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

土壤生物群代表着测试相互竞争的群落组合模型的独特机会，因为它的特点是惊人的多样性。令人惊讶的是，只有几项研究直接涉及土壤中的中性(人口随机性，有限扩散)与生态位(环境异质性竞争)过程。我们将研究丛枝菌根真菌、跳虫和甲螨在天然草地上形成的群落组合，并检验四个假设：(1)在研究的最小尺度上(单植物冠层)群落是随机聚集的(生态漂移)；(2)在样地尺度(≈1m)，植物之间的距离是群落相似性的主要预测因子(扩散限制)；(3)在较大尺度(样带，5-10m)，包括环境异质性(如土壤质地和水分)，物种组成随机变化(生态位重叠)；(4)在所有尺度上，地理距离足以预测物种分布。土壤将以水分、pH和有机碳等关键变量为特征，AMF群落将在根部和土壤中进行分子评估，而微节肢动物将进行形态评估。没有比较研究详细讨论不同生物体组合可能出现分歧的不同规模。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。这项研究将加深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.