Author(s): Ge Gao; Jia Liu; Yicheng Wang; Josep Penuelas
Linked Author(s):
Keywords: Climate change; Hydrometeorological factors; NPP; Soil carbon-nitrogen; Typical grassland
Abstract: Climate warming and intensified human activities are reshaping the carbon-nitrogen-productivity dynamics of grassland ecosystems. Focusing on a typical grassland watershed in the upper Xilin River, we used an HRU-based DNDC model to simulate SOC, TN, and NPP dynamics from 1981-2019, and applied an interpretable random forest approach to identify key hydrometeorological drivers and their thresholds. Results reveal a pronounced warming-drying trend that has substantially reduced growing-season soil moisture and led to declines in SOC, TN, and NPP. Four factors, May soil water, July soil water, total precipitation, and accumulated temperature, dominate system variability. Threshold analysis indicates sharp NPP reductions when soil moisture falls below 42.5 mm (May) or 55 mm (July, peak growth), whereas SOC and TN accumulation decline markedly once annual accumulated temperature exceeds ~1480-1680 °C. Temperature and moisture exert contrasting controls, with warming enhancing productivity only under sufficient water supply but accelerating soil organic matter decomposition. These findings identify critical hydrometeorological thresholds regulating grassland C-N cycling and productivity, offering insights for ecohydrological resilience assessment and adaptive management under continued climate change.
Year: 2026