Characteristics Of CO₂Emission And Its Effect Factors From Carex Dominated Wetland In Poyang Lake

Poyang Lake is the largest freshwater lake in China, located at latitude28°22′²9°45′, longitude115°47′¹16°45′. It belongs to a subtropical region, and hasplay an important role for regional climate regulation. Poyang Lake’s uniquephysiographic conditions and the complex water regimen of the Yangtze River, allthose from a unique lake wetland ecosystem. The research sites is located in the Nanjiwetlands of Poyang Lake National Nature Reserve. Taked the dominant plant（Carexcinerascens） as constructive species of bottomland wetlands. Including twoexperimental treatments: set up soil-plant system（TC）, cut off the aerial parts of plants-（TJ）（Represent respectively the ecosystem and soil respiration）. Used sealedbox-Gas to determine CO₂-flux in Poyang Lake. At the same time, the soil moisture,temperature, Carex plant productivity, biomass, was measured. Following questionsare explored:1) Carex biomass, the seasonal variation and the interannual variabilityof the productive forces;2) The distribution-characteristics of Organic Carbonmoss inthe Carex dominated wetland in Poyang Lake;3) Characteristics of CO₂emission andeffect factors of Carex dominated wetland;4) The temperature sensitivity of CO₂emission from Carex dominated wetland. The further researches，we can assess thePoyang Lake wetland carbon balance, forecast the regional climate change, draw upscientific basis that response to climate-change. The main research results are asfollows:（1） The biomass of Carex performs obvious seasonal variation and inter-annualchanges. The below-ground biomass and aboveground biomass scale show similarseasonal variation pattern. The maximum value of aboveground biomass is1770.67g·m^-2, it emerges in April of2010, the lowest value of aboveground biomass is146.08g·m^-2, it emerges in October of2010. The aboveground and undergroundbiomass of spring is higher than the fall, for example, the maximum value ofbelowground biomass in spring is1.68times to the fall of the same year（from2009to2010）. Throughout the experimental period, Sedge aboveground and belowgroundbiomass in spring was significantly higher than that in autumn, and belowgroundbiomass is significant different to the aboveground biomass（t=15.5, P<0.01）, the ratioof the two has changeed with the seasons changing, ranged from2.08to17.44, andit’s average is5.19. Seasonal changes of Carex NPP showed a changing trend: Carexin Spring is higher than that in Autumn. （2） During the whole experiment, soil respiration （TJ） and ecosystem respiration（TC）, both showed obviously similar seasonal variations mode in Poyang Lake typicalmeadow. but the emission rate are significantly different. The average of fluxe rate ofCO₂is586.57mg·m^-2·h^-1, and the ecological system respiration rate changed from89.57mg·m^-2·h^-1to1359.25mg·m^-2·h^-1, the highest value was appear in the in May, thelowest values appear in January, The highest value is15times to the minimum value.The soil respiration rate is changed from is75.30mg·m^-2·h^-1to960.94mg·m^-2·h^-1, andthe the time that appears consistent with the ecological system respiration rate. but theemission rate are significantly different（t=4.99, P<0.01）.（3） CO₂emission rate, temperature at5cm in soil, surface temperature, and airtemperature were highly positive correlation. The temperature, ecosystem respirationrate, and soil respiration showed significant correlation（r=0.89;0.83，n=22，P<0.01）.However, the soil respiration rate and content of soil moisture showed not highlycorrelation.（4） The Q₁₀values of ecosystem respiration and soil respiration system value inwarm-season is1.68and1.62. Howere the Q₁₀values of ecosystem respiration andsoil respiration system value in cool-season is2.74and2.11.Conpared the Q₁₀inwarm-season and that in cool-season, the Q₁₀values of ecosystem respiration and soilrespiration in cool-season were higher than that in warm-season. As temperatures rise,the Q₁₀values of ecosystem respiration and soil respiration in the cold season reduce.