淹水条件与植被类型对洱海湖滨带微生物群落特征及脱氮功能基因丰度的影响

Effects of flooding conditions and vegetation types on the microbial community characteristics and the abundance of denitrification functional genes in the ecotone of Lake Erhai

为探究淹水条件与植被类型对湖滨带微生物群落结构、脱氮功能基因的影响,以洱海湖滨带3种淹水条件(不淹水、间歇淹水、持续淹水)和6种植被类型(草地、林地、林草地、挺水、沉水、无植被)土壤/底泥中的微生物为研究对象,采用16S rRNA基因高通量测序和荧光定量PCR技术,分析淹水条件和植被类型对洱海湖滨带土壤和底泥微生物群落结构以及微生物脱氮功能基因丰度的影响。结果表明:交界区作为湖滨带物质交换与能量流动最频繁的区域,受水位波动影响环境条件复杂,其土壤/底泥中氮循环的重要微生物类群(如绿弯菌门和硝化螺旋菌门等)的相对丰度及α多样性均高于陆向区和水向区;而植被类型主要影响水向区底泥的微生物群落组成和α多样性。微生物脱氮功能基因丰度的差异进一步说明湖滨带脱氮微生物的空间分布特点,陆向区和交界区更高的功能基因丰度说明微生物脱氮活动更强烈。含水率、碳氮比、有机碳和亚硝氮是洱海湖滨带土壤/底泥脱氮过程功能基因丰度的关键影响因素,其浓度变化是淹水条件和植被类型影响脱氮功能基因丰度差异的主要原因。

In order to investigate the effects of flooding conditions and vegetation types on the microbial community structure and denitrification function genes of the ecotone zone of Lake Erhai,the microorganisms present in the soil and sediment of the ecotone zone of Lake Erhai were investigated under three flooding scenarios(no-flooding area,intermittent inundation area,constant inundation area)and with six different types of vegetation cover(grassland,woodland,forest-grassland,emergent vegetation,submerged vegetation,and no vegetation).The investigation was conducted using the 16S rRNA gene high-throughput sequencing and fluorescence quantitative PCR technologies to determine changes in microbial community structure and functional gene abundance and the impact of flooding and vegetation cover on soil and sediment microbial communities in the ecotone zone of Lake Erhai.The results showed that as the area with the most frequent material exchange and energy flow in the lakeshore,the interface zone was affected by water level fluctuations,so it became a complex environmental condition.The relative abundance of important microbial groups in nitrogen cycling in this soil/sediment,such as Chloroflexi and Nitrospirota,was higher than in the land and water zone.The vegetation cover mainly affected the microbial community composition andαDiversity in the sediment in the water land.The difference in the abundance of microbial denitrification functional genes revealed the spatial distribution characteristics of denitrification microorganisms in the ecotone zone.A higher abundance of functional genes in landward and interface zones indicated a stronger microbial denitrification activity.The abundance of functional genes during the removal of nitrogen from soil or sediment in the lakeshore of Lake Erhai was affected by several key factors,including water content,carbon-to-nitrogen ratio,organic carbon,and nitrite nitrogen.The difference in the concentration of these factors was the primary cause of the variation in the abundance of functional genes for nitrogen removal under various flooding conditions and vegetation cover.