Bacterial communities and enzyme activities during litter decomposition of Elymus nutans leaf on the Qinghai-Tibet Plateau

The dominant plant litter plays a crucial role in carbon (C) and nutrients cycling as well as ecosystem functions maintenance on the Qinghai-Tibet Plateau (QTP). The impact of litter decomposition of dominant plants on edaphic parameters and grassland productivity has been extensively studied, while its decomposition processes and relevant mechanisms in this area remain poorly understood. We conducted a three-year litter decomposition experiment in the Gansu Gannan Grassland Ecosystem National Observation and Research Station, an alpine meadow ecosystem on the QTP, to investigate changes in litter enzyme activities and bacterial and fungal communities, and clarify how these critical factors regulated the decomposition of dominant plant Elymus nutans (E. nutans) litter. The results showed that cellulose and hemicellulose, which accounted for 95% of the initial lignocellulose content, were the main components in E. nutans litter decomposition. The litter enzyme activities of β-1, 4-glucosidase (BG), β-1, 4-xylosidase (BX), and β-D-cellobiosidase (CBH) decreased with decomposition while acid phosphatase, leucine aminopeptidase, and phenol oxidase increased with decomposition. We found that both litter bacterial and fungal communities changed significantly with decomposition. Furthermore, bacterial communities shifted from copiotrophic-dominated to oligotrophic-dominated in the late stage of litter decomposition. Partial least squares path model revealed that the decomposition of E. nutans litter was mainly driven by bacterial communities and their secreted enzymes. Bacteroidota and Proteobacteria were important producers of enzymes BG, BX, and CBH, and their relative abundances were tightly positively related to the content of cellulose and hemicellulose, indicating that Bacteroidota and Proteobacteria are the main bacterial taxa of the decomposition of E. nutans litter. In conclusion, this study demonstrates that bacterial communities are the main driving forces behind the decomposition of E. nutans litter, highlighting the vital roles of bacterial communities in affecting the ecosystem functions of the QTP by regulating dominant plant litter decomposition.