淹水增加对闽江河口淡水潮汐湿地孔隙水地球化学特征及CO2和CH4排放通量的影响

海平面上升使得河口潮汐湿地淹水高度增加,对CO_2和CH_4的排放通量产生重要影响,但目前绝大多数研究集中在淹水增加对河口盐沼湿地的影响,淹水增加对于河口淡水潮汐湿地的影响缺乏数据.鉴于此,本研究利用模拟潮汐池和中型生态系,研究淹水增加15 cm和30 cm后对闽江河口淡水潮汐湿地孔隙水(NH_4+、NO_3-、DOC、溶解性CH_4和DIC)浓度及CO_2和CH_4排放通量的影响.结果表明,淹水高度增加15 cm和30 cm后,CO_2的排放通量分别下降28. 53%和36. 56%;淹水增加15 cm时,CH_4的排放通量没有显著变化,增加至30 cm后,CH_4的排放通量显著增加29. 27%;淹水高度增加15 cm和30 cm,孔隙水CH_4的浓度分别增加47. 83%和73. 91%.淹水增加对孔隙水DOC浓度变化影响不显著.淹水增加促进孔隙水NH_4+浓度,并降低孔隙水DIC和NO_3-的浓度.淹水增加降低CO_2和CH_4排放通量的温度敏感性.根据研究结果,未来海平面上升50 a和100 a后,闽江河口淡水潮汐湿地的综合增温潜势将分别降低28%和35%.

Effect of Increasing Tidewater Inundation on Porewater Geochemistries and CO2 and CH4 Effluxes in the Tidal Freshwater Marshes of the Minjiang River Estuary, Southeast China

While the effect of increasing tidewater inundation caused by sea-level rise on carbon cycling had been well studied in saltmarshes, little is known about the effect of increasing tidewater inundation on CO₂ and CH₄ effluxes in the tidal freshwater marsh soils. Herein, the effects of tide inundation on porewater geochemistries (NH₄⁺, NO₃^-, DOC, dissolved CH₄, and DIC) and CH₄ and CO₂ effluxes were examined in the soils of tidal freshwater marshes in the Minjiang River Estuary, East China Sea. By applying "mesocosm" and a simulated tide pool, the tide inundation height increased by 15 cm and 30 cm over the control (CK). The CO₂ effluxes decreased by 28.53% and 36.56%, and the dissolved CH₄ concentrations increased by 47.83% and 73.91%, in treatments (CK+15 cm) and (CK+30 cm), respectively. The CH₄ effluxes did not change significantly in the treatment (CK+15 cm), but increased by 29.27% in treatment (CK+30 cm). The increasing tidewater inundation had no significant impact on DOC concentrations, but increased NH₄⁺ concentrations and decreased DIC and NO₃^- concentrations. Increasing tide inundation also reduced the temperature sensitivity of CH₄ and CO₂ effluxes. The study highlighted that the sea level rise-induced increase in tidewater inundation would decrease the annual global warming potential of tidal freshwater wetlands by 28% and 35% in the next 50 and 100 years, respectively.