Belowground niche partitioning is maintained under extreme drought

Belowground niche partitioning presents a key mechanism maintaining species coexistence and diversity. Its importance is currently reinforced under climate-change-altering soil hydrological conditions. However, experimental tests examining the magnitude of its change under climate change are scarce. We combined measurements of oxygen stable isotopes to infer plant water-uptake depths and extreme drought manipulation in grasslands. Belowground niche partitioning was evidenced by different water-uptake depths of co-occurring species under ambient and extreme drought conditions despite an increased overlap among species due to a shift to shallower soil layers under drought. A co-occurrence of contrasting strategies related to change of species water-uptake depths’ distribution was likely key for species to maintain some extent of belowground niche partitioning and could contribute to stabilizing coexistence under drought. Our results suggest that belowground niche partitioning could mitiga...地下生态位分化（belowground niche partitioning）是维持物种共存与生物多样性的核心机制之一。在气候变化改变土壤水文条件的当下，其重要性愈发凸显。然而，针对气候变化背景下地下生态位分化程度变化的实验验证研究仍较为匮乏。本研究结合氧稳定同位素（oxygen stable isotopes）测定以推断植物吸水深度，并在草原群落中开展极端干旱操控实验。结果表明，尽管干旱胁迫下物种会向浅层土壤迁移，导致种间吸水深度的重叠度上升，但在对照与极端干旱条件下，伴生物种间的吸水深度差异仍可证明地下生态位分化的存在。物种吸水深度分布呈现出截然相反的响应策略，这一共存特征可能是物种在干旱条件下维持一定程度地下生态位分化的关键，或有助于稳定干旱环境中的物种共存格局。本研究结果表明，地下生态位分化或可缓解……