Soil moisture causes dynamic adjustments to root reinforcement that reduce slope stability
Soil moisture causes dynamic adjustments to root reinforcement that reduce slope stability
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DOI：
10.1002/esp.4039
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发表时间：
2017-04-01
影响因子：
3.3
通讯作者：
Miniat, Chelcy F.
中科院分区：
文献类型：
--
作者：
Hales, Tristram C.;Miniat, Chelcy F.
在陡峭的土壤覆盖的景观中，浅层滑坡的发生受到植被分布的强烈控制，植被的根加固了土壤。根的加固程度取决于穿过潜在破坏面的根的数量、直径分布、方向和力学性能。了解森林中这些特性在空间和时间上的变化仍然是一个重大挑战。在这里，我们检验了沿山坡根系加固的时空变化是地形土壤湿度梯度的函数的假设。为了验证这一假设，我们比较了美国北卡罗来纳州阿巴拉契亚山脉南部相对干燥、发散的鼻子和相对潮湿、收敛的空洞的根加固测量结果。我们的初步结果表明，在土壤湿度较高的地区，由于根的抗拉强度降低，根的钢筋减少。事后室内实验进一步证明，根的抗拉强度随着根含水量的增加而降低。这一效应与其他关于茎材的实验结果一致，表明细胞壁含水量的增加会降低抗拉强度。我们的实验数据表明，根系可以在数小时内适应外部根系水分条件的变化，这表明根系水分含量会在大风暴事件（小时-天）的时间尺度上发生变化。在无限边坡稳定模型中，我们评估了根系抗拉强度的动态变化对表观黏聚强度的影响。当降水驱动的饱和土壤深度的增加既增加孔隙压力又减少根系加固时，边坡的稳定性会大大降低。版权所有：John Wiley & Sons， Ltd。
In steep soil-mantled landscapes, the initiation of shallow landslides is strongly controlled by the distribution of vegetation, whose roots reinforce the soil. The magnitude of root reinforcement depends on the number, diameter distribution, orientation and the mechanical properties of roots that cross potential failure planes. Understanding how these properties vary in space and time in forests remains a significant challenge. Here we test the hypothesis that spatio-temporal variations in root reinforcement along a hillslope occur as a function of topographic soil moisture gradients. To test this hypothesis we compared root reinforcement measurements from relatively dry, divergent noses to relatively wet, convergent hollows in the southern Appalachian Mountains, North Carolina, USA. Our initial results showed that root reinforcement decreased in areas of higher soil moisture because the tensile strength of roots decreased. A post hoc laboratory experiment further demonstrated that root tensile strength decreased as root moisture content increased. This effect is consistent with other experiments on stem woods showing that increased water content in the cell wall decreases tensile strength. Our experimental data demonstrated that roots can adjust to changes in the external root moisture conditions within hours, suggesting that root moisture content will change over the timescale of large storm events (hours-days). We assessed the effects of the dynamic changes in root tensile strength to the magnitude of apparent cohesion within the infinite slope stability model. Slopes can be considerably less stable when precipitation-driven increases in saturated soil depth both increase pore pressures and decrease root reinforcement. Copyright (c) 2016 John Wiley & Sons, Ltd.