Drivers of phenology shifts and their effect on productivity in northern grassland of China during 1984–2017—evidence from long-term observational data.

Plant phenology under changing climate is a critical factor controlling terrestrial vegetation productivity. However, large uncertainties exist due to different data sources and phenological parameter extraction methods. In this study, we took advantage of a suite of long-term field observational data in northern grassland of China to investigate the drivers of phenological shifts and their effect on the maximum aboveground net primary productivity (ANPPmax) across four representative grassland types during 1984–2017. Results showed that drivers of phenological events (i.e., start (SOS), end (EOS), and length (GSL) of the growing season) with warming influence dramatically differed among grassland types, indicating that the synergistic effect of temperature and precipitation should be highlighted. For temperate desert steppe and alpine meadow, GSL of dominant species was both significantly lengthened with temperature rising with averaged 0.94 days year−1 (P < 0.001) and 1.15 days year−1 (P < 0.001), respectively, while for typical temperate grassland, GSL was considerably shortened by an average of 0.58 days year−1 (P < 0.01) as a result of water deficit caused by sharp warming and precipitation decreasing in summer and autumn. For most grassland types in our study, both SOS and GSL were significantly correlated with ANPPmax under different precipitation gradients with SOS advanced and GSL extended leading to higher ANPPmax. Only the typical temperate grassland presents a relatively poor correlation between phenological events and productivity. Furthermore, compared with GSL, ANPPmax was more sensitive to the advancement of SOS for every 1-day phenological change. However, the effect of EOS on ANPPmax across the four grassland types was much weaker and unstable. There were spatial response differences between ANPPmax and phenological transition events, with the temperate meadow grassland tending to be more sensitive compared with three other grassland types. [ABSTRACT FROM AUTHOR]