Abstract: Using high-throughput sequencing technology, we analyzed the structure and diversity of soil bacterial community in cropland and natural grassland in different regions along the agro-pastoral ecotone of Inner Mongolia. The results showed that the relative abundance of soil bacteria in cropland and grassland was similar in the same regions while differing in different regions. Proteobacteria, Actinobacteria, and Acidobacteria were the dominant phyla in soils, accounting for more than 75.1% of the total abundance. The Chao1 index of soil bacteria in grasslands was significantly higher than that of croplands in West Liaohe Plain, Yanshan hilly area, north foot of Yinshan Mountain and Hetao Plain. The Chao1 and Shannon indices of soil bacteria of maize croplands  were significantly higher than those of other croplands. Results of cluster analysis showed that soil bacterial communities could be classified into five categories according to geographical latitude and vegetation types, namely, low latitude, middle latitude, high latitude, grassland, and cropland.

Key words: Inner Mongolia, agro-pastural ecotone, cropland, grassland, soil bacteria, diversity.