arizona soils and their importance - maricopa
Post on 11-Apr-2022
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Arizona Soils and Their Importance
What is the world’s most valuable natural resource?
What is one of the world’s most extensive natural resource?
Soil is!
Why is soil the world’s most valuable natural resource?
• Food – plants depend on soil to grow, animals depend on plants to live
• Water holding capabilities• Pollution filter• Temperature control• Habitat for plants and animals• Many important biological processes
carried out here
Soil
• Minerals derived from rocks
• Organic material derived from life
The 5 C’s of Arizona• Copper• Cotton• Citrus• Cattle• Climate (tourism)
How many of these depend at some level on soil?Cotton- it grows in soil
Citrus- grows in soil also
Cattle- eat what grows from soil
Climate- some aspects of Arizona’s tourism industry depend on soil (plants, animals, food)
Some other Arizona C’s
Cacti- dependant on soil
Canyons- soil developed from them but not dependant on soil
Cactus wren- dependant on plants which are dependant on soil
What is soil?
• The unconsolidated mineral or organic material on the immediate surface of the earth that serves as a natural medium for the
growth of land plants
What makes a soil?
1. Soil starts as a rock2. Weathering breaks down the rock
-Heat, water, freezing, wind, plant roots3. Rock particles (sand, silt, and clay)
separate into horizons through further weathering
Development of soil
Development of soil
Soil Air
• Air is trapped between grains • Air diffuses through soil to and from the
atmosphere• Provides organisms with O2 and other
gasses• Removes CO2 and other gasses released
by organisms
Soil Water
• Water is trapped between grains • Water percolates down through soil• Minerals and organic molecules dissolve
in the water• Dissolved materials are leeched
downward
Alluvial Fan Soil
Soils
Alluvial Fan Soil
Soil Horizons
• Organic Horizon-O• Topsoil-A (organic and
mineral)
• Pale Soil-E (leeched)
• Subsoil-B (leechate)
• Quiet Horizon-C(sand & gravel)
• Bedrock-R (solid rock)
What people typically think
of soil
What typical desert soil is
like-Black organic matter from plants near surface
-Loose, lots of space for air and water
-Not as complicated
-Tan to red in color
-Organic matter from plants nearly absent
-A lot more complex
Soil from near Oracle, Arizona
• Parent material deposited by running water
• Arid climate• Steep topography,
alluvial fan• Desert scrub vegetation• Time: 2 million years
Source: CD from Environmental Science:Toward a Sustainable Future, 9/e, Richard T. Wright
Desert Soils• Coarse textures = high water infiltration• Fine textures = low water infiltration
Desert Soils• Cryptobiotic crusts
– Microscopic algae, lichens and mosses
– Easily destroyed by trampling and off-road vehicles
– Current area of research
Desert Soils
• Desert pavement
Desert Soils• Desert varnish
Desert Soils• Desert pavement
Distribution of soil
Plants and soil
Plant roots
Soil Bacteria
• Decomposers• Mineralizers
Rooting structure
Soil interactions
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