Soil microbial life in vivo is a major component of soils throughout the whole process of soil development. The living environment for soil microorganisms is a very sensitive early-warning indicator of change in soil ecosystems. Using slope cropland as a contrast, we investigated the main soil microbial populations, microbial biomass carbon (MB_C), nitrogen (MB_N), and phosphorus (MB_P) and their fractal characteristic model, as well as soil enzyme activities under seven grain-for-green patterns (cultivation of Zenia insignis, Toona sinensis, Castanea mollissima, Citrus reticulate, Zenia insignis + Guimu No. 1 forage, Guimu No. 1 forage, and abandoned cropland) in depressions between karst hills. The main soil microbial populations differed under different grain-for-green patterns. Actinomycetes were 71.28% to 96.44% of the microbial population in the slope cropland, Zenia insignis + Guimu No. 1, Guimu No. 1, and abandoned cropland. Differences in their populations covered up to three orders of magnitude. Bacteria dominated in the other four soils, being 55.24% to 71.79% of the microbial population, but fungi were less than 1%. Bacteria were highest under Guimu No. 1 and abandoned cropland, and were lowest in the slope cropland. Fungi populations were in the order: abandoned cropland > Zenia insignis > Guimu No. 1 > Citrus reticulate > Castanea mollissima > slope cropland > Toona sinensis > Zenia insignis + Guimu No. 1, with significant differences between them. All the grain-for-green patterns except Zenia insignis increased total soil microbial populations. The differences between Guimu No. 1, abandoned cropland, and Zenia insignis + Guimu No. 1 were significant (P<0.05), and were significantly higher than the others. Microbial biomass carbon (MB_C) in the all grain-for-green patterns except Zenia insignis was significantly higher than in the slope cropland, and was highest in the abandoned cropland. Microbial biomass nitrogen (MB_N) varied within a small range, showing a downward trend. Differences in MB_N between cultivation of Zenia insignis + Guimu, Citrus reticulata, Zenia insignis and slope cropland were significant (P<0.05). Microbial biomass phosphorus (MB_P) varied widely in Toona sinensis, Castanea mollissima, abandoned cropland and Guimu No. 1 but was significantly higher than in slope cropland. MB_C was well correlated with bacteria (D=-4.07, R=0.81, P<0.01), followed by the correlation between MB_C and actinomycetes (D=3.82, R=0.44, P<0.05) and that between MB_N and fungi (D=0.58, R=0.61, P<0.01). However, there was no fractal relationship between the other microbial biomass and microbial populations. Compared with the slope cropland, all the grain-for-green patterns except Guimu No. 1 forage significantly increased the activities of soil sucrase, urease and phosphatase, suggesting an increase in carbon and nitrogen cycling. Under different grain-for-green patterns, the activity of soil sucrase was highest under Toona sinensis, reaching (29.10±7.73) mg g^-1 d^-1, while the activity of soil urease was highest in the abandoned cropland, reaching (540.7±34.77) μg g^-1 d^-1, and the activity of soil phosphatase was highest under Castanea mollissima, reaching (991.1±76.28) μg g^-1 d^-1. All the grain-for-green patterns improved soil microbial properties, suggesting important benefits arising from fragile ecosystem restoration and reconstruction in depressions between karst hills.