Stochastic processes of soil production and transport: Erosion rates, topographic variation and cosmogenic nuclides in the Oregon Coast Range
Stochastic processes of soil production and transport: Erosion rates, topographic variation and cosmogenic nuclides in the Oregon Coast Range
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DOI：
10.1002/esp.209
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发表时间：
2001-05-01
影响因子：
3.3
通讯作者：
Finkel, RC
中科院分区：
文献类型：
--
作者：
Heimsath, AM;Dietrich, WE;Finkel, RC
只有当当地的土壤产量等于或超过当地的侵蚀速度时，活跃的隆起和侵蚀地区的景观才能保持土壤覆盖。土壤生产率随土壤深度而变化，因此土壤深度的局部变化可以提供侵蚀率空间变化的线索。如果隆起和随之而来的侵蚀速率在空间和时间上足够均匀，那么就会有由侵蚀过程形成的平衡地貌的趋势。土壤覆盖层的厚度会进行调整，使土壤生产与侵蚀相匹配。先前在俄勒冈州海岸山脉的研究表明，当地可能存在山坡侵蚀和产沙量平衡的趋势。这里的结果从一个新的方法的基础上宇宙成因的放射性核素积累的基岩矿物在土壤柱的基础上报告。我们量化土壤生产如何在南部俄勒冈州海岸山脉土壤厚度的变化，并进一步探讨景观平衡的问题。表观土壤生产力被确定为土壤深度的反指数函数，最大的推断生产率为268米马（-1）发生在土壤深度为零。然而，这个速率取决于下面基岩的风化程度。随机和大规模的性质，土壤生产的生物过程导致大的时间和空间变化的土壤深度;土壤深度的空间变化既不支持也不拒绝平衡形态。然而，我们观察到的流域平均侵蚀速率为117 m Ma（-1），与其他人对该地区的估计相似，也与陡峭山脊典型的薄土和中等土壤下的土壤生产率相似。我们认为，部分的俄勒冈州海岸山脉可能会以大致相同的速度侵蚀，但当地的排水网络和情节侵蚀事件之间的竞争，导致地貌是当地的平衡，并有一个空间变化的土壤地幔。版权所有（C）2001约翰威利父子有限公司
Landscapes in areas of active uplift and erosion can only remain soil-mantled if the local production of soil equals or exceeds the local erosion rate. The soil production rate varies with soil depth, hence local variation in soil depth may provide clues about spatial variation in erosion rates. If uplift and the consequent erosion rates are sufficiently uniform in space and time, then there will be tendency toward equilibrium landforms shaped by the erosional processes. Soil mantle thickness would adjust such that soil production matched the erosion. Previous work in the Oregon Coast Range suggested that there may be a tendency locally toward equilibrium between hillslope erosion and sediment yield. Here results from a new methodology based on cosmogenic radionuclide accumulation in bedrock minerals at the base of the soil column are reported. We quantify how soil production varies with soil thickness in the southern Oregon Coast Range and explore further the issue of landscape equilibrium. Apparent soil production is determined to be an inverse exponential function of soil depth, with a maximum inferred production rate of 268 m Ma(-1) occurring under zero soil depth. This rate depends, however, on the degree of weathering of the underlying bedrock. The stochastic and large-scale nature of soil production by biogenic processes leads to large temporal and spatial variations in soil depth; the spatial variation of soil depth neither supports nor rejects equilibrium morphology. Our observed catchment-averaged erosion rate of 117 m Ma(-1) is, however, similar to that estimated for the region by others, and to soil production rates under thin and intermediate soils typical for the steep ridges. We suggest that portions of the Oregon Coast Range may be eroding at roughly the same rate, but that local competition between drainage networks and episodic erosional events leads to landforms that are out of equilibrium locally and have a spatially varying soil mantle. Copyright (C) 2001 John Wiley & Sons, Ltd.