Effects of climate change on plant growth and phenology
For Kobresia humilis , soil temperature was the most important factor impacting the green-up period (significantly delayed), the flowering period (significantly delayed), and the withering period (significantly advanced), and the optimum thresholds were 38, 54, and 54 days. Maximum air temperature was the most important factor for the fruiting period (significantly delayed), with an optimum threshold of more than 60 days (Tables S2 and S3, Fig. 4a).
For Astragalus laxmannii , soil temperature was the most important factor impacting the start of the rapid growth phase (significantly delayed), with an optimum threshold of 58 days. Air temperature was the most important factor impacting maximum growth (significantly delayed), with an optimum threshold of 48 days. Maximum air temperature was the most important factor determining the end of the rapid growth phase (significantly delayed), and the optimum threshold was more than 60 days (Tables S2 and S3, Fig. 4b).
For Stipa purpurea and Artemisia scoparia , soil temperature was the most important factor impacting the green-up period (significantly delayed), with an optimum threshold of 58 days (Artemisia scoparia ) and 56 days (Stipa purpurea ). Soil temperature was also the most important factor impacting the withering period (significantly advanced) of Artemisia scoparia (optimum threshold of 48 days), whereas for Stipa purpurea , temperature was the most important factor, with an optimum threshold of 40 days (Tables S2 and S3, Fig. 4c and 4d).
Fig. 1 Trends of green-up, flowering, fruiting, and withering periods for Kobresia humilis , Astragalus laxmannii ,Artemisia scoparia , and Stipa purpurea over time. Dots indicate the Julian day, the line indicates the trend of the Julian day by the linear model, grey areas represent the 95% confidence intervals. The solid line indicates p -values < 0.05, the dashed line indicates p -values > 0.05. The blue line represents significant positive correlations, and the red line represents significant negative correlations.
Fig. 2 Trends of the start of the rapid growth phase, the timing of maximum growth and the end of the rapid growth phase forKobresia humilis , Astragalus laxmannii , Artemisia scoparia , and Stipa purpurea over time. Dots indicate the Julian day, the line indicates the trend of the Julian day by the linear model, grey areas represent 95% confidence intervals. The solid line indicatesp -values < 0.05, the dashed line indicatesp -values > 0.05. The blue line represents the significant positive correlations, and the red line represents the significant negative correlations.
Fig. 3 Trends of annual peak height, intrinsic growth rate, and biomass of Kobresia humilis , Astragalus laxmannii ,Artemisia scoparia , and Stipa purpurea over time. Dots indicate annual peak height, intrinsic growth rate, and biomass. The lines indicate the trends of annual peak height, intrinsic growth rate, and biomass by the linear model, grey areas represent 95% confidence intervals. The solid line indicates p -values < 0.05, the dashed line indicates p -values > 0.05. The blue line represents the significant positive correlations, and the red line represents the significant negative correlations.