Interplay between the soil microbiome and tree species richness as well as tree species identity in subtropical forests of China

土壤微生物通过影响养分的吸收和循环，塑造植物多样性和生产力，对森林生态系统的运行起着至关重要的作用。在过去的十年里，测序技术的进步极大地激发了人们对土壤微生物多样性和群落结构的了解。这为解决大型和多学科项目中的微生物生态问题开辟了新的途径。在北京森林基金会-中国研究室的前几个阶段，我们使用高通量焦标测序技术对A和B两个地点的比较研究样地(CSPs)和主要实验中的土壤微生物群落进行了分析，发现CSPs中的林龄、植物群落和土壤微生物群落之间存在着很强的相关性。主要试验结果表明，树种同一性和树种丰富度对土壤真菌群落的影响在林木育苗初期就已经明显。随着植物的不断生长，微生物群落组成的进一步变化是可以预期的。对于森林生态系统来说，众所周知，初级生产的主要部分要么作为根分泌物转移到土壤中，要么作为死亡有机物质转移到土壤中。这将根际和粗木屑定义为植物对森林土壤微生物群落影响的两个热点。这些热点的探索性较弱，但可望在高度多样化的亚热带森林中发挥重要作用。在北京森林基金会-中国研究单元的第三阶段，SP7将重点研究亚热带森林生态系统中植物生物多样性和地下微生物多样性之间的功能关系。根际和粗木屑(CWD)都将作为控制养分循环和获取的两个关键土壤区段进行调查。我们的两个目标是：(1)在北京森林基金会-中国主要实验范围内，分析单一树种根际土壤微生物群落多样性和群落组成随植物物种丰富度梯度的变化。(2)利用SP10设计的多功能多多样性阵列(MMA)，研究树种特性、木材性状、腐烂率、林隙和植物多样性水平对微生物群落分解(CWD)的影响。我们将使用靶向真菌ITS rDNA焦标签和原核生物16S rDNA Illumina配对末端测序方法。解决这一广泛的土壤微生物群落将使我们能够分析特定的微生物功能群和树种的共生和相互作用网络的模式，以便从机理上了解根际和CWD热点地区的植物-微生物相互作用。这一结果将加深我们对植物微生物群在维持森林生态系统中植物多样性和生产力方面的作用的理解。

Soil microorganisms play a crucial role for the functioning of forest ecosystems by influencing uptake and cycling of nutrients and shaping plant diversity and productivity. In the last decade knowledge on microbial diversity and community structure in soils has been triggered dramatically by advances in sequencing technologies. This opens new avenues to address microbial ecological questions in large and multidisciplinary projects. In the previous phases of the Research Unit BEF-China we used high-throughput pyrotag sequencing to analyse soil microbial communities both in the Comparative Study Plots (CSPs) and in the Main Experiment at both Sites A and B. We found a strong relationship between forest age, plant community and soil microbial community in the CSPs. Results from the Main Experiment indicated clear effects of both tree species identity and tree richness on the soil fungal community already at this early stage of tree seedling establishment. Further shifts in the microbial community composition are to be expected with ongoing growth of the plants. For forest ecosystems it is known that the major part of the primary production is transferred to the soils either as root exudates or as dead organic matter. This defines the rhizosphere and coarse wood debris as two hot spots of plant influence on soil microbial communities in forests. These hot spots are only weakly explored, but can be expected to be of major importance especially in the highly diverse subtropical forests.In the 3rd phase of the BEF-China research unit SP7 will focus on understanding the functional relationships between plant biodiversity and below ground microbial diversity in subtropical forest ecosystems. Both the rhizosphere and coarse wood debris (CWD) will be investigated as the two key soil compartments where cycling and acquisition of nutrients are controlled. Our two objectives are: (1) To analyse changes in the diversity and community composition of the rhizosphere soil microbiomes of single tree species along increasing plant species richness gradients within the BEF-China Main Experiment. (2) To study the impact of tree species identity, wood trait, decay rate, canopy gap and plant diversity levels on the microbial communities decomposing (CWD), using the multi-functionality multi-diversity array (MMA) designed by SP10. We will employ both targeted fungal ITS rDNA pyrotag and prokaryotic 16S rDNA illumina paired end sequencing approaches. Addressing this broad array of the soil microbial communities will enable us to analyse the patterns of cooccurrence and interaction networks of specific functional groups of microbes and the tree species in order to obtain a mechanistic understanding of the plant-microbe interactions in the rhizosphere and CWD hot spots. The results will improve our understanding of the role of the plant microbiome in maintaining plant diversity and productivity in forest ecosystems.