- Attributes of Soil
- Quantitative definitions of taxa reduce subjectivity and clarify criteria
- Taxa apply to real soil bodies as they occur rather than concepts
- Based on soil properties that can be observed or measured rather than inferred
- Can accomodate new knowledge
- Should provide for all soils of the world and the landscape continuum
- Structure of the Taxonomic System
- Hierarchical system of 6 categories
Categories from highest to lowest levels of generalization
ORDER 12 SUBORDER 66 GREAT GROUP 320 SUBGROUP 1,400 FAMILY 8,000 SERIES 19,000
- Basic Concept of Each Taxonomic Category
Category Nature of Criteria for Differentiating Order major soil forming processes ; diagnostic horizons Suborder genetic similarity; moisture regime, organic matter composition, parent material effects Great Group diagnostic layers, base status, horizon expression, clay activity Subgroup central concept of Great Group (Typic) or intergrades or extragrades Family properties important for soil use (texture, mineralogy,temperature) Series kind and arrangement of horizons, specific chemical mineralogical properties of horizons
- SOIL ORDERS
AND THEIR FORMATIVE
Order Formative Element Mnemonicon Derivation Histisol ist histology Gr. histos, tissue Spodosol od Podzol ; odd Gr. spodos,wood ashes Andisol and Ando Sp. Andes Oxisol ox oxide Fr. oxide Vertisol ert invert L. verto, turn Aridisol id arid L. aridos, dry Ultisol ult ultimate L. ultimus, last Mollisol oll mollify L. mollis, soft Alfisol alf Pedalfer Inceptisol ept inception L. inceptum, beginning Entisol ent recent Gelisol el gelifluction L. gelare, freeze
Forest soils of cool moist climates, light colored, slightly to moderately acid with illuvial layer high in silicate clays.
Soils derived from volcanic materials.
Arid soils common to western United States, often alkaline with salted horizons
Very young soils in new parent materials or where alluvial deposition or erosion limits profile development (slopes).
Soils that commonly have a dark organic surface layer and mineral layers underlain by permafrost. These soils are commonly in the tundra regions of Alaska.
Young soils, with only those horizons that form quickly.
Prairie soils of the Great Plains. Dark, thick, good structure, high base A horizon.
Highly weathered tropical soils. Has subsurface horizon low in weatherable minerals but high in aluminum or sesquioxide clays.
Light colored acid forest, often coniferous, soils of cool humid regions as in northeast United States.
Highly weathered soils of warm climates, low base, often leached, acid, and infertile.
High in swelling clays. When dry, large deep cracks form that surface soil falls into, mixing the soil.
TAXONOMIC CLASS: Fine, kaolinitic, thermic Typic Kanhapludults
Great Group: Kanhapludult
Subgroup: Typic Kanhapludult
Family: Fine, Kaolinitic, Thermic