自然增温对南亚热带森林土壤微生物群落与有机碳代谢功能基因的影响

Abstract

基于海拔高度下降气温上升的关系，将模拟的生态系统（含植物和土壤）从高海拔整体移位至低海拔地区，实现自然增温的效果。通过对自然增温条件下土壤环境因子及其相关理化性质的动态监测，结合磷脂脂肪酸分析与宏基因组学方法，测定土壤微生物群落结构以及与土壤有机碳分解相关基因丰度，探究自然增温对鼎湖山南亚热带山地常绿阔叶林土壤有机碳代谢的影响及其微生物学机制。结果表明：（1）增温处理显著改变了0-10 cm土壤温度与湿度：2016-2018年间土壤温度显著上升2.48℃，湿度显著下降23.93%。（2）增温处理下，干季土壤有机碳含量与湿季土壤硝态氮含量显著降低，其他土壤理化因子无显著变化。（3）增温处理下，干季和湿季土壤微生物群落结构发生改变，且湿季变化显著。土壤湿度是影响干季和湿季土壤微生物群落结构变化的主要因子，解释了干季50.2%的变异度与湿季79.2%的变异度。（4）宏基因组结果表示：增温抑制了干季山地常绿阔叶林土壤有机碳代谢基因丰度，增强了湿季山地常绿阔叶林土壤有机碳代谢基因丰度。以上结果表明，增温通过改变土壤微生物生物量和群落结构以及有机碳代谢相关功能基因的丰度，最终影响南亚热带山地常绿阔叶林土壤有机碳代谢过程。;Global warming is one of the environmental problems that cannot be ignored in the world today, which has significant impacts on soil carbon dynamics and soil microorganisms. Soil microorganisms affect the soil nutrient cycling process and play a leading role in the net carbon balance of terrestrial ecosystems. Further exploration of microbial responses to climate warming is important for predicting the feedback and carbon budget of terrestrial ecosystems in warmer climates. In this study, soil organic carbon content and microorganisms were investigated in a natural warming experiment using a whole ecosystem transplanting approach. Plots of plants and soil in a subtropical mountain evergreen broadleaf forest at high altitude (600 m asl) were moved to low altitude (30 m asl) in Dinghu Mountain to experience natural warming treatment. Plots with similar plants and soil at the high altitude were used as the control. To explore the effect of natural warming on soil organic carbon metabolism and its microbiological mechanism, soil physical and chemical properties, soil organic carbon, and soil microbial community structure were measured for the control and warmed plots. Meta-genomic method was used for soil microbial community structure and abundance of genes involved in soil organic carbon decomposition. Results showed that:(1) warming treatment significantly changed soil temperature and moisture of the 0-10 cm soil layer. From 2016 to 2018, the soil temperature was significantly increased by 2.48℃, and the soil moisture was significantly decreased by 23.93% (relative change). (2) Warming treatment significantly reduced soil organic carbon content in the dry season and the soil nitrate nitrogen content in the wet season, while other soil physical and chemical factors had no significant changes under warming treatment. (3) Warming treatment changed the soil microbial community structure in both dry and wet seasons, and the change was significant in wet season. The results of principal component analysis showed that soil moisture was the main factor affecting the variation of soil microbial community structure in dry season and wet season, which explained the variation degree of 50.2% in dry season and 79.2% in wet season. (4) The metagenomic analysis showed that increasing temperature inhibited the abundance of soil organic carbon metabolism genes of mountain evergreen broadleaf forest in the dry season, and enhanced them in the wet season. Our results showed that although warming treatment did not significantly change soil microbial biomass in the subtropical mountain evergreen broadleaf forest, it reduced soil organic carbon by changing soil microbial community structure and abundance, and significantly affected soil organic carbon metabolic processes and ecosystem carbon cycling.