Effects of snow cover thickness on soil key physiological groups of cultivable bacteria in the organic layer of Abies faxoniana forest

Global climate change is affecting the alpine snow cover pattern. In this context, different snow cover patches with different thickness may strongly affect soil microbial community structure by affecting soil temperature and humidity, and then influence the microbial-driven soil ecological process, but it lacks necessary attention. The effects of snow thickness on the characteristics of cultivable bacteria and physiological bacteria groups in the soil organic layer of Abies faxoniana forest were analyzed by using the plate culture method and the most probable number method, which have been used widely in measuring numbers of specific microbial physiological groups. The results showed that, at the end of seasonal freezing and thawing in alpine forest, snow cover thickness significantly influenced the numbers of bacteria and its physiological groups in the organic layer, and the response of culturable bacteria and their physiological groups in different soil layers were obviously different. In general, the number of ammonifying bacteria, nitrifying bacteria and anaerobic cellulose decomposing bacteria was relatively high under the thickest snow patch than under the other patches, and the number of denitrifying bacteria decreased with the increase of snow cover thickness, while the number of aerobic cellulose decomposing bacteria was less affected by snow cover thickness. At the end of seasonal freeze-thaw, the overall quantitative change trend of bacterial physiological groups in the organic layer of alpine forest under different snow patches was ammonifying bacteria > denitrifying bacteria > nitrifying bacteria > aerobic cellulose decomposing bacteria > anaerobic cellulose decomposing bacteria. The study provides important theoretical and scientific basis for understanding the seasonal transformation of soil ecological process in the alpine forests under the background of climate change.