The Rainy Zone of West China, which is located along the brim of the Sichuan Basin, is a large scale and complicated ecotone and characterized by year-around cloudy and wet climate. There has been an extensive distribution of moist evergreen broad-leaved forest in the rainy zone, but this type of forest had been artificially destroyed because of local concept that evergreen broadleaved forest is “Shaw”. The vegetation in this zone has been effectively recovered in recent years with the execution of “returning sloping cropland to forest" and "natural forest conservation” in our country.
The soil microbial community can have large impacts on plant community dynamics, and the abundance of microbial species in the soil usually is affected by the composition of the plant community. Many studies suggest that the soil microbial community varies with plant community composition, and soil microorganisms can be important drivers of vegetation changes. However, little is known about how soil microbial communities change along a gradient of vegetation succession. In this study, the numbers, composition, microbial flora and diversity of microorganisms were measured using the method of “space-for-time substitution” in different recovery phases of forest at Anzi River Nature Reserve and Qionglai Tiantai National Forest Park. The results indicated that: (1) the quantity of soil microorganisms in different recovery phases of moist evergreen broad-leaved forest showed significant difference (p<0.05). 5 to 40 years after revegetation, the quantity of soil microorganism and bacteria and actinomycetes increased with recovery age and achieved maximum value of 1.06×106 CFU (Coromy Forming Unit) g^-1 dry soil, 9.81×105 CFU g^-1 dry soil and 6.8×104 CFU g^-1 dry soil respectively. The number of soil fungi reached maximum in natural forest (100a) with 9.01×104 CFU g^-1dry soil. There was similar composition of soil microbial community in different recovery phases. Soil microbial flora was mainly composed of bacteria, accounting for 79.06%-93.78% of total microorganisms, and fungi for 0.52%-15.38% and actinomycetes for 4.61%-11.24%; (2) number of soil bacteria and fungi in summer were more than that in spring and in autumn. However, numbers of soil actinomycetes in spring and in autumn were more than that in summer. (3) there were different soil microbial flora and various dominant groups during the process of revegetation. There were 10 genuses that belonged to bacteria and 7 genuses to fungi and 9 genuses to actinomycetes according to identification. Among bacteria, the frequency of the presence of Achromobater, Corynebacterium, Brevibacterium and Bacillus were high; the isolated fungi mainly belonged to Deuteromycetes and Zygomycetes, and the distribution of Trichoderma, Pythium, Penicillium and Absidia in the studied plots were very extensive; of 9 actinomycetes genuses, 8 genuses belonged to Streptomyces and the other genus to Micromonospora. Among them, Albosporus, Aureus and Griseorubroviolaceus had higher distribution frequency. (4) there were higher Shannon-Wiener index and Simpson index at the initial stage of revegetation and the secondary forest (30a) as well as the final recovery phases. After revegetation for 5a to 50a, Shannon-Wiener index and Simpson index of fungi and actinomycetes showed an increasing trends in the fluctuating way with the maximum in the secondary forest (50a), and showed downtrend after 50a, which indicated that the soil environment in the recovery process of from 30a to 50a was suitable for growth of fungi and actinomycetes.