Effects Of N And P Additions On Foliar Litter Decomposition And Nutrient Release In A Subtropical Evergreen Broad-leaved Forest

Forest litter is the main form of forest ecosystem nutrient return. the nutrients (N, P, K) of litters release is important to soil fertility, plant growth, and nutrient use availability, and also plays an important role in promoting ecosystemmaterial circulation and nutrient balance. Litter as the basic carrier of nutrients, is connected in nutrient cycling in plants and soil. The study of different types of forest litter decomposition rate under the conditions of different external factors and nutrient release dynamics, is benefit to know the the forest ecosystem functions.This experiment studied the C, N, P, K, Ca element dynamics of two dominant species in evergreen broad-leaved forest in Shitai,anhui Province,using the mesh bag method,in codition of soil exogenous N,P. The experiments were set in Large Mountain and Rocky beach,4plots in the former (including control group, nitrogen, nitrogen+high phosphorus, low nitrogen) and3plots in the later(the control group, high nitrogen+phosphorus, nitrogen). The specific design) of nutrients added as follows:nitrogen100kg N·hm-2·a-1, nitrogen+high phosphorus100kg N·hm-2·a-1+50kg P·hm-2·a-1, low nitrogen50kg N·hm-2·a-1; every month applied. Let the NH4NO3or Ca (H2PO4)2dissolved in20L of water in a back sprayen and sprayed evenly to the corresponding forest plots, the control area is sprayed with the same amount of water to reduce the different effects caused by extra water added. more than a year later, the decomposition experiment results showed that:(1) According to experiments, litter decomposition rates vary in different environment and in different fertilization conditions, in this experiment, the emergence of a significant difference of litter decomposition rate main due to exogenous elements complement. In the final of decomposition (decomposition480days) nitrogen+phosphorus and nitrogen decomposition rate was significantly lower than the control treatment and low nitrogen treatment. Indicated that excessive nitrogen added has a decomposition suppressive effect. Secondly, whether in high nitrogen+phosphorus, nitrogen,low nitrogen or control treatment, the first half of the mass loss are faster, significantly higher than the decomposition late.(2) By Olson exponential decay model analysis indicated that the time of decompose50%(T0.5) and95%(T0.95) of each litter is nitrogen+phosphorus> nitrogen> Low N> control. The total time was7-17years,which made with previous conclusions. we can see that the initial litter N concentration exogenous factors on the element through microbial supplement litter, lignin/N ratio, and hydrothermal factor is main effect on litter decomposition speed.(3) P elements under both in different environments and in different fertilization appear to have a net fixed hysteresis phenomenon, P released mainly in the form of composite function. Especially in the high nitrogen+phosphorus. This phenomenon is decided by initial P content and exogenous factors P which through microbial supplemented. While the P decomposers of litter and regulatory role remains to be further studied.C constitutes a major component of litter elements and presents a upward trend. Judging from the element dynamic model, C,N elements all have the element itself release and dry matter disappearance of dual release pattern, where C is to be recognized as an important factor in controlling N cycling. studies have found that the process of litter decomposition is sensitive to temperature, which affect its C-element solid stagnation and release, because some momentum enzyme associated with the decomposition is very sensitive to temperature changes.The decomposition of N is significant, C/N ratio is considered to be the best indicator reflecting the decomposition rate, the initial N concentration and C/N is the first to be used to reflect the value of the decomposition rate. Different elements litter transfer method determines the speed of missing elements.by applying N fertilizer, litter N concentration changes affect lignin, indirectly affect the balance of decomposition.This experiments litter N content increases is closely related to microbial solid N, precipitation, and the absorption of mycorrhizae. Element Ca fluidity is poor.The experiment showed that, with the time run off, different plots showed a slowly release.