不同土地利用方式下细菌群落对土壤碳矿化速率的影响

Effects of bacterial community on soil’s carbon mineralization rate change under different land use types

利用高通量测序技术分析长江流域(重庆段) 4种典型土地利用方式(纯林、混交林、草地、裸地)土壤碳矿化速率与土壤细菌丰度、多样性及其功能之间的关系,揭示土壤微生物群落驱动的碳循环机制。结果表明:不同土地利用方式下土壤碳矿化速率动态变化基本一致,均呈先升高后下降最后趋于稳定的趋势,土壤累积碳矿化量大小依次为混交林、纯林、草地、裸地;土壤细菌群落Shannon、Simpson、Chao 1及ACE指数存在差异,但差异并不显著,纯林土壤细菌多样性最高,混交林细菌丰度最高,裸地土壤细菌多样性和丰度都最低;FAPROTAX细菌功能分组主要以化能异养、发酵、木聚糖分解、硝化、氮呼吸、好氧氨氧化作用等为主,其中参与碳氮循环的功能细菌在混交林丰度较高,表明土壤细菌功能群落的组成对土壤碳矿化速率影响较大。

The paper is aimed to make an exploration of the mechanism of the carbon circulation driven by the soil’s microbial communities so as to provide a theoretical basis for the soil quality improvement management in different land use types.And,for such a purpose,we have managed to analyze the relationship between the soil’s carbon mineralization rates and its bacterial abundance,diversity and functional changes under the4 typical different types of land use( i. e. the pure forest one,the mixed forest one,the grassland one,and the bare poor one)along the Chongqing section of Yangtze River Basin through the high-throughput sequencing process. The changes with the soil’s CO2 emission flux can have been observed for the 1 st,3 rd,5 th,7 th,9 th,15 th,20 th till the 30 th day in the airtight greenhouse incubation( 25 ℃) and recorded via the basic titration. At the same time,we have also managed to analyze the soil’s bacterial abundance and the high diversified function throughout the sequencing technique. And,so,we have accomplished a comprehensive analysis of the physical and chemical properties of the soil and its bacterial diversity with the dynamic changes of its carbon mineralization for the different land use types through proper comparison. The results of the above comparison and analysis demonstrate that,for the 4 different land-use types,the increasing process of the soil’s carbon mineralization rate tends generally to reveal the same changing regularity with the same characteristic features. That is to say,the mineralization rate tends to rise first,then decrease slowly,and finally tends to get stabilized. In such an evolving tendency,the soil’s carbon mineralization rate and the cumulative mineralization proportion may turn to be from bigger to smaller so as to be getting into a mixed forest,a pure forest,a grassland,and eventually into a piece of bare land. And,then,in the similar way,the soil’s bacterial diversity may reveal a significant positive correlation with the soil’s physicochemical properties. That is to say,there can be found no significant difference in Shannon,Simpson,Chao 1 and ACE index of the soil’s bacterial community due to the different land use types,suggesting that there appears a sequential downward order as shown below: the mixed forest > the pure forest> the grassland > the bare land. In other words,the bacterial function prediction by using FAPROTAX can mainly be focused on the chemo-heterotrophy,fermentation,xylanolysis,nitrification,nitrogen respiration,and aerobic ammonia oxidation,and then abundance of the functional bacteria involved in higher carbon and nitrogen circulation in the mixed forest. Thus,given study can be interpreted that the soil ’s carbon mineralization process is actually affected by a variety of factors. For the above said 4 different land use types,the soil’s bacterial diversity and functional microbial composition should be the chief influential factors of the above process under examination.