Lecture 10: Chapter 19- Soil Classification Flashcards
pedon
the smallest sampling unit of soil that displays the full range of characteristics (1-10 m^2)
polypedon
made up of pedons with similar properties
epipedon
a horizon that forms at or near the SURFACE and in which most of the rock structure has been destroyed (darkened)
describe the classification criteria of soil taxonomy for soil orders and suborders
soils are named by the presence/absence of diagnostic surface horizons (epipedons) and/or subsurface horizons
moisture regime: aquic
-soil is saturated with water
-virtually free of gaseous oxygen for sufficient periods of time
-evidence of poor aeration (gleying and mottling)
-common in wetlands
epipedon: anthropic (A)
-human transported or modified materials like glass
-can have puddled condition (rice paddies)
epipedon: folistic (O)
-organic horizon saturated for less than 30 days per normal year
-more or less freely drained horizon that formed in organic material
epipedon: histic (O)*
-a 20-60 cm thick layer of ORGANIC SOIL MATERIALS (peat or muck) overlying mineral soil
-formed in wet areas
-black to dark brown color
-very low density
-saturated horizon
epipedon: melanic (A)*
-thick, black, high in organic matter (>6% organic carbon)
-common in volcanic ash soils
epipedon: mollic (A)*
-thick (generally >25 cm)
-dark colored
-high base saturation
-well developed structure
-most common in grassland soils
epipedon: ochric (A)*
-lighter in color
-lower in organic matter or thinner than a mollic
-may be hard and massive when dry
epipedon: plaggen (A)
-human made sod-like horizon created by years of manuring
-often with artifacts and spade marks
epipedon: umbric (A)*
similar to mollic except low base saturation
moisture regime: udic
-soil moisture is sufficiently high year round in most years to meet plant requirement
-common in humid regions
moisture regime: ustic
-soil moisture is intermediate between udic and aridic regimes
-generally plant available moisture during the growing season
-severe periods of drought may occur
-common in semi arid regions
moisture regime: aridic
-soil is dry for at least half of the growing season
-moist for less than 90 consecutive days
-common in arid (desert-like) regions
moisture regime: xeric
-found in mediterranean-type climates
-cool, moist winters and warm, dry summers
-long periods of drought in the summer
alfisols
alf
well developed
andisols
and
organic
aridisols
id
desert, rocky, not a lot of vegetation, need stable land surface
entisols
ent
gelisols
el
tundra frozen below 1m
soil needs to be frozen for at least 2 years
histosols
ist
no particular climate just organic
inceptisols
ept
baby soils
pretty common in temperate areas
