Annual and Seasonal Trends of Vegetation Responses and Feedback to Temperature on the Tibetan Plateau since the 1980s

The vegetation-temperature relationship is crucial in understanding land-atmosphere interactions on the Tibetan Plateau. Although many studies have investigated the connections between vegetation and climate variables in this region using remote sensing technology, there remain notable gaps in our understanding of vegetation-temperature interactions over different timescales. Here, we combined site-level air temperature observations, information from the global inventory modeling and mapping studies (GIMMS) dataset, and moderate-resolution imaging spectroradiometer (MODIS) products to analyze the spatial and temporal patterns of air temperature, vegetation, and land surface temperature (LST) on the Tibetan Plateau at annual and seasonal scales. We achieved these spatiotemporal patterns by using Sen's slope, sequential Mann-Kendall tests, and partial correlation analysis. The timescale differences of vegetation-induced LST were subsequently discussed. Our results demonstrate that a breakpoint of air temperature change occurred on the Tibetan Plateau during 1994-1998, dividing the study period (1982-2013) into two phases. A more significant greening response of NDVI occurred in the spring and autumn with earlier breakpoints and a more sensitive NDVI response occurred in recent warming phase. Both MODIS and GIMMS data showed a common increase in the normalized difference vegetation index (NDVI) on the Tibetan Plateau for all timescales, while the former had a larger greening area since 2000. The most prominent trends in NDVI and LST were identified in spring and autumn, respectively, and the largest areas of significant variation in NDVI and LST mostly occurred in winter and autumn, respectively. The partial correlation analysis revealed a significant negative impact of NDVI on LST during the annual scale and autumn, and it had a significant positive impact during spring. Our findings improve the general understanding of vegetation-climate relationships at annual and seasonal scales.

Automated summary

The study explores the vegetation-temperature relationship on the Tibetan Plateau by analyzing air temperature, vegetation, and land surface temperature (LST) patterns using various datasets. The findings reveal a significant greening response in NDVI during the spring and autumn seasons, with earlier breakpoints and more sensitivity in recent warming phases. Both MODIS and GIMMS data show an increase in NDVI on the Tibetan Plateau for all timescales, with MODIS exhibiting a larger greening area since 2000. Trends in NDVI and LST are most prominent in spring and autumn, respectively, and significant variations in NDVI and LST mostly occur in winter and autumn. The partial correlation analysis reveals a negative impact of NDVI on LST at the annual scale and in autumn, and a positive impact in spring. These findings enhance our understanding of vegetation-climate relationships at annual and seasonal scales.