Desert soils typically exhibit weakly developed soil horizons, often featuring a prominent B horizon.
Here's a breakdown of typical soil horizons found in desert environments:
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O Horizon (Organic Layer): Often absent or very thin due to limited vegetation. When present, it consists of decomposed or partially decomposed organic matter.
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A Horizon (Topsoil): Usually a thin, light-colored layer. It is a mineral horizon, meaning it's composed primarily of sand, silt, and clay with very little organic matter mixed in.
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B Horizon (Subsoil): This is the most distinctive horizon in many desert soils. It's a zone of accumulation where materials leached from the A horizon are deposited. Common accumulations include:
- Caliche: A hardened layer of calcium carbonate (CaCO3). This can range from scattered nodules to a thick, cement-like layer that restricts root growth and water infiltration.
- Gypsum: Accumulation of gypsum (calcium sulfate) in arid environments.
- Salts: Various salts (e.g., sodium chloride) can accumulate near the surface due to high evaporation rates. Salty soils are termed "saline soils."
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C Horizon (Parent Material): Partially altered parent material from which the soil developed. This layer is less weathered than the horizons above. It might consist of fractured bedrock or unconsolidated sediments.
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R Horizon (Bedrock): The underlying bedrock, if present near the surface.
Important Considerations:
- Variability: Desert soils are incredibly variable depending on factors like climate, parent material, topography, and time.
- Desert Pavement: In some areas, a layer of tightly packed rocks and gravel (desert pavement) protects the underlying soil from erosion.
- Crusts: Physical or biological crusts can form on the soil surface, influencing water infiltration and erosion.
- Depth: Desert soils can range from very shallow to quite deep.
