研究揭示干旱对植物群落的调控机制
近日，中科院沈阳生态所生态计量化学团队以植物群落养分计量为核心，基于草地样带调查和控制实验的多源数据开展定量评估，阐释了植物对长期和短期水分胁迫的响应机制。相关成果发表于《生态学》（Ecology）。
在全球气候变化背景下，内蒙古草原干旱强度和频度呈多发趋势。水分是该生态系统植物生存和繁衍的主要驱动因子，干旱事件将对草原生态系统结构和功能产生深远影响。
氮和磷是影响陆地生态系统植物生存、生长和繁殖的主要因子。因此，该团队以群落养分计量为全新理念和视角，探究水分胁迫对生态系统结构和功能影响的内在机制和过程，厘清种内和种间的竞争作用关系对群落结构和动态的影响，旨在为理解草地退化机制、加快退化草地恢复提供参考。
研究结果显示，长期水分胁迫下，植物通过内稳态机制提高养分浓度，增强群落的抵抗能力，物种周转是该过程的主要影响因素，但在短期干旱条件下，群落养分对水分胁迫的响应更复杂。整体而言，群落氮浓度上升、磷浓度下降时，种内竞争和物种周转共同影响该生态过程。此外，不同区域群落养分响应程度具有明显差异。极度干旱地区，植物群落养分抵御水分胁迫的能力最强，响应最迟缓。
该团队表示，未来研究应建立大型联网干旱实验平台，紧密结合控制实验和自然梯度实验，提高实验结果的准确性和有效性，为建立草地生态系统自然评估体系提供重要理论依据。（来源：中国科学报唐凤）
Differential responses of canopy nutrients to experimental drought along a natural aridity gradient
Abstract The allocation and stoichiometry of plant nutrients in leaves reflect fundamental ecosystem processes, biotic interactions, and environmental drivers such as water availability. Climate change will lead to increases in drought severity and frequency, but how canopy nutrients will respond to drought, and how these responses may vary with community composition along aridity gradients is poorly understood. We experimentally addressed this issue by reducing precipitation amounts by 66% during two consecutive growing seasons at three sites located along a natural aridity gradient. This allowed us to assess drought effects on canopy nitrogen (N) and phosphorus (P) concentrations in arid and semiarid grasslands of northern China. Along the aridity gradient, canopy nutrient concentrations were positively related to aridity, with this pattern was driven primarily by species turnover (i.e., an increase in the relative biomass of N‐ and P‐rich species with increasing aridity). In contrast, drought imposed experimentally increased N but decreased P concentrations in plant canopies. These changes were driven by the combined effects of species turnover and intraspecific variation in leaf nutrient concentrations. In addition, the sensitivity of canopy N and P concentrations to drought varied across the three sites. Canopy nutrient concentrations were less affected by drought at drier than wetter sites, because of the opposing effects of species turnover and intraspecific variation, as well as greater drought tolerance for nutrient‐rich species. These contrasting effects of long‐term aridity vs. short‐term drought on canopy nutrient concentrations, as well as differing sensitivities among sites in the same grassland biome, highlight the challenge of predicting ecosystem responses to future climate change.