Spatiotemporal variations and hydrothermal controls in the sensitivity of vegetation productivity and ecosystem respiration to precipitation across terrestrial biomes
摘要
The sensitivity of vegetation productivity and ecosystem respiration to precipitation, namely SGPP and SER, is an intrinsic characteristic of vegetation and a key metric for understanding the variations in ecosystem carbon cycle under changing climate. Previous studies typically treat SGPP or SER independently, overlooking their potential interrelationship. Besides, beyond the direct effects of precipitation, temperature likely plays a significant role in shaping both SGPP and SER. In this study, we leveraged the FLUXNET2015 dataset to analyze the global spatiotemporal patterns of SGPP and SER, and applied a mixture regression model to investigate their hydrothermal regulations. The results showed that SGPP and SER varied greatly across biomes, with the higher values in arid ecosystems, while forest ecosystems exhibited relatively low values. Temporal analysis indicated that SGPP and SER significantly increased over time in shrubland, while SER in evergreen needleleaf forest and SER in grassland significantly increased and decreased, respectively. The relationship between SGPP and SER decoupled with increasing leaf area index, with a breakpoint occurring at 1.61 m2 m−2. Across ecosystem types, the decoupling of SGPP and SER was primarily observed in closed-canopy forests, with hydrothermal conditions identified as the key drivers of this phenomenon. Specifically, in forests, SGPP was predominantly regulated by the joint influence of temperature and precipitation, whereas SER was mainly controlled by precipitation alone. Across all ecosystems, SER shifted from being co-regulated by precipitation and temperature to predominantly precipitation-driven as mean annual precipitation (MAP) exceeded 1000 mm, while SGPP transitioned to primarily temperature-dependent above 1500 mm MAP. This study underscores how hydrothermal conditions shape the complex SGPP-SER interplay, providing critical insights for future forest ecosystem research.