Evaluation Of Shanghai Chongming Wetland Ecosystem Services And Functions

Wetland ecosystem is located in the transition zone between land and water. It is a multifunctional ecosystem, and it has very important and diversified ecosystem services and functions. As a representative kind of animal-insects and typical wetland plants play important roles in functioning its functions and supporting services for human respectively.Chongming island is an impact island which located in the estuary of the Changjiang river, and it is praised as the last clean land of Shanghai. There are large area of wetland plants on Chongming island, and the most representative species are Phragmites australis、Scirpus mariqueter、Spartina alterniflora. The insects which survive in the reed are the important component of the food web. As an important ecological island, Chongming island plays an important role in sustainable development of Shanghai. So it is significant for Chongming island, or even for the whole city of Shanghai to fully aware of the wetland ecosystem services and functions, protect the ecological environment efficiently in this area.This study focuses on insect and typical wetland plants emphatically, evaluate the ecosystem services and functions of Chongming island from these two aspects. From March to October in2011, we investigated the aboveground biomass of typical wetland plants in the whole island. As Chongming Dongtan wetland is a very important area in Chongming island, we choose this area as the special sample site. From March to October in2012, we investigated the insect community in reed, and Nitrogen and Phosphrous content in reed. The main conclusions of experiment were as follows:(1) Totally12585insects belonged to140species,80families,11orders were collected. The dominant species are Coleoptera, Diptera, Hymenoptera and Homoptera. The individual number of Diptera is the largest, but the richness of Hymenoptera is the highest. After it was spring, the number of insect increased, then it peaked in May for about3909, the number was31.06%of the total. June is the beginning of summer, in this time, the temperature was rising continually, but as the influence of many kinds of atrocious weather, the number of insect declined totally. The number was1002in August. When it was autumn in September and October, and the number of insect down to the lowest. After calculating the diversity index of insect, we can find that Shannon-Wiener index was with a large variation range. It is minimum in March for about1.35, and maximum in the August for about3.50. The variation tendency of Shannon-Wiener index and Pielou’ Evenness were the same, but the tendency of Shannon-Wiener index and Simpson’s Dominance are complementary.(2) The growth peak of P. australis occurred during March to May, with the carbon fixation ability of1.02±0.12kg·m-2·a-1. The dynamic of growth of P. australis community had a close relation with change of leaf N. The community of S. mariqueter mainly distributed in the south coast, its growth peak showed during March to May, stagnated in June, then kept growing, and carbon fixation ability was0.33±0.05kg·m-2·a-1. The community of S. alterniflora distributed from east of the north lake to the east beach, with threatening to survival of the native species badly. The community of S. alterniflora kept growing for all growing season, but rapid growth in July to September, with a highest carbon fixation ability of1.32±0.10kg·m-2·a-1. The accumulation of carbon fixation in the wetland plants in Chongming Island increased quickly during April to July, the carbon fixation ability in south coast showed a highest carbon fixation ability, reaching a total carbon dioxide fixation ability of2.5×105t·a-1for the whole island. The result implies that the plant community in Chongming Island has a strong carbon fixation ability, but with an obviously spatial-temporal change, the wetland at the Chongming Island play an important role in fixation enhancement and emission mitigation of greenhouse gases in Shanghai.(3) The variation tendency of every part of biomass of reed was the same as the total aboveground biomass, and the maxmum value of every part appeared in September except tassel. Content of nitrogen and phosphorus of each part was the highest at the beginning of growth, then as the effect of "attenuation", the content began to decline gradually, the minimum of content appeared in September or October. There was significant difference between nitrogen and phosphorus content of different components. The maximum storage of nitrogen and phosphorus of the whole aboveground biomass were12632.7g/m2and1044.74g/m2, and both of the maximum storage appeared in June or July. Therefore, harvesting the aboveground biomass of P. australis at the period of this time can transfer nitrogen and phosphorus from ecosystem efficiently, so that the water can be purified.In a word, Chongming wetland ecosystem plays an important ecosystem function in protecting the diversity of insect, and provides significant services in carbon sink and water purification. We should value and protect Chongming wetland ecosystem well, so that it can develop healthily and sustainably.