Abstract: With a combined approach of phospholipid fatty acid (PLFA), community level physiological profiles (CLPPs) and amplified ribosomal DNA restriction analysis (ARDRA), this paper evaluated the effects of methamidophos continuously applied for2 and 4 years on the structural, functional and genetic diversities of soil microbial communities. The results showed that the application of methamidophos reduced the microbial biomass but enhanced the quantity of Gram-negative bacteria, and increased the functional diversity of micriboal communities while decreased their genetic diversity. After 2 years application, high dosage methamidophos had more significant effect on the microbial communities than low dosage methamidophos, while after 4 years application, these two dosages had the similar significant effect, suggesting that different concentrations of methamidophos applied for a long period all had a distinguishable and severe impact on soil microbial communities.

Key words: C-D effect, Reciprocal equation, Cunninghamia lanceolata