Abstract: The expansion of construction land during urbanization is bound to occupy the cultivated land, grassland, and other ecological lands, and to destroy ecosystem structure and function. Clarifying the change of ecological risk in urban expansion is of great significance for urban land planning and risk control. Here, we established an ecological risk evaluation system of “Hazards Exposure InfluenceResponse” based on the urban land expansion in Hohhot. The ecological risk of Hohhot in 1990, 2001, 2010, and 2016 was assessed and ranked. The results showed that the scope of urban land in Hohhot was expanding continuously, with increasing expansion rate and intensity. There were significant differences in the expansion intensity and change tendency of construction land among the four precincts of Hohhot. Temporally, the comprehensive ecolo-gical risk of Hohhot and its four precincts showed an upward trend. The ecological risk increased from low level to moderate level. There was a strong correlation between risk value and urbanization intensity index. Spatially, the comprehensive ecological risk level was gradually reduced from urban center to the edge. The spatial variation of risk value was affected by urbanization intensity. The highest risk proportion in Hohhot was from lower level to moderate level. There was a significant difference in the proportion of risk levels among the four precincts. The comprehensive ecological risk values of the four precincts were represented by Yuquan > Huimin > Saihan > Xincheng, which is consistent with the urbanization intensity index.

Key words:  , mechanistic model of light-response, light-use efficiency,  , tomato, model of light-use efficiency.