Soils Flashcards
What is soil? Why is it vital (4)?
- “skin of the Earth” Soils are less than 1 m thick. Array of recently dead material and inorganic material.
1. medium for root growth and nutrient uptake
2. major site for nutrient cycling
3. extremely heterogeneric (physical, chemical, biological)
4. complex – driven by abiotic soil architecture and high diversity
What are the 3 layers underneath soil?
- surface soils- subsurface is less complex; less MO’s, less diverse; aerobic
- vadose zone- oligotrophic (low nut) and thickness varies
- Not productive and not in wetlands; inorganic - saturated zone- shallow aquifers, intermediate aquifers, deep aquifers
- oligotrophic; water table can rise or fall
What is the water table? What affects the water tables movements?
- Where vadose zone meets saturated zone
- How much O2 there is
What are aquifers? 3 types?
Disconnected zones by clay
- Shallow
- aerobic
- lots of H2O movement
- why shallow water not good for drinking
- Able to recharge daily - Intermediate
- recharge slower
- not contaminated
- not old or anaerobic - Deep
- very slow recharge
- anaerobic
- not good drinking water
What are wetlands?
- Saturated
- Bogs have deep layers of peat- undecomposed plant remains- good at preservation
- anaerobic
- highly acidic (pH 3.2 to 4.2)- plants evolve to live here
- peat contains antimicrobial agents
What are bog bodies?
- Bodies preserved in peat
- No bones
- Harsh death
- Anaerobic env- not good at decomposing
What does the type of soil that develops reflect?:
-geologically derived parent material • climate • vegetation and other organisms • time (decades to millions of years) • and topography
What are 12 major soil orders?
Gelisols- permafrost
Histosols
Organic matter; mainly contains soils commonly called bogs, moors, peat lands, muskegs, fens, or peats and mucks.
Spodosols
Wood ash; Acidic, and have low fertility and low clay content.
Andisols
weathering of volcanic materials such as ash, resulting in minerals in the soil with poor crystal structure
Oxisols
Tropical; Dominated by iron oxides, quartz, and highly weathered clay minerals such as kaolinite.
Vertisols
Clay-rich soils; shrink as they dry and swell when they become wet.
Aridisols
In climates that are dry; contain accumulations of salt, gypsum, or carbonates, and are found in hot and cold deserts worldwide.
Ultisols
Formed in humid areas and are intensely weathered
Mollisols
Prairie or grassland soils that have a dark colored surface horizon, are highly fertile, and are rich in chemical “bases”
Alfisols
Similar to Ultisols but are less intensively weathered and less acidic. More fertile
Inceptisols
Moderate degree of soil development, lacking significant clay accumulation in the subsoil.
Entisols
Exhibit little to no soil development other than the presence of an identifiable topsoil horizon.
Is sediment soil? Bedrock?
NO
What are 2 groups of soil?
- Mineral soils
• Derived from rock weathering and other inorganic
materials - Organic soils
• Derived from decomposition of organic material
What does soil development depend on? (3)
Weathering, water movement, and organic decomposition (all influenced by climate)
What are the layers of soil(5)? Describe each (O has 3 subtypes)
- O- Organic Horizon- Layer of undecomposed plant materials
- L- litter layer (undecomposed plant debris)
- F-partially decomposed organic matter
- H – Humus layer (well decomposed)
- A- Leached Horizon- Surface soil (high in organic matter, dark in color, is tilled for agriculture; plants and large numbers of microorganisms grow here; microbial activity high)
- B- Accumulation Horizon- Subsoil (minerals, humus, and so on, leached from soil surface accumulate here; little organic matter; microbial activity detectable but lower than at A horizon)
*C- Partially weathered horizon- Soil base (develops directly from underlying bedrock; microbial activity
generally very low)
*Parent material
What are components of a typical soil?
- 45% mineral (Si, Fe, Al, Ca, K, Mg, Na)
- most abundance elements in crust are Si (47%) and O (27%) - 50% pore space (air and water)
- 1-5% organic matter
Whats the input of the organic matter from?
From plant, animal, and microbial biomass
What are some traits of Humus?
- aromatic, complex
- very effective at absorbing water and solutes
- slowly utilized by soil organisms
What does quantity of OM depend on?
-Climate
-Temperate soils have increased levels of organic
matter
-desert = 0.1% OM
-temperate forests = 3 to 5% OM
- bogs and wetlands = 20% OM
Whats the solid phase of soil development (1st phase)?
-45-50% by volume
• soil particles do not remain as individual entities
• aggregate into 2nd’ary structures or peds
• peds are held together with microbial gums, polysaccarides and other microbial metabolites
• clay containing soils have well-defined peds • sandy soils are less well-defined
Whats a primary surface soil structure? Secondary?
1 structure = soil particles + organic matter (humus) + roots + microorganisms
2 structure = aggregate or ped = stability
What is soil stabilized by?
By clay-organic complexes, microbial polysaccharides, fungal hyphae and plant roots.
Go label the Diagram on lecture 3 slides page 17
GOOD JOB!
What are peds? 6 types?
- Soil structure results from secondary aggregates known as pets.
1. Granular
2. Platy
3. Blocky
4. Prismatic
5. Single grain
6. Massive
What are the pore spaces in soils?
Air and water spaces
-Between the aggregate particles and in the aggregate particles
Whats the liquid phase in soils?
• aqueous phase and gas phase exist in pores between particles
• soil solutions are a vital component
• soil solutions flow preferentially through large pores • complex chemistry happens here
• dynamic
-Runoff, cation exchange, mircoorganisms, plant roots, precipitation
Whats the gas phase in soils?
The composition of the earth’s atmosphere is approximately 79% nitrogen, 21% oxygen, and 0.03% carbon dioxide. Microbial activity in the soil can change the local concentration of these gases especially in saturated areas.
