Restoring marsh elevation in a rapidly subsiding salt marsh by thin-layer deposition of dredged material
Restoring marsh elevation in a rapidly subsiding salt marsh by thin-layer deposition of dredged material
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DOI：
10.1016/s0925-8574(98)00061-5
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发表时间：
1999-02-01
影响因子：
3.8
通讯作者：
Lynch, JC
中科院分区：
文献类型：
--
作者：
Ford, MA;Cahoon, DR;Lynch, JC
利用高压喷射疏浚技术(Jet-Spraze(R)(2))在沿海沼泽上薄层沉积疏浚材料，已被提出作为一种机制，以最大限度地减少与传统斗式疏浚技术相关的湿地影响，并恢复密西西比河三角洲退化沼泽的土壤海拔。在路易斯安那州沿海以互花米草为主的0.5公顷盐沼中，对喷雾疏浚对植被沼泽和邻近浅水栖息地(以前是退化为开阔水域的植被沼泽)的影响进行了评估。疏浚沉积物的厚度是根据人工土壤标志层确定的，土壤高程变化是根据喷洒前在喷洒沼泽和参考沼泽中建立的沉积-侵蚀表(SET)确定的。同时进行垂直淤积和高程变化测量，以计算浅层(类似于5米深)下沉(淤积减去高程变化)。1996年7月喷洒后立即进行的测量表明，互花米草的茎被喷雾的力量击倒，并覆盖了23毫米的疏浚材料。互花米草的茎很快就恢复了，到1997年7月，互花米草的盖度比项目前增加了三倍。因此，疏浚的材料层足够薄，可以让互花米草植物存活，而不会随后被较高沼泽区典型的植物物种殖民。到1998年2月，该站点积累了62毫米的垂直淤积，几乎没有干扰的迹象。在喷雾沼泽和参考沼泽，土壤高程的变化虽然不显著，但平均而言大于吸积，这表明根生物量增加和/或孔隙水储量增加所引起的地下膨胀影响了该沼泽地区的高程。在邻近的浅水池，由于喷洒，1996年7月沉积了129毫米的泥沙，尽管最初的浅层下沉和持续到1998年2月的侵蚀，但水底高度上升到足以使互花链霉菌从邻近的沼泽通过根茎生长入侵。因此，疏浚材料在该地点的薄层沉积在1.5年后有效地恢复和维持了沼泽高程。然而，如果开阔水域的沉积物不能很快通过进一步的植被殖民而完全稳定下来，侵蚀最终可能会降低海拔到新兴植被无法持续的水平。(C)1999年爱思唯尔科学公司。版权所有。
Thin-layer deposition of dredged material on coastal marsh by means of high-pressure spray dredging (Jet-Spray(R)(2)) technology has been proposed as a mechanism to minimize wetland impacts associated with traditional bucket dredging technologies and to restore soil elevations in deteriorated marshes of the Mississippi River delta. The impact of spray dredging on vegetated marsh and adjacent shallow-water habitat (formerly vegetated marsh that deteriorated to open water) was evaluated in a 0.5-ha Spartina alterniflora-dominated salt marsh in coastal Louisiana. The thickness of dredged sediment deposits was determined from artificial soil marker horizons and soil elevation change was determined from sedimentation-erosion tables (SET) established prior to spraying in both sprayed and reference marshes. The vertical accretion and elevation change measurements were made simultaneously to allow for calculation of shallow (similar to 5 m depth) subsidence (accretion minus elevation change). Measurements made immediately following spraying in July 1996 revealed that stems of S. alterniflora were knocked down by the force of the spray and covered with 23 mm of dredged material. Stems of S. alterniflora a soon recovered, and by July 1997 the percent cover of S. alterniflora had increased three-fold over pre-project conditions. Thus, the layer of dredged material was thin enough to allow for survival of the S. alterniflora plants, with no subsequent colonization by plant species typical of higher marsh zones. By February 1998, 62 mm of vertical accretion accumulated at this site, and little indication of disturbance was noted. Although not statistically significant, soil elevation change was greater than accretion on average at both the spray and reference marshes, suggesting that subsurface expansion caused by increased root biomass production and/or pore water storage influence elevation in this marsh region. In the adjacent shallow water pond, 129 mm of sediment was deposited in July 1996 as a result of spraying, and despite initial shallow subsidence and continual erosion through February 1998, water bottom elevation was raised sufficiently to allow S. alterniflora a to invade via rhizome growth from the adjacent marsh. Hence, thin-layer deposition of dredged material at this site was effective at restoring and maintaining marsh elevation after 1.5 years. However, if the open water sediment deposits are not soon completely stabilized via further vegetative colonization, erosion may eventually lower elevations to the level where emergent vegetation cannot persist. (C) 1999 Elsevier Science BV. All rights reserved.