Effects Of Vegetation Types And Harvesting Methods On Emissions Of CO₂ And N2_O In Sediments In A Typical Coastal Wetland

Coastal wetland is the world’s one of the most important source or sink of greenhouse gases, but it is also the most powerful human disturbance ecology system. CO2 and N2 O is two important greenhouse gas. In recent years, the eutrophication of coastal wetland, biodiversity decreasing and the ecological environment problem increasingly prominent.In our country, due to the need of wetland students elements to remove excessive, and paper industries demand of Phragmites, harvest of vegetation has become one of the most common way of management of wetland vegetation in the winter.Although the wetland ecosystem has carried out a lot of fruitful research previous on greenhouse gas emissions and influencing factors, at present the different cover types, especially in the winter harvest differences under the influence of sediment in the typical greenhouse gas emissions and its change of exploration is still inadequate.This paper takes a Yangtze river estuary typical coastal wetland, chongming dongtan wetland as the prototyping area, to Phragmites, Spartina alterniflora and other vegetation in winter and not reap management, respectively, after the harvest of different number of days, spring, summer, autumn and winter four seasons to collect sediment samples, adopt the method of indoor cultivate(30℃, 40℃), with the aid of instruments such as GC, the Phragmites, Phragmites- Spartina ecotone, Spartina, Bare Eidalflat 4 kinds of sediment under cover the difference of CO2 and N2 O emissions, synchronization to compare different season 4 plant was taken a variety of greenhouse gas emissions. The project is expected to wetland CO2 and N2 O emission assessment and regulation research provides theory basis.The main results were as follows:(1) Under the condition of 30 ℃, Bare Eidalflat sediment CO2 emissions is highest in spring and winter festival, Spartina alterniflora and Phragmites sediment CO2 release peak in winter. Bare Eidalflat and Phragmites sediment N2 O emissions is highest in the summer, In comparison, Spartina alterniflora sediments seasonal change of N2 O emission is not obvious.When the temperature rose to 40℃, the four vegetation zone all CO2 emissions peak appeared in the spring.N2 O emissions is significantly as temperature increased.Correlation analysis showed that is beneficial to the release of CO2, the condition of high carbon nitrogen ratio under the condition of low carbon and nitrogen ratio, nitrogen easier to reduction of N2 O.After temperature increased from 30℃ to 40℃, the relationship between the sediment physical properties and the accumulation of CO2 and N2 O emissions become weak.(2) at 30℃, Spartina alterniflora and Spartina alterniflora-Phragmites interaction vegetation harvest did not increase the incidence of sediment release CO2(P<0.05), but after the temperature rise to 40℃, vegetation harvest may increase the quantity of sediment CO2 release.Between different types of vegetation, Phragmites sediment of CO2 release is significantly lower than the Spartina alterniflora and Spartina alterniflora-Phragmites interaction zone,This suggests that Spartina alterniflora and Spartina alterniflora-Phragmites interaction sediment carbon breathing is less than vegetation of Phragmites. Hence, In terms of the mechanism of sediments keep carbon sink, Phragmites vegetation is more favorable.Correlation analysis showed that the sediment sand content is higher, or increase carbon nitrogen ratio may significantly increase the quantity of sediment of CO2 release.(3) under 30℃, harvesting Phragmites may increase the release of N2O(P<0.05), but when the temperature increased to 40℃, the Phragmites harvest did not increase the release of N2 O,This suggests that(future) temperature may change sediment nitrogen reduction approach or strength. The harvest of Spartina alterniflora significantly reduces the sediment N2 O release(P<0.05),as the temperature increases, N2 O release is increase.In comparison the two temperatures, the release of N2 O of have cover deposits are aways higher than Bare Eidalflat.Correlation analysis showed that the higher of the organic carbon, total nitrogen and nitrate nitrogen content, the higher of the sediments accumulated N2 O release.In general, 4 vegetation types, the quantity of sediment N2 O accumulated release are change in 0.1~0.6 mg/kg, but the CO2 is higher in1024~2645 mg/kg. Therefore, wetland vegetation harvest in winter is not significantly the greenhouse effect impact of N2 O, but selective harvesting Spartina alterniflora is expected to reduce sediment carbon breathing loss.