Effects of snow thickness on the abundance of archaeal and bacterial amoA genes and gene transcripts during dwarf bamboo litter decomposition in an alpine forest on the eastern Tibetan Plateau

Abstract

Accompanying the seasonal soil freeze-thaw cycle, microbial decomposition of litter exhibited different dynamic response to various snow thicknesses. In this study, we used real-time qPCR to investigate the abundance of bacteria, archaea, ammonia-oxidizing archaea (AOA) and bacteria (AOB), and the amoA gene transcripts, during the decomposition of dwarf bamboo (Fargesia nitida) litter under different snow patches at various snow-cover stages in an alpine forest on the eastern Tibetan Plateau in China. The effects of snow thickness were significant, with thicker snow patches resulting in higher microbial abundance and the amoA gene transcripts, while the degree of the effects were different. Compared with AOB, AOA were more abundant on the majority of sampling dates during the freeze-thaw period, and as well as their amoA gene transcripts. AOA are more persistent and abundant than AOB, and the higher AOA/AOB ratios were observed clearly in shrub litter and continued to decrease as the snow thickness increased, meanwhile gradually increased under uniform snow thickness over time. Our results suggested that the reduced seasonal snow cover and shortened freeze-thaw cycle periods caused by winter warming would significantly affect the ammonia oxidizers particularly tied to the ammonia oxidation process, and then could contribute to N cycle as related to litter in alpine forest ecosystems.