Carbon Sink In Communities Of Salix Triandroides And Carex Brevicuspis In Dongting Lake Wetlands

Dongting Lake is the second largest freshwater lake in China and one of the most important lakes connecting to rivers in the middle and lower reaches of the Yangtze River.There is abundant of carbon storage in the lake.Due to the carbon cycle process,such as vegetation carbon sequestration,sediment deposition carbon sequestration,litter decomposition are affected by complex wetland factors such as hydrology.The research on wetland carbon sink is relatively scarce.In this study,the native woody vegetation S.triandroides and the most typical herbaceous vegetation C brevicuspis in Dongting Lake wetland were taken as research objects.Evaluates the carbon sink potential of woody and herbaceous plant communities comprehensively,according to the carbon storage and carbon sequestration(vegetation carbon sequestration,sediment deposition carbon sequestration),carbon decomposition.Provides theoretical for wetland scientific management.The results show:(1)Based the study of carbon storage and components of S.triandroides and C brevicuspis community under three water level gradients in Dongting Lake wetland.It is found: The average vegetation carbon storage of S.triandroides and C brevicuspis community were 5.6 kg/m2 and 2.3 kg/m2 respectively.In the middle and low water level areas,the vegetation carbon storage of S.triandroides and C brevicuspis community was significantly higher than the high water level areas.The average soil organic carbon storage of S.triandroides and C brevicuspis community were 16.7 kg/m2 and 15.0 kg/m2 respectively.In the middle and high water level areas,the soil organic carbon storage of S.triandroides and C brevicuspis community was significantly higher than the low water level areas.The contents of soil organic carbon and humus carbon(humic acid carbon,fulvic acid carbon and humin carbon)in the two plant communities were 0-20 cm layer higher than the surface layer,and humin was the main component.The middle and high water level areas soil organic carbon storage of S.triandroides and C brevicuspis communities was significantly higher than the low water level areas.The total organic carbon storage of S.triandroides and C brevicuspis community is 22.3 kg/m2 and 17.2 kg/m2 respectively.And show the characteristics that the high water level area are significantly lower than the low and middle water level area.Compared with vegetation carbon,soil organic carbon accounts for the main part of plant community organic carbon storage,low water level area is conducive to vegetation carbon accumulation,high water level area is conducive to soil carbon accumulation.(2)Based on the analysis of vegetation biomass new increased carbon,litter organic carbon and sediment deposition input organic carbon of S.triandroides and C brevicuspis community under three water level gradients in Dongting Lake wetland,the results showed:The vegetation biomass new increased carbon,litter organic carbon and sediment deposition input organic carbon of S.triandroides community are 228.2 g/m2,206.9 g/m2,925.7 g/m2 respectively,and the vegetation biomass new increased carbon,litter organic carbon and sediment deposition input organic carbon of C brevicuspis community are 193.8 g/m2,8.9g/m2,823.2 g/m2 respectively.The vegetation biomass new increased carbon of S.triandroides community and C brevicuspis community in the middle water level is the highest,in the high water level is the lowest.The litter organic carbon of S.triandroides community in the middle and low water level are significantly higher than the high water level,while the litter organic carbon of C brevicuspis community has no significant difference in three water levels.With the increased of water level,the sediment deposition input organic carbon in the communities of S.triandroides and C brevicuspis decreased,following the sediment deposition law of "high water deposition,low water erosion" in the flood season in Dongting Lake.In Dongting Lake wetland.The vegetation carbon sequestration of S.triandroides community and C brevicuspis community is the highest in the middle water level area,followed by the low water level area and the lowest in the high water level area.(3)Litters of three plant species(S.triandroides leaf,S.triandroides branch and C.brevicuspis leaf)placed under the two burial depths(0 cm soil layer and-5 cm soil layer)of the Dongdongting Lake wetland island beach.The dynamic observation of carbon decomposition found: During the experiment,the decomposition rate of litter organic carbon was as follows: C brevicuspis leaf(95.0%)>S.triandroides leaf(64.3%)>S.triandroides branch(38.1%).The burial depth of litter has a significant effect on the decomposition rate of organic carbon.The decomposition rate of organic carbon of C brevicuspis leaf and S.triandroides leaf is the highest at the burial depth of 0 cm,while the decomposition rate of organic carbon of S.triandroides branch is the highest at the burial depth of-5 cm.(4)The annual carbon sink of S.triandroides and C brevicuspis community in the high water level,middle water level and low water level areas of Dongting Lake wetland is1464.1 g/m2,1282.3 g/m2,964.0 g/m2,and 1382.5 g/m2,907.5 g/m2,762.1 g/m2,respectively.At the same water level,the carbon sink of S.triandroides community was significantly higher than C brevicuspis community.With the increase of water level,carbon sink potential of S.triandroides community and C brevicuspis community increased.