The Variations Of Soil Microbial Biomass N,P In An Oak Forest And A Pine Plantation In Xiashu Experinmental Site

MB-N and MB-P play an important role in plant nutrients availability and circulation of N and P in soil. To clarify the seasonal variation of MB-N,MB-P and the effection of litter falls on them, at the same time, to understand the difference of MB-N,MB-P between pine plantation and oak secondary forest, we conducted this experinment in Xiashu Experinmental Site from April of 2006 to April of 2007.1. The seasonal variation of MB-N was indicated that maximum of MB-N was in the summer at both control and litter exclusion treatment, its minimum was in the spring at the litter exclusion treatment, in autumn at the control treatment.2. The seasonal variation of MB-P was as follows: Oak and Pine had two peak values; the maximum was in the summer and early winter in the litter exclusion treatment and in the control site. MB-P minimum was in spring at control in pine and oak, at litter exclusion sites in pine, But MB-P minimum was in latter winter (February) at litter exclusion sites in oak.3. The seasonal variation of Avail-P was as follows: there were two peak values in the oak forest, and one in the pine plantation. Avail-P in the oak forest was bigger than that in the pine plantaiton.4. To compare MB-N and MB-P between two stands, MB-N and MB-P in the oak forest were bigger than that in the pine plantation. MB-N and MB-P in the control site were higher than that in the litter exclusion site.5. The sensitivity of MB-N and MB-P to plant litter fall was in order as MB-N in the oak forest >MB-P in the oak forest >MB-P in the oak forest >MB-N in the pine plantation.6. The litter fall in the oak forest was higher than that in the pine plantation. The maximum of litter fall in the pine plantation was in the October and the minimum was in January. The maximum in the oak forest was in the December, and the minimum in the March.