Groundwater controls ecological zonation of salt marsh macrophytes.
Groundwater controls ecological zonation of salt marsh macrophytes.
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DOI：
10.1890/13-2183.1
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发表时间：
2015-03
期刊：
影响因子：
4.8
通讯作者：
Alicia M. Wilson;T. Evans;W. Moore;C. A. Schutte;S. Joye;Andrea H Hughes;Joseph L. Anderson
中科院分区：
文献类型：
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作者：
Alicia M. Wilson;T. Evans;W. Moore;C. A. Schutte;S. Joye;Andrea H Hughes;Joseph L. Anderson
盐沼植物生态区划受水文因素的影响较大，但对这些因素的了解较少。我们研究了美国东南部两个盐沼泽表层沉积物中的地下水流动模式，以量化不同生态区之间的水文差异。这两个地点包括靠近小溪岸边的高型或中型互花米草；位于沼泽中部的短型互花米草；位于高地沼泽的盐滩和盐角草；以及毗邻高地的淡咸水区和淡水区的罗曼鱼。这两个地点都有相对较小的沙质高地，相似的地层由覆盖在更深的沙层上的沼泽泥浆组成。我们发现这四个生态区之间存在显著的水文差异。在互花米草聚居区，垂直水流方向呈半日潮振荡。通过互花米草高地带的净流量(14天平均值)是下降的，而较短的互花草带包括明显的地下水净向上流周期。对这些地点的潮汐效率的研究表明，控制互花米草高大地带宽度的是净水流模式，而不是潮汐衰减。与互花链霉菌带不同，维吉尼亚链霉菌生长的高盐度带的特点是在小潮期间咸水持续向上流动。罗曼鱼栖息的较淡水区表现出与高盐度区相似的物理流动模式，但上升的孔隙水是淡水而不是咸水区。这些水流模式受到沼泽水文地质格局的影响，特别是高地地下水位和潮汐小溪之间的水头差异。我们观察到在两个沼泽下面的砂层中，从小溪到高地的水力水头增加了大约40厘米，这与之前的观察一致，即细粒沼泽土壤下的砂质含水层是从高地流向潮汐小溪的管道。这一水文框架支持了小溪附近相对良好的排水，增加了沼泽中部的内涝，以及邻近淡水高地的高盐度的发展。这些水文差异反过来又支持不同的生态区。
Ecological zonation of salt marsh macrophytes is strongly influenced by hydrologic factors, but these factors are poorly understood. We examined groundwater flow patterns through surficial sediments in two saltmarshes in the southeastern United States to quantify hydrologic differences between distinct ecological zones. Both sites included tall- or medium-form Spartina alterniflora near the creek bank; short-form Spartina alterniflora in the mid-marsh; salt flats and Salicornia virginica in the high marsh; and Juncus roemarianus in brackish-to-fresh areas adjacent to uplands. Both sites had relatively small, sandy uplands and similar stratigraphy consisting of marsh muds overlying a deeper sand layer. We found significant hydrologic differences between the four ecological zones. In the zones colonized by S. alterniflora, the vertical flow direction oscillated with semi-diurnal tides. Net flow (14-day average) through the tall S. alterniflora zones was downward, whereas the short S. alterniflora zones included significant periods of net upward groundwater flow. An examination of tidal efficiency at these sites suggested that the net flow patterns rather than tidal damping controlled the width of the tall S. alterniflora zone. In contrast to the S. alterniflora zones, hypersaline zones populated by S. virginica were characterized by sustained periods (days) of continuous upward flow of saline water during neap tides. The fresher zone populated by J. roemarianus showed physical flow patterns that were similar to the hypersaline zones, but the upwelling porewaters were fresh rather than saline. These flow patterns were influenced by the hydrogeologic framework of the marshes, particularly differences in hydraulic head between the upland water table and the tidal creeks. We observed increases in hydraulic head of approximately 40 cm from the creek to the upland in the sand layers below both marshes, which is consistent with previous observations that sandy aquifers below fine-grained marsh soils act as conduits for flow from uplands to tidal creeks. This hydrologic framework supports relatively good drainage near the creek, increased waterlogging in the mid-marsh, and the development of hypersalinity adjacent to the freshwater upland. These hydrologic differences in turn support distinct ecological zones.