Non-linear Responses of Soil Diazotrophs to Aridity in Xinjiang Grasslands

Although drought strongly affects soil microbial communities and ecosystem functioning, the threshold responses and assembly mechanisms of diazotrophs along aridity gradients remain poorly understood. Here, we investigated diazotrophic communities across 155 grassland sites in Xinjiang, China, spanning a broad natural aridity gradient (1−AI: 0.46–0.88). By integrating segmented regression, null and neutral community models, structural equation modeling, and network stability analysis, we identified critical aridity thresholds and clarified the mechanisms underlying diazotroph community assembly under increasing aridity.尽管干旱可强烈影响土壤微生物群落与生态系统功能，但沿干旱梯度分布的固氮微生物（diazotrophs）的阈值响应及群落组装机制仍未被充分阐释。本研究针对中国新疆境内155个草地样地展开调查，样地覆盖了跨度为0.46~0.88的自然干旱梯度（1-干旱指数：0.46–0.88）。通过整合分段回归、零模型与中性群落模型、结构方程模型及网络稳定性分析方法，本研究明确了关键干旱阈值，并阐明了随干旱程度加剧时固氮微生物群落组装的内在机制。