Data from: Changes in ectomycorrhizal fungal community composition and declining diversity along a 2-million-year soil chronosequence

Ectomycorrhizal (ECM) fungal communities covary with host plant communities along soil fertility gradients, yet it is unclear whether this reflects changes in host composition, fungal edaphic specialization or priority effects during fungal community establishment. We grew two co-occurring ECM plant species (to control for host identity) in soils collected along a 2-million-year chronosequence representing a strong soil fertility gradient and used soil manipulations to disentangle the effects of edaphic properties from those due to fungal inoculum. Ectomycorrhizal fungal community composition changed and richness declined with increasing soil age; these changes were linked to pedogenesis-driven shifts in edaphic properties, particularly pH and resin-exchangeable and organic phosphorus. However, when differences in inoculum potential or soil abiotic properties among soil ages were removed while host identity was held constant, differences in ECM fungal communities and richness among chronosequence stages disappeared. Our results show that ECM fungal communities strongly vary during long-term ecosystem development, even within the same hosts. However, these changes could not be attributed to short-term fungal edaphic specialization or differences in fungal inoculum (i.e. density and composition) alone. Rather, they must reflect longer-term ecosystem-level feedback between soil, vegetation and ECM fungi during pedogenesis.外生菌根（Ectomycorrhizal, ECM）真菌群落沿土壤肥力梯度与宿主植物群落呈共变关系，但目前尚不清楚这种共变关系究竟反映的是宿主组成的变化、真菌的土壤生境特化，还是真菌群落建立过程中的优先效应。本研究选取两种伴生的外生菌根植物物种以控制宿主同一性，将其种植于沿200万年年代序列采集的土壤中——该序列代表了显著的土壤肥力梯度；同时通过土壤操控处理，厘清土壤理化性质与真菌接种体各自的影响。外生菌根真菌群落组成随土壤年代增加发生改变，物种丰富度随之下降；上述变化与土壤形成作用驱动的土壤理化性质变迁密切相关，尤以pH值、树脂交换态磷与有机磷的变化最为显著。然而，当固定宿主同一性、消除不同土壤年代间的接种势或土壤非生物性质差异后，不同年代序列阶段的外生菌根真菌群落及其丰富度差异便不复存在。本研究结果表明，即便在相同宿主条件下，外生菌根真菌群落在长期生态系统发育过程中仍会发生显著变化。但这类变化无法仅归因于短期的真菌土壤生境特化，或是真菌接种体（即接种体密度与组成）的差异。相反，其必然反映了土壤形成过程中，土壤、植被与外生菌根真菌之间长期的生态系统级反馈作用。