Bidirectional dependency between vegetation and terrestrial water storage in China

Alterations in water availability strongly impact vegetation growth, and vegetation could affect terrestrial water storage (TWS) by altering surface hydrological processes. Understanding the relationships between vegetation change and terrestrial water conditions in ecosystems is crucial. In the research, the partial correlation was implemented to identify time-lag effects and revealed a non-linear interaction between TWS and the normalized difference vegetation index (NDVI) using the Granger causality approach. The results showed that most vegetation in China underwent significant greening from January 2003 to December 2020, and TWS showed a spatial distribution pattern of increasing in the south and decreasing in the north. TWS and NDVI both had significant mutual lag responses. The proportion of the area with a significant correlation between TWS and NDVI increased from 42 % to 63 % after considering the time-lag effect. NDVI was generally influenced by TWS, with 55 % of TWS in the vegetation cover of China having a causal effect on NDVI; conversely, two different vegetation greening methods regulated TWS in vegetated areas in China, and > 59 % of TWS changes were dependent on NDVI. The effect of vegetation dynamics on surface hydrological processes may increase with increasing aridity. Determining the existence of Granger causality between NDVI and TWS has significant implications in terms of comprehending the relationships between terrestrial vegetation and water within the context of a changing climate and for the sustainable use of carbon–water cycle ecosystem services.