The Effects of Asymmetric Diurnal Warming on Vegetation Growth of the Tibetan Plateau over the Past Three Decades

Temperatures over the past three decades have exhibited an asymmetric warming pattern between night and day throughout the Tibetan Plateau. However, the implications of such diurnally heterogeneous warming on vegetation growth is still poorly understood. In this paper, we evaluate how vegetation growth has responded to daytime and night-time warming at the regional, biome, and pixel scales based on normalized difference vegetation index (NDVI) and meteorological data from 1982 to 2015. We found a persistent increase in the growing seasonal minimum temperature (T-min) and maximum temperature (T-max) over the Tibetan Plateau between 1982-2015, whereas the rate of increase of T-min was 1.7 times that of T-max. After removing the correlations between T-min, precipitation, and solar radiation, we found that the partial correlation between T-max and NDVI was positive in wetter and colder areas and negative in semi-arid and arid regions. In contrast, the partial correlation between T-min and NDVI was positive in high-cold steppe and meadow steppe and negative in montane steppe or wet forest. We also found diverse responses of vegetation type to daytime and night-time warming across the Tibetan Plateau. Our results provide a demonstration for studying regional responses of vegetation to climate extremes under global climate change.