Environmental stress is increasing worldwide, yet we lack a clear picture of how stress disrupts the stability of microbial communities and the ecosystem services they provide. Here, we present the first evidence that naturally-occurring microbiomes display network properties characteristic of unstable communities when under persistent stress. By assessing changes in diversity and structure of soil microbiomes along 40 replicate stress gradients (elevation/water availability gradients) in the Florida scrub ecosystem, we show that: (1) prokaryotic and fungal diversity decline in high stress, and (2) two network properties of stable microbial communities—modularity and negative:positive cohesion—have a clear negative relationship with environmental stress, explaining 51–78% of their variation. Interestingly, pathogenic taxa/functional guilds decreased in relative abundance along the stress gradient, while oligotrophs and mutualists increased, suggesting that the shift in negative:positive cohesion could result from decreasing negative:positive biotic interactions consistent with the predictions of the Stress Gradient Hypothesis. Given the crucial role microbiomes play in ecosystem functions, our results suggest that, by limiting the compartmentalization of microbial associations and creating communities dominated by positive associations, increasing stress in the Anthropocene could destabilize microbiomes and undermine their ecosystem services.

世界范围内的环境压力正在增加，但我们不清楚压力如何破坏微生物群落的稳定性及其提供的生态系统服务。在这里，我们提出了第一个证据，表明天然存在的微生物组在持续压力下表现出不稳定群落的网络特性。通过评估佛罗里达灌丛生态系统中 40 个重复应力梯度（海拔/水可用性梯度）土壤微生物群落多样性和结构的变化，我们表明：(1) 原核生物和真菌多样性在高应力下下降，以及 (2) 两个网络稳定微生物群落的特性——模块化和负：正凝聚力——与环境压力有明显的负相关关系，解释了 51-78% 的变异。有趣的是，致病性分类群/功能性群落沿胁迫梯度的相对丰度下降，而寡养生物和共生生物增加，表明负：正内聚力的转变可能是由于负：正生物相互作用减少，这与应力梯度假说的预测一致。鉴于微生物群落在生态系统功能中发挥的关键作用，我们的研究结果表明，通过限制微生物群落的划分和创建以正向关联为主的群落，人类世压力的增加可能会破坏微生物群落的稳定性并破坏其生态系统服务。积极的生物相互作用与压力梯度假说的预测一致。鉴于微生物群落在生态系统功能中发挥的关键作用，我们的研究结果表明，通过限制微生物群落的划分和创建以正向关联为主的群落，人类世压力的增加可能会破坏微生物群落的稳定性并破坏其生态系统服务。积极的生物相互作用与压力梯度假说的预测一致。鉴于微生物群落在生态系统功能中发挥的关键作用，我们的研究结果表明，通过限制微生物群落的划分和创建以正向关联为主的群落，人类世压力的增加可能会破坏微生物群落的稳定性并破坏其生态系统服务。