Seasonal Dynamics Of DOC And Responses Of Its Export To Warming And Water-table Drawdown In Zoige Pratland

As the highest area of peatland organic carbon storage in China, Zoige wetland is locatedin northeast of Tibetan plateau and very sensitive to global climate change. Facing withclimate warming and human activities (such as ditching) in recent years, Zoige peatlanddegraded seriously to the point where its carbon storage and carbon cycle probably wereunstable, likely to cause potential damage to ecosystem of itself and downstream.Based on Carex muliensis peatland in Zoige, firstly, we observed dissolved organiccarbon (DOC) concentration in pore water and several environment factors, such peattemperature and precipitation, to analyze seasonal dynamics of DOC compounds andcorresponding influence factors; secondly, we experimentally warmed and controlledwater-table in large mesocosms containing intact peat monoliths in a fully crossed factorialdesign to determine the impacts of manipulated warming and water-table variation in Zoigepeatland on annual export and concentration of DOC, discharge and relative content ofaromatic and colored components.(1) The research of seasonal dynamics of DOC and its influencing factors shows thatboth concentration of DOC and its compositions in pore water of Zoige peatland hadsignificant and varying season variations. From May to October, DOC concentrationexperienced a single apex, with minimum value (26.27mg L-1) in May and maximum value(42.77mg L-1) in August respectively. Correlated analysis indicated temperature of peat andsurface and humidity were the major influencing factors of seasonal dynamic of DOCconcentration (R2=0.52, P<0.01; R2=0.49, P<0.05; R2=0.37, P<0.05).(2) The components of DOC compound, including humification degree measured byE4/E6, aromatic content measured by Abs254nm/DOC and colored composition measured byAbs400nm/DOC, also showed significant seasonal trends. Correlated analysis revealedprecipitation was dominated in the seasonal variations of coloured components andhumification degree (r=0.75, r=-0.60; n=6), and humification degree was also influenced bytemperature of peat and surface (r=0.74, r=0.72; n=12).(3) Results of response of DOC loss to water-table and temperature variation showedthat Results showed that DOC export could response rapidly to water-table and temperaturemanipulation, and water-table variation had a greater impact on DOC export than warming treatment. It shows DOC export significantly increased with water-table drawdown (P<0.01),and annual DOC export was increased by69%and102%when water-table at surface levelexperimentally declined by10cm and20cm through higher DOC concentration and largerdischarge volume. By contrast, warming treatment significantly promoted DOC concentration(P<0.01), with limited effect on DOC export and water discharge (P>0.05; P>0.05).(4) It also demonstrated increases in colored and aromatic constituents of DOCcompound flowing into downstream under lower water-table and higher peat temperature,which would affect the water quality in aquatic ecosystem.Thus, the study helps to reveal carbon cycle process in Zoige peatland and its featuresunder global change, and also indicates the potential impacts of climatic change andanthropogenic drainage on the carbon cycle and/or water storage in peatland andsimultaneously incurs potential damage to downstream ecosystems. Further, this simulationexperiment gives a warning for local protection and sustainable development, and alsohighlights the need for more research to better understand the impacts of climatic change andartificial disturbance on peatland degradation in Zoige. Thus, it would help with its restorationand formulation of protection measure in Zoige peatland.