Decomposition Of Leymus Chinensis And Phragmites Communis Litter Responses To Simulated Warming And Nitrogen Application In Songnen Grassland

This thesis focuses on Leymus chinensis community and Phragmites communis community litter in Songnen Plain. We examined litter decomposition quality, litter decomposition rate responses to manipulations of four treatments: control, warming, nitrogen application, and warming plus nitrogen application. Meanwhile, the research on organic C content, total nitrogen content, total phosphorus content and microorganism biomass in L. chinensis community and P. communis community litter were completed during the period from 2006 to 2007.After 2 years (we examined 180 days every year), the result showed that acrossing warming and nitrogen application both significant varied litter decomposition rates in a certain extent. The order of decomposition residual rate of L. chinensis community were warming+nitrogen application (69.30%), nitrogen application (75.75%), warming (81.20%), control (83.80%); The order of decomposition residual rate of P. communis community were warming+nitrogen (78.85%), nitrogen application (83.25%), control (85.60%), warming (86.50%); Olson model predicted that warming+nitrogen, nitrogen application and warming treatments shortened the periods of L. chinensis community litter up to 50.02%, 64.71%, 84.61%; meanwhile, warming+nitrogen, nitrogen application treatments shortened periods of P. communis community up to 64.84%, 81.80%. The linear regression showed that the regression coefficient of bacteria was the max among four treatments of two species; we can explain that bacterial biomass was the most important factor during litter decomposition.In the course of litter decomposition, the litter decomposition quality was positively with organic C content (L. chinensis community R2=0.9623, P. communis community R2=0.9549), and that there was no significant variation of relativity acrossing warming+nitrogen, nitrogen application and warming treatments. That is, organic C content with its cooperative substances were the primary decomposed substances in initial decomposition stage. Moreover, we found that the total nitrogen and total phosphorus content have existed settling phenomena, which up to significance in Stat. (L. chinensis community Sig=0.002, P. communis community Sig=0.000), warming and nitrogen application treatments may promote these settling phenomena (L. chinensis community Sig=1.175, P. communis community Sig=0.050).