三江平原生长季沼泽湿地CH4、N2O排放及其影响因素

 2003年6～9月采用静态箱_气相色谱法,对三江平原生长季不同淹水条件下沼泽湿地CH₄、N₂O的排放进行了同步对比研究,并探讨了影响气体排放的主要影响因素。结果表明, 生长季沼泽湿地CH₄和N₂O排放具有明显的时空变化特征。长期淹水的毛果苔草（Carex lasiocarpa）和漂筏苔草(Carex pseudocuraica)植物带CH₄的平均排放强度分别为259.2和273.6 mg?m^-2?d^-1,高于季节性淹水的小叶章(Deyeuxia angustifolia)植物带的排放强度(38.16 mg?m^-2?d^-1)（p<0.00 0 1）;而生长季N₂O的平均排放强度分别为0.969、0.932 和0.983 mg?m^-2?d^-1, 植物带间无显著差异（p=0.967）。相关分析表明,气温和5 cm深地温对沼泽湿地CH₄生长季排放通量的影响较大,而水位则是影响长期淹水沼泽N₂O排放通量的主要因素;不同类型湿地间CH₄平均排放强度的差异主要受水位的控制,而强烈的还原环境可能是导致不同类型湿地具有近似的N₂O排放强度的原因。

EMISSIONS OF CH4 AND N2O FROM A WETLAND IN THE SANJIANG PLAIN

In order to understand more about mechanisms of and  factors that influence CH4 and N2O production in wetlands, fluxes of CH4 and N2O were measured using static_chamber and gas_chromatography methods in a marsh wetland, located at  the Honghe Farm in eastern part of Heilongjiang Province, China (47°35′17.8″  N,  133°37′48.4″ E), from June to September, 2003. Three plant communities, Carex pseudocuraica, Carex lasiocarpaand Deyeuxia angustifolia,were selected to measure fluxes of CH4 and N2O to contrast the variance of the emission rates of both  greenhouse gases in these different plant zones. Air temperature and soil temperature at 5 cm depth, soil redox potential (0-100 cm), and standing water depth  at  each site also were measured to determine the main factors that control CH4 and N2O emissions within and among plant zones.The wetland was a source of both CH4 and N2O during the growing season and emissions showed conspicuous temporal and spatial variations. Similar temporal variations of CH4 and N2O fluxes were observed in the C. pseudocuraica and C . lasiocarpasites. Emission rates of CH4 were higher in July and August while emissions of N2O were higher in July and September. However, the highest emissions of CH4 and N2O in the C. angustifoliasite occurred about one month earlier than in the C. pseudocuraicaand C. lasiocarpasites. The highest CH4 emissions observed in  the wetland were in the C. pseudocuraicasite on July 19 with a rate of 696. 24 mg?m-2?d-1, and the highest N2O emissions were in the D. angustifolia site on June 12 with a rate of 2.53 mg?m-2?d-1. The average CH4 flux from the C. pseudocuraica site was 273.6 mg?m-2?d-1, the highest among the three sites over the growing season but was not significantly different from 259.2 mg?m-2?d-1 of the C. lasiocarpasite. However, both were significantly higher than the 38.16 mg?m-2?d-1 measured in the D. angustifolia site (p<0.000 1 ). These results showed  that average CH4 fluxes in submerged wetlands were higher than in seasonal wetlands. N2O fluxes from the C. pseudocuraica, C. lasiocarpa and D. angustifoliasites were not significantly different (p=0.967) with an average flux of 0.969, 0.932 and 0.983 mg?m-2?d-1, respectively, suggesting  that submerged and seasonal wetlands had similar rates of N2O emissions.Air temperature, soil temperature, soil redox potential and standing water depth  were important factors influencing emission rates of CH4 and N2O from the wetlands. Relationship analysis showed that CH4 fluxes were correlated weakly with  air temperature and soil temperature at 5 cm depth within a site (0.201