Time-lag effects of NDVI responses to climate change in the Yamzhog Yumco Basin, South Tibet

Vegetation dynamics and their response to climate change is critical for determining the mechanisms of climate derived variations in terrestrial ecosystems. Here, the Normalized Difference Vegetation Index (NDVI) and monthly temperature and precipitation data were employed to examine the spatiotemporal patterns in vegetation dynamics and investigate the time-lag effects of vegetation responses to climate variables in the Yamzhog Yumco Basin, South Tibet, during 2000-2018. The results reveal that the annual average growing season NDVI in the basin was 0.28, with lower values in the mountainous regions and higher values broadly distributed in the lake and river zones. An increasing NDVI trend was observed in nearly 62% of the total vegetation area, with significant changes observed in the western and southern boundaries of the basin. The vegetation areas in the eastern part of basin exhibited a decreasing NDVI trend. The growing season NDVI was positively correlated with temperature and precipitation, with temperature being the primary driving factor for vegetation growth across the entire basin. The cumulative temperature and precipitation of the current and previous months had the strongest impact on NDVI variations. The correlation coefficients between the NDVI, and temperature and precipitation were greater than 0.6 in approximately 72% and 60% of the vegetation area, respectively, with Lag 0-1 accounting for most of these larger correlation coefficients. Future development targets for grassland conservation projects, such as the reasonable livestock capacity, should consider the time-lag effects on vegetation dynamics.

Automated summary

The study focused on vegetation dynamics and their response to climate change in the Yamzhog Yumco Basin from 2000 to 2018. The results showed an increasing trend in NDVI, with temperature being the primary driving factor. Future grassland conservation projects need to consider the time-lag effects on vegetation dynamics.