Chapter 14 - The Critical Zone in Desert Environments

Abstract

Abstract Critical Zones represent the near-surface environment where complex geologic, hydrologic, and biologic processes interact. The integrated nature of those interactions is unique to the environmental setting including deserts. Arid land environments make up a large portion of the Earth (over 35%) and desert soils encompass over 46 million km2. The prevailing environmental conditions of low moisture and sparse vegetation that characterize deserts result in a unique Critical Zone. Desert soils are commonly poorly developed with shallow profiles and low organic content. Reduced weathering rates lead to coarse texture and concentrations of salts and carbonates. This chapter reviews the unique characteristics of the Critical Zone in arid land environments and the geomorphic and geologic factors that contribute to the formation of the desert soils. The focus is on the development and processes involved with regolith in the desert Critical Zone, which includes all material in the soil/sediment profile above fresh, unweathered bedrock. An overview of the Critical Zone in arid lands is presented including the nature of desert soils and surfaces. Weathering processes and soil hydrology in desert environments are examined including a review of numerical modeling of soil and regolith development and hillslope movement processes. Finally, case studies on regolith processes in the Mojave Desert are presented including the contribution of aeolian dust to the desert Critical Zone and an examination of soil and landscape development on stone pavements and sand ramps.