Northeastern US salt marshes face multiple co-stressors, including accelerating rates of relative sea level rise (RSLR), elevated nutrient inputs, and low sediment supplies. In order to evaluate how marsh surface elevations respond to such factors, we used surface elevation tables (SETs) and surface elevation pins to measure changes in marsh surface elevation in two eastern Long Island Sound salt marshes, Barn Island and Mamacoke marshes. We compare marsh elevation change at these two systems with recent rates of RSLR and find evidence of differences between the two sites; Barn Island is maintaining its historic rate of elevation gain (2.3 ± 0.24 mm year⁻¹ from 2003 to 2013) and is no longer keeping pace with RSLR, while Mamacoke shows evidence of a recent increase in rates (4.2 ± 0.52 mm year⁻¹ from 1994 to 2014) to maintain its elevation relative to sea level. In addition to data on short-term elevation responses at these marshes, both sites have unusually long and detailed data on historic vegetation species composition extending back more than half a century. Over this study period, vegetation patterns track elevation change relative to sea levels, with the Barn Island plant community shifting towards those plants that are found at lower elevations and the Mamacoke vegetation patterns showing little change in plant composition. We hypothesize that the apparent contrasting trend in marsh elevation at the sites is due to differences in sediment availability, salinity, and elevation capital. Together, these two systems provide critical insight into the relationships between marsh elevation, high marsh plant community, and changing hydroperiods. Our results highlight that not all marshes in Southern New England may be responding to accelerated rates of RSLR in the same manner.

中文翻译：

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两个长岛峡盐沼中海拔和植被的年代际尺度变化相反。

美国东北盐沼面临着多重共同压力，包括相对海平面上升（RSLR）的速度加快，营养物质输入增加和沉积物供应不足。为了评估沼泽地表高程对这些因素的响应，我们使用了表面高程表（SET）和表面高程图钉来测量两个长岛东部盐沼，谷仓岛和Mamacoke沼泽中沼泽地表高程的变化。我们将这两个系统的沼泽海拔变化与最近的RSLR速率进行比较，并找到两个站点之间差异的证据。谷仓岛（Barn Island）保持其历史性增高速率（2003年至2013年为2.3±0.24毫米- ¹年），不再与RSLR保持同步，而Mamacoke显示了近期速率增加的证据（4.2±0.52毫米- ^1年）（从1994年到2014年）保持相对于海平面的海拔高度。除了这些沼泽地区短期海拔响应的数据外，两个地点都有关于历史植被物种组成的长达半个多世纪的异常长而详尽的数据。在此研究期内，植被模式跟踪海拔高度相对于海平面的变化，其中谷仓岛植物群落向低海拔地区发现的植物转移，而Mamacoke植被模式的植物组成变化很小。我们假设这些地点的沼泽高程出现明显的对比趋势是由于沉积物可利用性，盐度和高程资本的差异。这两个系统共同提供了对沼泽海拔，高沼泽植物群落，和不断变化的水文期。我们的结果表明，并非所有新英格兰南部的沼泽地都以同样的方式对RSLR的加速发展做出反应。