华北亚高山土壤细菌群落及氮循环对退耕还草的响应

Response of Soil Bacterial Community and Nitrogen Cycle during the Natural Recovery of Abandoned Farmland in Subalpine of the North China

退耕还草是生态恢复的重要措施,地上植被演替是驱动微生物变化的最重要因素之一。在生态系统相对脆弱的华北亚高山草甸,微生物群落结构和氮循环的潜在功能受退耕还草的影响尚不清楚。利用16S rRNA基因的Illumina MiSeq测序和q PCR技术,研究了山西省宁武云中山亚高山退耕还草区不同恢复年限(农田、15 a、20 a、30 a)的草地土壤细菌群落结构及其氮循环功能基因的变化特征。结果表明,农田和不同恢复年限的草甸地上植被多样性指数(Shannon index)和丰富度指数(Richnessindex)以及土壤理化性质(土壤总碳、总氮、碳氮比、硝态氮、铵态氮和土壤含水率)和酶活性(过氧化氢酶、脲酶和蔗糖酶)差异显著(P<0.05)。优势细菌类群是放线菌门(Actinobacteria)、变形菌门(Proteobacteria)和酸杆菌门(Acidobacteria),土壤细菌群落多样性沿退耕时间序列显著增加,结构也有显著差异。土壤总碳、总氮、碳氮比与铵态氮含量是细菌群落结构变化的重要驱动因子(P<0.05)。植物群落与细菌群落的α多样性显著相关(P<0.05)。参与氮循环的功能基因nif H、amo A-AOA、amo A-AOB的丰度随自然恢复时间而增加(P<0.05)。可见,亚高山草地自然恢复过程中植被多样性、土壤理化性质、土壤细菌群落结构与氮循环相关功能发生了显著的变化。研究结果将为华北亚高山退耕还草区生态保护措施的制定提供数据支持。

The conversion of farmland to grass is an important measure for ecological restoration, and succession of vegetation is one of the most important factors driving soil microbial community. However, the change of microbial community structure and potential function of the nitrogen cycle with conversion of farmland to grass in the ecologically fragile subalpine meadow of North China remain unclear. Using the Illumina Miseq sequencing of 16S r RNA gene and q PCR technology, we investigated the bacterial community structure and functional genes of the nitrogen cycle in soils with farmland and meadow of different recovery years(15years, 20 years, 30 years) in the Yunzhongshan mountain conversion area of Ningwu, Shanxi Province. The results showed that there were significant differences in the aboveground vegetation diversity index, richness index, soil physicochemical properties(Soil total carbon, total nitrogen, carbon nitrogen ratio, nitrate nitrogen, ammonium nitrogen and water content) and enzyme activities(Catalase,Urease and Sucrase) between farmland and meadow with different restoration years(P<0.05). The dominant bacterial groups were Actinobacteria, Proteobacteria and Acidobacteria. The diversity of soil bacterial community increased significantly along the time series of abandoned farmland, and the structure was also significantly different. Soil total carbon, total nitrogen, carbon nitrogen ratio and ammonium nitrogen content were important driving factors for the change of the bacterial community structure(P<0.05). The abundance of functional genes nif H, amo A-AOA, amo A-AOB involved in the nitrogen cycle increased with time during meadow natural recovery(P<0.05). The results indicated that the natural restoration of subalpine meadow changed the vegetation diversity,soil properties, soil bacterial structure and function genes related to nitrogen cycle, providing a sufficient theoretical basis for the ecological protection of subalpine areas in North China.