Nutrient enrichment shifts peak water‐use efficiency to wetter conditions in an alpine meadow

作者：Tingting Li, Furong Wang, Yicheng He, Ruiyang Zhang, Jinsong Wang, Shuli Niu, Dashuan Tian · 发表于：Journal of Ecology · 年份：2025 · DOI：10.1111/1365-2745.70077 · 被引用次数：3 · 研究领域：Plant Water Relations and Carbon Dynamics、Hydrology and Watershed Management Studies、Tree-ring climate responses

Abstract Ecosystem water‐use efficiency, the ratio of gross ecosystem productivity to plant transpiration, is found to show a hump‐shaped response to extreme water variations (with a peak at moderate water level). This peak water‐use efficiency represents maximum carbon gain per unit of water consumed, with its associated water threshold indicating the optimal water level to maximize carbon uptake. However, it remains unclear whether widespread nutrient enrichment alters this peak water‐use efficiency and its associated water threshold. Here, we conducted a 6‐year field experiment involving precipitation reduction and multiple nutrient additions in an alpine meadow on the Qinghai‐Tibet Plateau. A wide water gradient is created by combining experimental precipitation manipulation and interannual precipitation fluctuations. Our results showed a consistent hump‐shaped response of ecosystem water‐use efficiency to water variations in control, nitrogen addition, nitrogen + phosphorus addition and nitrogen + phosphorus + potassium addition treatments. While nutrient addition had little effect on peak water‐use efficiency, it significantly increased the associated water threshold by 16.9%–25.2% (from 540 mm to 631–676 mm). This increase was primarily caused by a U‐shaped transpiration response, but not the positive responses of gross ecosystem productivity to precipitation across all treatments. Specifically, nutrient addition elevated the transpiration water threshold (the water le...