Abstract: Th ecological distribution and biochemical activity of soil microorganisms have notable differences under six forest types: 1. the total number of soil microbes and that of bacteria and actinomycetes are greatest under evergreen broadleaved forest,then under broadleavedconiferous and homana mixed forest, and least under masson-pine forest, but the number of soil fungi under Chinese fir and masson pine forests is greater than that under Illicium verum and homana forests. 2. the species, groups and genera of bacillus, streptomyces and fungi are more abuncant under broadleaved and coniferous mixed forest and evergreen broadleaved forent than those under mascon pine and Chinese fir forests. 3. the activities of soil microbes and roil enzymes and the soil respiration rate are higher under evergreen broadleaved forest and broadleaved-coniferous mixed forest, and lower under Chinese-fir and masson-pine forests. These results indicate the quick transformation of organic matter, intense biological metabolism and higher fertility and productivity of soils under evergreen broadleaved forest and broadleaved-coniferous mixed forest.

Key words: Inner Mongolia typical steppe, grassland degradation, grassland restoration, carbon sequestration potential, scaling, uncertainty analysis