process and physical and chemical properties of soil. The results of this study provide a theoretical foundation and scientific basis for further research on the material cycle of terrestrial ecosystems in the black soil region of northeast China in the context of climate warming.