研究揭示干旱對植物群落的調控機制
近日，中科院沈陽生態(tài)所生態(tài)計量化學團隊以植物群落養(yǎng)分計量為核心，基于草地樣帶調查和控制實驗的多源數(shù)據開展定量評估，闡釋了植物對長期和短期水分脅迫的響應機制。相關成果發(fā)表于《生態(tài)學》（Ecology）。
在全球氣候變化背景下，內蒙古草原干旱強度和頻度呈多發(fā)趨勢。水分是該生態(tài)系統(tǒng)植物生存和繁衍的主要驅動因子，干旱事件將對草原生態(tài)系統(tǒng)結構和功能產生深遠影響。
氮和磷是影響陸地生態(tài)系統(tǒng)植物生存、生長和繁殖的主要因子。因此，該團隊以群落養(yǎng)分計量為全新理念和視角，探究水分脅迫對生態(tài)系統(tǒng)結構和功能影響的內在機制和過程，厘清種內和種間的競爭作用關系對群落結構和動態(tài)的影響，旨在為理解草地退化機制、加快退化草地恢復提供參考。
研究結果顯示，長期水分脅迫下，植物通過內穩(wěn)態(tài)機制提高養(yǎng)分濃度，增強群落的抵抗能力，物種周轉是該過程的主要影響因素，但在短期干旱條件下，群落養(yǎng)分對水分脅迫的響應更復雜。整體而言，群落氮濃度上升、磷濃度下降時，種內競爭和物種周轉共同影響該生態(tài)過程。此外，不同區(qū)域群落養(yǎng)分響應程度具有明顯差異。極度干旱地區(qū)，植物群落養(yǎng)分抵御水分脅迫的能力最強，響應最遲緩。
該團隊表示，未來研究應建立大型聯(lián)網干旱實驗平臺，緊密結合控制實驗和自然梯度實驗，提高實驗結果的準確性和有效性，為建立草地生態(tài)系統(tǒng)自然評估體系提供重要理論依據。（來源：中國科學報唐鳳）
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Differential responses of canopy nutrients to experimental drought along a natural aridity gradient
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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.