| In recent years, the change of global climate caused by carbon dioxide (CO2), methane (CH4) and other greenhouse gases in the air has been one of the common concern of mankind, which has profound huge impacts on ecosystems. A study pointed out that due to the widespread impact of global warming, the balance of absorb and emission on global greenhouse gases, the control mechanism, and how to take effective activity in reducing emissions of greenhouse gases such as CO2 has become the focus of attention of major environmental science research plan. Soil respiration, as one of the main CO2 emission modes, has great significance to the carbon source/sink of the ecological system.Therefore, we observed the CO2 flux between coastal reclamed wetland ecosystem of Chongming Dongtan and atmosphere from January 2013 to December 2014, continuously, researching the dynamic characteristics of CO2 flux indifferent temporalscales. Combined the micro-meteorological data and the simulated soil carbon fluxes in 2013 to analysis the values of soil carbon flux contribution to ecosystem carbon fluxes. The main conclusions are as follows:(l)Net carbon accumulation in 2013is 1115.654g·m-2·a, net carbon accumulation in growing season is 972.249 g·m-2, net carbon accumulation in non-growing season is 143.405 g·m-2, net carbon accumulation in summer is 611.709 g·m-2,. net carbon accumulation in winter is 88.42 g·m-2.July is the month with the largest amount of carbon sequestration, and the smallest amount of carbon sequestration in January. Net carbon accumulation in 2014 is 1033.723g·m-2·a, net carbon accumulation in growing season is 983.442 g·m-2, net carbon accumulation in non-growing season is 20.281 g· m-2, net carbon accumulation in summer is 524.324 g·m-2,. net carbon accumulation in winter is 63.398g·m-2.July is the month with the largest net carbon accumulation, and the smallest net carbon accumulation is in January. Net carbon accumulation in 2013 was higher than 2014, but the difference was not significant.(2)In 2013,the ecosystem respiration accumulation is 3242.828 g·m-2·a, and the growing season is 2636.523 g·m-2, while, non-growing season the ecosystem respiration accumulation is 606.305 g·m-2, the ecosystem respiration accumulation in summer is 1441.667g·m-2, the ecosystem respiration accumulation in winter is 266.905g·m-2. The largest ecosystem respiration is in July, The largest ecosystem respiration is in January. In 2014, the ecosystem respiration accumulation is 2946.589 g·m-2·a, and the growing season is 2314.417 g·m-2, while, non-growing season the ecosystem respiration accumulation is 632.172 g·m-2, the ecosystem respiration accumulation in summer is 1185.435 g·m-2, the ecosystem respiration accumulation in winter is 287.996 g·m-2. The largest ecosystem respiration is in July, The largest ecosystem respiration is in January. Ecosystem respiration was higher in 2014 than in 2013, but the difference was not significant.(3) The logistic-power function model Rs=a/1+exp(b(c-Ts)) Msdon Soil CO2 flux is the best fitting, R2=0.733,and the driving factors is soil temperature and volumetric soil moisture content.(4) In 2013, CO2 flux in soil range the 0.909-28.871 g·m-2·d-1,the average was 8.519 g·m-2·d-1. The average annual contribution of soil CO2 flux to ecosystem carbon emissions is 56.84%, the minimum contribution 17.00% comes in spring (March 4), maximum contribution rate appeared in the summer 128%(August 13). About 53.97% contribution of soil CO2 flux to ecosystem respiration is more than 50%. The average contribution in spring is 45.19%, and summer is 81.76%. The average contribution in autumn is 64.70%, and winter is 35.33%. The average contribution rate in spring, summer and winter of soil CO2 flux is not significant (P>0.05), but the average contribution rate of soil CO2 flux in autumn is significant (P<0.05). |
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