Variation in plant phenological changes and contributions by climatic drivers across six grassland and desert...

Plant spring phenology advancements have been broadly observed, but the change in autumn phenology has varied greatly among different regions and species under global warming. Moreover, how plant phenology responds to climate change in grasslands and deserts is not well understood compared with that in forests. Here, we used long-term (2005 ~ 2020) phenological and climatic in situ observation data from six grassland and desert sites in China to analyze temporal trends in the start (SOS) and end (EOS) of the growing season for 27 herbaceous and shrub species and their responses to climatic factors. The results demonstrated that 70% of the species presented an earlier SOS and that 59% of the species presented an earlier EOS, which resulted in a shortened growing season (LOS) for 41% of the species. The LOS trends were driven by EOS trends, which had greater variation (1.2 days yr^- 1) than did the SOS trends (0.5 days yr^- 1). The significant changes in EOS were associated mainly with soil moisture in autumn for shrub species. We should be cautious in using the relationship between EOS and SOS to simulate the EOS in models because their correlation is statistically significant only for a small subset of species. This study highlights a greater variability of autumn phenological changes in grassland and desert ecosystems and reveals the critical contributions of spring daytime temperature and autumn soil moisture to phenological changes. We recommend considering the divergent autumn phenological responses to climate factors, especially soil moisture, among plant life forms and species in terrestrial ecosystem models by improving the model structure and involving species-specific parameters.