DataSheet1_Nitrogen Addition and Arbuscular Mycorrhizal Fungi Beta Diversity: Patterns and Mechanisms.pdf

Global nitrogen eutrophication, which is disrupting the intimate plant–arbuscular mycorrhizal fungi (AMF) symbiosis, can alter the diversity and physiological functions of soil AMF greatly. However, shifts of beta diversity and the intrinsic patterns of AMF community dissimilarities in response to nitrogen addition remain unclear. Based on a 7-year nitrogen addition experiment in a Qinghai–Tibet Plateau alpine meadow, we detected the changes in soil AMF alpha diversity (richness and genus abundance) and the community composition beta diversity by partitioning the two components of Simpson and nestedness dissimilarities along (turnover) and within (variation) nitrogen addition treatments, and fitted with environmental factor dissimilarities. We found that nitrogen addition decreased AMF richness by decreasing the most dominant AMF genus of Glomus but increasing the abundance of the rare genera. The turnover of the AMF community overall beta diversity along the nitrogen addition gradients was induced by the increased nestedness dissimilarity, while the variation within treatments was explained by both increased Simpson and nestedness dissimilarities, which was significantly correlated with soil pH. Our study found both Simpson and nestedness dissimilarities worked on the AMF community dissimilarity after nitrogen addition and the significant variation within the same treatment, which would be important in the future for predicting global AMF or microbial diversity changes in response to nitrogen eutrophication.

全球氮富营养化会破坏植物与丛枝菌根真菌（arbuscular mycorrhizal fungi, AMF）之间的紧密共生关系，可显著改变土壤AMF的多样性与生理功能。然而，氮添加驱动下AMF群落β多样性的变化及其群落相异度的内在格局仍不明确。
本研究依托青藏高原高寒草甸为期7年的氮添加控制实验，通过拆分氮添加处理下沿梯度方向（群落周转）与处理组内（组内变异）的辛普森相异度（Simpson dissimilarity）与嵌套相异度（nestedness dissimilarity）两个组分，探究了土壤AMFα多样性（包括丰富度与属级丰度）及群落组成β多样性的变化，并将其与环境因子相异度进行拟合分析。
研究结果显示：氮添加通过降低土壤中优势AMF属——球囊霉属（Glomus）的丰度，同时提升稀有属的丰度，显著降低了AMF群落的物种丰富度。沿氮添加梯度的AMF群落整体β多样性周转，主要由嵌套相异度的升高所驱动；而处理组内的群落变异则同时受辛普森相异度与嵌套相异度升高的共同解释，且该组内变异与土壤pH值显著相关。
本研究证实，氮添加后辛普森相异度与嵌套相异度共同参与调控AMF群落的相异格局，且同一处理组内仍存在显著的群落变异，这为未来预测全球氮富营养化响应下AMF或微生物多样性的变化提供了重要理论依据。