科尔沁沙地植被重建区土壤磷转化菌群的次生演替研究

Soil phosphorus 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 phosphorus transformation. It is still unknown how the diversity of soil phosphorus transformation microbe is naturally restored and how the microbial community structure evolves after re-vegetation on secondary bare land. In this project, the representative sand-fixation plantations planted on the moving sand dunes in the Horqin Sandy Land will be selected as study objects. Based on purposeful considerations of the functional genes encoding key enzymes and phosphate transporters in the process of soil phosphorus transformation, the genetic diversities and their temporal and spatial variations of soil phosphorus-dissolving, mineralizing, and transporting related microbes will be studied. The purposes of this project are to reveal the dominant population fluctuations, community structure evolvement of soil phosphorus transformation microbes along vegetation development, and the temporal and spatial heterogenities of soil matrix attributes, microbiological properties, sand-fixation plantation structure, and phosphorus-transforming function. Furthermore, the main environmental factors driving the secondary succession of soil phosphorus transformation microflora, the biological mechanism of the variation in soil phosphorus availability, and the interactions among microbial community structure, vegetation development, soil environment, and phosphorus-transforming function will be determined. The achievements submitted by this project will enrich the basic data of soil microbial diversity in the semi-arid sandy area, and will provide some scientific basis for understanding the process and mechanism of ecological restoration of degraded sandland ecosystem, the evaluations of soil quality and stability of plant community, and the management of sand-fixing plantations.

磷是沙地植物生长发育最主要的限制因子之一，土壤微生物在磷转化过程中起核心作用。次生裸地重建植被后，土壤磷转化微生物多样性的自然恢复、菌群结构的重建和演变规律尚不清楚。本项目以科尔沁沙地流动沙地为起点的人工固沙植物群落为对象，以编码磷转化过程关键酶和磷转运体的功能基因为切入点，研究土壤磷的溶解、矿化和转运等相关微生物类群的遗传多样性及其时空变化。阐明植被发育进程中土壤磷转化微生物种群消长、菌群结构形成和演变特征，确定土壤磷转化菌群次生演替的主要环境驱动因子；分析植物群落结构、土壤基质性质、生物活性以及磷转化功能的时空异质性，厘清土壤磷转化菌群结构与土壤环境、植被发育和土壤磷转化功能之间的互动关系，揭示土壤磷有效性转化的生物学机制。研究成果将丰富半干旱风沙区土壤微生物多样性的基础数据，为阐明沙地退化生态系统恢复重建的生态过程和机制、土壤质量和植物群落稳定性的评价以及固沙植被的管理提供科学依据。

以科尔沁沙地典型地区流动沙地和原生天然植被分别作为演替的起点和演替顶级，研究了沙地植被重建区土壤磷转化菌群的演替规律，对比分析了植被类型对磷转化菌群结构的影响。以土壤碱性磷酸酶基因(phoD)、醌蛋白葡萄糖脱氢酶基因(gcd)、无机磷酸盐转运系统基因(pitA)、磷酸盐特异性转运系统基因(pstS)和膦酸乙醛水解酶基因(phnX)为标记基因，解析了人工固沙植物群落土壤有机磷矿化、无机磷水解、磷运输通道相关的功能微生物遗传多样性、菌群组成、结构和数量的时空变化特征；研究了土壤磷转化菌群结构与土壤环境、植被发育和土壤磷转化功能之间的互动关系，确定了驱动菌群演替的主要土壤因子。取得的主要结果：①获得了科尔沁沙地土壤磷转化相关微生物多样性的基础数据，掌握了磷转化微生物的区系组成、优势类群及其消长规律；②发现植被类型和土壤因子对磷转化微生物的数量、菌群结构和优势种动态有显著影响；③证实了木本植物群落土壤磷转化功能和微生物多样性显著高于半灌木；④发现许多土壤固氮菌具有磷转化功能，表明土壤磷转化作用与土壤固氮作用可协同发生；⑤证明了土壤因子对磷转化菌群演替有直接驱动作用，不同的土壤因子对菌群结构变化的驱动作用不同，其中pH、有机质、全氮和速效养分是多数磷转化菌群结构演替的主要直接驱动因子。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、植被重建土壤质量评价与演变趋势的预测、以及揭示土壤磷有效性转化的生物学机制提供了重要的科学依据。