Abstract: Since most species of microorganisms in soils are not cultivable in the laboratory, the investigation of their communities is a time-consuming and hard work by traditional culture procedure. Moreover, some wrong conclusions may be drawn. In the past decades, three kinds of culture-independent methods have been developed so that great progress has been made in this field. The biochemical method is to determinate the microbial communities by analysis of phospholipid fatty acids(PLFA)of cell membrane. The metabolism-based approach, through observations of the utilization patterns of 95 single-carbon sources performed on the BIOLOG microplates, can provide a lot of information about the microbial functional groups in the soils. The third method, molecular techniques, is most prevalently used to explore the microbial communities. Briefly, the molecular approach was started with the extraction and purification of total DNA from sample soils, followed by PCR-amplification of 16SrRNA gene with universal or special primers. As the analysis procedure of PCR products is different, a variety of approaches, for example, DGGE, RFLP and T-RFLP, have been established since 1990s. Among them, T-RFLP was developed based on the RFLP in 1997. This method combined ribosomal database project(RDP)into the analysis of microbial communities, and the number and constituents of species within a community were inferred just according to the number and intensity of the terminal restriction fragments of 16S rRNA gene. Performing T-RFLP is simple, with high resolution, and can be carried out automatically. Therefove it will play more and more important role in future research in microbial ecology of soils.

Key words: Urban forests, Structure, Vegetation quantity, Human disturbance