| The upper areas of Minjiang River are a great important yardstick in our country, compounding type ecological intermediate zone, it is the fragile district of an ecosystem too. Studying its forest ecosystem C and N pattern and dynamics has profound important to the stability,constant and biological productivity of the artificial forests ecosystem. According to setting up fixed standard area and disturbance experimental plots, and based on calculating the forests biomass and analyzing fixed sample (plant and soil),this paper studied four kinds of typical artificial forests(Cercidiphyllum japonicum, Pinus yunnanensis, Picea asperata, Betula utilis) ecosystem C and N allocation, C,N releasing of litter-fall and nutrient N circulation biological characteristic of the upper reach of Minjing River. In addition, through exerting C source (cane sugar ) and N source (NH4NO3) to artificial disturbance forest, we studied forest ecosystem C and N dynamic change regularity. The main result and conclusion are as follows:1. Allocation of C and N in Forest ecosystem(1)N element content in stems is the lowest, the leaves' is the highest. The forest N is distributed pattern: C.japonicum: leaves>roots >branches>barks> stems; P.yunnanensis and P.asperata have unanimous regularity, namely leaves>branches>roots>barks>stems; B.utilis: leaves >branches>roots>barks>stems. Different forests organ N Allocation was great diversity. C content is close among organs; it is relatively a bit higher in stems. The forest C allocation is: C.japonicum: stems> bran ches>roots>leaves>barks; P.yunnanensis: stems>Leaves>fruits >branches>roots >barks; B.utilis: leaves>roots>stems>branches>barks; P.asperata: barks> stems>leaves>branches>roots. Compared mass loss in the forest with living tree, C and N contents in leaves,branches and barks reduced very notably.(2)The order of total organic N storage of forest ecosystems was: P.yunnanensis 8694.12 kg/hm2, P.asperata7461.72 kg/hm2, C.japonicum 6043.50 kg/hm2, B.utilis 5075.64 kg/hm2. In general, tree layer accounts for 4.74%-10.74% of total N storage in the forest, mass loss layer of proportions is very small, it is only 0.14%-0.69%, the soil layer accounts for... |
