Abstract：
Investigations into the carbon cycle and how it responds to climate change at the national scale are important for a comprehensive understanding of terrestrial carbon cycle and global change issues. Contributions of carbon fluxes to the terrestrial sink and the effects on climate change are still not fully understood. In this study, we aimed to explore the relationship between ecosystem production (GPP/SIF/NDVI) and net ecosystem carbon exchange (NEE) and to investigate the sensitivity of carbon fluxes to climate change at different spatio-temporal scales. Furthermore, we sought to delve into the carbon cycle processes driven by climate stress in China since the beginning of the 21st century. To achieve these objectives, we employed correlation and sensitivity analysis techniques, utilizing a wide range of data sources including ground-based observations, remote sensing observations, atmospheric inversions, machine learning, and model simulations. Our findings indicate that NEE in most arid regions of China is primarily driven by ecosystem production. Climate variations have a greater influence on ecosystem production than respiration. Warming has negatively impacted ecosystem production in Northeast China, as well as in subtropical and tropical regions. Conversely, increased precipitation has strengthened the terrestrial carbon sink, particularly in the northern cool and dry areas. We also found that ecosystem respiration exhibits heightened sensitivity to warming in southern China. Moreover, our analysis revealed that the control of terrestrial carbon cycle by ecosystem production gradually weakens from cold/arid areas to warm/humid areas. We identified distinct temperature thresholds (ranging from 10.5 to 13.7 °C) and precipitation thresholds (approximately 1400 mm yr-1) for the transition from production-dominated to respiration-dominated processes. Our study provides valuable insights into the complex relationship between climate change and carbon cycle in China.
摘要：
对碳循环及其在国家范围内如何应对气候变化的调查对于全面了解陆地碳循环和全球变化问题至关重要。碳通量对陆地汇的贡献以及对气候变化的影响仍未完全了解。在这项研究中,我们的目的是探索生态系统生产（3GPP/SIF/NDVI）与净生态系统碳交换（NEE）之间的关系，并在不同时空尺度上研究碳通量对气候变化的敏感性。此外，自21世纪初以来，我们试图深入研究中国由气候压力驱动的碳循环过程。为了实现这些目标，我们采用了相关性和敏感性分析技术，利用广泛的数据源，包括地面观测，遥感观测，大气反转,机器学习,和模型模拟。我们的发现表明，中国大多数干旱地区的NEE主要是由生态系统生产驱动的。气候变化对生态系统生产的影响大于呼吸。变暖对中国东北地区的生态系统生产产生了负面影响，以及亚热带和热带地区。相反，降水的增加加强了陆地碳汇，特别是在北部凉爽干燥的地区。我们还发现，中国南方的生态系统呼吸对变暖的敏感性增强。此外，我们的分析表明，从寒冷/干旱地区到温暖/潮湿地区，生态系统生产对陆地碳循环的控制逐渐减弱。我们确定了从生产主导到呼吸主导的过程的不同温度阈值（范围为10.5至13.7°C）和降水阈值（约1400mmyr-1）。我们的研究为中国气候变化与碳循环之间的复杂关系提供了宝贵的见解。
