| The forest litter is an important carbon and nutrient pool of the forest ecosystem, and plays an important role in maintaining the structure and function of forest ecosystem. Litter decomposition affected the soil carbon storage, organic nutrient mineralization and inorganic nutrient content changes and the formation of carbon balance. Research in quality and nutrient change characters of litter decomposition, and the influencing mechanism of litter on forest ecosystem nutrient cycling and carbon flow, could provide scientific refrence for futher explore in forest ecosystem nutrient cycling and energe flow. This research adopts the method of the nylon netting, the comparative study that four representative tree species (Pinus massonana、 Cyclobalanopsis glauca、Cunninghamia lanceolata、Liquidambar formosana) of sub-tropical on dynamic changes of leaf litters decomposition rate and nutrient in 1 hectares fixed sample plot of Choerospondias axillaries deciduous broadleaved forest. The main results are:(1) There were obvious difference initial chemical compositions and C/N ratio、 C/P ratio、 N/P ratio in leaf litter of four tree species. The initial N and P content of broadleaf trees were higher than coniferous trees, and the C content were lower than coniferous trees. Except the content of C、N, the other initial chemical composition of deciduous broad-leaved species litter were higher than evergreen broad-leaved species.(2) After 24 months the dry mass remainsing rates from high to low is PM(45.78%)>CL(42.31%)>LF(37.24%)>LG(29.11%).The dry mass remaining of four leaf litters were not significantly different.The leaf litter decomposition can be divided into three stage:slow early period (0-10months), fast middle period (10-18months) and slowest later period (18-24months). Leaf litter decomposition coefficient values were:LG(0.0.525)>LF(0.0447)>CL(0.0370)>PM(0.0365). The LG leaf litter decomposition was the fastest, t50% was 1.18 a, t95% was 4.84 a; the PM was the slowest, tso% was 1.60 a, t95% was 6.79 a, t50% of LF was 1.38 a, t95% was 5.67 a, t50% of PM was 1.44 a, t95% was 6.70 a.(3) After 24 months the release amount of C were:CL> LG> PM> LF, the release amount of N were:LG> LF> CL> PM, the release amount of P were LF> LG> CL> PM, the release amount of soluble sugar were:CL> LF> LG> PM, the starch release amount were:CL>LF>PM>LG.(4) C showed the leaching-enrichment-leaching model, except the C of LG decayed by linear, other tree species were negative exponential decay model; N、P of four tree species were enrichment-release model, the leaf litter of LF appeared four times enrichment-release, the PM was three times, the LG was twice. The fitting curve of LF and CL was linear wquation, the LG was cubic equation, and PM was negative exponential decay model. The P of LF, LG and PM appeared twice enrichment-release; the P of CL has been in a state of enrichment. Only was the fitting curve of LF significant, it was negative exponential decay model. The release characters of soluble sugar and starch of four leaf litters were similar with C. The soluble sugar and starch of PM and LG were negative exponential decay model, CL was cubic equation, and the soluble sugar of LF was cubic equation, the starch of LF was negative exponential decay model.(5) Higher content of C and C/N ratio、C/P ratio、 N/P ratio in leaf litter, the decomposition rate was lower. On the contrary, the higher N and P content of leaf litter were benefit in leaf litter decomposition, indicating that leaf litter chemical compositions are important factor for decomposition rate. Higher N and P content of leaf litter are conducive to nutrient release, while the C content, C/N ratio, C/P ratio, N/P ratio are not conducive to nutrient release. |
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