Artificial light at night (ALAN) is an emerging environmental stressor in grassland cities, yet its vegetation impacts remain insufficiently quantified at landscape scales. This study examined four representative cities in Inner Mongolia, China—Hailar, Xilinhot, Hohhot, and Bayannur—using VIIRS VNP46A3 nighttime lights (NTL), MODIS MOD13A1 normalized difference vegetation index (NDVI), and MCD12Q1 land-cover data from 2021 to 2023. A harmonized monthly 500 m grassland-pixel dataset was constructed, and seasonal-trend decomposition using LOESS (STL), ordinary least squares (OLS), and geographically weighted regression (GWR) were applied to characterize the NTL-NDVI relationship and its spatial heterogeneity. An integrated framework was then developed to delineate ecological lighting boundaries (E-LB) and light-ecological sensitivity zones (LESZ). Results showed expanding ALAN exposure across grasslands and a persistent out-of-phase seasonal pattern between NTL and NDVI. During the growing season, the NTL-NDVI relationship was predominantly negative, with stronger local associations concentrated in peri-urban grasslands and along transport corridors. E-LB/LESZ mapping identified ring-like spillover around built-up areas and corridor-shaped extensions along linear infrastructure, forming high-sensitivity belts that often extended beyond administrative boundaries. These findings support the use of E-LB/LESZ as a spatially explicit basis for dark-sky conservation and differentiated lighting management in grassland cities. • A novel 500 m monthly grassland dataset links VIIRS NTL with MODIS NDVI across four Inner Mongolian cities. • Artificial light at night (ALAN) over grasslands shows persistent expansion, with overall intensity decreasing Hohhot > Bayannur > Xilinhot > Hailar. • The NTL–NDVI relationship is characterized by a stable seasonal mismatch and a spatially heterogeneous negative correlation. • Our Ecological Lighting Boundary (E-LB) and Light-Ecological Sensitivity Zone (LESZ) framework delineates ring-like and corridor-shaped ALAN spillover, pinpointing high-risk peri-urban belts and transport corridors. • This integrated framework offers a dynamic, operational tool for dark-sky conservation and targeted lighting governance in grassland cities.
Ding et al. (Wed,) studied this question.