Effects Of Simulated Saltwater Intrusion On Greenhouse Gas Production And Emission From Freshwater Marshes Of The Min River Estuary

Wetlands are an important source or sink of atmosphere greenhouse gas, which also are one of the most sensitive ecosystems to climate change and human activities. The effect of saltwater intrusion caused by sea level rise on coastal wetlands has become a global environmental problem with a profound impact on wetlands greenhouse gas production and emission. For more in-depth understanding of saltwater intrusion on greenhouse gas production and emission in estuarine wetlands, and effective management of wetlands, the effect of simulated saltwater intrusion on the greenhouse gases production and emission processes were studied in the Cyperus malaccensis freshwater marshes via field collection and laboratory incubation and experiments mesocosms in the Minjiang River estuarine. The main conclusions are as follows(1) Simulated saltwater intrusion (with a salinity more than 10%o) demonstrated a significant inhibitory effect on CH4 production potential from the estuarine freshwater wetland soils, while less than 10%o saltwater intrusion had no significant effect on the CH4 production.0.5-7.5%o salinity range of simulated saltwater intrusion promoted CO2 production from freshwater wetland soils in some extent, while more than 15%o saltwater intrusion exhibited a significant inhibited effect. Simulated saltwater intrusion showed no significantly effect on the N2O production.(2) CH4 emission was significantly effected by the interaction of tide and salinity. CH4 emission appeared different response to the salinity during different tidal stages. Before flooding, the CH4 emission was inhibited by the simulated saltwater intrusion with different salinity. During the flooding and after ebbing, the CH4 emission was not significantly changed by the simulated saltwater intrusion with different salinity.(3) CO2 emission was significantly effected by the interaction of tide and salinity. CO2 emission appeared different response to the salinity during different tidal stages. Before flooding and during the flooding, the CO2 emission was not significantly changed by the simulated saltwater intrusion with different salinity. After ebbing, CO2 emission significantly increased by the simulated saltwater intrusion with different salinity. Simulated saltwater intrusion showed no significantly effect on the N2O emission after ebbing.(4) The experimental mesocosm showed that the CH4 emission in the freshwater marsh ecosystem was significantly inhibited by the simulated salt input, while significantly promoted by the organic carbon input. CH4 emission was not significantly changed by the inputs of ferric, a couple of salt and organic carbon, and a couple of salt and ferric.(5) CO2 emission in the freshwater wetland ecosystem was significantly promoted by organic carbon input, while the CO2 emission was not significantly changed by the inputs of salt, the ferric, a couple of salt and organic carbon, and a couple of salt and ferric.(6) N2O emission in the freshwater wetland ecosystem was significantly inhibited by the inputs of organic carbon, the ferric, and a couple of salt and organic carbon. While the N2O emission was not significantly changed by the inputs of salt, and a couple of salt and ferric.(7) CH4 and CO2 emission were positive correlated with the activity of β-1,4-glucosidase (βG) and cellobiohydrolase(CBH), N2O emission was positive correlated with the activity of β-1,4-N-acetylglucosaminidase(NAG) and acid phosphatase(AP).(8) Under simulated saltwater intrusion-scenario, based on the global warming potential(GWP) at 100-years scale, CO2 emission was the largest contributor in the global warming potential (GWP) with more than 90% in each experimental treatments. Organic carbon input, saltwater intrusion coupled organic carbon input significantly promoted the combined global warming potential of the three greenhouse gases.