Introduction / Context:
The USDA soil taxonomy groups soils into orders based on diagnostic horizons and climate/vegetation settings. Recognizing which order dominates a region helps in agriculture, forestry, and land management decisions.
Given Data / Assumptions:
- Region: southeastern USA (humid subtropical climate, older landscapes).
- We compare typical soil orders found in different climates and biomes.
- We assume standard USDA order names and properties.
Concept / Approach:
Ultisols are highly weathered, acidic soils with subsurface clay accumulation (argillic/kandic horizons) and low base saturation, typical of warm, humid, and geologically old terrains—exactly the southeastern U.S. from the Piedmont to the Coastal Plain.
Alfisols have higher base saturation and are more common in temperate forests and some Midwestern regions.
Aridisols are desert soils, not suited to humid Southeast.
Mollisols are fertile, dark grassland soils of the Great Plains and other steppe regions, not the humid Southeast.
Step-by-Step Solution:
Match climate: warm, humid → intense weathering and leaching.Identify diagnostic features: low base saturation, clay-enriched subsurface → Ultisols.Exclude Aridisols (arid), Mollisols (grassland), and many Alfisols (higher base status).
Verification / Alternative check:
USDA soil maps highlight large Ultisol coverage in states like Georgia, Alabama, Mississippi, and the Carolinas, confirming regional dominance.
Why Other Options Are Wrong:
Alfisols: More fertile temperate forest/transition settings; less typical across the Southeast at large scale.Aridisols: Require aridity; not applicable.Mollisols: Grassland soils of the Great Plains, not the humid Southeast.
Common Pitfalls:
Assuming “fertile = common everywhere.” Despite lower fertility, Ultisols dominate due to long-term weathering in humid climates.
Final Answer:
ultisols
Discussion & Comments