| The forest of China degenerates seriously. The reforestation and rebuilding of the forest become more important. Soil microorganism is very important fact of the reforestation and rebuilding of the forest ecosystem, and also is one of significant assessment index. Up today, the study of soil microorganism of forest in different reforestation stage and their function have not been reported. To study soil microorganism of the evergreen broad-leaved forest in different reforestation stage in western Sichuan and the relation between them and the succession of plants and soil fertility, plots in the same surrounding and background condition were set by the way of time instead of space . The results revealed as the following:1. The numbers of bacteria, actinomycetes and fungi in different reforestation stage and their percentages in total numbers were different. The changes of the numbers and populations of soil microbes were divided into two stages: 50 years ago and 50 years later. In 5 to 40 years forest, the numbers of bacteria and actinomycetes increased with the adding of succession years and reached the growth peak in 40 years forest, which was 9.1 X 105 and 4.9 X 104cfu/g dry soil respectively, the percentage was 94.00% and 5.14% respectively. While in 5-50 years, the number of fungi was stable and the percentage was only 0.87%. After 40 years, the numbers of bacteria dropped down a little. To 100 years, the percentage of bacteria reached the lowest, and was 79.06%; while the number of fungi increased very fast and reached the highest at this stage and the percentage increased from 0.87% to 15.38%. At this stage, the forest ecosystem and the numbers and groups of soil microorganism became relatively stable.The results showed that the litters of secondary forest were decomposed mainly by the bacteria in 50 years; while in 100 years the decomposition ability of bacteria declined, that of the fungi increased.2. The growth rate of soil microbes in 20 years ago was higher than 20 years later, and the soil organic matter and total nitrogen was the same. So in 20 years ago, the soil fertility rose very quickly; it increased slowly from 20 to 40 years.3. During the reforestation of evergreen broad-leaved forest in western Sichuan, soil microbial community also succeeded. The fungi belonged to Deuteromycetes and Zygomycetes. The frequency of Trichoderma, Pythium, Penicillium, Absidia in the samples was higher and the distribution of Absidia increased gradually with succession. The composition of dominant genus of fungi in different stage was different. With the succession, the variety of dominant genus became richer.In nine groups, the eight groups of the actinomycetes belonged to Streptomyces . The other group was Micromonospora and its distribution density decreased with the succession. Albosporus, Aureus, Griseorubroviolaceus and Micromonospora had higher frequency. With the succession, the variety of dominant genus became richer, and the number and composition also changed. Aureus increased and Micromonospora decreased.As for bacteria, Corynebacterium, Brevibacterium and Bacillus had higher frequency in different stage. In 5 years and 20 years, Corynebacterium and Brevibacterium was dominant genus. In 30 years Cellulomonas(26%) appeared. In 40 years and 50 years, Brevibacterium was the dominant genus. The percentage of Corynebacterium decreased.4. In 5-40 year forest, the total number of soil microorganism was significantly correlated with the diversity of plants, and the contents of soil organic matter, total nitrogen, alkaline hydrolysis nitrogen, total potassium, CEC. The correlation index of soil microbial numbers in autumn with Marglef, Simpsom, Shannon-winner, soil organic matter, total nitrogen, alkaline hydrolysis nitrogen, total potassium and CEC was 0.999*, 0.953*, 0.989*, 0.942*, 0.947*, 0.928*, -0.897*, and 0.917* respectively.5. The activity of invertase and urease reached the highest in 20 years. In other succession years, the activity of the two kinds of enzymes increased with the suc...
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