冻融对色季拉山高寒森林土壤微生物群落结构的影响

高寒森林土壤是最脆弱的陆地碳库之一,随着全球气候的变暖,冻融格局受到影响,这将导致土壤微生物群落结构发生变化进而影响土壤微生态过程。以西藏色季拉山不同海拔土壤为研究对象,基于16S rRNA测序技术探究微生物群落结构及多样性对季节性冻融的响应。结果表明:门水平上,冻融现象并未改变土壤细菌和真菌群落的优势菌群,变形菌门(Proteobacteria)、放线菌门(Actinobacteriota)和酸杆菌门(Acidobacteria)为细菌群落的优势菌门,担子菌门(Basidiomycota)和子囊菌门(Ascomycota)为真菌群落的优势菌门;属水平上,冻融前后微生物群落结构和组成差异较大,且细菌群落受冻融影响更剧烈,真菌群落受海拔影响更剧烈;OTU水平上,冻融使各海拔细菌群落和海拔3500 m、4300 m处真菌群落的α-多样性有较大提升,主要受黏粒和粉粒含量的影响;冻融使微生物群落组成在不同海拔间差异增大,且冻融前后的关键驱动因子不同,冻融前主要受碳氮比、速效钾、碳酸盐、土壤含水率、黏粒和粉粒含量的影响,冻融后主要受pH和有效磷的影响;相比于细菌,真菌群落结构的影响因素在海拔间的差异更大。本研究为深入理解气候暖化背景下不同海拔高寒森林土壤微生物对冻融的响应提供重要依据。

Effects of freeze-thaw on soil microbial community structure in alpine forest of Mount Segrila

Alpine forest soil is one of the most fragile terrestrial carbon pools, faces heightened vulnerability as a result of global climate warming. The intricate freeze-thaw pattern, influenced by rising temperatures, is expected to undergo modifications, consequently impacting the structure of soil microbial communities and disrupting essential soil microecological processes. To gain insights into these dynamics, this study employed 16S rRNA sequencing technology to examine the response of microbial community structure and diversity to seasonal freeze-thaw in soils at different elevations of Mount Segrila in Tibet. The findings of this study reveal that the occurrence of freeze-thaw events did not induce significant shifts in the dominant bacterial and fungal groups at the phylum level. The prevailing bacterial groups identified were Proteobacteria, Actinobacteriota, and Acidobacteria, while the dominant fungal phyla were Basidiomycota and Ascomycota. At the genus level, notable variations were observed in the microbial community structure and composition before and after freeze-thaw events. Interestingly, bacterial communities exhibited greater susceptibility to freeze-thaw, while the fungal community displayed a heightened sensitivity to changes in elevation. Furthermore, this study explored the impact of freeze-thaw events on the alpha-diversity of microbial communities at different elevations. At the operational taxonomic units level, the results indicated a significant increase in bacterial community diversity across all elevations, as well as in the fungal community at elevations of 3500 m and 4300 m. The increase in diversity was primarily influenced by the clay and silt content within the soil matrix. Additionally, the study revealed that the differences in microbial community composition became more pronounced at varying elevations, with distinct driving factors identified before and after freeze-thaw events. Prior to freeze-thaw, factors such as C/N, available potassium, CO₃^2-, soil moisture, clay and silt content played significant roles in shaping the microbial community. Conversely, after freeze-thaw events, pH and available phosphorus emerged as the main influencing factors. Compared with bacteria, the influence factors of fungal community structure were more different between elevations. The comprehensive understanding gained from this study on the response of soil microorganisms to freeze-thaw events in alpine forests at different elevations holds profound implications. As the threat of climate change looms, comprehending the intricate relationships between environmental factors and microbial communities becomes increasingly imperative to predict and mitigate the potential consequences on ecosystem stability. This study provides an important basis for further understanding the response of soil microorganisms to freeze-thaw in alpine forests at different elevations under the background of climate warming.