Long-term changes in plant phenology, growth, and biomass
Over the 21 years, all phenological periods (green-up, flowering, fruiting, and withering periods) of Stipa purpurea andArtemisia scoparia , except the flowering time of Stipa purpurea , were significantly (p < 0.05) delayed. In contrast, all phenological periods of Astragalus laxmannii were significantly (p < 0.05) advanced. The green-up and fruiting periods of Kobresia humilis were significantly (p< 0.05) delayed, whilst the withering period was significantly (p < 0.05) advanced. The flowering and withering periods of Kobresia humilis were not significantly changed (Fig. 1).
From 1997 to 2017, only the start of the rapid growth phase (Fig. 2a) and the growth peak (Fig. 2b) of Kobresia humilis were significantly (p < 0.05) advanced. Annual peak height, intrinsic rate, and aboveground biomass of Kobresia humilis andAstragalus laxmanni were significantly (p < 0.05) increased (Fig. 2). Aboveground biomass of Artemisia scoparia (Fig. 3i) was significantly (p < 0.05) decreased, but that of Stipa purpurea (Fig. 3l) was not significantly (p > 0.05) changed.