Microclimate Driven Grassland Greenness Asymmetry Between West- and East- Facing Slopes on the Tibetan Plateau

Slope orientation creates microclimate by modulating water and heat flux between the land surface and the atmosphere, thereby regulating vegetation growth and its response to background climate change. However, the potential asymmetry in vegetation greenness between west- and east-facing slopes remains underexplored. Analyzing the normalized difference vegetation index derived from Landsat reflectances in the Tibetan Plateau (TP) grassland, we identified that west-facing slopes were greener than east-facing slopes in the western TP, while the opposite appeared in the eastern TP. We also detected a stronger greening trend on west- than east- facing slopes over the entire TP grassland from 1991 to 2020. These disparities result from distinct microclimates on the two contrasting slopes: west-facing slopes tend to be wetter and colder than east-facing slopes under similar background climate. Our findings underscore the crucial role of slope orientation in shaping vegetation greenness and its response to climate change.