Salinity effects on greenhouse gas emissions from wetland soils are contingent upon hydrologic setting: a microcosm experiment
Salinity effects on greenhouse gas emissions from wetland soils are contingent upon hydrologic setting: a microcosm experiment
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DOI：
10.1007/s10533-018-0486-2
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发表时间：
2018-09-01
期刊：
影响因子：
4
通讯作者：
Bernhardt, Emily S.
中科院分区：
文献类型：
--
作者：
Ardon, Marcelo;Helton, Ashley M.;Bernhardt, Emily S.
沿海森林湿地提供了重要的生态系统服务，如固碳、养分保留和防洪，但它们也是温室气体排放的重要来源。人类对地表水的占用以及沿海平原景观的广泛沟渠和排水与海平面上升相互作用，增加了咸水入侵以前淡水沿海湿地的频率和规模。预计水文变化和盐水入侵都将改变沿海森林湿地的碳和养分循环。我们进行了一个全因子实验，我们将来自沿海森林湿地的完整土壤岩心暴露于实验海盐处理和两种水文处理中。我们在112天内测量了由此产生的处理对二氧化碳（CO2）、甲烷（CH4）和氧化亚氮（N2O）排放的影响。比较了四种处理的盐度效应，以分离离子强度增加的影响和添加终端电子受体（SO42-）的影响。我们比较了对照处理（添加DI）、人工盐水（ASW，目标盐度为5ppm）和单独添加硫酸盐（SO42-，浓度为5ppt盐水）和去除硫酸盐的盐水（ASW-SO42-，通过添加额外的NaCl维持5 ppt的目标盐度）的处理。我们发现，在干旱和淹水处理中，所有盐处理都抑制了CO2的产生。与我们的预期相反，与ASW和ASW- so42 -处理相比，淹水岩心的CH4通量分别增加了300 - 1200%。在干旱处理中，我们几乎没有看到任何岩心释放CH4，而添加硫酸盐的人工海水使N2O通量比DI控制增加了160%。相比之下，在我们的淹水处理中，盐和硫酸盐使N2O通量降低了72%。研究结果表明，沿海平原森林湿地的盐渍化可能具有温室气体排放增加所导致的重要气候反馈，并且这些排放的大小和方向取决于湿地水文。
Coastal forested wetlands provide important ecosystem services such as carbon sequestration, nutrient retention, and flood protection, but they are also important sources of greenhouse gas emissions. Human appropriation of surface water and extensive ditching and draining of coastal plain landscapes are interacting with rising sea levels to increase the frequency and magnitude of saltwater incursion into formerly freshwater coastal wetlands. Both hydrologic change and saltwater incursion are expected to alter carbon and nutrient cycling in coastal forested wetlands. We performed a full factorial experiment in which we exposed intact soil cores from a coastal forested wetland to experimental marine salt treatments and two hydrologic treatments. We measured the resulting treatment effects on the emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) over 112days. Salinity effects were compared across four treatments to isolate the effects of increases in ionic strength from the impact of adding a terminal electron acceptor (SO42-). We compared control treatments (DI addition), to artificial saltwater (ASW, target salinity of 5 parts per thousand) and to two treatments that added sulfate alone (SO42-, at the concentration found in 5 ppt saltwater) and saltwater with the sulfate removed (ASW-SO42-, with the 5 ppt target salinity maintained by adding additional NaCl). We found that all salt treatments suppressed CO2 production, in both drought and flooded treatments. Contrary to our expectations, CH4 fluxes from our flooded cores increased between 300 and 1200% relative to controls in the ASW and ASW-SO42- treatments respectively. In the drought treatments, we saw virtually no CH4 release from any core, while artificial seawater with sulfate increased N2O fluxes by 160% above DI control. In contrast, salt and sulfate decreased N2O fluxes by 72% in our flooded treatments. Our results indicate that salinization of forested wetlands of the coastal plain may have important climate feedbacks resulting from enhanced greenhouse gas emissions and that the magnitude and direction of these emissions are contingent upon wetland hydrology.