Using soil residence time to delineate spatial and temporal patterns of transient landscape response
Using soil residence time to delineate spatial and temporal patterns of transient landscape response
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DOI：
10.1029/2006jf000568
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发表时间：
2007-08-15
影响因子：
3.9
通讯作者：
Hales, T. C.
中科院分区：
文献类型：
--
作者：
Almond, Peter;Roering, Josh;Hales, T. C.
在山坡上，土壤运输和生产之间的平衡决定了当地土壤的厚度和组成土壤的颗粒的年龄分布（年龄是指从基岩脱离后经过的时间）。这种年龄分布的平均值被定义为停留时间，在具有时不变地形（即形态稳态）的景观中，土壤生产的空间均匀性保证了土壤的停留时间在空间上是不变的。因此，在土壤形成因子不变的情况下，土壤性质的空间变化反映了土壤生产不均匀导致的停留时间差异。空间上广泛的土壤数据库通常以电子形式免费提供，提供了一种廉价和易于获得的分析土壤停留时间模式和量化景观动态的方法。在这里，我们使用土壤时间序列来校准描述俄勒冈海岸山脉土壤变红的时间函数，然后用它来量化土壤停留时间的空间分布。与俄勒冈海岸山脉经历均匀侵蚀的流行观念相反，我们观察到土壤停留时间的系统变化是由河流捕获、深层滑坡和横向河道迁移驱动的。在Siuslaw河- Long Tom Creek流域分水岭以西，土壤停留时间短（色相10年）的大片连续区域出现，而色相较红的7.5年或5年的土壤斑块表明停留时间较长，景观条件短暂。这些红壤带（5YR）位于Siuslaw - Long Tom分界线以东，与第四纪排水逆转造成的低梯度山脊和山谷地形和深冲积山谷相吻合。在我们研究区域的不同地点，红壤斑块也与深层滑坡有关。由于这里使用的简单风化指数的局限性和时间函数校准的不确定性，我们计算的土壤停留时间似乎会被高估。尽管如此，我们的土壤停留时间估计似乎准确到一个数量级，并在地貌时间尺度上对景观动态提供了有用的约束。
On hillslopes the balance between soil transport and production determines local soil thickness and the age distribution of particles that comprise the soil ( where age refers to the time elapsed since detachment from bedrock). The mean of this age distribution is defined as the residence time, and in a landscape with time- invariant topography ( i. e., morphologic steady state), the spatial uniformity of soil production ensures that the residence time of soils is spatially invariant. Thus, given constant soil- forming factors, spatial variation of soil properties reflects differences in residence time driven by nonuniform soil production. Spatially extensive soil databases, which are often freely available in electronic form, provide a cheap and accessible means of analyzing patterns of soil residence time and quantifying landscape dynamics. Here we use a soil chronosequence to calibrate a chronofunction describing the reddening of soils in the Oregon Coast Range, which is then used to quantify the spatial distribution of soil residence time. In contrast to the popular conception that the Oregon Coast Range experiences uniform erosion, we observe systematic variations in soil residence time driven by stream capture, deep- seated landsliding, and lateral channel migration. Large, contiguous areas with short residence time soils ( hue 10YR) occur west of the Siuslaw River - Long Tom Creek drainage divide, whereas soil patches with redder hues of 7.5YR or 5YR indicate longer residence times and transient landscape conditions. These zones of red soils ( 5YR) occur east of the Siuslaw - Long Tom divide, coinciding with low- gradient ridge and valley topography and deeply alluviated valleys resulting from drainage reversal in the Quaternary. Patches of red soils are also associated with deep- seated landslides at various locations in our study area. Our calculated soil residence times appear subject to overestimation resulting from limitations of the simple weathering index used here and chronofunction calibration uncertainties. Nonetheless, our soil residence time estimates appear accurate to within an order of magnitude and provide a useful constraint on landscape dynamics over geomorphic timescales.