Marsh edge erosion and associated carbon dynamics in coastal Louisiana: A proxy for future wetland-dominated coastlines world-wide
Marsh edge erosion and associated carbon dynamics in coastal Louisiana: A proxy for future wetland-dominated coastlines world-wide
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DOI：
10.1016/j.ecss.2019.106289
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发表时间：
2019-10-15
影响因子：
2.8
通讯作者：
White, John R.
中科院分区：
文献类型：
--
作者：
Sapkota, Yadav;White, John R.
在路易斯安那州，沼泽边缘侵蚀导致的沿海湿地流失是一个严重的问题。大多数关于沿海土地损失的研究使用航空和卫星摄影分析，而实地和特定地点的测量是有限的。本研究的目的是在空间和时间上测量海岸沼泽边缘侵蚀，并探讨影响侵蚀差异的因素，包括海岸线朝向、土壤理化性质、风速和持续时间。在路易斯安那州Barataria盆地北部的6个岛屿上共建立了33个样带。海岸线上面向不同罗盘方向的横断面被测量了长达2年的侵蚀情况。分析了土壤的理化性质，包括容重、有机质、总碳、氮和磷。进行了水深测量，以确定海湾底部侵蚀剖面的程度。此外，对1.5 ~ 1.6 m的基底有机质进行了C-14定年。侵蚀速率为49.27 ~ 324.85 cm y(-1)，平均值为141.69±22.45 cm y（-1）。正如预期的那样，在受保护和未受保护的地点之间，侵蚀速率显著不同（p < 0.001）。侵蚀速率与风速（r = -0.07）不相关，与岸线罗经方向（r = 0.25）和水位（r = 0.25）相关较弱，与风时（r = 0.60）相关较强。土壤侵蚀速率与容重呈负相关（r = -0.45），与土壤表层有机质含量呈正相关（r = 0.42）。随着时间的推移，沼泽被侵蚀至1.5米的深度，这相当于每米海岸线长度每年损失1.82 +/- 0.29米(3)的沼泽体积，其中包括有机质（141.5 +/- 22.55千克米（-1））和碳（63.32 +/- 10.09千克米（-1））的损失，这些物质以前保存了长达850年。因此，Barataria盆地的年二氧化碳排放量估计为1.56 +/- 0.26万tCO(2)e（-1）。结果可以为海岸管理者提供最脆弱的湿地恢复工作的信息。由于路易斯安那州沿海地区的海平面相对上升较高，这些结果也可以用来告知世界上稳定的海岸线，在不久的将来，由于预计的海平面上升，它们的沿海沼泽相对脆弱。因此，在不久的将来，全球海岸线的侵蚀可能是二氧化碳排放的一个重要来源，因为千年储存的土壤碳在相对较短的时间内释放出来，可能会压倒人类减缓大气二氧化碳水平上升的努力。
Coastal wetland loss through marsh edge erosion is a serious problem in Louisiana. The majority of studies on coastal land loss use aerial and satellite photographic analysis while field and site-specific measurements are limited. The aim of this study was to spatially and temporally measure coastal marsh edge erosion and investigate factors responsible for differences in erosion including shoreline orientation, soil physio-chemical properties, and wind speed and duration. A total of 33 transects across six island sites in northern Barataria Basin, Louisiana were established. Transects on shorelines facing different compass directions were measured for erosion for up to 2 years. Soils were analyzed for physiochemical properties including bulk density, organic matter, total carbon, nitrogen, and phosphorus. Bathymetric surveys were conducted to determine the extent of the erosive bay bottom profile. In addition, C-14 dating of the basal organic matter (1.5-1.6 m) was conducted. Erosion rates ranged from 49.27 to 324.85 cm y(-1) with a mean value of 141.69 +/- 22.45 cm y(-1). As expected, erosion rates were significantly different (p < 0.001) between protected and unprotected sites. The erosion rate was not correlated with wind speed (r = -0.07), weakly correlated with compass direction of shoreline (r = 0.25) and water level (r = 0.25) but strongly correlated with duration of wind (r = 0.60). Erosion rate was negatively correlated (r = -0.45) with bulk density and positively correlated with organic matter content (r = 0.42) of the top 40 cm of the soil. Over time, the marsh is eroded down to a depth of 1.5 m, which correlates to annual loss of 1.82 +/- 0.29 m(3) volume of marsh per meter shoreline length including a loss of organic matter (141.5 +/- 22.55 kg m(-1)) and carbon (63.32 +/- 10.09 kg m(-1)) previously preserved for up to 850 years. As a consequence, annual CO2 emissions for Barataria Basin were estimated to be 1.56 +/- 0.26 million tCO(2)e y(-1). Results can inform coastal managers as to the most vulnerable marshes to target restoration efforts. Due to high relative sea level rise in coastal Louisiana, these results can also be used to inform the world's stable coastlines on the relative vulnerability of their coastal marshes in the near future, due to projected eustatic sea level. Consequently, the eroding coastlines across the globe may be a significant source of CO2 emissions in near future, as millennial age stored soil carbon is released in a relatively short time, potentially overwhelming human efforts to slow rising atmospheric CO2 levels.