生长季与非生长季小叶章湿地N2O通量特征及排放贡献

 ：２００３年５月－２００４年４月，利用静态箱－气相色谱法对生长季与非生长季三江平原小叶章湿地N₂O 通量特征及排放贡献进行了研究。结果表明，生长季N₂O 呈脉冲式排放，通量介于０．００５～０．１１１ｍｇ／（ｍ^２·ｈ），５月较低通量与降水较多有关，６月通量骤然增加与冻层融通有关，７－８月与降水少及蒸发旺盛有关，９月与土壤中较多氮有关。N₂O 通量与５ｃｍ 地温呈显著正相关（P＜０．０１）；非生长季N₂O 表现为“吸收－排放”，通量介于－０．００１５～０．０４９７ｍｇ／（ｍ^２·ｈ）。N₂O 通量与气温、土壤融化时间均呈指数关系（P＜０．０１），说明在冻结期，温度仍是控制微生物活性的主要因素，而在融化期，温度和冻层融通是导致N₂O 通量迅速增加的重要原因。总之，生长季N₂O 排放量为２０５．５４ｍｇN₂O／ｍ^２，为N₂O 的“源”，非生长季N₂O 排放量为－２６．９７ ｍｇN₂O／ｍ^２，为N₂O 的“汇”，全年N₂O 排放量为１７８．５７ｍｇN₂O／ｍ^２，为N₂O 重要释放“源”。

N_2O flux characteristics and emission contributions of Calamagrostis angustifolia wetland during growth and non-growth seasons

The nitrous oxide (N_2O) flux characteristics and emission contributions of Calamagrostis angustifolia wetland in the Sanjiang Plain during growth and non-growth seasons were observed in situ with static-chamber and GC methods from May 2003 to April 2004. The range of N_2O fluxes during the growth season was 0.005-0.111 mg/(m~2·h) and showed pulse emission characteristics. The lower N_2O fluxes in May were correlated with abundant precipitation, while the sharply increased fluxes in June were correlated with the thaw of frozen layers. Between July and August, the N_2O fluxes were correlated with less precipitation and greater evaporation, and in September, the flux depended on available nitrogen in the soil. Further analysis indicated that the N_2O fluxes during the growth season were significantly (P<0.01) positively correlated with 5 cm ground temperature. The range of N_2O fluxes during the non-growth season was -0.001 5-0.049 7 mg/(m~2·h), presenting "absorption-emission" characteristics. Further analysis indicated that the relationship between the N_2O fluxes and atmospheric temperatures or soil thaw days was in accord with exponential model (P<0.01) indicating that, in the frozen period, temperature was still the main factor controlling microbial activity. In the thaw period, temperature and thaw of frozen layers were important for induction of the rapid increase in N_2O fluxes. In conclusion, the N_2O emission amount during growth season was 205.54 mg N_2O/m~2, acting as the emission "source", while during non-growth season, it was -26.97 mg N_2O/m~2, the "sink". Overall, the N_2O emission over the whole year was 178.57 mg N_2O/m~2, an important N_2O emission "source".