Fertilizer legacies meet saltwater incursion: challenges and constraints for coastal plain wetland restoration
Fertilizer legacies meet saltwater incursion: challenges and constraints for coastal plain wetland restoration
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DOI：
10.1525/elementa.236
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发表时间：
2017-07-31
影响因子：
3.9
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.
沿海湿地恢复是适应气候变化和缓解过量养分径流的重要工具。然而，恢复后的沿海湿地提供多种生态系统服务的能力受到压力因素的限制，例如来自上游农田的过量养分、现场高养分残留以及下游盐度上升。这些压力因素的影响因水文循环的加速而加剧，预计将导致更长时间的干旱，并夹杂着更严重的风暴。我们使用了大片（440公顷）恢复湿地的七年地表水和六年土壤溶液水化学来研究肥料残留、水文变化和干旱引起的盐化如何影响溶解养分和碳浓度。为了更好地了解恢复湿地的恢复轨迹，我们还对一片活跃的农田和两片成熟的森林湿地进行了采样。我们的结果表明，与两个成熟的森林湿地相比，恢复的湿地土壤溶液中的氮 (N) 和磷 (P) 浓度高出 2-10 倍，这可能是由于重新淹没而释放了残留肥料。尽管相对于参考湿地养分浓度有所升高，但恢复后的湿地持续减弱了上游农场输送的氮和磷脉冲。即使持续加载，自最初的洪水以来，整个恢复的湿地地表水中的氮和磷浓度仍然下降。我们的结果表明，农田恢复的湿地的高养分浓度和输出可能是一个严重但暂时的问题。如果田地向湿地转变要成为改善养分径流和使沿海平原生态系统适应气候变化的更广泛的方法，我们就应该采用新的方法来最大限度地减少湿地恢复工作的初始输出阶段。
Coastal wetland restoration is an important tool for climate change adaptation and excess nutrient runoff mitigation. However, the capacity of restored coastal wetlands to provide multiple ecosystem services is limited by stressors, such as excess nutrients from upstream agricultural fields, high nutrient legacies on-site, and rising salinities downstream. The effects of these stressors are exacerbated by an accelerating hydrologic cycle, expected to cause longer droughts punctuated by more severe storms. We used seven years of surface water and six years of soil solution water chemistry from a large (440 ha) restored wetland to examine how fertilizer legacy, changes in hydrology, and drought-induced salinization affect dissolved nutrient and carbon concentrations. To better understand the recovery trajectory of the restored wetland, we also sampled an active agricultural field and two mature forested wetlands. Our results show that nitrogen (N) and phosphorus (P) concentrations in soil solution were 2-10 times higher in the restored wetland compared to two mature forested wetlands, presumably due to legacy fertilizer mobilized by reflooding. Despite elevated nutrient concentrations relative to reference wetlands, the restored wetland consistently attenuated N and P pulses delivered from an upstream farm. Even with continued loading, N and P concentrations in surface water throughout the restored wetland have decreased since the initial flooding. Our results suggest that high nutrient concentrations and export from wetlands restored on agricultural lands may be a severe but temporary problem. If field to wetland conversion is to become a more widespread method for ameliorating nutrient runoff and adapting coastal plain ecosystems to climate change, we should adopt new methods for minimizing the initial export phase of wetland restoration efforts.