岩溶地区不同土地利用方式土壤固碳细菌群落结构特征

Community Structure of CO_2-fixing Soil Bacteria from Different Land Use Types in Karst Areas

固碳细菌是土壤碳循环重要的微生物群落,研究其群落结构特征对认识土壤生态系统的固碳机制具有重要意义.以桂林毛村岩溶实验场的岩溶区、混合区与非岩溶区为研究样区,采集稻田、玉米和柑橘园表层土壤,以cbb LR为固碳细菌的指示基因,采用高通量测序方法,对比在三类区域土壤中固碳细菌的群落丰度、组成及多样性特征的异同.结果表明,三类区域土壤中固碳细菌属于变形菌门和放线菌门.其中,变形菌门的α-变形菌纲(α-Proteobacteria,24.6%)为三类区域土壤中的优势纲,以根瘤菌为主的兼性自养菌是主要的固碳细菌.在岩溶区,伯克氏菌目(Burkholderiales)、红假单胞菌属(Rhodopseudomonas)、固氮螺菌属(Azospirillum)、费氏根瘤菌(Sinorhizobium fredii HH103)、豌豆根瘤菌(Rhizobium leguminosarum bv.trifolii)等微生物的丰度均高于混合区和非岩溶区;而慢生根瘤菌属(Bradyrhizobium)为混合区与非岩溶区土壤中的优势种群.冗余分析(redundancy analysis)表明,pH、土壤有机碳(SOC)、可溶性有机碳(DOC)、总氮(TN)和阳离子交换量(CEC)等土壤因子是影响固碳细菌群落结构差异的主要生态因子.以上结果表明,岩溶区的土壤特性对固碳细菌的群落结构有显著影响.

Carbon dioxide (CO2)-fixing bacteria are important microbial communities of the soil carbon cycle. It is important to study their community structure characteristics in karst areas to understand the carbon-sequestration mechanism of the soil ecosystem. The top soil samples of paddy fields, maize fields, and citrus orchards were collected in a karst area, mixed zone, and non-karst area at the Maocun karst experimental site in Guilin.The community abundance, composition, and diversity of CO2^-fixing bacteria were analyzed using high-throughput sequencing technology with cbbLR as indicating gene. The results show that most of the CO2^-fixing bacteria can only be classified as the shallow taxonomic group including bacteria and actinomycetes. The α-Proteobacteria of Proteobacteria was the dominant class in the three areas. Facultative autotrophic bacteria dominated by rhizobia were the main CO2^-fixing bacteria. The abundances of Burkholderiales, Rhodopseudomonas, Azospirillum, Sinorhizobium fredii HH103, Rhizobium leguminosarum bv. trifolii were higher in the karst area than in the other two areas. However, Bradyrhizobium is the dominant species in the mixing and non-karst areas. The redundancy analysis shows that the pH, soil organic carbon, soluble organic carbon, cation exchange capacity, and total nitrogen are the main ecological factors affecting the community structure of CO2^-fixing bacteria. The above-mentioned results show that the soil properties in the karst area can significantly affect the community structure of CO2^-fixing bacteria.