Liaohe Delta Wetlands Of Different Vegetation Types And Methane Fluxes Breathing Flux Studies

Wetland ecosystem has been considered as one of the most important carbon sink around the world which plays a key role in world carbon cycling. However, because of the emission of CO2and CH4, coastal wetland can also become carbon source, therefore it is of vital importance to take this part of flux into account when caculating global carbon budget. To study the patterns of ecosystem respiration rate and ecosystem methane emission among different vegetation types,5study sites were built along3vegetation types which were common reed(Phragmites Australis), seablite (Suaeda Salsa) and rice(Oryza Sativa),which also helps to evaluating carbon sequestration potential in Liaohe delta. A enclosure chamber measurement method was adapted to investigate ecosystem respiration and ecosystem methane emission monthly, at the same time, environmental factors such as soil water content, bulk density, soil temperature at5cm depth, chamber temperature, soil oxidation-reduction potential(Eh or ORP), pH, aboveground biomass, aboveground biomass, air pressures and bicarbonate concentrations were collected during each measurement. Several published references were also combined to evaluate the significance of each environmental factors on ecosystem respiration rate as well as methane emission rate. Carbon sequestration potential of each vegetation type was evaluated via estimating annual ecosystem respiration amount and methane emission amount in Liaohe delta.The ecosystem respiration rate and CH4emission rate in seablite sites ranges from3.192mg m-2h-1to934.83mg m-2h-1and from-0.105mg m-2h-1to0.775mg m-2h-1,respectively. Each site has a significant variations in different season which means both rate have a high level in summer and low in other seasons. Among all the environmental factors which influence both rates, temperature and water level are the key ones.The ecosystem respiration rate and CH4emission rate in reed sites ranges from37.229mg m-2h-1to3338.843mg m-2h-1and from0.073mg m-2h-1to68.624mg m-2h-1,respectively. CH4emission rate has a great variance in different sites and time of a year. Similarly both rate reach a highest level at summer, under the control of various environmental factors such as temperature, water lever and reed species differences. The ecosystem respiration rate and CH4emission rate in rice site ranges from-1.674mg m-2h-1to1831.801mg m-2h-1and from0.009mg m-2h-1to19.080mg m-2h-1,respectively. Ecosystem respiration rate decrease after irrigation and then increase because of the growth of rice plant. Before harvest time on November both rates decrease drastically. Key factors are temperature and the growth process of rice plant. Reed wetland and rice paddies account for most part of ecosystem respiration as well as CH4emission in Liaohe delta while seablite has a huge potential of carbon sequestration because of its lower rates (sometimes absorbing CH4). Reed wetland and rice paddies are significant sources of CH4. Considering that reed and rice were harvested every year, it is obvious that energy has been exported periodically. Thus further data about it should be collected to determine whether they are net sink or source of carbon element.During a30min incubation, concentration of CO2in dark chamber increase in a almost constant rate. Comparing the result of two method, Enclosure chamber-Gas Chromatography method may cause a underestimation in flux caculation.