科學(xué)家提出,，淡水沼澤比咸水濕地相對較弱可能有助于解釋卡特琳娜颶風(fēng)和麗塔颶風(fēng)過后海岸侵蝕的模式。為了比較淡水和咸水濕地對颶風(fēng)驅(qū)動的海浪的抵抗力,，Nick Howes及其同事測試了美國的墨西哥灣沿海高鹽度和低鹽度沼澤的土壤剪切強度,。這組科學(xué)家發(fā)現(xiàn)了淡水濕地土壤的一個薄弱區(qū)與植物根系的基礎(chǔ)重合。來自高鹽度濕地的土壤沒有這種弱區(qū),，而且含有更深的根系,。
這組作者說，在這個弱區(qū)的土壤強度低于計算出的卡特琳娜颶風(fēng)產(chǎn)生的海浪的剪切力,，這可能解釋了在這場颶風(fēng)期間低鹽度沼澤比咸水沼澤的破壞率更高,。海岸濕地因為它們保護內(nèi)陸地區(qū)不受劇烈的風(fēng)暴沖擊的能力而具有價值。這組作者提出,，目前向墨西哥灣沿海地區(qū)附近的內(nèi)陸沼澤引入淡水的計劃可能削弱保護性的海岸屏障,，讓內(nèi)陸區(qū)域更容易遭受颶風(fēng)破壞。(生物谷Bioon.com)
生物谷推薦原文出處：
PNAS doi: 10.1073/pnas.0914582107
Hurricane-induced failure of low salinity wetlands
Nick C. Howesa,1, Duncan M. FitzGeralda, Zoe J. Hughesa, Ioannis Y. Georgioub, Mark A. Kulpb, Michael D. Minerb, Jane M. Smithc, and John A. Barras d
aDepartment of Earth Sciences, Boston University, 675 Commonwealth Avenue, Boston, MA 02215;
bPontchartrain Institute for Environmental Sciences, University of New Orleans, New Orleans, LA 70148;
cUnited States Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199; and
dUnited States Army Engineer Research and Development Center, Environmental Laboratory, Wetlands Environmental Technology Research Facility, Baton Rouge, LA 70803
During the 2005 hurricane season, the storm surge and wave field associated with Hurricanes Katrina and Rita eroded 527 km2 of wetlands within the Louisiana coastal plain. Low salinity wetlands were preferentially eroded, while higher salinity wetlands remained robust and largely unchanged. Here we highlight geotechnical differences between the soil profiles of high and low salinity regimes, which are controlled by vegetation and result in differential erosion. In low salinity wetlands, a weak zone (shear strength 500–1450 Pa) was observed ～30 cm below the marsh surface, coinciding with the base of rooting. High salinity wetlands had no such zone (shear strengths > 4500 Pa) and contained deeper rooting. Storm waves during Hurricane Katrina produced shear stresses between 425–3600 Pa, sufficient to cause widespread erosion of the low salinity wetlands. Vegetation in low salinity marshes is subject to shallower rooting and is susceptible to erosion during large magnitude storms; these conditions may be exacerbated by low inorganic sediment content and high nutrient inputs. The dramatic difference in resiliency of fresh versus more saline marshes suggests that the introduction of freshwater to marshes as part of restoration efforts may therefore weaken existing wetlands rendering them vulnerable to hurricanes.
