Salinity increases with water table elevation at the boundary between salt marsh and forest
Salinity increases with water table elevation at the boundary between salt marsh and forest
复制标题
盐沼和森林边界处的盐度随着地下水位的升高而增加
DOI：
10.1016/j.jhydrol.2022.127576
复制
发表时间：
2022
影响因子：
6.4
通讯作者：
Fagherazzi, Sergio
中科院分区：
文献类型：
--
作者：
Nordio, Giovanna;Fagherazzi, Sergio
盐沼沿沿海地区向森林的迁移，现在有充分的记录。海平面上升和风暴通过增加地下水位和盐度威胁沿海森林。在北美，盐碱化是森林变成盐沼的主要原因。本文研究了位于美国德尔马瓦半岛下部森林和盐沼交界处的两口井的地下水位和盐度。上面的井位于再生森林中，在那里仍然有可能招募，而下面的井位于持久森林中，那里只有成熟的树木存活。上井的地下水在根深处是新鲜的，而下井的平均盐度为8 ppt。我们的数据表明，降雨对盐度和地下水位有瞬时影响，但它不会在较长时间内（几周到几个月）影响盐度和地下水位。地下水位和盐度反映了向沼泽方向的水力梯度（流出水量的代表）、上坡的水力梯度（流入水量的代表）和温度（蒸发蒸腾的代表）。当地下水位高时，盐度增加。为了解释这一结果，我们提出了一个假设，即高水位有利于地表淡水向沼泽的通量，以及淡水通过蒸散作用的损失。这些损失可能会被深层流动的更咸的水补充。
The migration of salt marshes into forests along coastal regions is nowadays well documented. Sea level rise and storms threaten coastal forests by increasing groundwater levels and salinity. Salinization is the main cause of forest conversion to salt marsh in North America. In this paper we study groundwater levels and salinity in two wells installed at the border between forest and salt marsh in the lower Delmarva peninsula, USA. The upper well is located in the regenerative forest, where recruitment is still possible, while the lower well is located in the persistent forest, where only mature trees survive. Groundwater in the upper well is fresh at the root depth, while in the lower well the mean salinity is 8 ppt. Our data suggest that rainfall has an instantaneous effect on salinity and groundwater levels, but it does not affect salinity and groundwater levels on longer periods (weeks to months). Groundwater levels and salinity reflect the hydraulic gradient toward the marsh (a proxy for outgoing water fluxes), the uphill hydraulic gradient (a proxy for incoming water fluxes) and temperature (a proxy for evapotranspiration). Salinity increases when groundwater levels are high. To explain this result, we put forward the hypothesis that a high water table favors the flux of surficial, fresh water to the marsh, and loss of freshwater by evapotranspiration. These losses are likely replenished by saltier water moving at depth.