Spatial and temporal dynamics of plant water source distribution in China

Plant water use strategies play a crucial role in regulating soil moisture, mediating plant-climate feedbacks, and influencing species competition and symbiotic relationships. However, the lack of long-term and large-scale studies on plant water sources has significantly limited comprehensive estimations of the spatiotemporal variations in plant water sources and their impacts on ecohydrological processes. To address this challenge, this study compiled literature data from 210 study regions across China and applied a multivariate random forest model to generate a 0.25° × 0.25° spatial resolution map of plant water source distributions in China from 2001 to 2022. The model estimated the proportions of water uptake by plants from different soil depths and groundwater, and analyzed the variations in water sources across different vegetation types, as well as the key factors influencing plant water sources. The model results aligned well with existing experimental studies, demonstrating their reliability in capturing the spatiotemporal distribution and trends of plant water sources. Nationally, plants derived on average 34.64 ± 6.45 % of their water from shallow soil (0–30 cm), 24.60 ± 3.42 % from middle soil (30–60 cm), 32.68 ± 6.74 % from deep soil (>60 cm), and 8.08 ± 4.7 % from groundwater. Significant differences in plant water sources were observed between southern and semi-arid northern regions of China, with plants in the southern regions predominantly relying on shallow and middle depth soil water, while those in the northwestern regions showed a greater dependence on deep soil water and groundwater. The correlation between soil water content and precipitation with variations in plant water sources was found to be more pronounced. Specifically, shallow soil moisture content and precipitation were positively correlated with the proportion of water absorbed by plants from shallow soil, but negatively correlated with the proportion of water absorbed from deep soil. From 2001 to 2022, there was a nationwide trend of an increased proportion of plant water uptake from shallow and deep soil layers, while the proportion from middle and groundwater decreased. This study fills a critical gap in the large-scale integrated study of plant water sources in China, providing valuable data and methodological references for related scientific research. The results of this study also contribute to the understanding of the ability to enhance vegetation adaptation to environmental changes, provide important driving data for ecohydrological model simulations and important data to support a more accurate assessment of ecosystem adaptation and water resource changes in the context of current extreme climate change.