Exploring the dominant drivers affecting soil water content and vegetation growth by decoupling meteorological indicators

Long-term meteorological drought can cause soil moisture deficiency and hinder vegetation growth, however, the dominant driving force leading to alteration of soil water content (SWC) and vegetation growth condition is still not clearly defined due to the natural coupling between meteorological elements. Here, we decoupled the relationship between precipitation, evaporation and temperature to explore the main driver of impacting SWC and solar-induced chlorophyll fluorescence (SIF) in China by means of binning, partial correlation analysis and structural equation modelling. We found that precipitation led to a positive change in SWC nationally (nonstandardized path coefficient (NSPC) = 0.75, P < 0.001), while its influence gradually decreased from temperate to tropical climate areas. Precipitation had a positive effect on SIF, except in tropical areas (NSPC = 0.7, P < 0.001). The results of the three research methods indicated that the primary factor influencing SIF was evaporation (NSPC = 0.69, P < 0.001), with a significant correlation between SIF and evaporation in approximately 75 % of the country's area. The binning analysis revealed that SIF initially increased and then decreased as evaporation increased. Partial correlation results showed that temperature had a negative impact on both SWC and SIF, while binning results showed that temperature had no significant impact on SWC, and structural equation modelling result showed temperature had relatively less impact on SWC (NSPC = -0.21, P < 0.05) and SIF (NSPC = -0.19, P < 0.01) than precipitation and evaporation. In addition, we found the dominant drivers' influence weakened from temperate to tropical climate areas, which revealed by the area percentage of partial correlation between evaporation and SIF, precipitation and SWC. The same distribution pattern can be seen from NSPC of evaporation and SIF, NSPC of precipitation and SWC.