Climate factors (CFs) are key variables shaping the interannual variability (IAV) of terrestrial ecosystem carbon sinks. However, the dominant CFs influencing the IAV of terrestrial carbon sinks remains debated, as CFs are coupled via land-atmosphere interactions. Here, the dominant factors influencing the IAV of global terrestrial net ecosystem production (NEP) were quantified using the convergent cross-mapping (CCM) technique. This analysis was conducted with distinct global terrestrial NEP datasets deriving from process-based ecosystem models, machine learning techniques, and eddy covariance flux towers. Results revealed that the spatial patterns of IAV of global terrestrial NEP were dominated by water availability (WA) and temperature (Ts). Ts mainly controlled the IAV of terrestrial NEP in mid to high-latitude regions of the Northern Hemisphere (NH), while WA exerted dominance over low and mid-latitude regions in both the NH and the Southern Hemisphere. Moreover, the energy limitation and water limitation explained the spatial pattern of Ts and WA dominant on NEP. Further analysis found that WA and Ts also played a dominant role in gross primary productivity (GPP) and terrestrial ecosystem respiration (TER), proving that WA and Ts were the dominant factors affecting NEP. In addition, we found a weakening trend in causal linkages of CFs to NEP in the temporal domain. This study used causal analysis to reveal the spatial patterns of water and heat dominating the NEP, providing support for improved assessment and prediction of terrestrial carbon sinks under climate change.

中文翻译：

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因果推断揭示了复杂的环境-陆地生态系统中碳汇年际变化的主导作用


气候因素（CF）是影响陆地生态系统碳汇年际变化（IAV）的关键变量。然而，影响陆地碳汇 IAV 的主要 CF 仍存在争议，因为 CF 通过陆地-大气相互作用耦合。在这里，使用收敛交叉制图（CCM）技术对影响全球陆地净生态系统生产（NEP）IAV的主导因素进行了量化。该分析是使用源自基于过程的生态系统模型、机器学习技术和涡协方差通量塔的独特全球陆地 NEP 数据集进行的。结果表明，全球陆地 NEP 的 IAV 空间格局主要受可用水量 (WA) 和温度 (Ts) 的影响。 Ts主要控制北半球中高纬度地区陆地NEP的IAV，而WA则对北半球和南半球中低纬度地区起主导作用。此外，能源限制和水资源限制解释了Ts和WA在NEP上占主导地位的空间格局。进一步分析发现，WA和Ts对总初级生产力（GPP）和陆地生态系统呼吸（TER）也起主导作用，证明WA和Ts是影响NEP的主导因素。此外，我们发现 CF 与 NEP 的因果联系在时域上有减弱的趋势。本研究利用因果分析揭示了主导NEP的水和热的空间格局，为改进气候变化下陆地碳汇的评估和预测提供支持。