| Climate warming is a global environmental issue nowadays, and one of its main reasons is the continuous increase of greenhouse gas concentration in the atmosphere, among which, CO2 CH4 and N2 O are considered the most important greenhouse gases. Apart from the well-known chemical fuel combustion, the biogeochemical process of terrestrial ecosystem plays an extremely important role in the increase of the concentration of CO2 CH4 and N2 O in the atmosphere. As a special type of wetland ecosystem, the ditch is an important component of the terrestrial ecosystem, and it plays an extremely important role in carbon storage, production of such trace gases as CO2 CH4 and N2 O as well as other aspects. The research selects representative three ditches in Linshan Town, Yanting County of Sichuan Province as experimental subjects: an agricultural source ditch, an ecological ditch which mainly discharges rural domestic sewage and an agro forestry source ditch. The research adopts static box-meteorological chromatography, conducts observation and research on the emission and consumption of the major greenhouse gases(CO2 CH4 and N2O) of wetlands ecosystem of the three ditches at the same time, and meanwhile, conducts observation and research on climate, water and other environmental factors at the same time.The results of the study are as follows:(1)As a whole, as a special wetland ecosystem, the absolute area of the ditch is less than that of rivers, lakes, marshes and other wetlands, but in the context of the current study, the main greenhouse gas flux data of the wetlands ecosystem of Sichuan hilly basin are far more than that of other wetland types. in this research, the CO2 flux average of farmland ditch wetland ecosystem is 350.6mg Cm-2h-1; the N2 O flux average of ecological ditch soil system reaches 232.4ug Nm-2h-1; CH4 flux average of ecological ditch soil system reaches 8846.35 ug Cm-2h-1.(2)By the horizontal comparison of the three different types of ditches, CO2 flux averages of the ditch ecosystem are: farmland ditch>ecological ditch>agro-forestry ditch; N2 O flux averages are: ecological ditch> agro-forestry ditch> farmland ditch; and CH4 flux averages are: ecological ditch> farmland ditch> agro-forestry ditch. Among them, the fluxes of CO2ã€CH4 and N2 O of the agro-forestry ditch, CO2 flux of the ecological ditch and CO2 and N2 O fluxes of the farmland ditch are all: with plant> without plant; while CH4 and N2 O average fluxes of the ecological ditch and CH4 flux of the farmland ditch are both: without plant> with plant.(3)CO2 flux range of the agro forestry ditch ecosystem is between 10.76-343.38 mg Cm-2h-1, and that of the farmland ditch is between 177.04-507.13 mg Cm-2h-1 and 1.1-121.63 mg Cm-2h-1; N2 O flux range of the agro forestry ditch ecosystem is between 1.16-176.66 ug Nm-2h-1, that of the ecological ditch is between 11.98-441.53 ug Nm-2h-1, and that of the farmland ditch is between 3.57-167.07 ug Nm-2h-1; CH4 flux range of the agro forestry ditch ecosystem is between-38.72-328.59 ug Cm-2h-1, that of the ecological ditch is between-32.72-44803.69 ug Cm-2h-1, and that of the farmland ditch is between64.2-21313.25 ug Cm-2h-1. To sum up, under the state of the ditches ecological system plants which is natural and without human disturbance, the major greenhouse gases(CO2ã€CH4 and N2O) in Sichuan hilly ditch wetland ecosystem are all mainly in the discharge state.(4)For the agro forestry ditch, the temperature is the main factor affecting its greenhouse gas emissions, and total nitrogen also has an important influence on CH4 flux of the ditch; The greenhouse gas flux of ecological ditch wetland ecosystem is the result of the comprehensive action of temperature and ditch sediment nutrient content, among which, the seasonal variation trends of temperature and CO2 flux are relatively consistent; Soluble deposits organic carbon, ammonium nitrogen, nitrate nitrogen and total nitrogen content present a significantly positive correlation with CH4 flux. |
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