Fine Root Decomposition Dynamics during Freeze-Thaw Season in the Subalpine/Alpine Forests Characteristics of ammonia-oxidizing bacteria and ammonia-oxidizing archaea abundance in soil organic layer under the subalpine/alpine forest Activities of soil oxidordeuctase and their response to seasonal freeze-thaw in the subalpine/alpine forests of western Sichuan Soil bacterial diversity in the subalpine/alpine forests of western Sichuan at the early stage of freeze-thaw season Dynamics of soil nutrients and their response to seasonal freeze-thaw in the subalpine-alpine forests of western Sichuan