Topographic gradients of soil physical, chemical, and mineralogical properties in central Kentucky sinkholes

Abstract

An estimated 20% of the world's land surface is underlain by lithologies favorable for karst formation. Karst features (e.g., sinkholes) and soils coevolve, likely influencing local pedogenesis, soil carbon storage, and hydrologic patterns. While karst is widespread, our understanding of the influence of karst geomorphology on pedogenesis remains limited. To better estimate the impact of karst geomorphology on pedogenesis, we characterized nine pedons as a function of landscape position (i.e., toposequence) in two subsidence sinkholes located in the Inner Bluegrass physiographic region of central Kentucky; we characterized a suite of soil physical, chemical, and mineralogical properties. The Inner Bluegrass is underlain by a phosphatic limestone and is susceptible to karst formation. Expectedly, total carbon was greater in lowland positions relative to upland landscape positions. However, inverse relationships between elevation and clay content, selective iron, aluminum, and silicon extracts contradicted previous toposequence trends. Clay mineralogy differences between toeslope and summit positions suggested sediment transport from summit to toeslope positions. Karst geomorphology may limit pedogenesis and facilitate more rapid material export through karst conduits compared to other lithologies. Given the extent of karst terrains and lithologies susceptible to karst formation, future work is needed to understand the magnitude of the impact of karst on pedogenesis and other earth system processes. INTRODUCTIONKarst topography is complex; the rapid dissolution of carbonates leads to unique landscape features such as disappearing streams, abundant springs, extensive cave systems, lack of surface drainage, and sinkholes (Ford and Williams, 2007;Palmer, 2007). Karst hydrology is highly interconnected with rapid flowpaths that connect the soil surface to deeper groundwater (Chen et al.,

Microtopography effects on pedogenesis in the mudstone-derived soils of the hilly mountainous regions

“…This is because the soils in the sequence typically share the same parent material and have similar conditions such as climate, vegetation, and time 10 , 13 . A series of toposequences derived from granite, sandstone-gneiss, limestone, and slate have shown that topography plays an essential role in pedogenesis 14 – 18 . Therefore, the difference between large- and micro-topography in the impact on soil formation process makes it necessary to explore the pedogenesis under the influence of small-scale terrain, especially in hilly mountainous regions with little relief.…”