Root biochemistry:Microbial composition and function across an old-field chronosequence

As mediators of biogeochemical cycles, understanding the ecological forces structuring soil microbial communities is of ecosystem-level significance. Due to gradual shifts in plant species composition and litter addition through time, succession can be used as a model to understand how plant communities shape microbial community composition and function in soil. Numerous studies have investigated microbial biomass and diversity along successional gradients, yet few have quantified changes in microbial communities. Using the established successional dynamics experiment at Cedar Creek, principal investigators Lauren C. Cline and Donald R. Zak investigated the influence of plant community composition in structuring microbial community composition and function. Specifically, their research addressed the following questions: 1. Do shifts in saprotrophic microbial communities correlate to changes in plant community composition through successional time? 2. What is the relative influence of soil properties and plant community characteristics in determining microbial community dynamics? Cline and Zak sampled soils from 8 established abandoned agricultural fields (e054), as well as three adjacent forests representing potential late-successional ecosystems, to investigate microbial dynamics using three complementary approaches: targeted sequencing of fungal and bacterial communities, quantitative PCR, and shotgun metagenomics. Further, the characterization of soil properties across the chronosequence will enable us to disentangle the impact of abiotic factors in structuring microbial communities.作为生物地球化学循环的介导者，解析塑造土壤微生物群落的生态驱动力具有重要的生态系统层面意义。随着时间推移，植物物种组成逐渐发生改变，同时枯落物输入也随之变化，因此群落演替可作为研究模型，用以解析植物群落如何调控土壤中微生物群落的组成与功能。已有诸多研究围绕演替梯度下的微生物生物量与多样性展开探讨，但针对微生物群落动态变化的定量分析仍较为匮乏。依托锡达溪（Cedar Creek）已建立的演替动态实验平台，首席研究员劳伦·C·克莱因（Lauren C. Cline）与唐纳德·R·扎克（Donald R. Zak）探究了植物群落组成对土壤微生物群落组成与功能的塑造作用。具体而言，其研究围绕以下两个核心问题展开：1. 随演替时间推移，腐生微生物群落的动态变化是否与植物群落组成的改变存在相关性？2. 土壤理化性质与植物群落特征在调控微生物群落动态过程中的相对影响力分别如何？克莱因与扎克从8个已废弃的农田样地（编号e054）以及3个毗邻的、代表潜在顶级演替生态系统的森林样地中采集土壤样品，采用三种互补的实验方法解析微生物动态：真菌与细菌群落的靶向测序、定量聚合酶链式反应（quantitative PCR）以及鸟枪宏基因组学（shotgun metagenomics）。此外，对该时间序列演替样地的土壤理化性质进行表征，将有助于我们厘清非生物因子在塑造微生物群落过程中的具体影响。