Abstract: The environmental heterogeneity caused by topographical diversity is an important mechanism underlying the formation and maintenance of bio-geographic pattern of diversity distribution at the micro-scale, and the prerequisite for the difference in species richness. With the help of GIS and S-Plus, the GAM model was used to study topographic indexes influencing the distribution of grasshopper from July to August, and the relationship between the regional locust richness and terrain complexity was also studied based on the quantitative analysis of topographic variation characteristics of the upper reaches of the Heihe River on the northern slope of the Qilian Mountains. The results showed that in total 13 species (including 3 149 individuals) belonging to 3 families and 10 genera were collected in 36 samples. The order that the richness of grasshopper was influenced by topographical factors was elevation>slope>aspect>profile>plane>position. Grasshopper distribution was almost balanced in the plane of curvature and the gradient profile curvature, and presented a two parabola distribution in elevation, slope and the whole position of slope gradient, showing a decreasing trend. On the regional distribution, there were higher richness of grasshoppers in the whole regions, but they were mainly located in the region with altitudes of 2 600-2 700 m, and mainly concentrated in the northwest and west slopes, which was consistent with actual observation. The relationship between grasshopper richness and terrain factors as well as the grasshopper distribution indicates that the redistribution of water and heat conditions due to topographical factors caused the diversification and fragmentation of grasshopper distribution patterns.

Key words:  Grasslands, grasshoppers, species richness, spatial pattern, topography, generalized additive model (GAM), Qilian Mountains