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 systematic 3087 soil samples in total in the BTM plot between 2013 and 2016. (2) And 1764 soil samples in total, systematically sampled 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 400 subplots with the size of 3 × 3 m in the BTM plot. (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时空格局及其与（木本和草本）植物多样性的数量关系，采用方差分解和回归模型相结合的方法来定量分解不同空间尺度上生态位过程与中性过程在宝天曼森林群落维持上的贡献程度，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。

近些年森林生态系统生物多样性的研究主要关注植物多样性，作为森林生态系统重要组成部分的土壤微生物多样性及其与植物多样性的关系，因研究的难度和没有受到应有的重视非常薄弱。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尝试研究土壤微生物多样性与木本植物多样性的数量关系。主要研究有：（1）宝天曼森林土壤微生物多样性特征初步分析。对宝天曼大样地内10个植物多样性梯度群落的土样进行高通量测序分析共检测到土壤微生物236个类群（分类学属的水平），并给出各类群的相对丰度值；宝天曼森林土壤微生物优势类群有Acidobacteriaceae、Bradyrhizobium、Xanthobacteraceae、Planctomycetaceae、Bryobacter、Candidatus_Solibacter、Sinobacteraceae、Acidothermus、Burkholderia、Mycobacterium等。（2）宝天曼大样地森林植物多样性特征初步分析。宝天曼大样地共监测木本植物59569株，分别属于126种、77属、39科，样地木本植物主要由壳斗科（Fagaceae）、椴树科（Tiliaceae）、槭树科（Aceraceae）、松科（Pinaceae）、山茱萸科（Cornaceae）、桦木科（Betulaceae）等组成，优势树种有锐齿槲栎、葛罗枫等；对样地主要木本植物多度分布、物种分布、地形特征等进行了初步分析，这些为以后深入研究奠定了基础。（3）宝天曼大样地森林植物多样性与土壤微生物多样性的关系初步分析。我们尝试用多种模型（包括线性、指数、多项式、对数、幂等）对森林土壤微生物多样性与植物多样性关系进行拟合，结果显示多项式模型相对较好，初步研究结果显示宝天曼森林木本植物多样性与土壤微生物类群多样性之间呈弱单峰型关系模式，但由于受样本量等的影响，这些初步结果需要进一步研究才能确认。本项目是一年期小额资助，我们在有限时间有限经费情况下集中围绕植物多样性与土壤微生物多样性的关系开展了一些前期研究，这为揭示植物多样性与土壤微生物多样性的数量关系及进一步深入探讨森林生物多样性维持机制奠定了基础。