Abstract:

Effects of nitrogen deposition on soil microorganism were evaluated in a Chinese fir plantation subjected to simulated nitrogen deposition for seven years at Shaxian State Forest Farm of Fujian Province, China. Nitrogen loadings were designed at 4 levels as N0 (control), N1, N2 and N3 at the doses of 0, 60, 120 and 240 kg·hm^-2a^-1N, respectively. Low nitrogen deposition (N1) promoted soil microbial biomass, microbial activity, and ability of carbon source utilization by microbes, but intermediate and high nitrogen deposition (N2, N3) showed the opposite effect. All kinds of nitrogen deposition were able to influence microbial community functional diversity. The low nitrogen deposition increased the richness and evenness of microbial community, while the intermediate and high nitrogen deposition reduced these parameters. Principal component analysis (PCA) in substrates indicated that the main carbon sources for soil microbes were carbohydrates and carboxylic acid in all treatments and there were significant differences in carbon substrate utilization patterns between treatments. Our results indicated that functional diversity of soil microbes was altered by nitrogen deposition and the ability of microbes to utilize carbon source and the type of carbon sources were affected by different nitrogen deposition intensities.

Key words: nitrogen deposition, Cunninghamia lanceolata plantation, soil microorganism, BIOLOG