Abstract: In order to understand the spatiotemporal variation of soil microbial biomass N and its main controlling factors in subtropical forest regions in China, 0-10, 10-25, and 25-40 cm soil samples were collected from the evergreen broadleaf forest (EBF, 500 m a.s.l.), coniferous forest (CF, 1200 m a.s.l.), subalpine dwarf forest (DF, 1800 m a.s.l.), and alpine meadow (AM, 2100 m a.s.l.) along an altitude gradient in the Wuyi Mountains National Nature Reserve, Fujian Province from April 2006 to January 2007. With increasing altitude, the soil microbial biomass N increased significantly, being 106.7, 140.8, 254.9 and 355.8 mg·kg^-1 in 0-10 cm soil layer under EBF, CF, SDF, and AM, respectively, and there was a significant difference (P<0.05)among different altitudes. Soil microbial biomass N was the highest in 0-10 cm layer, and decreased gradually with soil depth. In the four ecosystems, there was a consistent seasonal variation of soil microbial biomass N, i.e., the highest in winter, tended to decrease in spring, and the lowest in summer. Correlation analysis showed that in 0-10 cm soil layer, the main factors controlling the spatial variation of soil microbial biomass N along the altitude gradient were soil moisture, organic matter, and total N, while the main factors regulating the temporal variation of soil microbial biomass N were soil moisture and temperature.

Key words: Arbuscular mycorrhizal fungi, Ecological distribution, Soil, Wild plants