Carbon Estimating Model Of Vegetation In Coastal Wetland Of Chongming Island And Estimation Of Some Parameters

Along with the problems caused by greenhouse effect arise more and more attention from the public, carbon cycle of ecosystem has increasingly become the hot topic for scientists who are interested in the effective ways to increase carbon absorption and reduce carbon emission. As a special ecological type, wetland has considerable carbon sequestration capacity, and it is one of the important terrestrial ecosystem carbon stocks. Meanwhile, it plays an important role in maintaining global ecological balance and biodiversity. According to statistics, wetland carbon reserve in the world is more than the total carbon storage of agriculture, tropical rain forest and temperate forest ecosystem. Thus it can be seen that, studies on the carbon cycle of wetland ecosystem is very necessary.In this study the carbon estimation model of coastal wetland vegetation in Chongming Island has been preliminarily established, and its dynamic model also has been successfully operated with the help of Vensim software. If this model can successfully simulate the real situation, it would be used as a good tool to estimate the spatial distribution pattern of carbon storage and carbon emission, monitor carbon flux in the vegetation of Chongming coastal wetland at a later date. Then, combined with field investigation, remote sensing data and the results of other researchers, the vegetation type of coastal wetland can be roughly divided into Scirpus mariqueter area, Spartina alterniflora area, Phragmites australis area and farmland area in Chongming Island. In this paper, these two parameters of stomatal conductance and light extinction coefficient which exist in different types of wetland vegetation are estimated through a certain amount of sample information obtained by the statistics of relevant research data. Whether in biology or in model control, stomatal conductance and light extinction coefficient are important parameters. Stoma is the main gateway to control CO2and H2O importing and exporting leaves, stomatal conductance refers to the degree of stomatal opening and closing which is directly related with the plant photosynthesis and transpiration. As an important characteristic parameter of canopy radiative transfer, light extinction coefficient reflects the canopy structure and light distribution in the canopy of plant. The main results of this study are as follows:(1)In this study the carbon model of vegetation in Chongming coastal wetland is preliminary established, including the module of carbon fixation, carbon storage and carbon emission, carbon flux estimation, carbon transport within plants, litter fall, hydrology submodel, soil temperature model and climatic submodel, in which the climate change, soil situation and hydrological conditions have been considered.(2)The estimation range of stomatal conductance in different vegetation types are obtained under the confidence level of95%. The numerical value of stomatal conductance in Scirpus mariqueter area, Spartina alteniflora area, Phragmites australis area and farmland area respectively range from0.165to0.177,0.237to0.253,0.193to0.205and0.401to0.433. Stomatal conductance in these four vegetation types of wetland give the following subsequence (from great to little): farmland area> Spartina altrniflora area> Phragmites australis area> Scirpus mariqueter area.(3)When the confidence level is95%, the numerical value of light extinction coefficient in Scirpus mariqueter area, Spartina alterniflora area, Phragmites australis area and farmland area respectively range from0.342to0.360,0.598to0.619,0.757to0.780and0.839to0.871. In these four vegetation types, the maximum and minimum numeral value of light extinction coefficient is farmland area and Scirpus mariqueter area respectively. The value of extinction coefficient in Spartina alterniflora area is less than Phragmites australis area.In this carbon model, these two parameters of stomatal conductance and light extinction coefficient are the most important parameters in the carbon fixation module, and estimating these two parameters pave the way to help the model to simulate the real condition, which have great reference value. In the process of dynamic simulation with Vensim software, we can see how the results will change through the ways of regulating the numerical values of these two parameters, by which we can find ways to increase the carbon absorption of wetland ecosystem in Chongming Island.