Understanding the relative role of ecological neutrality and niche based competition in structuring the soil community: a comparative field study on arbuscular mycorrhizal fungi and microarthropods

土壤生物群的特点是惊人的多样性，因此它为测试相互竞争的群落组合模式提供了一个独特的机会。令人惊讶的是，只有少数研究直接解决了土壤中的中性（有限分散的人口随机性）和生态位（与环境异质性的竞争）过程。本研究将对天然草地上丛枝菌根真菌（AMF）、collebolans和oribatid螨虫的群落组合进行研究，并验证四个假设：(1)在研究的最小尺度（单个植物冠层）上，群落是随机聚集的（生态漂移）；(2)在样地尺度（≈1m）上，植物间距离是群落相似性（扩散限制）的主要预测因子；(3)在包含环境异质性（如土壤质地和湿度）的较大尺度（样带，5 ~ 10 m）上，物种组成随机变化（生态位重叠）；(4)在所有尺度上，地理距离都足以预测物种分布。土壤将通过水分、pH和有机c等关键变量来表征。AMF群落将在分子、根和土壤中进行评估，而微节肢动物将在形态学上进行评估。目前还没有比较研究详细说明在不同的尺度上，不同生物的组合可能会出现分歧。鉴于AMF和微节肢动物在生态系统中的功能作用（例如碳循环），这是一个热门问题。这项研究将增强我们对自然群落形成过程的理解。

Soil biota represents a unique opportunity for testing competing models of community assembly since it is characterized by an astonishing diversity. Surprisingly, there are only a few studies that directly addressed neutral (demographic stochasticity with limited dispersal) vs. niche (competition with environmental heterogeneity) processes in the soil. We will study the assemblages formed by arbuscular-mycorrhizal fungi (AMF), collembolans and oribatid mites in a natural grassland and we will test four hypotheses: (1) at the smallest scale of the study (the single plant canopy) community is randomly assembled (ecological drift); (2) at the plot scale (≈ 1m), distance between plants is the main predictor of community similarities (dispersal limitation); (3) at larger scales (transects, 5-10 m), that encompass environmental heterogeneities (e.g. soil texture and moisture), species composition varies randomly (niche overlap); (4) at all scales geographic distances is sufficient to predict species distribution. Soil will be characterized by key variables such as moisture, pH and organic C. AMF communities will be assessed molecularly, in the roots and the soil, while microarthropods will be assessed morphologically. There are no comparative studies that addressed in detail the different scales at which assemblages of different organisms may diverge. This is a topical issue, given the functional role of AMF and microarthropods in the ecosystem (e.g. carbon cycling). This research will enhance our understanding of processes shaping natural communities.