lecture #6 – plant nutrition and soils
DESCRIPTION
Lecture #6 – Plant Nutrition and Soils. Image – a soil profile. Key Concepts:. Resources Which are required How they are used Essential elements What they are What they do Soils and soil forming factors The rhizosphere Some alternate methods to acquire nutrients. - PowerPoint PPT PresentationTRANSCRIPT
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Image – a soil profile
Lecture #6 – Plant Nutrition and Soils
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Key Concepts:• Resources
Which are requiredHow they are used
• Essential elementsWhat they areWhat they do
• Soils and soil forming factors• The rhizosphere• Some alternate methods to acquire
nutrients
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Resource requirements for plant growth???
Solar energy The sunCO2 The atmosphereO2
Water The soilNutrients
?
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Where do plants get these resources???
Solar energy The sunCO2 The atmosphereO2
Water The soilMineral Nutrients
?
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Where do plants get these resources???
Solar energy The sunCO2 The atmosphereO2
Water The soilMineral Nutrients
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Diagram – plant resource requirements and sources
Image – root system of a grass
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Plant tissue composition by weight:
• Fresh herbaceous tissue is 80-85% water• Little water is incorporated into plant tissue
What does water contribute to tissue???• Most water is in the cell solution, in the
vacuoles, or passing through in the transpiration stream
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Critical Thinking
• Does wood have such a high percentage of water???
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Critical Thinking
• Does wood have such a high percentage of water???
• Typically not – wood is dead tissue and xylem often becomes plugged up by resins, etc in the interior of the treeThis is what we call “heartwood” and it is often
very beautiful
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Plant tissue composition by weight:
• Fresh herbaceous tissue is 80-85% water• Little water is incorporated into plant tissue
What does water contribute to tissue???• Most water is in the cell solution, in the
vacuoles, or passing through in the transpiration stream
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Plant tissue composition by weight:
• Fresh herbaceous tissue is 80-85% water• Little water is incorporated into plant tissue
Water supplies all the H to carbohydrates; electrons and protons for photosynthesis
• Most water is in the cell solution, in the vacuoles, or passing through in the transpiration stream
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Plant tissue composition by weight:
• Fresh herbaceous tissue is 80-85% water• Little water is incorporated into plant tissue
Water contributes H to carbohydrates; electrons and protons for photosynthesis
• Most water is in the cell solution, in the vacuoles, or passing through in the transpiration stream
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DRY plant tissue composition by weight:
• 45% carbon• 45% oxygen• 6% hydrogen• 5% inorganic mineral nutrients
Each a tad under 45%
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DRY plant tissue composition by weight:
• 45% carbon – from ?? CO2
• 45% oxygen – from ?? CO2
• 6% hydrogen – from ?? water• 5% inorganic mineral nutrients – from ??
soil
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DRY plant tissue composition by weight:
• 45% carbon – from CO2
• 45% oxygen – from• 6% hydrogen – from• 5% inorganic mineral nutrients – from
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DRY plant tissue composition by weight:
• 45% carbon – from CO2
• 45% oxygen – from CO2
• 6% hydrogen – from water• 5% inorganic mineral nutrients – from
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Diagram – what goes into photosynthesis and what comes out
C, H, O – source and fate in photosynthesis
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DRY plant tissue composition by weight:
• 45% carbon – from CO2
• 45% oxygen – from CO2
• 6% hydrogen – from water• 5% inorganic mineral nutrients – from soil
0.75-1% of wet weight, but many are essential to plant growth and function
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Critical Thinking
• What is the difference between a chemical element, a molecule and a macromolecule???
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Dia
gram
– s
truct
ure
of c
hlor
ophy
ll m
olec
ule
Critical Thinking
• What is the difference between a chemical element, a molecule and a macromolecule???
• N vs. N2 vs. chlorophyll
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Essential Elements• Chemical elements
Not molecules, though some are delivered in that form – N vs. NO3
-
• Required for growth and function of the plant• Can’t be replaced by some other element
• Some contribute to structural components• Some contribute to metabolic processes or
the maintenance of homeostasis
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Essential elements in structural plant components:
• What are some essential molecules used in structural components???
?
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Essential elements in structural plant components:
• Cellulose – ??• Lignin – ??• Pectin – ??• Cell membranes – ??• Proteins (cell membrane, cytoskeleton) – ??
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Essential elements in structural plant components:
• Cellulose – C, H, O• Lignin – C, H, O, S• Pectin – C, H, O, Ca• Cell membranes – C, H, O, P• Proteins (cell membrane, cytoskeleton) –
C, H, O, N, sometimes S
Note – C H and O are in ALMOST ALL organic molecules
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Essential elements for metabolic processes:
• What are some essential molecules used in metabolic processes???
?
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Essential elements for metabolic processes:
• Chlorophyll – ??• Nucleic acids – ??• ATP – ??• Enzymes and other proteins – ??• Enzyme cofactors – ??• Elements that control water, charge and
solute balance – ??
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Essential elements for metabolic processes:
• Chlorophyll – C, H, O, N, Mg• Nucleic acids – C, H, O, N, P• ATP – C, H, O, N, P• Enzymes and other proteins – C, H, O, N..S• Enzyme cofactors – many micronutrients• Elements that control water, charge and
solute balance – K, Cl, P, Ca, others
Note – C H and O are in ALMOST ALL organic molecules
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Macro Nutrients vs. Micro Nutrients
• Nitrogen• Potassium• Calcium• Magnesium• Phosphorous• Sulfur
• Chlorine, Iron, Boron, Manganese, Zinc, Copper and Molybdenum
• Some plants also require Nickel, Sodium, Silicon, Selenium or others
mass
All used in large quantities to support the structures and processes listed before
Mostly used in enzymes, as enzyme cofactors or in electron transfers – often reused, less required
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Table – essential nutrients, both macro and micro
Study table in book!
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Memory device in honor of my friend and mentor, Dr. Chuck Davey –
celebrated in 2006 for 50 years of service to soil science!!!
“C HOPKNS CaFe, Mg, Mn B CuZn Mo, Cl”
C. Hopkin's cafe, mighty good, managed by cousin Mo, waitress Clara
Nickel may also be essential
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Images – various plants that use additional elements
Silicon in horsetails
Sulfur in mustards
Uranium in macadamia nuts
Some minerals required, some by chance…
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Critical Thinking
• How do you tell which are required???
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Diagram – a hydroponic experiment
Critical Thinking
• How do you tell which are required???
• Hydroponics!
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Critical Thinking
• How do you tell which are required???
• Hydroponics!• How would elements NOT required
enter the plant tissue???
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Critical Thinking• How do you tell which are
required???• Hydroponics!• How would elements NOT required
enter the plant tissue???• They are pulled toward the root in the
transpiration stream, and enter through any membrane channel they can fit through
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Images – signs of deficiency
All plants will exhibit signs of deficiencies…..
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Critical Thinking
• If the deficiency appears first in the older leaves, is that nutrient mobile or immobile???
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Critical Thinking
• If the deficiency appears first in the older leaves, is that nutrient mobile or immobile???
• Mobile – it’s being translocated from the older tissues to the new, growing tissues
• How???
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Critical Thinking
• If the deficiency appears first in the older leaves, is that nutrient mobile or immobile???
• Mobile – it’s being translocated from the older tissues to the new, growing tissues
• How???• In the phloem!!!
The older tissue acts as a sourceThe younger tissue is the sink
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Mg deficiency in older leaves (mobile)
Fe deficiency in younger leaves (immobile)
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Critical Thinking
• Why would some elements be mobile, and others not???
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Critical Thinking
• Why would some elements be mobile, and others not???
• Must be soluble in water – phloem sap is water based…
• Some get locked into membranes or other components that can’t be broken down
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Image – roots
Most plants get most of their nutrients from the soil – absorbed
through the roots
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Soil is not just Dirt!
• Soil is the “skin” of the earth
• Soil provides for virtually all our food
• Soil supports the forests that maintain the hydrological cycle
• Soil supports virtually all terrestrial ecosystems – from micro-organisms to charismatic macro-fauna
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Image – erosion after tropical deforestation
The results of deforestation are ecological, economic and social disaster ( )Rosie
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Removing the plants removes the soil’s protective “blanket” and erosion is almost inevitable
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More images – erosion
Erosion from deforestation in
Madagascar
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Image – sediments from eroded land flooding out to sea
Sedimentation from erosion – this represents a huge loss of soil “capital”
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Image – sediments eroding off Haiti into the sea
Sediments eroding off Haiti
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Image – the political boundary is clear from the deforestation
Haiti
Dominican Republic
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Image – the drought in Haiti, where residents eat mud to survive
Haiti’s drought is caused largely by deforestation – the hydrological cycle has been snapped
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Maps – deforestation in England and in the US
Deforestation in Warwickshire, England
Deforestation in the US
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Map – soil loss in the Southern Piedmont of the US due to deforestation and abusive agricultural practices
Piedmont soil erosion in the
southeastern US
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Image – eroded land in the Southern Piedmont
The USFS Calhoun Experimental Forest in the 1950’sUnion County, South Carolina
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Maps – loss of farms, rise of industrial forestry, creating the biological deserts of pine plantations
Loss of soil (along with the boll weevil)
nearly eliminated productive
agriculture in the Southern Piedmont after the 1920’s – now most of the Piedmont is in industrial pine
plantations because it can no longer
support productive agriculture
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Social
JusticeYou can help!!!
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Compassionate Thinking
• What can you do to help???
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Compassionate Thinking
• What can you do to help???• Give – time, money• Conserve – resources• Learn• Think• Talk• Activate – take leadership roles
• VOTE!!!!!
There are 3 R’s
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Soil:
A dynamic natural body in which plants grow, composed of mineral and organic materials, air, water,
and living organisms
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Soil:
A dynamic natural body in which plants grow, composed of mineral and organic materials, air, water,
and living organisms
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Soil:
A dynamic natural body in which plants grow, composed of mineral and organic materials, air, water,
and living organisms
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Soil:
A dynamic natural body in which plants grow, composed of mineral and organic materials, air, water,
and living organisms
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Soil:
A dynamic natural body in which plants grow, composed of mineral and organic materials, air, water,
and living organisms
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Soil:
A dynamic natural body in which plants grow, composed of mineral and organic materials, air, water,
and living organisms
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Soil:
A dynamic natural body in which plants grow, composed of mineral and organic materials, air, water,
and living organisms
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Soil:
A dynamic natural body in which plants grow, composed of mineral and organic materials, air, water,
and living organisms
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Soil:
A dynamic natural body in which plants grow, composed of mineral and organic materials, air, water,
and living organisms
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Soil:
A dynamic natural body in which plants grow, composed of mineral and organic materials, air, water,
and living organisms
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Soil Forming Factors:
Parent MaterialClimate
Living OrganismsTopography
Time
All soil forming factors interact!!!
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Parent Material
• The substrate from which soil forms
• May be bedrock or some deposited material (sediments, organic material…)
• Determines soil texture, mineral content
• Influences soil structure and pH
71Igneous rocks form from molten rock
Sedimentary rocks form from deposited
materials
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Metamorphic rocks form from igneous or sedimentary rocks that have been altered by heat and pressure
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In the Charleston area, our soils form from unconsolidated Coastal Plain sediments
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Critical Thinking
• Why???
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Critical Thinking
• Why???• We were under water from ~ 140 mya to
less than 100,000 years ago
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Sediments were deposited on top of the crystalline bedrock during all this time
Soil develops from what’s on top!
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PM determines
soil texture = percentage of sand, silt and
clay
Loam soils have ~ equal percentage of each texture
class
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CLAY
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Clays are especially important• Tiny (<2um)
Huge surface area per unit mass (1000X more than same volume of sand)
• Typically platy in structure = vast additional internal surface area (800 m2/gm)
• Typically clay minerals carry a negative charge
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Critical Thinking
• Why is a huge surface area of negative charge important to soil fertility???
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Critical Thinking
• Why is a huge surface area of negative charge important to soil fertility???
• Many essential elements are in the soil solution in cation formClay particles hold these cations and limit
leaching• Water is also held (remember it’s polar)
Plus, smaller pore size holds more water
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Most clays carry negative charge on both external
and internal surfaces
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Cation Exchange – remember the root cap – protons displace cations
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Texture also influences soil
moisture – clays hold onto more
water
Small pore size and negative
charge
Relationship between soil texture, field capacity and
water availability
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Hands On• Determine soil texture• Take some soil from your jar and dampen
slightly – use the flow chart• Mix the soil with your hands – can you make
a firm ball of soil???• Can you make a ribbon of clay with your
fingers???• Rub a bit of soil between your fingers – can
you feel the grit of sand??? The powder of silt and clay???
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Hands On
• Add water to your jar and shakeHave a ruler ready
• Set the jar down and mark the timeMeasure sediments after 40 seconds = sandMeasure again at 30 minutes = sand + siltRemainder is clay – we may have to wait until
tomorrow to get final measurementsDivide the depth of each layer by the total to get
percentage of sand, silt and clayUse textural triangle to determine soil texture
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Parent materials
are weathered
by other soil forming
factors to form soil
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Soils are typically
layered, in horizons,
because of downward movement of water, clays, etc
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Critical Thinking
• Which soil horizon has the most biological activity???
• Why???O
A
B
C
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Critical Thinking
• Which soil horizon has the most biological activity???
• The “A” horizon – the topsoil• Why???• More air, water and organic materials from
the surface
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“A” Horizon
The topsoil is the most
biologically active horizon – more air, water
and organic materials from
the surface
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Soil Profile – a cut that reveals the horizons
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Climate
• Primarily temperature and precipitation patterns
• Temperature controls freeze-thaw cycles that contribute to physical weathering
• Temperature also affects the rate of biochemical reactions
• Temperature also affects the rate of decomposition by fungi, bacteria, and other living organisms
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Climate
• Precipitation contributes to soil moisture, which affects plant growth and the activity of decomposing organisms
• Precipitation affects erosion (the physical loss of soil particles) and leaching (chemical losses from the soil solution as water passes through the soil – this contributes to profile formation)
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Major biomes are determined by climate – microclimate is also important in soil development
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Living Organisms
• Macro-organisms, including plants and animals
• Micro-organisms, including bacteria, fungi, single-celled “protists”, and micro-fauna
• Human activity typically results in abrupt and very negative changes to soil
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Living Organisms – Plants• Contribute organic material – both from
above (shoots) and below (roots), and both sources affect horizonation
• Help to mix the soil – root channels, wind throws
• Cycle nutrients from soil to plant and back (sometimes through animals, always through decomposers)
• Help prevent soil erosion by breaking the force of rain, providing a litter layer
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Same parent material will
develop into a different soil
under different plant communities
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Critical Thinking
• Why are grassland soils so dark at the surface???
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Critical Thinking• Why are grassland soils so dark at the
surface???• Organic material!• Grasses have a lot• of fine roots and very• quick root turnover• A lot of OM is• contributed
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Living Organisms – Animals
• Contribute organic material when they die
• Contribute to nutrient cycling
• Help to mix the soil by burrowing, some even “eat” soil (earthworms)
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Critical Thinking
• How do animals contribute to nutrient cycling???
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Critical Thinking
• How do animals contribute to nutrient cycling???
• Plants absorb nutrients from the soil• Animals turn plant into animal• Dead animals (plus “excess” biomass)
return those nutrients to the soil via decomposing fungi, bacteria, etc
• Plants absorb nutrients from the soil…
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Living Organisms – Micro-orgs• Decompose organic material, cycle
nutrients, add OM• Trillions/kg of soil (double handful of soil….)• N-fixing bacteria = supply virtually all N for
plant growth, either free living or in nodulethe nitrogen paradox….bacteria convert
atmospheric N to forms suitable for plant uptake• Mycorrhizae = mutual symbiotic association
between fungi and roots, present in most plants, required by some
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Small animals, soil dwelling micro-fauna, fungi, bacteria, and other micro-organisms decompose dead
OM, cycling nutrients back into the soil
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Living Organisms – Micro-orgs• Decompose organic material, cycle
nutrients, add OM• Trillions/kg of soil (double handful of soil….)• N-fixing bacteria = supply virtually all N for
plant growth, either free living or in noduleThe nitrogen paradox….bacteria convert
atmospheric N to forms suitable for plant uptake• Mycorrhizae = mutual symbiotic association
between fungi and roots, present in most plants, required by some
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N-fixing bacteria in symbiotic mutualisms, mostly with legumes
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N-fixing bacteria in trees!
• Mosses on old-growth trees in the coastal Pacific Northwest forests host significant populations of N-fixing cyanobacteria
• Rain washes the nitrogen into the soil• Trees absorb from soil• Trees > 100 years old
Must be old for moss• Published 2011
http://www.sciencedaily.com/releases/2011/06/110607121144.htm
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Living Organisms – Micro-orgs• Decompose organic material, cycle
nutrients, add OM• Trillions/kg of soil (double handful of soil….)• N-fixing bacteria = supply virtually all N for
plant growth, either free living or in nodulethe nitrogen paradox….bacteria convert
atmospheric N to forms suitable for plant uptake• Mycorrhizae = mutual symbiotic association
between fungi and roots, present in most plants, required by some
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Critical Thinking
• What do you think mycorrhizae might contribute to the symbiosis???
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Critical Thinking
• What do you think mycorrhizae might contribute to the symbiosis???
• Surface area – LOTS
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Mycorrhizae are symbiotic mutualisms between fungi and plants – fungal hyphae vastly
increase surface area for water and nutrient absorption – 85% of plants depend on them
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Hands On
• Shake up class sample of soil / water to mix• Examine a drop of soil “solution” for
microorganisms
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Living Organisms – The human impact
• Removing vegetation dramatically increases erosion, cultivation exacerbates
• Deforestation can snap hydrological cycles• Excessive fertilizer and pesticide use
contaminates both soil and water• Improper irrigation salinates soil• Wetland drainage damages wetland soils• and on….
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Topography – the shape of the land
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Topography – the shape of the land• Determines the movement of water, thus
affecting erosion and leaching rates• Determines where water accumulates, which
affects soil moisture, which affects organismal activity, which affects soils….
• Aspect affects the amount of solar radiation at the surface, and thus soil temperature
• Large topographic features influence precipitation patterns
• Even micro-topography influences plant distribution
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Topographic Aspect – red and blue face S and W; green and
yellow face N and E
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Critical Thinking
• Why are the north and east slopes of a hill cooler???
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Critical Thinking
• Why are the north and east slopes of a hill cooler???
• The hill itself shades those sides
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Topography – the shape of the land• Determines the movement of water, thus
affecting erosion and leaching rates• Determines where water accumulates, which
affects soil moisture, which affects organismal activity, which affects soils….
• Aspect affects the amount of solar radiation at the surface, and thus soil temperature
• Large topographic features influence precipitation patterns
• Even micro-topography influences plant distribution
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Orographic lifting makes it rain
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Critical Thinking
• What the heck is orographic lifting and why does it cause rain???
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Critical Thinking
• What the heck is orographic lifting and why does it cause rain???
• Orographic means that an air mass is being forced by wind to go up and over a mountain
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Critical Thinking
• What the heck is orographic lifting and why does it cause rain???
• Orographic means that an air mass is being forced by wind to go up and over a mountain
• The air mass cools at higher elevations, condenses, and precipitation falls
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Orographic lifting causes cooling and precipitation, rain shadow to the leeward
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Topography – the shape of the land• Determines the movement of water, thus
affecting erosion and leaching rates• Determines where water accumulates, which
affects soil moisture, which affects organismal activity, which affects soils….
• Aspect affects the amount of solar radiation at the surface, and thus soil temperature
• Large topographic features influence precipitation patterns
• Even micro-topography influences plant distribution
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Small change in elevation…
…big change in the plant
community!
Images showing pond embedded within longleaf pine community
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Hands On
• Let’s go outside for this one….• Trays of soil at different slopes to
demonstrate erosion x slope + erosion vs. leaching
• Pour water from same height and at same rate on different slopes
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Time….
• The length of time all these factors have been acting determines the characteristics of the soil
• The same parent material will develop different soils as time passes
• Major component of primary succession
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Soil development on glacial till
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Soil Forming Factors:
Parent MaterialClimate
Living OrganismsTopography
Time
Remember – all soil forming factors interact!!!
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The RhizosphereThe area of interaction between root and soil.A huge volume of soil, but a very narrow zone
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The rhizosphere is the zone of cation exchange, nutrient and water uptake
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The Rhizosphere
• Complex zone with many interacting factors• Plant affects soil through compounds
secreted by the plant’s roots• Relative proportions of nutrients in the soil
solution can affect uptake of all nutrients• Also, different species have different
nutrient requirements• Rhizosphere is the control zone for
plant/soil interactions
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Some plants use alternate methods to absorb some nutrients
• Parasites, saprophytes, carnivores
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Key Concepts: QUESTIONS???• Resources
Which are requiredHow they are used
• Essential elementsWhat they areWhat they do
• Soils and soil forming factors• The rhizosphere• Some alternate methods to acquire
nutrients
139
Hands On
• What can you tell from this data???
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Extra Credit
• Putz around on the USDA soils site• http://
soils.usda.gov/education/resources/college/index.html