黄河口不同恢复阶段湿地土壤N2O产生的不同过程及贡献

采用时空替代法,选择黄河口生态恢复前后未恢复区(R0)、2007年恢复区(R2007)和2002年恢复区(R2002)的芦苇湿地为研究对象,分析了生态恢复工程对湿地土壤N2O产生不同过程与贡献的影响.结果表明,尽管不同恢复阶段湿地土壤N2O总产生量差异明显,但总体均表现为N2O释放.恢复区湿地土壤的N2O产生量大于未恢复区.N2O的产生主要以硝化作用和硝化细菌反硝化作用为主,而反硝化作用对N2O的产生有较大削弱作用,这与不同恢复阶段湿地土壤理化性质密切相关.非生物作用对N2O产生量贡献较大,这与黄河口为高活性铁区,Fe的还原作用关系密切.尽管黄河口不同恢复阶段湿地土壤N2O的产生是生物作用与非生物作用共同作用的结果,但由于非生物作用对N2O产生的影响较大,应受到特别关注.温度和水分对不同恢复阶段湿地土壤N2O产生过程的影响不尽一致,这与土壤微生物活性对温度和水分的响应差异有关.黄河口不同恢复阶段湿地土壤的N2O总产生量介于(0.37±0.08)～(9.75±7.64)nmol·(kg·h)-1,略高于闽江口互花米草湿地的N2O总产生量,但明显低于富氧森林土壤、草原土壤和闽江口短叶茳芏湿地的N2O总产生量.研究发现,黄河口生态恢复工程的长期实施明显促进了N2O的产生,因而下一步生态恢复工程应统筹考虑景观恢复与温室气体削弱这两方面因素.

Contribution of Different Processes in Wetland Soil N2O Production in Different Restoration Phases of the Yellow River Estuary, China

By using the method of time-space mutual substitution, the contribution of different processes in wetland soil N₂O production was studied in the un-restoration wetland (R₀), restoration wetland since 2007 (R₂₀₀₇) and restoration wetland since 2002 (R₂₀₀₂) of the Yellow River estuary to evaluate the effectiveness of the restoration projects. Results showed wetland soil total N₂O production had a significant difference in different restoration phases, but the N₂O release was the main source. The N₂O production in restoration wetland was higher than that in un-restoration wetland. The N₂O production was mainly due to the nitrification and nitrifier denitrification processes, while the denitrification process had great weakening effects on N₂O production, which was closely related to the physical and chemical properties of wetland soils in different restoration phases. The non-biological processes made greater contributions to N₂O production and these were mainly due to that iron was reductive, while the Yellow River estuary was an area of highly active iron. Although N₂O production in wetland soils was the results of biological processes combined with non-biological processes in different restoration phases, non-biological processes had larger influences and should be paid a special attention. There were different influences on wetland soil processes generating N₂O between temperature and water content, indicating responses of soil microbial activities to temperature and water content were different. In addition, the N₂O production contents ranged from 0.37±0.08 nmol·(kg·h)^-1 to 9.75±7.64 nmol·(kg·h)^-1 in marshes of the Yellow River estuary, which was slightly higher than those in the S. alterniflora wetland soils of the Min River estuary, but significantly lower than those in the C. malaccensis wetland soils of the Min River estuary, the grassland soils and the aerobic forest soils. We found that the long-term implements of ecological restoration project in the Yellow River estuary obviously promoted N₂O production, so we should consider two factors of landscape restoration and weakening greenhouse gases in the next wetland restoration project.