Long-term warming rather than grazing significantly changed total and active soil procaryotic community structures

Abstract

There is a paucity of knowledge in understanding the effects of warming and grazing on soil microbes and their active counterparts, especially on the Tibetan Plateau which is extremely sensitive to global warming and human activities. A six-year field experiment was conducted to investigate the effects of asymmetric warming and moderate grazing on total and active soil microbes in a Tibetan Kobresia alpine meadow. Soil bacterial abundance and 16S rDNA transcriptional activity were determined using real-time PCR. Total and active soil procaryotic community structures were analyzed through MiSeq sequencing based on 16S rDNA and rRNA, respectively. The results showed that the soil procaryotic community was more sensitive to the warming than the grazing. The warming significantly decreased soil microbial respiration rates, 16S rDNA transcription activity, and dispersion of total procaryotic community structures, but significantly increased the α diversity of active procaryotes. Warming also significantly increased the relative abundance of oligotrophic microbes, whereas decreasing the copiotrophic lineage proportions. The functional profiles predicted from the total procaryotic community structures remained unaffected by warming. However, the rRNA-based predictions suggested that DNA replication, gene expression, signal transduction, and protein degradation were significantly suppressed under the warming. The grazing only significantly decreased the 16S rDNA transcription and total procaryotic richness. Overall, these findings suggest that warming can shift soil procaryotic community to a more oligotrophic and less active status, highlighting the importance of investigating active microbes to improve our understanding of ecosystem feedbacks to climate change and human activities.