关键词: 水循环变化, 净初级生产力, 气候枢轴点, 干旱梯度

Abstract: Understanding the variations of net primary productivity (NPP) in arid regions of China and the responses to change of water cycle under global climate change is of great significance for optimal allocation of water resource and ecosystem management in arid regions. Based on the water cycle data, climate data and NPP data simulated by CASA model from 2003 to 2017, we analyzed the characteristics of water cycle change and its impact on NPP in arid regions of China. The climate pivot point method was used to quantify the response coefficients and threshold of NPP to changes in water cycle under different drought gradients. The results showed a trend of warming and wetting in the arid regions in China. The annual increase of precipitation, evapotranspiration and soil moisture was 2.94 mm·a^-1, 1.79 mm·a^-1 and 0.0005 m³·m^-3·a^-1 respectively, indicating that water cycle was accelerating in arid regions. The mean NPP in the arid regions of China was 146.82 g C·m^-2·a^-1, with a mean annual increase of 0.93 g C·m^-2·a^-1. The increase areas mainly occurred in northern Shaanxi, Shanxi, southeastern Inner Mongolia and the edge of the Tarim Basin in Xinjiang. Precipitation, evapotranspiration, and soil moisture were significantly positively correlated with NPP (r=0.593, 0.781, and 0.702, P<0.05). NPP was mostly sensitive to evapotranspiration. When precipitation, evapotranspiration, and soil moisture reached the thresholds of 349.05 mm, 391.34 mm, and 0.081 m³·m^-3, NPP changed from below average to above average. Under different drought gradients, NPP in semi-arid region was mostly sensitive to the change of water cycle. The results are helpful for better understanding the interaction between vegetation and water in water-limited areas, and provide theoretical reference for sustainable development and ecological environmental protection in arid areas.

Key words: change of water cycle, net primary productivity, climate pivot point, drought gradient.