ABSTRACT Sandstone- and shale-derived soils are common in southern California where they function in watersheds, support wildland ecosystems, and are subject to residential and infrastructure development. Because little is known about these soils on texturally contrasting parent materials, this study was designed to interpret their pedogenesis and accompanying soil physical behavior. The study area is in the chaparral-covered foothills of the San Gabriel Mountains, where the 400-mm mean annual precipitation comes as rain during the winter and summers are hot and dry. The soil on sandstone is an Alfisol with a fine-loamy argillic horizon and mixed mineralogy. It is leached of carbonates and has pH values of 5.7 to 6.8. The shale-derived soil is a clayey, smectitic Vertisol with accumulated calcium carbonate, indicating less leaching than the Alfisol. Soil organic carbon storage in the Alfisol (7.96 kg m−2) and Vertisol (9.87 kg m−2) is similar, but the Vertisol has additional carbon (4.88 kg m−2) in the form of calcium carbonate. The Vertisol has high shrink-swell potential, with coefficient of linear extensibility values mostly 0.09 to 0.12. The Alfisol has minimal shrink-swell potential. Available water capacities for the Alfisol soil horizons (4%–20%) range higher than those of the Vertisol (4%–11%), but the thicker regolith profile of the Vertisol means it can store more plant-available water overall. Field saturated hydraulic conductivity was similar for the soils during the wet season (0.2–1.6 cm h−1), but was higher in the extensively cracked Vertisol during the dry season. The available water capacities (4%) and saturated hydraulic conductivities (0.2–0.4 cm h−1) of the Cr horizons of both soils indicate that these weathered bedrocks are functional parts of the soil hydrologic system. The divergent properties of the soils are related to the nature of the parent material and its evolution in response to soil-water dynamics.

中文翻译：

---

南加州砂岩和页岩土壤的成因和物理行为

摘要砂岩和页岩衍生的土壤在加利福尼亚南部很常见，它们在流域中发挥作用，支持荒地生态系统，并受制于住宅和基础设施的发展。由于对质地对比母质材料上的这些土壤知之甚少，因此本研究旨在解释它们的成土作用和伴随的土壤物理行为。研究区域位于圣盖博山脉灌木丛覆盖的山麓，那里的年平均降水量为 400 毫米，因为冬季和夏季炎热干燥。砂岩上的土壤是具有细壤土的泥质层和混合矿物的 Alfisol。它从碳酸盐中浸出，pH 值为 5.7 至 6.8。页岩衍生的土壤是一种粘质的、具有积聚碳酸钙的蒙脱石 Vertisol，表明比 Alfisol 更少的浸出。Alfisol (7.96 kg m-2) 和 Vertisol (9.87 kg m-2) 中的土壤有机碳储存量相似，但 Vertisol 有额外的碳 (4.88 kg m-2) 以碳酸钙的形式存在。Vertisol 具有很高的收缩膨胀潜力，线性延伸系数值大多为 0.09 至 0.12。Alfisol 具有最小的收缩膨胀潜力。Alfisol 土壤层的可用水容量 (4%–20%) 范围高于 Vertisol (4%–11%)，但 Vertisol 更厚的风化层剖面意味着它可以储存更多的植物可用水。在湿季（0.2-1.6 cm h-1）土壤的田间饱和导水率相似，但在旱季广泛开裂的 Vertisol 中更高。两种土壤的 Cr 层的可用水容量 (4%) 和饱和导水率 (0.2-0.4 cm h-1) 表明这些风化基岩是土壤水文系统的功能部分。土壤的不同特性与母质的性质及其响应土壤-水动力学的演变有关。