WasserCluster Lunz GmbH - Inter-university Center for Aquatic Ecosystem Research, 3293 Lunz am See, Austria; LEAF - Linking Landscape, Environment, Agriculture and Food, Instituto Superior de Agronomia, University of Lisbon, 1349-017 Lisbon, Portugal; Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, 1180 Vienna, Austria.
WasserCluster Lunz GmbH - Inter-university Center for Aquatic Ecosystem Research, 3293 Lunz am See, Austria; Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, 1180 Vienna, Austria.
Sci Total Environ. 2020 May 1;715:136980. doi: 10.1016/j.scitotenv.2020.136980. Epub 2020 Jan 28.
The parafluvial zone is frequently exposed to drying-rewetting cycles with critical consequences for the biogeochemistry of soil and sediment in river-floodplain landscapes. Upon restoration of the hydrological connectivity, substantial changes in biogeochemical processes are expected. The effects of water fluctuation on the magnitude of GHG emissions were investigated in the parafluvial zone of a restored river floodplain in Austria. Sediment composition, DOM quality and NO, CO, CH fluxes were quantified during distinct hydrological periods (intermittent, desiccation and post flood) and along a hydrological gradient. The hydrological gradient ranged from non-flooded plots in the floodplain soil (used as reference plots after restoration), to rarely-flooded and frequently flooded sediment plots in the parafluvial zone. Enhanced biogeochemical turnover rates were identified during the intermittent period, when NO and CO emissions peaked. In particular, the frequently flooded plots showed significantly higher CO and CH emissions compared to non-flooded and rarely-flooded plots. This indicates a strong effect of water level fluctuation on GHG emissions, with higher emissions occurring during transitional stages of drying and rewetting. Strong positive relationships were found between individual GHG fluxes, suggesting a tight link between C and N cycles. Both the C and N cycles are dependent on similar substrate characteristics that are governed by the quality of the DOM pool. Interestingly, drier sediments in the rarely-flooded plots were also active areas for emissions. This highlights the importance to include dry phases and sites in the overall C and N emission estimates of riverine landscapes. From the restoration point of view, NO emissions in the parafluvial zone did not differ significantly from the emissions in the reference plots, whereas CO and CH fluxes did. When making management decisions to restore connectivity, one needs to carefully consider the interplay between nutrient removal from water versus GHG emissions, to reach maximum environmental benefits.
滨河带经常经历干湿交替过程，这对河流泛滥平原景观土壤和沉积物的生物地球化学具有重要影响。在恢复水连通性后，预计生物地球化学过程会发生重大变化。本研究在奥地利一个恢复后的河流泛滥平原的滨河带中，调查了水波动对温室气体排放强度的影响。在不同的水文时期（间歇性、干燥和洪水后）和沿水文梯度量化了沉积物组成、DOM 质量以及 NO、CO、CH 通量。水文梯度范围从泛滥平原土壤中的非洪水区（恢复后用作参考区）到滨河带中很少洪水区和经常洪水区的沉积物区。在间歇性时期，NO 和 CO 排放峰值时，发现生物地球化学转化速率增强。特别是，与非洪水区和很少洪水区相比，经常洪水区的 CO 和 CH 排放量显著更高。这表明水位波动对温室气体排放有强烈影响，在干燥和再湿润的过渡阶段排放更高。个别温室气体通量之间存在强烈的正相关关系，表明 C 和 N 循环之间存在紧密联系。C 和 N 循环都依赖于类似的底物特征，而这些特征又受到 DOM 池质量的控制。有趣的是，很少洪水区的干燥沉积物也是排放活跃区。这强调了在河流景观的整体 C 和 N 排放估算中纳入干燥阶段和地点的重要性。从恢复的角度来看，滨河带的 NO 排放与参考区的排放没有显著差异，但 CO 和 CH 通量有显著差异。在做出恢复连通性的管理决策时，需要仔细考虑从水中去除养分与温室气体排放之间的相互作用，以实现最大的环境效益。
