土壤微生物群落结构及碳循环功能对高寒草甸退化和人工建植的响应

Responses of soil microbial structure and carbon cycling functions to degradation and artificial restoration of alpine meadows

为了解土壤微生物群落及其碳循环功能对草地退化和人工建植的响应及驱动因素,本研究以青藏高原退化高寒草甸及人工建植草地为对象,借助宏基因组技术,分析退化和建植过程中微生物结构及碳循环功能基因的变化特征,并进一步探索微生物碳循环功能基因变化的驱动因素。结果表明:高寒草甸退化及人工建植过程显著改变了土壤和植被因子;在退化及建植过程中,土壤微生物丰富度及多样性的上升及优势种相对丰度的下降表明微生物群落趋于均质化分布;土壤碳循环功能基因多样性表现为显著上升-稳定-上升的趋势;微生物群落相对丰度前15的优势种对碳循环功能基因的贡献超过40%,但随退化和建植明显下降;单独的土壤或植被因子对土壤微生物群落结构的影响高于微生物碳循环功能基因的影响,但土壤和植被的互作对后者的影响要强于前者;土壤营养元素有效态(铵氮和硝氮)及植被因子(盖度、生物量及多样性)与碳循环功能基因多样性和丰度关系密切。研究结果有助于增强理解高寒草甸退化及人工建植过程中碳循环过程的微生物机制。

We examined the impacts of degradation and artificial restoration of alpine grasslands on microbial communities and the related carbon cycling functions,with experiments being conducted on degraded alpine meadows and artificially restored grasslands in the Qinghai-Tibet Plateau.With metagenomic techniques,we analyzed the change of microbial structures and carbon cycling functions,and further explored the environmental factors driving the changes of carbon cycling functional genes.The results showed that degradation and artificial restoration of grasslands significantly altered soil and vegetation characteristics.The increase of soil microbial richness and diversity and the decrease of the relative abundance of dominant species indicated that microbial community tended to be homogeneous during degradation and artificial restoration of grasslands.The diversity of soil carbon cycling functional genes showed a trend of increasing,stabilizing,and increasing.The top 15 dominant species contributed more than 40%to carbon cycle functional genes,and such contribution decreased significantly under degradation and restoration of grasslands.The effect of individual soil or vegetation on microbial community structure was greater than that on microbial carbon cycling functional genes,while soil and vegetation interaction had stronger effect on the latter than the former.Specifically,carbon cycling functional gene diversity and abundance were significantly related to soil available nitrogen(ammonium nitrogen and nitrate nitrogen)and vegetation factors(coverage,biomass,and diversity).Our results contribute to a better understanding of microbial mechanisms of carbon cycling during meadow degradation and artificial restoration.