Assessment of the importance of increasing temperature and decreasing soil moisture on global ecosystem productivity using solar‐induced chlorophyll fluorescence

The accurate assessment of the global gross primary productivity (GPP) of vegetation is the key to estimating the global carbon cycle. Temperature (Ts) and soil moisture (SM) are essential for vegetation growth. It is acknowledged that the global Ts has shown an increasing trend, yet SM has shown a decreasing trend. However, the importance of SM and Ts changes on the productivity of global ecosystems remains unclear, as SM and Ts are strongly coupled through soil-atmosphere interactions. Using solar-induced chlorophyll fluorescence (SIF) as a proxy for GPP and by decoupling SM and Ts changes, our investigation shows Ts plays a more important role in SIF in 60% of the vegetation areas. Overall, increased Ts promotes SIF by mitigating the resistance from SM's reduction. However, the importance of SM and Ts varies, given different vegetation types. The results show that in the humid zone, the variation of Ts plays a more important role in SIF, but in the arid and semi-arid zones, the variation of SM plays a more important role; in the semi-humid zone, the disparity in the importance of SM and Ts is difficult to unravel. In addition, our results suggest that SIF is very sensitive to aridity gradients in arid and semi-arid ecosystems. By decoupling the intertwined SM-Ts impact on SIF, our study provides essential evidence that benefits future investigation on the factors the influence ecosystem productivity at regional or global scales.准确评估全球植被的总初级生产力 (GPP) 是估计全球碳循环的关键。温度 (Ts) 和土壤湿度 (SM) 是植被生长的必要条件。人们承认, 全球温度呈现上升趋势, 但SM却呈现下降趋势。然而, SM和Ts的变化各自对全球生态系统生产力的重要性仍不清楚, 因为SM和Ts通过土壤-大气相互作用而紧密耦合。住用太阳诱导的叶绿素荧光 (SIF) 作为GPP的代表, 对SM和Ts的变化进行解耦, 我们的研究表明, 在60%的植被区Ts升高的促进作用大于SM降低对SIF影响。总的来说, Ts增加可以缓解SM的减少带来的阻力来促进SIF。然而, SM和Ts的重要性在不同植被类型中有所不同。结果表明, 在湿润区, Ts的变化对SIF起着更重要的作用, 但在干旱和半干旱区, SM的变化起着更重要的作用; 在半湿润区, SM和Ts的重要性的差异很难解开。此外, 我们发现SIF对干旱和半干旱生态系统中的干旱梯度非常敏感。通过解耦SM-Ts对SIF的影响, 我们的研究提供了重要的证据, 有利于今后在区域或全球范围内对影响生态系统生产力的因素进行研究。.