Dynamic monitoring of vegetation phenology on the Qinghai-Tibetan plateau from 2001 to 2020 via the MSAVI and EVI

Vegetation phenology is a key parameter for monitoring ecosystems and climate change. In response to the shortcomings of the Normalized Difference Vegetation Index (NDVI) in previous studies, the Modified Soil-Adjusted Vegetation Index (MSAVI) was applied to the Qinghai-Tibetan Plateau (QTP) for the first time in this study. The MSAVI and Enhanced Vegetation Index (EVI) were used to extract the vegetation phenology of the QTP from 2001 to 2020 via the dynamic threshold method. The results revealed that the slope of the start of the growing season (SOS) was − 0.11 days per year (d/a) (p > 0.05), with a mean value of 131.10 days; the slope of the end of the growing season (EOS) was 0.22 d/a (p < 0.05), with a mean value of 266.64 days; and the slope of the length of the growing season (LOS) was 0.33 d/a (p < 0.05), with a mean value of 135.54 days. Compared with the results of previous studies based on the NDVI, the increase in and range of the LOS in this study were smaller. In addition, we found that the EOS, rather than the SOS, played a dominant role in increasing the LOS in this study. The findings of this study are valuable for vegetation monitoring and ecological conservation on the QTP.