Worldwide, human activities have modified hydrology and nutrient loading regimes in coastal wetlands. Understanding the interplay between these drivers and subsequent response of wetland plant communities is essential to informing wetland management and restoration efforts. Recent restoration strategies in Louisiana proposes to use sediment diversions from the Mississippi River to build land in adjacent wetlands and reduce the rate of land to open water conversion. In conjunction with sediment delivery, diversions can increase nutrient loads and water levels in the receiving basins. We conducted a greenhouse mesocosm experiment in which we exposed three common tidal freshwater and brackish marsh plants (Panicum hemitomon, Sagittaria lancifolia, and Spartina patens) to two nitrate loading rates [high (35 g N m² year⁻¹) and low (0.25 g N m² year⁻¹)], and two flooding treatments (with and without diversion pulsing). Experimental units were set at two different elevations within the treatment tanks to simulate both a healthy and degraded marsh. Plant growth metrics and soil physicochemical properties were measured monthly. Final total biomass was determined at the study’s conclusion. Growth responses differed between species but were not significantly influenced by the treatments. Soil redox potential decreased significantly following the increase in flooding associated with the diversion pulse, but recovered to pre-diversion levels after a 3-month recovery period. Our study suggests short flooding pulses with a recovery period may be key for maintaining healthy marshes, however there remains a need for longer-term empirical studies to understand marsh response to pressures associated with river sediment diversions over time.

中文翻译：

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潮汐沼泽植被对洪水和氮的脉冲增加的响应

在世界范围内，人类活动已经改变了沿海湿地的水文和养分含量。了解这些驱动因素与湿地植物群落的后续反应之间的相互作用对于告知湿地管理和恢复工作至关重要。路易斯安那州最近的恢复策略建议利用密西西比河的泥沙分流在邻近的湿地中建立土地，并降低土地转化为开放水的速度。结合泥沙输送，转移会增加接收盆地的养分负荷和水位。我们进行了温室中观试验，暴露了三种常见的潮汐淡水和淡淡的沼泽植物（Panicum hemitomon，Sagittaria lancifolia和Spartina patens）到两个硝酸盐加载速率[高（35 g N m ²年^-1）和低（0.25 g N m ²年^-1））]，以及两种驱油处理（带或不带导流脉冲）。将实验装置放置在处理池中的两个不同高度处，以模拟健康和退化的沼泽。每月测量植物生长指标和土壤理化特性。最终总生物量由研究结论确定。物种之间的生长反应有所不同，但不受处理的影响很大。在与分流脉冲相关的洪水增加后，土壤氧化还原电势显着下降，但在3个月的恢复期后恢复到分流前水平。我们的研究表明，短暂的洪水脉冲和恢复期可能是维持健康沼泽的关键，