Diverse Responses of Phenology in Multi-Grassland to Environmental Factors on Qinghai–Tibetan Plateau in China.

Studying grassland vegetation growing seasons' spatial patterns and their environmental controls are crucial to promoting vegetation ecological restoration, formulating effective disaster prevention and reduction measures and building a stable ecological barrier. However, multi-grassland phenological factors are different, and this has not been well studied before. In this paper, the spatiotemporal patterns of the start of the growing season (SOS) and the end of growing season (EOS) in the grassland were investigated using the Normalized Difference Vegetation Index (NDVI) on the Qinghai–Tibetan Plateau (QTP) from 2000 to 2019. At the same time, we analyzed the environmental factors (including extreme, mean climate, drought, solar radiation, etc.) regulating grassland phenology under the ongoing conditions of climate change. The results show that the SOS appeared first in mountain meadow, shrub tussock, temperature steppe and desert, and then in alpine steppe and alpine meadow, showing a significant advancing tendency in all types. The EOS occurred first in the temperature steppe, alpine steppe and alpine meadow, and then in the mountain meadow, shrub-tussock and desert. Further analysis indicated that reductions in the annual lowest value of daily min temperature (TNN), annual highest value of daily min temperature (TNX) and temperature vegetation dryness index (TVDI), and increases in annual maximum consecutive 5‐day precipitation (RX5day) advanced the grassland spring phenology, whereas the increase in solar radiation (SR) delayed the grassland spring phenology. We also found that the decrease in TVDI and TNN and the increase in yearly mean value of temperature (MAT_MEAN), yearly mean value of daily maximum temperature (MAT_MAX) and yearly mean value of daily minimum temperature (MAT_MIN) advanced the autumn phenology. The EOS and its change rate advanced and increased with increasing altitude, respectively. [ABSTRACT FROM AUTHOR]