Abstract: 【Aim】 Carabid beetles are one of the most abundant groups which inhabit soil surface, and they are more sensitive to the change of habitats. The objective of this study is to reveal the mechanisms of formation and stabilization of carabid species biodiversity by analyzing the effects of topographic factors on the distribution pattern of carabid species diversity in the Helan Mountains, northwestern China. 【Methods】 The community structure and species diversity of carabid beetles were investigated from July to August 2015 using pitfall traps in the Helan Mountains. Carabid beetles were caught from 98 sampling plots of five vegetation habitats along the elevation gradient, i.e., mountain needle-leaf forest, mountain broadleaf forest mountain shrub, mountain grassland and piedmont desert grassland. Based on a survey of the 98 sampling plots in the study area, canonical correspondence analysis (CCA) was performed to analyze the relationships between diversity indices and topographic factors, and generalized additive model (GAM) was employed to model the response curves of diversity indices to elevation. 【Results】 A total of 10 989 carabid beetles belonging to 65 species and 21 genera were collected. Of these beetles, Pterostichus gebleri and Harpalus salinus were the dominant species in the area, accounting for 44.93% and 11.33% of the total number of individuals, respectively. Among the habitats, the carabid beetle community in mountain broadleaf forest had the highest species richness while that in mountain needleleaf forest had the highest Shannon-Wiener diversity index. The evenness in piedmont desert grassland was the highest, while its diversity and species richness were the lowest. It was observed that elevation, slope aspect, slope grade, topographic wetness index and profile curvature had significantly integrative effects on the distribution patterns of carabid species diversity. Elevation had significant effects on the distribution patterns of total carabid communities in all the five vegetation habitats, and slope aspect only affected the distribution patterns of mountain needle-leaf forest and piedmont desert grassland significantly. Species richness and the number of individuals had a unimodal pattern with elevation, Shannon-Wiener diversity index increased at first and then remained stable, while the evenness index had a V-shape trend. 【Conclusion】 The distribution patterns of carabid beetles in the Helan Mountains are formed by the synthetic action of a variety of topographic factors, among which elevation plays an important role.

Key words: Carabid beetles, species diversity, distribution pattern, topography, mountainous region, Helan Mountains