Key Laboratory of Humid Sub-tropical Eco-geographical Process of Ministry of Education, Fujian Normal University, Fuzhou 350007, China; College of the Environment and Ecology, Xiamen University, Xiamen 361102, China.
CSIC, Global Ecology CREAF-CSIC-UAB, Bellaterra, 08193 Barcelona, Catalonia, Spain; CREAF, Cerdanyola del Vallès, 08193 Barcelona, Catalonia, Spain.
Sci Total Environ. 2019 Jun 1;667:648-657. doi: 10.1016/j.scitotenv.2019.02.429. Epub 2019 Feb 28.
Estuarine tidal marshes sequester significant quantities of carbon and are suffering from anthropogenic nitrogen (N) enhancement. However, the effects of this N loading on carbon gas emissions from freshwater-oligohaline tidal marshes are unknown. In this paper, we report on our evaluation of the effects of a N gradient (0, 24, 48 and 96 g NHNO-N m y) on the methane (CH) and carbon dioxide (CO) emissions from freshwater and oligohaline tidal marshes in the Min River estuary, southeast China. On an annual scale, the oligohaline marsh has significantly higher CO emissions, while it has slightly lower CH emissions relative to freshwater marsh. The addition of N increased CH emission from the freshwater marsh and decreased CH emission from the oligohaline marsh, although there was no statistically significant difference in CH emission between either of the two marshes and the control. The addition of 96 g NHNO-N m y significantly increased CO emission from the freshwater marsh, while it did not significantly influence CO emission from the oligohaline marsh. CH and CO emission levels were positively correlated with soil temperature under all conditions. The CH flux resulting from both the control and the addition of N was negatively correlated with porewater SO and Cl concentrations and soil EC in the oligohaline marsh. Overall, N addition significantly increased carbon gas emissions under freshwater conditions while slightly inhibiting carbon gas emissions from the oligohaline marsh. Our findings suggested that even under low salinity conditions, the effects of N loading on CH and CO emissions from freshwater and oligohaline tidal marshes can vary. We propose that the addition of N to estuarine tidal marshes has a significant effect on the carbon cycle and promotes soil carbon loss, phenomena which may be influenced by salinity.
河口潮汐沼泽湿地储存了大量的碳，并且正受到人为氮（N）增强的影响。然而，这种氮负荷对低盐度潮汐沼泽湿地的碳气体排放的影响尚不清楚。本文报告了我们对氮梯度（0、24、48 和 96gNHNO-Nm y）对中国东南闽江河口淡水和低盐度潮汐沼泽湿地甲烷（CH）和二氧化碳（CO）排放影响的评估。在年度尺度上，低盐度沼泽湿地的 CO 排放明显更高，而相对于淡水沼泽湿地，CH 排放略低。氮的添加增加了淡水沼泽湿地的 CH 排放，减少了低盐度沼泽湿地的 CH 排放，但在两个沼泽湿地和对照之间，CH 排放没有统计学上的显著差异。添加 96gNHNO-Nm y 显著增加了淡水沼泽湿地的 CO 排放，但对低盐度沼泽湿地的 CO 排放没有显著影响。在所有条件下，CH 和 CO 排放水平与土壤温度呈正相关。在低盐度沼泽湿地中，无论是对照还是添加氮的情况下，CH 通量都与孔隙水 SO 和 Cl 浓度和土壤 EC 呈负相关。总的来说，氮的添加显著增加了淡水条件下的碳气体排放，而对低盐度沼泽湿地的碳气体排放略有抑制。我们的研究结果表明，即使在低盐度条件下，氮负荷对淡水和低盐度潮汐沼泽湿地的 CH 和 CO 排放的影响也可能有所不同。我们提出，向河口潮汐沼泽湿地添加氮对碳循环有显著影响，并促进土壤碳损失，这些现象可能受盐度影响。
