Abstract: We explored the impacts of different mixed trees on the improvement of soil microecological environment in rhizosphere of Parashorea chinensis, including pure P. chinensis plantation (WC), mixed P. chinensis and Dalbergia odorifera plantation (WJ), mixed P. chinensis and Eucalyptus urophylla × E. grandis plantation (WA). Soil physical and chemical properties were analyzed. The characteristics and distribution of soil microbes in the rhizosphere were measured by the methods of Biolog-Eco micro plate and phospholipid fatty acid methyl ester (PLFA). Soil water content, soil pH, organic matter, total nitrogen, total potassium content and the activities of sucrase, urease and acid phosphatase in rhizosphere soil of WA were significantly higher than those of WC and WJ, without difference between WC and WJ. There were no significant differences in the contents of nitrate nitrogen, ammonium nitrogen, and available potassium between WA and WJ, which were obviously higher than those in WC. There were significant differences in total phosphorus and available phosphorus contents among the three stands, with an order of WJ>WA>WC. The average color change rate (AWCD), Shannon index, Simpson index, McIntosh index and the utilization of six types of carbon source substrates in microorganisms were the highest in the rhizosphere soil of WA, followed by WJ and WC. Results of principal component analysis showed that carbohydrates, amino acids and phenolic acids were the main carbon sources for microbial utilization. In WA, the PLFA content of rhizosphere soil microorganism, bacteria, fungi and actinomycetes was the highest, followed by WJ and WC. There were significant positive correlation between soil physical and che-mical properties and the microbial characteristics. Combining the physical and chemical properties of soil and the functional and structural characteristics of microbial communities, the mixed P. chinensis and E. urophylla × E.grandis plantation may be most conductive to the improvement of the rhizosphere microecological environment and increase soil available nutrients at the young tree phase of P. chinensis.

Key words: Parashorea chinensis, microbial community, rhizosphere, soil