大兴安岭永久冻土区7种沼泽类型土壤温室气体排放特征

Characteristics of greenhouse gas emissions from seven swamp types in the permafrost region of Daxing′an Mountains,northeast China

气候变暖及永久冻土退化将会增加冻土湿地的温室气体排放,但关于大兴安岭永久冻土区沼泽湿地温室气体通量及主控因子尚不明确。采用静态箱-气相色谱法,同步原位观测大兴安岭永久冻土区7种天然沼泽类型(草丛沼泽-C、灌丛沼泽-G、毛赤杨沼泽-M、白桦沼泽-B、落叶松苔草沼泽-LT、落叶松藓类沼泽-LX、落叶松泥炭藓沼泽-LN)土壤CO2、CH4和N2O通量及土壤温度、水位、化冻深度及土壤碳氮含量、碳氮比、pH值及含水量,揭示永久冻土区沼泽土壤温室气体通量及其主控因子。结果表明:1)7种沼泽类型土壤CO2年均通量(125.12-163.33 mg m^-2 h^-1)相近;2)CH4年均通量(-0.007-0.400 mg m^-2 h^-1)呈草丛显著高于其他沼泽5.6-65.7倍(P<0.01);3)N2O年均通量(1.52-37.90μg m^-2 h^-1)呈阔叶林沼泽显著高于其他类型2.0-23.9倍,针叶林沼泽显著高于草丛、灌丛沼泽2.9-6.2倍(P<0.05);4)CO2主控因子为土壤温度和水位;CH4主控因子为土壤温度和化冻深度;N2O受到多种环境因子综合调控,共同可以解释N2O变化的26%-99%;5)土壤增温潜势(11.05-15.37 t CO2 hm^-2 a^-1)相近,且均以CO2占绝对优势地位,但草丛以CH4占次要地位,森林沼泽则以N2O占次要地位。综合对比国内外现有研究结果发现目前大兴安岭永久冻土区沼泽土壤仍处于CO2、CH4和N2O低排放阶段。

Climate warming and permafrost degradation will increase greenhouse gas emissions from the permafrost swamps.However,the fluxes of these trace gases have been scarcely quantified in cold temperate zone continuous permafrost region.The seasonal variation and the influence factors(temperature,water level,depth of thawing,and soil organic carbon and nitrogen content)of emission fluxes of greenhouse gas including CO2,CH4,and N2O from seven kinds of natural swamps(Carex schmidtii marsh-C,Betula ovalifolia-C.schmidtii shrub swamp-G,Alnus sibirica-C.schmidtii swamp-M,B.platyphylla-C.schmidtii swamp-B,Larix gmelinii-C.schmidtii swamp-LT,Larix gmelinii-moss swamp-LX,and Larix gmelinii-Sphagnum spp.swamp-LN)were studied over a one-year period by static chamber-GC technique in continuous permafrost region at the Daxing′an Mountains,northeast China.The results showed that:(1)the CO2 annual average emission flux(125.12-163.33 mg m^-2 h^-1)was similar.(2)CH4 annual average emission flux(-0.007-0.400 mg m^-2 h^-1)exhibited a different trend in C greater than that of others(5.6-65.7 times greater than the others,P<0.01).(3)N2O annual average emission flux(1.52-37.90μg m^-2 h^-1)had significant differences among all the sites(M,B was 2.0-23.9 times higher than that of others,P<0.05,LT,LX and LN was 2.9-6.2 times greater than C and G,P<0.05);(4)The three greenhouse gases emissions from seven kinds of wetlands were controlled partly by soil temperature,water level,thaw depth,soil organic carbon and nitrogen content,carbon to nitrogen ratio,pH value,and water content.The CO2 emissions were mainly controlled by soil temperature,and that of B,LT,LX,and LN were also controlled by the water level.The CH4 emissions were mainly controlled by soil temperature and thaw depth.The N2O emissions were controlled partly by soil temperature,water level,thaw depth,soil organic carbon and nitrogen content,carbon to nitrogen ratio,pH value,and water content.Above environmental factors can explain the variation of soil N2O flux by 26%-99%.(5)The global warming potential(GWP)of the seven natural wetland soils were similar ranged in 11.05-15.37 t CO2 hm^-2 a^-1,which all were dominated by CO2.The C took CH4 as the secondary position and forested wetlands took N2O as the secondary position.Based on the results,it was found that these swamp soils in the permafrost region of Daxing′an Mountains are still in the low emission stage of CO2,CH4 and N2O.