Abstract: y using the approaches of grid and stratum sampling, twenty seven 0-20 cm soil samples located by GPS were collected from Chengdu suburbs to study the spatial distribution and species diversity of Bacillus spp. The isolation, counting, and identification of Bacillus spp. were made with conventional methods, and the spatial variability was performed by the software ArcGIS 90 with geostatistical component. The total number of culturable Bacillus spp. was comparatively high, being 4.30×10³-8.53×10⁵ cfu·g^-1 dry soil, and the Bacillus mainly exhibited strip and partially aggregative spatial distribution patterns. The individuals of soil Bacillus increased gradually from southwest to northeast, and the spatial probability distribution of Bacillus spp. (>1.693×10⁵ cfu·g^-1 dry soil) mainly presented strip or partially aggregative shape, with the probability grade increased gradually from south to north and from west to east. Based on the characteristics of morphology and physiology/biochemistry, 21 Bacillus species from 333 isolates were identified, among which, B. circulans, B. megaterium, B. licheniformis, and B. cereus were the dominant species. The richness index, species diversity index and evenness index were high, being 7.259±1.375, 1.368±0.237 and 0.698±0.115, respectively, but the ecological dominance index was low (0.319±0.094), which suggested that in Chengdu suburbs, soil Bacillus spp. were comparatively abundant and had a relative balance among the species, but the prevalent species were not obvious.

Key words: Black soil, Water-stable aggregate, Nutrient status