Abstract: By using GIS spatial analysis method and L3JRC remote sensing data, the spatiotemporal patterns of grassland fire on the Mongolian Plateau in 2000-2007 were examined, and the difference in the grassland fire activities between Inner Mongolia and Mongolia was compared. The effects of vegetation, climate, and human disturbance on the grassland fire were also analyzed. There existed significant difference (P<0.001) in the burned area ratio among three vegetation types, and decreased in the order of meadow steppe > typical steppe > desert steppe. The grasslands in Mongolia had significantly higher burned area ratio than those in Inner Mongolia (P<0.001), and the fire frequency had the same pattern with the burned area ratio. The fire activity differed significantly among years. The burned area ratio was negatively correlated with the annual precipitation in meadow steppe (r²=-0.54, P<0.05) and typical steppe (r²=-0.61, P<0.05). Fire activity also showed monthly variation, occurring mostly in spring and autumn when the weather was dry and windy. It was found that Inner Mongolia had much higher human population and livestock density but lower burned area ratio than Mongolia, suggesting that human disturbance, overgrazing in particular, was the major factor inducing the different patterns of grassland fire between Inner Mongolia and Mongolia.

Key words: Mongolian Plateau, grassland, fire activity, burned area, burned area ratio, fire frequency, soil organic matter, spatial interpolation, regression Kriging, geographically weighted regression Kriging.