Transcript Entisols - Laboratory of Tree

If it ain’t anything else, it’s an…
Entisol
Rebecca Franklin
SWES 541
What is an Entisol?
• Soils of recent origin
• Central concepts:
–
–
–
–
soils developed in unconsolidated parent material
usually no genetic horizons except an A horizon
All soils that do not fit into one of the other 11 orders are Entisols
Characterized by great diversity in environmental setting and
land use.
• Many Entisols are found in steep, rocky settings.
• Also, Entisols of large river valleys and associated
shore deposits provide cropland and habitat for
millions of people worldwide.
What is an Entisol? continued
• weakly-developed soils
• lack of strong development often due to one of
several factors:
–
–
–
–
–
persistent high water table
parent material composed mainly of quartz sand
location on an eroding slope
location on a very young landscape
are extremely young because recently disturbed by
human activity
Environmental conditions
conducive to Entisol formation
•
•
•
•
•
Climate
Vegetation
Relief
Parent Material
Time
Entisol Processes and Properties
•Environment can inhibit
soil forming processes
•Waterlogged
•Sparse vegetation
•Compactness of rock
•May be in equilibrium
with environment
•Ochric epipedon
•Albic horizon
•Maybe some fragmented
diagnostic horizons
When you look at an Entisol you
see…
• No commonly observed diagnostic horizons or
properties.
• Some representative horizon sequences? Yes.
A
Bw
C
A
A
C
Development of
color/structure;
little or no
accumulation of
illuvial materials
(Bw not cambic
due to being too
sandy)
Bs
C
Accumulation of
sesquioxides of
Fe and Al
Where in the world do you find Entisols?
• Entisols = ~17.9% of the Earth's ice-free land
area, the largest percentage of any of the soil
orders
Concentration of Entisols in U.S.
What type of Entisols are in the United States?
SUBORDERS
• Aquents - Entisols with
a water table at or near
the surface for much of
the year
• Arents - Entisols that
have been disturbed and
contain fragments of
diagnostic horizons that
are not arranged in any
discernable order
• Psamments - very
sandy Entisols
• Fluvents - alluvial
Entisols commonly found
on floodplains
• Orthents - common
Entisols that don't meet
criteria of other
suborders
For what do we use Entisols?
% Wld
%US
Use
Natural
fertility
Psamments
3.14
2.81
Crops,
Range
Low
Fluvents
2.2
1.7
Crops
Moderate
Aquents
<0.01
1.4
Wetlands,
Crops
Moderate
Orthents
10.58
5.93
Forest,
Range,
Crops
Low to
Moderate
Fluvents
SW Wisconsin
• Recent water-deposited
sediments on:
– Flood plains
– Fans
– Deltas along rivers or small
streams
• Fluvents are frequently
flooded, unless protected
by dams or levees
• Stratification of materials
normal.
• Fluvent use:
–
–
–
–
–
Rangeland
Forest
Pasture
Wildlife habitat
Cropland
Udifluvent in east-central Louisiana
Psamment
• Psamments widespread, mainly:
–
–
–
–
–
–
–
Nebraska
California
Minnesota
Wisconsin
Michigan
Arizona
Florida.
• Sandy in all layers- among the
most productive rangeland soils
in some arid and semiarid
climates.
• Psamments that are nearly bare
subject to soil blowing and
drifting (bad driving).
• Psamments use:
– Rangeland
– Pasture
– Wildlife habitat
Typic Psamment
(in glacial outwash
too sandy to be
cambic, slight accum.
of sesquioxides)
Xeric Psamment (in eolian sand)
Aquents
Permentantly or usually wet soils
formed on river banks, tidal
mudflats etc.
General wetness limits development.
Dominate some of the delineations
along southern Atlantic, gulf
coasts, flood plains along
Mississippi River, and along other
rivers and streams.
Some Aquents are forming in sandy
deposits, mostly in recent
sediments. They support
vegetation that tolerates
permanent or periodic wetness.
Use:
Pasture
Cropland
Forest
Wildlife habitat.
Example from an athletic
field: sandy fill material
(anthrotransported deposits)
placed over buried hydric
soils
Arents
• Mixed horizons, not permanently saturated with
water
• Exhibit fragments of diagnostic horizons below
the Ap (plowed/disturbed layer) horizon
• Deeply disturbed by farming, mining, or
construction.
• Also termed anthropogenic soils: diagnostic
horizons cannot develop because of continued
deep mixing through plowing, spading, or other
methods of moving by humans.
Orthents
•
•
•
•
•
•
•
Very shallow soils
Completely devoid of weatherable
minerals
Found on recent erosional
surfaces or very old landforms
Lack horizon development due to
either steep slopes or parent
materials that contain no
permanent weatherable minerals
(i.e. ironstone)
Orthents are exceedingly shallow
soils, referred to as "skeletal soils"
or Lithosols
Any former soil either completely
removed or so truncated so
diagnostic horizons typical of all
orders other than Entisols are
absent
Orthent use:
– Rangeland
– Pasture
– Wildlife habitat
To review…
• Summary:
–
–
–
–
–
Vegetation: not specified, bare soil
Climate: pergelic to hypothermic
Soil moisture regime: dry to aquic
Major soil property: featureless soil bodies
Diagnostic horizons: typically absent, albic (horizon
free from clay and iron oxides)
– Epipedon: ochric
– Characteristic: little or no evidence of soil
development