Abstract: Choosing the 20 cm,40 cm and 60 cm soil layerof different landuse patterns such as woodland and farmland in Guilin,Chongqing and Guizhou,andusing dilution plate method,the number of soil Bacteria,Actinomycetes,Fungi have been counted,the results show that:(1) Compared with non-karst areas,theBacteria and Actinomycetes were significantly higher in karst areas,but the the number of Fungi is opposite,and the total amount of microbes in karst area is higher than that in non-karst area;(2) In the soil of karst areas,thenumber of Bacteria was superior.Its proportion reaches 94.7% in summer and 93.8% in autumn,followed by Actinomycetes,33.1% in summer and 55.4% in autumn,then the Fungi reaches 55.9% in summer and 4.4% in autumn;(3) The amount of microorganisms changes with the time and space.In summer the amount ofmicroorganisms is significantly higher than that in autumn,and the amount of Bacteria exists the same trend in different regins but this trend is not significant in the Fungi and Actinomycetes.The factors causing such differences include soil physical and chemical properties,microbial physiological characteristicsand other factors.

Key words: karst environment, soil microbial quantity, comparative study, southwest China