Topographic and ecologic controls on root reinforcement
Topographic and ecologic controls on root reinforcement
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DOI：
10.1029/2008jf001168
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发表时间：
2009-08-25
影响因子：
3.9
通讯作者：
Band, L. E.
中科院分区：
文献类型：
--
作者：
Hales, T. C.;Ford, C. R.;Band, L. E.
在陡峭、土壤覆盖的地形中，浅层滑坡是一个重大危险。在强降雨条件下，浅层滑坡的分布受景观梯度变化、土壤和根系的摩擦和粘聚特性以及地下水文响应的控制。虽然可以通过数字高程模型估计坡度，但关于土壤和根系特性的信息仍然很少。通过对美国北卡罗莱纳州南部阿巴拉契亚山脉15种原生树种下坡土坑根系的分布和抗拉强度的测量，研究了地貌控制的生态变化是否影响根系黏聚力的空间分布。不同硬木树种的根抗拉强度相似，且始终高于唯一的本土灌木树种（杜鹃属）。在鼻状（发散地形区域）上发现的树木的根比那些在空心（未沟渠，收敛地形）上发现的树的根更强，这与纤维素含量的可变性一致。这种纤维素的变化可能与土壤水势的地形差异有关。所有树种的根系都集中在靠近土壤表面的地方，空心根系在土柱上的分布比鼻部根系更均匀。由于根拉力较大，位于鼻部的树木比位于空心处的树木具有更高的平均根内聚力。最大红木的根最浅，最弱，这表明该物种最近由于灭火而扩大，可能降低了一些空洞的根内聚力。对根系生长的生理控制和坡度水文之间的反馈进行量化，使我们能够创建一个基于曲率的根系黏聚力模型，这是对当前假设空间平均值的模型的重大改进。
Shallow landslides are a significant hazard in steep, soil-mantled landscapes. During intense rainfall events, the distribution of shallow landslides is controlled by variations in landscape gradient, the frictional and cohesive properties of soil and roots, and the subsurface hydrologic response. While gradients can be estimated from digital elevation models, information on soil and root properties remains sparse. We investigated whether geomorphically controlled variations in ecology affect the spatial distribution of root cohesion by measuring the distribution and tensile strength of roots from soil pits dug downslope of 15 native trees in the southern Appalachian Mountains, North Carolina, United States. Root tensile strengths from different hardwood tree species were similar and consistently higher than the only native shrub species measured (Rhododendron maximum). Roots were stronger in trees found on noses (areas of divergent topography) relative to those in hollows (unchanneled, convergent topography) coincident with the variability in cellulose content. This cellulose variability is likely related to topographic differences in soil water potential. For all species, roots were concentrated close to the soil surface, with roots in hollows being more evenly distributed in the soil column than those on noses. Trees located on noses had higher mean root cohesion than those in hollows because of a higher root tensile force. R. maximum had the shallowest, weakest roots suggesting that recent expansion of this species due to fire suppression has likely lowered the root cohesion of some hollows. Quantification of this feedback between physiologic controls on root growth and slope hydrology has allowed us to create a curvature-based model of root cohesion that is a significant improvement on current models that assume a spatially averaged value.