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Floods increase carbon dioxide and methane fluxes in agricultural streams
Freshwater Biology ( IF 2.7 ) Pub Date : 2020-09-08 , DOI: 10.1111/fwb.13614
Samuel R. Blackburn 1 , Emily H. Stanley 1
Affiliation  

  1. Changes in climate are causing floods to occur more often and more intensely in many parts of the world, including agricultural landscapes of southern Wisconsin (U.S.A.). How flooding and greater flood frequency affect stream carbon dioxide (CO2) and methane (CH4) fluxes and concentrations is not obvious. Thus, we asked how diffusive fluxes of CO2 and CH4 varied over time, particularly in response to floods, in agricultural streams, and what were likely causes for observed flood responses.
  2. We measured concentrations and diffusive fluxes of CO2 and CH4 at 10 stream sites in mixed agricultural and suburban catchments in southern Wisconsin (U.S.A.) during the growing season (March–November) in a year that experienced multiple floods. Habitat, hydrologic, and water chemistry attributes were also quantified to determine likely drivers of changes in gas concentrations and fluxes.
  3. Habitat and water chemistry, as well as CO2 and CH4 concentrations and fluxes were temporally erratic and lacked any seasonality. Carbon dioxide and CH4 concentrations and fluxes were higher during floods along with increased water velocity, turbidity, and dissolved organic carbon and decreases in dissolved oxygen, soft sediment depth, and macrophyte cover.
  4. Increased gas concentrations and fluxes were probably due to flushing of gases from soils, respiration of organic matter in the channel, and increased gas exchange velocities during floods.
  5. Flooding alleviated both supply and transfer limits on CO2 and CH4 emissions in these agricultural streams, and frequent and prolonged flooding during the growing season led to sustained high emissions from these streams. We hypothesise that such persistent increases in emissions during floods may be a common response to high precipitation periods for many agricultural streams.


中文翻译:

洪水增加了农业流中的二氧化碳和甲烷通量

  1. 气候变化导致洪水在世界许多地方发生得越来越频繁,而且更加激烈,包括美国威斯康星州南部的农业景观。洪水和更大洪水频率如何影响河流的二氧化碳(CO 2)和甲烷(CH 4)的通量和浓度尚不明显。因此,我们询问了农业流中CO 2和CH 4的扩散通量如何随时间变化,尤其是对洪水的响应,以及观察到的洪水响应的可能原因是什么。
  2. 我们在经历多次洪水的一年(3月至11月)的生长季节(3月至11月)中,测量了美国威斯康星州南部(农业)和郊区集水区的10个河流站点的CO 2和CH 4浓度和扩散通量。生境,水文和水化学属性也被量化,以确定气体浓度和通量变化的可能驱动因素。
  3. 生境和水化学以及CO 2和CH 4的浓度和通量在时间上是不稳定的,没有任何季节性。洪水期间二氧化碳和CH 4的浓度和通量较高,水速,浊度和溶解有机碳增加,溶解氧,软沉积物深度和大型植物覆盖减少。
  4. 气体浓度和通量的增加可能是由于土壤中的气体冲刷,河道中有机物的呼吸以及洪水期间气体交换速度的增加。
  5. 洪水减轻了这些农业流中CO 2和CH 4排放的供应和转移限制,并且在生长期频繁且长时间的洪水导致这些流中的持续高排放。我们假设洪水期间排放量的这种持续增加可能是许多农业流对高降水期的普遍反应。
更新日期:2020-09-08
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