| The global temperature rise caused by the increase of greenhouse gas concentration and the global climate change caused by it are one of the hot topics that governments and scientists all over the world focused on.Wetland ecosystem is of great importance for responding to global climate change,buffering extreme weather events,and absorbing and storing carbon.Dongting Lake is one of the two Yangtze River connecting lakes in China.Seasonal water level changes have formed a typical plant-like zone,which has triggered changes in the redox potential,which has a great impact on greenhouse gas emissions.In this study,West Dongting Lake was selected as the research area.Through simulation experiments,seasonal greenhouse gas emission of reed?Phragmites australis?,Carex?Carex cinerascens?and newly felled poplar forest?Populustomentosa Carr?plant-soil system under different submerged heights?0.3m,1.1.m,1.9m?were monitored.Nutrients concentration of water column such as total nitrogen,inorganic nitrogen,and total phosphorus were measured during flooding experiment.The effects of different submerged heights,overlying water nutrients on different plant-soil systems greenhouse gas emission fluxes.The main results were as follows:?1?The seasonal changes of greenhouse gas emissions of the three plant-soil systems were significant.The overall range of CO2emission flux of reed soil system was-25810.97?3084.64mg·m-2·h-1,the maximum value appeared in June before flooding,and negative values appeared in November and December after drainage.The overall variation range of CH4emission flux was between-0.34?289.75mg·m-2·h-1,and its maximum value occurs in September after flooding.The N2O flux was very low during the entire monitoring period,at-0.14?Between 0.59mg·m-2·h-1.The CO2flux emission of Carex-soil system was-5188.98?1408.70mg·m-2·h-1,the maximum value appears in June before flooding.CH4flux was-7.93?3.87mg·m-2·h-1,the maximum peak occurred in November after drainage.The N2O flux was very low during the entire monitoring period,between-2.00?0.40mg·m-2·h-1.The CO2flux emission range of newly felled poplar soil system was-625.92?3324.43mg·m-2·h-1the maximum value appeared in November after drainage.The CH4emission range was-0.83?16.82mg·m-2·h-1,the maximum emission flux appears in September?flooded period?.The N2O flux range is-0.03?0.60mg·m-2·h-1.?2?After flooding,the total nitrogen and ammonium nitrogen concentrations in the overlying water showed an increasing trend,the nitrate nitrogen concentration showed a decreasing trend,and the total phosphorus concentration in the reed soil system showed a trend of increasing first and then decreasing.Seasonal flooding height,plant-soil system and their interaction had significant effects on CO2and CH4fluxes.The N2O flux was at a low level during the entire monitoring period,and there is no obvious change trend.After flooding,the CO2emission flux of the reed soil system at a flooding height of 0.3m was not significantly reduced,and the CO2emission flux of each plant-soil system at the other flooding heights was significantly reduced?P<0.05?.After flooding,CH4flux increased obviously.During flooding,the average flux of CH4at different flooding heights under various plant-soil systems was ranked as follows:1.1m>0.3m>1.9m.?3?At 0.3m flooding height,the global warming potential?GWP?of different plant-soil systems ranked from large to small:reed?10873.11 kg/m2?>newly felled poplar forest?2346.33 kg/m2?>Carex?2346.33 kg/m2?,GWP under reed soil system was significantly higher than that of the other two plant-soil systems,about 4.6 times of GWP under Carex and newly felled poplar forest soil system.Under 1.1m flooding height,reed-soil GWP?17572.26 kg/m2?was about 4.6 times the GWP?3784.27kg/m2?of the Carex soil system,which was the same as the multiple at the 0.3m flooding height.At1.9m flooding height,the GWP of each plant-soil system was as follows:newly felled poplar forest?7712.30 kg/m2?>reed?2916.53 kg/m2?>Carex(424.53 kg/m2.Comprehensively considering the contribution of different plant-soil systems to GWP under different flooding heights,the contribution of reed soil system to GWP was significantly higher than that of Carex and newly felled poplar forest soil system to GWP. |
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