Data from: Soil microbial community variation correlates most strongly with plant species identity, followed by soil chemistry, spatial location and plant genus

Soil ecologists have debated the relative importance of dispersal limitation and ecological factors in determining the structure of soil microbial communities. Recent evidence suggests that "everything is not everywhere", and that microbial communities are influenced by both dispersal limitation and ecological factors. However, we still do not understand the relative explanatory power of spatial and ecological factors, including plant species identity and even plant relatedness, for different fractions of the soil microbial community (i.e. bacterial and fungal communities). To ask whether factors such as plant species, soil chemistry, spatial location, and plant relatedness influence rhizosphere community composition, we examined field-collected rhizosphere soil of seven congener pairs that occur at Bodega Bay Marine Reserve, CA, USA. We characterized differences in bacterial and fungal communities using Terminal-Restriction Fragment Length Polymorphism. Plant species identity was the single best statistical predictor of both bacterial and fungal community composition in the root zone. Soil microbial community structure was also correlated with soil chemistry. The third best predictor of bacterial and fungal communities was spatial location, confirming that everything is not everywhere. Variation in microbial community composition was also related to combinations of spatial location, soil chemistry, and plant relatedness, suggesting that these factors do not act independently. Plant relatedness explained less of the variation than plant species, soil chemistry, or spatial location. Despite some congeners occupying different habitats and being spatially distant, rhizosphere fungal communities of plant congeners were more similar than expected by chance. Bacterial communities from the same samples were only weakly similar between plant congeners. Thus, plant relatedness might influence soil fungal, more than soil bacterial, community composition.

土壤生态学家此前一直围绕扩散限制（dispersal limitation）与生态因子在塑造土壤微生物群落结构中的相对重要性展开了诸多争论。近期研究证据显示，微生物群落同时受扩散限制与生态因子的共同影响，且证实了"万物并非随处可得"的论断。然而，当前学界仍未明确空间因子与各类生态因子（包括植物物种属性乃至植物亲缘关系）对不同组分土壤微生物群落（即细菌群落与真菌群落）的相对解释力。为探究植物物种、土壤化学性质、空间位置以及植物亲缘关系等因子是否会对根际群落组成产生影响，本研究采集了美国加利福尼亚州博德加湾海洋保护区内的7组同属植物对的野外根际土壤样本，并采用末端限制性片段长度多态性（Terminal-Restriction Fragment Length Polymorphism, T-RFLP）技术对细菌与真菌群落的差异进行了表征。分析结果表明，植物物种属性是根际区域细菌与真菌群落组成的最优单一统计预测因子；土壤微生物群落结构同样与土壤化学性质呈显著相关；空间位置则是影响细菌与真菌群落的第三大预测因子，这一结果再次证实了"万物并非随处可得"的论断。微生物群落组成的变异同时与空间位置、土壤化学性质及植物亲缘关系的组合效应相关，表明这些因子并非独立发挥调控作用。相较于植物物种属性、土壤化学性质与空间位置，植物亲缘关系对群落变异的解释度更低。尽管部分同属植物占据了不同生境且空间距离较远，但同属植物的根际真菌群落相似性仍显著高于随机预期水平；而同一样本中的细菌群落，在同属植物间仅表现出微弱的相似性。由此可见，植物亲缘关系对土壤真菌群落组成的影响程度要高于其对土壤细菌群落的影响。