Widespread Increasing Ecosystem Water Limitation During the Past Three Decades in the Yellow River Basin, China

Terrestrial ecosystems provide crucial ecosystem services to human beings, and their functions are largely dependent on soil moisture availability. Although many studies have evaluated the effects of vegetation and climate changes on soil moisture at the ecosystem scale, changes in ecosystem water limitation remain poorly understood. This study evaluated the spatiotemporal changes of ecosystem water limitation in the Yellow River Basin (YRB)—the second largest river basin of China—during 1982–2016 and identified the major drivers by establishing ecosystem limitation index (ELI) using soil moisture, transpiration, net radiation, and air temperature. The results show a significant and widespread spatiotemporal increase in the water limitation of ecosystems in YRB during the 35-year study period. Temporally, areas with positive ELI (water-limited regime) exhibited a significant upward trend (p < 0.01). Spatially, above 75.0% of the total areas showed an upward trend in ELI. Almost all ecosystems showed significant upward trends in water limitation over this period. Further analysis using two different but comparable methods, partial correlation and Lindeman-Merenda-Gold, show that vegetation change was the major driver of changes in water limitation, with contributions of more than 35.0%. Air temperature and atmospheric CO₂ changes contributed comparably to changes in positive ELI, followed by precipitation changes. These findings improve the understanding of the spatiotemporal pattern and underlying mechanisms of ecosystem water limitation in the greening and warming YRB.