基于大型森林固定样地的土壤微生物多样性与植物多样性的数量关系及可能机制研究

Many important progresses of researches on plant diversity maintenance mechanisms had been made especially in the recent years. But these reports, mainly based on the data of woody species with DBH (diameter at the breast height) ≥1 cm and these habitat factors (topography, soil content, and space), clearly stated that some definite parts of the total variances of woody species diversity are still not explained by these data. One of the important reasons can be that some important environmental factors and ecological processes were not considered in these researches. This interesting riddle will be farther answered to a great certain extent if the data of microbial diversity in soil, woody species diversity with DBH ＜1 cm, and herbage species diversity could be considered into the related researches. This research will be carried out based on the important research platform of 25-ha Baotianman permanent forest plot (the BTM plot). The following researches will be done here. (1) The new generation of high-fluxed sequencing technology will be used to systematically detect the soil microbial diversity information (species/genus and abundance, richness and beta diversity) at the community level and the spatial-temporal pattern of soil microbial diversity, by the systematically designed 600 soil samples in the BTM plot. (2) And the systematically designed 750 soil samples in the BTM plot , will be analyzed for the main soil contents such as total C, total N, total P, available (N, P), bulk density, soil moisture and pH. (3) The plant diversity (richness and beta diversity), including the woody species diversity with DBH ＜1 cm and the herbage species diversity, will be surveyed in the 1600 subplots with the size of 2.5 × 2.5 m in the 1 ha plot in BTM. (4) The relationships between plant diversity (including woody species and herbage species) and soil microbial diversity will be quantified in this research, and the contribution degrees of the niche based processes and the neutral based processes to the Baotianman's forest community maintenance at the different spatial scales by the methods of PCNM (Principal Coordinate of Neighbor Matrices) and the regression model. This research, with new data input of the soil microbial diversity, woody species diversity with DBH ＜1 cm and the herbage species diversity, can explore some further progresses or new discover on the community maintenance mechanisms. And This research, based on the BTM plot, can provide a thought way or some experiences in the field of the relationships between plant diversity and soil microbial diversity and its mechanisms to the other large permanent forest plots in China or in the world.

近年来基于大型森林固定样地的植物多样性维持机制研究有了明显进展，但目前主要基于胸径≥1厘米木本植物数据和地形/土壤/空间的研究表明，仍然有一部分木本植物多样性变化总方差未能被解释，其中一个重要原因可能是一些重要的环境因素和生态过程未能纳入当前的研究中；若把作为森林群落重要组成部分的土壤微生物多样性、胸径＜1厘米木本植物和草本植物纳入相关研究将有望进一步揭开此谜底。本研究将以25公顷宝天曼森林固定样地为研究平台，借助于新近发展起来的新一代高通量测序技术首次从群落水平系统研究土壤微生物多样性（细菌）时空格局及其与植物多样性的数量关系，有望在群落维持机制上有显著进展或新发现，为我国乃至世界上其它大型样地等开展微生物多样性与植物多样性数量关系及机制研究提供思路和经验借鉴。

土壤微生物在森林生态系统中起着重要作用，然而由于研究方法等限制使得人们对森林土壤微生物多样性的了解还非常有限，对森林土壤微生物多样性与植物多样性之间的数量关系尚不清楚，而高通量测序技术的出现为进一步深入认识土壤微生物多样性提供了契机。本研究以25公顷宝天曼森林固定样地为研究平台，借助于新近发展起来的新一代高通量测序技术来研究宝天曼森林土壤微生物多样性（细菌）特征及其与植物多样性的数量关系，为群落维持机制深入研究奠定基础，其它大型样地开展微生物多样性与植物多样性数量关系及机制研究提供思路和经验借鉴。本研究分别用“圆形法”和“环形法”分析了土壤微生物采样点周围不同尺度上的植物物种多样性及其对应的香侬-维纳指数，进而定量刻画微生物多样性与植物多样性之间的关系。研究结果发现：（1）478个土壤样品中共检测出313767个OTU，分属于58个门、208个纲、417个目、693个科、1226个属。其中，在门、纲、目水平上的细菌优势类群分别是变形菌门、变形菌纲、Ellin6513目，它们所占的比例依次是32.60%、15.60%、9.35%。（2）用“圆形法”时，在1 m、2 m和3 m的尺度上，未检测到微生物OTU数目与植物物种数目之间存在显著的相关关系；从4 m到30 m(精度为1 m)的尺度上，检测到二者之间存在显著的负相关关系；而使用“环形法”时，仅在4 m的尺度上检测出二者之间存在显著的负相关关系，在其它尺度上未检测出显著相关关系。（3）用“圆形法”时，仅在2 m的尺度上，检测出微生物OTU的香侬-维纳指数与植物物种的香侬-维纳指数之间呈显著负相关关系，其它尺度上未检测出显著相关关系；用“环形法”时，仅在4 m尺度上检测出二者之间呈显著的负相关关系，在其它的尺度上未检测出显著相关关系。（4）本研究未发现pH值对宝天曼土壤细菌多样性有显著影响。宝天曼森林土壤细菌多样性有一定的季节变化（128个土壤样品）。