Variations Of Soil Microbial Biomass Along Elevation Gradients In Subtropical Area In Wuyi Mountain

Soil microbial biomass is an important component in carbon cycle of the terrestrial ecosystem. And it has a special status in material cycle and energy transformation of forest ecosystem. The study of soil microbial biomass has important meanings in understanding the transformation and cycle of soil nutrient. In the terrestrial ecosystem, the effect of soil microbial biomass to decomposition of organic material and release of soil greenhouse gas has been one of important problems during the global climate change. The study of soil microbial biomass supplies an important base for the influence of predicting the global change on ecosystems.Our research was conducted in a national nature reserve in Fujian Province, which is a typical type in subtropical forest ecosystem. The research on soil microbial biomass in different plant communities along elevation gradients in subtropical forest has not been reported. The article discussed dynamics of soil microbial biomass in different plant communities along elevation gradients and the relationship between soil microbial biomass and different ecological factors in subtropical forest,in Wuyi Mountain. Our object was to provide basic data for carbon flux and its controlling mechanism in subtropical forest ecosystem. The experiment was conducted from June, 2005 to June, 2006. And the data was collected once every two months. Four different plant communities were chosen such as Alpine meadow (AM, elevation: 2100m), Dwarf forest (DF, elevation: 1800m), Coniferous forest (CF, elevation: 1200m) and Evergreen broadleaf forest (EBF, elevation: 500m). Three repeated plots in each plant community were set up, respectively, totally 12 plots. The fumigation-incubation method was applied to measure the variation of soil microbial biomass and the dynamic-chamber IRGA method (Lico-6400) was applied to examine the monthly variation of soil respiration.The changes of soil microbial biomass in four different plant communities along elevation gradients,in central subtropical forest in Wuyi Mountain, and the relationship between soil microbial biomass and ecological factors were analyzed in this paper.The results showed:1. The soil microbial biomass was decreased with the increasing depth of the soil. Soil microbial biomass at 0-10cm depths of soil layer in EBF, CF, DF and AM was 1.32, 1.45, 1.69 and 1.82 times the amount of that at 10-20cm depths of soil layer, respectively. Soil microbial biomass between the upper and down was significantly different (P<0.05);2. The order of the amount of mean annual microbial biomass along elevation was: AM>DF>CF>EBF. Mean soil microbial biomass of AM was 4074.9mg/kg, and it was 2.06, 3.21 and 3.91 times the amount of that of DF, CF and EBF, respectively. The soil microbial biomass in AM was significantly higher than that of DF, CF and EBF (P<0.01); the soil microbial biomass in DF was significantly higher than that in EBF and CF (P<0.05); the differences of the soil microbial biomass in EBF and CF were not significant (P>0.05);3. Soil microbial biomass exhibited a positively significant correlation with the nutrient such as soil organic carbon, total nitrogen, total sulphur, and soil moisture (P<0.05), but it was not significantly related to soil C/N, soil pH value and soil respiration;4. The soil microbial biomass in four different plant communities was highest in early spring and lowest in summer. With elevation gradient increasing, soil microbial biomass in early spring was 2.56,3.31,3.13 and 3.11 times higher than that in summer, respectively. In early spring, soil microbial biomass of AM was1.77, 3.28 and 3.91 times higher than that of DF, CF and EBF, respectively. In summer, soil microbial biomass of AM was 1.78, 3.49 and 3.22 times the amount of that of DF, CF and EBF, respectively.5. Soil microbial biomass exhibited a positively significant correlation with soil moisture at different elevation gradients (P<0.05). Whereas, soil microbial biomass were not significantly related to soil temperature and litterfall biomass (P<0.05).Our research showed soil microbial biomass was increasing along elevation gradients in subtropical forest in Wuyi Mountain; Dynamics of the soil microbial biomass in four different plant communities were very significant, highest in early spring and lowest in summer, respectively; Soil organic carbon, total nitrogen and soil moisture are main controlling factors in soil microbial biomass. These provide basic data for us to indicate carbon flux and its controlling mechanism in subtropical forest ecosystem and further supply important theoretical base for us to predict global climate change.