###### Abstract  
Despite the fact that gross primary productivity (GPP) and water use efficiency (WUE) have been widely used as indicators to evaluate the water-carbon cycle, uncertainties exist in the patterns of GPP and WUE responses to climate variability along different aridity gradients. In this study, the aridity index was used to divide China into four arid-humid zones. The spatiotemporal variability of multiple vegetation types GPP and WUE in response to climate change under different arid-humid zones were investigated based on remote sensing data. The results indicated that the increasing trend of WUE in the four arid-humid zones of China was less pronounced than GPP from 2001 to 2021. The GPP value decreased gradually from the humid to the arid zone, and the WUE value in the arid zone was slightly higher than in the semi-arid zone. The GPP of all vegetation types in China showed a tendency to increase, while shrubland and wetland WUE tended to decrease. The major vegetation types (e.g., forest, cropland and grassland) in each aridity gradient contributed to the changes in local GPP and WUE. However, in individual arid-humid zones, wetland and shrubland also exhibited high GPP and WUE values that were not inferior to forest and cropland. Temperature and precipitation were the main climatic factors responsible for the increase in vegetation GPP in different aridity gradients, with a higher positive correlation for temperature than precipitation. WUE showed a distinct positive and negative correlation with the thermal factors (temperature and net radiation) and the moisture factors (precipitation and relative humidity); this pattern was more pronounced in the humid and semi-humid zones. Net radiation and precipitation may be the main climatic factors causing a slight upward trend in WUE across the arid-humid zones, while the decrease in shrubland and wetland WUE may be related to relative humidity and precipitation. GPP; WUE; aridity gradient; climate change; remote sensing; China 20231556317 17 March 202313 March 202313 March 202313 March 202313 March 2023133 March 202313  
that CO\({}_{2}\) fertilization can promote GPP, the GPP trend and influencing factors are still to be determined based on the frequency and intensity of external climate factors [6]. Meanwhile, vegetation carbon sequestration also means water loss, and water use efficiency (WUE) is an important indicator to quantify the coupling relationship between carbon sequestration and water loss [7]. Therefore, understanding the spatiotemporal variation of GPP and WUE as well as their responses to climate change will provide a reference for ecosystem management in the context of global warming. WUE is usually considered to be the ratio of GPP to evapotranspiration (ET), and its accuracy is still limited by the data of GPP and ET [8]. Many studies on the spatiotemporal patterns of GPP and ET have summarized their measurement methods, which can be roughly classified into three types: in-situ measurements, remote sensing techniques, and model simulations [9]. The in-situ measurements are too limited to represent the overall ecological structure of the region, while the complex physical mechanisms and numerous parameters in the model simulations bring greater difficulty and uncertainty to the research work [10; 11]. Remote sensing technology provides a reliable tool for large-scale GPP and ET assessment with the advantages of real-time transmission, rapid processing, and low-ground influence [12]. MOD16 is a global terrestrial evapotranspiration data product developed by the Penman-Monteith equation, with remotely sensed surface features. The accuracy rate of this dataset was 86%, as evaluated using the global flux measured data [13], which is advantageous for studying the spatiotemporal characteristics of ET on a regional scale. In addition, the MOD17 product of MODIS provides GPP data that have been widely used to study the global carbon cycle [14; 15]. [PERSON] et al.