Divergent transboundary patterns and ecosystem-dependent drivers of fires across the Mongolian Plateau

Fires, amplified by drought and heat, are increasingly threatening the ecologically fragile Mongolian Plateau (MP). Because of the need for a better understanding of fire dynamics in terms of their characteristics, especially on a diurnal time scale, we quantified spatiotemporal variability of fires and their sensitivity to daily meteorological variations on the MP using satellite observations and meteorological data over the past two decades. We found that forest steppe and grasslands on the eastern and northeastern MP feature the most prominent fire extents and intensities, with extreme fire years occurring approximately once per decade. Furthermore, in Inner Mongolia, fire frequency showed an increasing trend, while the average fire size declined with fluctuations (mean fire size: 2.24 km²). Conversely, Mongolia exhibited the opposite pattern, with a decrease in fire occurrence but an increase in fire size (mean fire size: 29.46 km²). Also, China-Mongolia transboundary fires increased overall, but with marked cross-border differences. In Inner Mongolia, transboundary fires mainly occurred within 5 km of the border, exhibiting declining trends. Conversely, transboundary fires on the Mongolian side displayed an area increase with distance from the border, stabilizing beyond 30 km. Extreme fire events across the MP were predominately driven by hot, dry climatic conditions, yet exhibited divergent ecosystem-dependent influences. Forest ecosystems on the MP showed a 2.02% nonlinear increase in burned area per W/m² rise in solar radiation, with precipitation suppressing it by 8.6%/mm. Steppe ecosystems in the Mongolian Plateau displayed high sensitivity to temperature, with 18.5 and 17.3% nonlinear increases in burned area per °C rise in maximum and minimum temperatures, respectively, whereas vapor pressure deficit induced a 9.42% area expansion per hPa increase.