The Effect of Aspect and Elevation on Critical Zone Architecture in the Reynolds Creek Critical Zone Observatory: A Seismic Refraction Study
The Effect of Aspect and Elevation on Critical Zone Architecture in the Reynolds Creek Critical Zone Observatory: A Seismic Refraction Study
复制标题
雷诺兹溪关键区天文台的坡向和高程对关键区建筑的影响：地震折射研究
作者：
T. Nielson;J. Bradford;W. Holbrook;M. Seyfried
在北半球以雪为主的山地流域，朝北的斜坡通常比朝南的斜坡风化更深。这是由于北面持续积雪造成的。持续积雪以单一的大脉冲将水释放到地下，这比朝南斜坡上间歇性积雪的一系列小脉冲特征更能将水传播到地下深处。约翰斯顿河是爱达荷州雷诺兹河临界区天文台的一个向东排水的集水区，跨越300米的海拔梯度。朝北的斜坡上有持续的积雪，增加了排水系统的体积，而朝南的斜坡在整个排水系统中有间歇性的积雪。我们假设两个方面之间的风化深度差异最大的地方是两个方面之间积雪量差异最大的地方。为了验证这一假设，我们在Johnston Draw进行了四次地震折射层析成像调查，从入口到出口，垂直于排水方向。根据这些测量结果，我们根据纵波速度剖面计算了风化带的厚度。我们得出的结论是，各个方面之间的风化差异最大，发生在从出水口向上游的3 / 4处，那里的积雪差异最大。在这一点以上和以下，地下风化更均匀，雪的积累更相似。我们还观察到风化带的厚度随海拔的降低而增加，并解释这与观测到的低海拔土壤湿度增加有关。我们的观察结果支持这样的假设，即当所有其他变量保持不变时，更深的积雪会导致更深的风化。一个警告是，密集的植被可能会通过土壤保留或更高的生物风化率，对朝北的斜坡造成更深的风化。
In the northern hemisphere within snow-dominated mountainous watersheds north-facing slopes are commonly more deeply weathered than south-facing slopes. This has been attributed to a more persistent snowpack on the north facing aspects. A persistent snowpack releases its water into the subsurface in a single large pulse, which propagates the water deeper into the subsurface than the series of small pulses characteristic of the intermittent snowpack on south-facing slopes. Johnston Draw is an east-draining catchment in the Reynolds Creek Critical Zone Observatory, Idaho that spans a 300 m elevation gradient. The north-facing slope hosts a persistent snowpack that increases in volume up drainage, while the south-facing slope has intermittent snowpack throughout the drainage. We hypothesize that the largest difference in weathering depth between the two aspects will occur where the difference in snow accumulation between the aspects is also greatest. To test this hypothesis, we conducted four seismic refraction tomography surveys within Johnston Draw from inlet to outlet and perpendicular to drainage direction. From these measurements, we calculate the weathering zone thickness from the P-wave velocity profiles. We conclude that the maximum difference in weathering between aspects occurs ¾ of the way up the drainage from the outlet, where the difference in snow accumulation is highest. Above and below this point, the subsurface is more equally weathered and the snow accumulations are more similar. We also observed that the thickness of the weathering zone increased with decreasing elevation and interpret this to be related to the observed increase soil moisture at lower elevations. Our observations support the hypothesis that deeper snow accumulation leads to deeper weathering when all other variables are held equal. One caveat is the possibility that the denser vegetation contributes to deeper weathering on north-facing slopes via soil retention or higher rates of biological weathering.
DOI：
10.1073/pnas.1404763111
发表时间：
2014-04
期刊：
Proceedings of the National Academy of Sciences
影响因子：
--
作者：
D. Rempe;W. Dietrich
通讯作者：
D. Rempe;W. Dietrich
通过电阻率断层扫描观察博尔德溪关键区天文台的地下结构
影响因子：
3.3
作者：
Leopold;Völkel;D. Dethier
通讯作者：
D. Dethier