科尔沁沙地植被重建区土壤氮转化菌群结构形成演变及环境驱动效应

Soil nitrogen is one of the most crucial limiting factors for the growth of plants in sandy land, and soil microbes play core roles in the processes of transformation and utilization of nitrogen. The diversity and community structure evolvement of nitrogen-cycling microbes due to re-vegetation on moving sand land have not been widely studied in most former researches. In this project, the representative sand-fixation plantations in the Horqin Sandy Land will be selected as study objects. Based on purposeful considerations of the key microbiological processes and the involved functional genes encoding corresponding enzymes in soil nitrogen cycle, the diversities and their temporal and spatial variations of soil nitrogen-fixing, nitrifying and denitrifying microbes in the re-vegetation areas will be studied by the techniques of modern molecular biology and bioinformatics. The purposes of this study are to discover the population fluctuations and structure evolvement of soil nitrogen-cycling microflora during the plantation development, and the temporal and spatial heterogenities of sand-fixation community structure, soil environment and nitrogen-transforming function. Furthermore, the coupling relationship among soil environment, vegetation, microflora structure and nitrogen-transforming function, the effect of environmental drive on the evolvement of soil microflora structure, and the biological mechanism of soil nitrogen variation will be revealed on the basis of above studies. The results submitted by this project will enrich the basic data of soil microbial diversity and its function in the semi-arid sandy area, and will provide some scientific fundamentals for the practices of biodiversity conservation, ecological restoration and soil quality evaluation, and sand-fixing vegetation management of sandy land.

氮素是沙地植物生长最主要的限制因子之一，而土壤微生物在氮素转化和利用方面起核心作用。流动沙地重建植被后，土壤氮转化微生物的多样性及菌群结构的形成演变规律一直缺乏系统的研究。本项目以科尔沁沙地典型人工固沙植物群落为对象，以编码土壤氮转化过程关键酶的功能基因为切入点，采用现代分子生物学和生物信息学技术，研究沙地植被重建区土壤固氮、硝化和反硝化微生物的多样性及其时空变化，厘清固沙植物群落发育进程中土壤氮转化微生物的种群消长、菌群结构的形成和演变规律，测定分析固沙植物群落结构、土壤环境和氮转化功能的时空异质性，以期阐明土壤环境、植被、氮转化菌群结构和氮转化功能之间的互动关系，揭示土壤氮转化菌群结构形成演变的环境驱动效应以及土壤氮素变化的生物学机制。研究成果可完善半干旱风沙区土壤微生物多样性及功能的基础数据，为沙地生态系统生物多样性保护、生态恢复和土壤质量的评价以及固沙植被的管理提供科学依据。

氮素是沙地植物生长发育的限制性因素，其生物地球化学循环过程主要由不同类群的微生物驱动，为揭示不同固沙群落下土壤氮转化菌群结构的形成发展及与环境因子的关系，本项目选取32年生小叶锦鸡儿、差巴嘎蒿、山竹岩黄蓍、小黄柳、杨树和樟子松人工固沙植被，以及不同年龄的小叶锦鸡儿群落为对象，以编码土壤氮转化过程关键酶的功能基因(nifH、amoA、nirK、nirS、norB、nosZ等)为分子标记，采用PCR-DGGE、克隆文库、Q-PCR和T-RFLP等技术，重点开展了植被类型对土壤氮转化微生物多样性及菌群结构的影响、土壤氮转化菌群结构在固沙植被发育进程中的形成演变、固沙植物群落、土壤环境及氮转化作用的时空异质性、以及固沙植物群落土壤氮转化菌群结构与环境功能的耦合关系等研究。通过研究获得了科尔沁沙地土壤固氮、氨氧化和反硝化微生物多样性的大量基础数据；植被类型对氮转化菌群结构有显著影响，土壤理化性质是引起土壤固氮、硝化和反硝化菌群结构演变的主要原因；土壤氮转化菌群结构与植物群落发育进程之间存在互动关系，沙地土壤氮转化微生物群落结构相对简单，优势种明显，土壤固氮、氨氧化和反硝化菌群均随着植物群落的发育出现优势种的消长；土壤氮转化菌群结构的形成演变与土壤因子有密切关系，不同的土壤因子对菌群结构形成的驱动作用不同。以上研究结果完善了半干旱风沙区土壤微生物多样性及功能的基础数据，为沙地生态系统生物多样性保护、沙地植被重建后土壤质量评价与演变趋势的预测，以及揭示土壤氮素变化的机制提供了重要的科学依据。