Divergent Shifts in the Climatic Controls of Phenology Across Great Plains Grasslands

Abstract Vegetation phenology serves as a highly sensitive indicator of climate change with the effects of warming on vegetation phenological dynamics extensively documented. However, the role of precipitation variability in shaping vegetation phenology remains relatively under‐explored, particularly in grassland ecosystems where precipitation is often a critical driver of seasonal vegetation dynamics. The Great Plains (GP), one of the largest grassland‐dominated regions globally, provides an ideal setting to investigate the climatic determinants of spatiotemporal variations in vegetation phenophases and their potential changes. Here, we used contiguous solar‐induced chlorophyll fluorescence data sets to derive the timing of three key phenophases—the start of the growing season (SOS), the peak of the growing season (POS), and the end of the growing season (EOS)—across GP grasslands from 2000 to 2021. Our findings indicate that temperature predominantly determined SOS and POS in the northern and central GP, whereas precipitation played a more dominant role in EOS. Notably, from 2000–2010 to 2011–2021, the influence of precipitation on all three phenological events increased while the influence of temperature decreased. These results were further corroborated using MODIS normalized difference vegetation index time series. Furthermore, projections suggest that temperature limitation on vegetation phenology will be alleviated with warming, while water limitation will intensify in the southern GP, potentially constraining warming‐induced advance of spring phenology.