Chapter 7: Soils Flashcards
What is the Meur Bleu bog?
The Meur Bleue bog is a 35km^2 protected wetland located east of Ottawa.
What type of soil does the Mer Bleue wetland have?
Peat. (deposits formed over 800 yrs and are up to 6m thick)
Why are Northern peatlands important?
They are storage reservoirs for carbon, holding about one 3rd of all carbon stored in soils.
How much energy does all the peat in the world contain?
8 billion terajoules
Fill in the blanks: The formation of peat is often the first step of ______, such as ________.
the first step of the [geological formation of fossil fuels] such as COAL
How does peat produce soil gases such as CO2 and CH4?
Through decomposition of organic matter
How does climate change affect soils?
Warming can lead soils to decompose at faster rates and thus release more soil gases, created a higher concentration of carbon-gas in the atmosphere.
What is the difference between soil and dirt?
Dirt: loose material derived from rock
Soil: A complex plant supporting system consisting of weathered rock, organic matter, water, gases, nutrients, and microorganisms
Define: Parent Material (soils)
the base geological material from which the soil is formed
What is soil solution?
Water that partially fills the open space in soils. This is never “pure” water, contains dissolved minerals and organics
How does the formation of soil begin?
When the parent material is exposed to the effects of the atmosphere/hydrosphere/biosphere(weathering)
Give examples of possible parent material for soils
Lava, volcanic ash, rock/sediment deposited by water bodies, most commonly bedrock(earth’s crust)
What are the processes most responsible for soil formation?
Weathering, erosion, deposition and decomposition of organic matter
Define: Regolith
Small, loose particles of mineral matter, precursors of soils
Give examples of physical weathering
temperature, wind, rain, ice, (thermal expansion/contraction)
How is the air in soil different from the air we breathe?
soil air contains gases that are released from underlying rock, and gases that infiltrate from above such as constituents from spilled gas and oil
Name and briefly describe the five factors that influence soil formation
CLIMATE: -soil forms faster in warm, wet climates
-heat accelerates weathering, decomposition, biological growth
ORGANISMS: -worms and other burrowing animals facilitate soil processes. organic matter affects soil’s composition
TOPOGRAPHY: -hills and valleys affect exposure to the sun,wind,water, influence how soil and water move.
-steep slope results in more runoff and erosion
PARENT MATERIAL: chem/physical attributes of parent material influence soils properties
TIME: soil formation occurs over long periods of time
Describe Biological Weathering
occurs when living things break down parent material by physical or chemical means(ex. lichens produce acid which chemically weathers rock)
Define: Humus
dark, spongy, crumbly material made up of complex organic compounds
Define: Horizon(soils)
Each layer of soil
Soil Profile
The whole cross section of soil, from surface to bedrock
Leaching
a process in which materials suspended or dissolved in liquid are transported through the soil subsurfacw
Litter
soil surface deposits of leaves, branches, animal waste etc.
Name the 5 major types of soil horizons in order
O, A, B, C, R (only able bodies can run)
O horizon
1st layer. peat deposits
A horizon
2nd layer. uppermost mineral horizon, TOPSOIL(most vital to ecosystems and agriculture)
B horizon
3rd layer. SUBSOIL, hard mineral rich layers
C horizon
4th layer, Broken parent material, transition zone
R horizon
5th layer, Unaltered parent material ROCK, layer
How are soils classified?
classified into 10 major groups called orders, with dozens of “great groups” and hundreds of “subgroups” . Classified using different properties such as colour, texture, structure, and pH
What is indicated by soil colour?
Colour of soil can indicate chemical composition and sometimes its organic content
What does dark soil indicate? Pale/white soil?
Black/dark brown: usually rich in organic matter
Pale grey/white: chalky composition, calcium carbonate deposits, salt deposits, leaching
What are the three categories of Soil Texture?
Clay: consists of particles less than 0.002 mm in diameter
Silt: 0.002 to 0.05mm
Sand: 0.05 to 2mm
What does the texture of soil determine?
- texture influence how porous the soil is
- influences permeability: the ease with which fluids can move (bigger grains, increased permeability)
- silt or loamy soils are best for plant growth
loam
mixture of clay,silt,sand
What is soil structure?
The measure of the organization or clumpiness of soil. Large soil clumps can discourage plant growth
Define plowpan
when farmers repeatedly till the same field, and end up forming a crusty hardpan layer that resists water infiltration
What is soil pH?
The degree of acidity(low pH) or alkalinity(high pH, basic) of a soil. Influence soil’s ability to support plant growth.
How do materials that move through soils gain their nutrients?
ION EXCHANGE: a process in which positively charged particles(cations) and negatively charged particles(anions) are exchanged between soil and soil solution.
Cation exchange
process that allows plants to gain nutrients
cation exchange capacity
a soil’s ability to hold cations, preventing them from leaching, thereby increasing their availability to plants(greatest in FINE soils)
When soil pH decreases, cation exchange capacity _______
diminishes, nutrients leach away
What are examples of positively charged pollutants?
Cadmium, lead, arsenic, mercury
What is nitrogen fixation and how can it be accomplished?
Nitrogen fixation is when nitrogen gas combines with hydrogen to form NH4(ammonium). This can be accomplished when air in the top layer of soil comes in contact with specialized nitrogen-fixing bacteria.
Define Nitrification
when specialized bacteria convert ammonium ions into nitrite ions(NO2-), then into nitrate ions(NO3-)
Define Denitrification
When bacteria converts nitrates in soil or water into gaseous nitrogen(N2). Completes the nitrogen cycle by releasing nitrogen back into atmosphere.
Why is soil important in the carbon cycle?
Soil is the largest ACTIVE terrestrial reservoir for carbon
What are the main carbon fluxes soil is involved in?
Photosynthesis and production of organic matter, followed by respiration and decay of organic matter
Wet soils are more likely to be _______ than dry soils
anaerobic(oxygenated)
How does rain affect soil productivity?
High amounts of rainfall can cause leaching of nutrients, therefore making the soil less productive
What continent is the proportion of soil erosion largest? Which continents is soil erosion a growing concern?
Europe. Africa and Asia.
What factors affect soil degradation?
Overgrazing(34%), deforestation(30%), cropland agriculture(28%), other overexploitation(7), industrialization(1)
What are the main limitations of soil productivity?
Shallow soil, contaminated soil, dry soil
Where is the majority of organic matter stored in tropical forests? In boreal/temperate forests? In desert biomes?
The majority of organic matter in tropical forests is stored ABOVE ground in plant biomass. In boreal/temperate forests, most organic matter is stored in soils. In deserts, there is little organic material because of the low amount of biomass.
How have humans increased erosion
Overcultivating fields, overgrazing(livestock), clear cutting forests
What type of erosion has the greatest potential to move topsoil?
Rill erosion, followed by sheet erosion and splat erosion
How does wind(aeolian) erosion work?
Wind erosion occurs when all loose, fine grained material is picked up from the surface and carried away by wind
What is the Universal Soil Loss Equation?
A= R K LS C P
(A = r kelly likes silly cat pictures)
A- predicted soil loss due to water erosion
R- erositivity factor
K- soil erodibility factor
LS- slope length and steepness
C- vegetative cover and management factor
P-erosion control practices factor(conservation)
What is splash erosion?
Splash erosion is when raindrops strike the ground with enough force to dislodge small amounts of soil
When does sheet erosion occur?
Sheet erosion occurs when thin layers of water travel broad expanses of sloping land
What does rill erosion do?
Rill erosion leaves small pathways along the surface where water has eroded topsoil
What is gully erosion?
Erosion that cuts deep into soil, leaving large gullies (think big holes in ground)
What does the wind erosion prediction equation stand for?
E = f(I C K L V)
E-predicted soil loss due to wind I- soil erodibility factor C- local wind erosion climate factor K- roughness factor L- length of field factor V- vegetative cover factor
What is the primary cause of soil erosion?
Humans(said to be 10 times more influential at moving soil than all other natural processes on earth combined)
What is desertification?
When formerly productive land becomes a desert as a result of climate change or prolonged drought.
How much of the earths land surface is affected by desertification?
about one third
What type of lands are most prone to desertification?
Arid and semi-arid lands(low precipitation)
What caused the 1930s Dust Bowl?
An increased amount of settlers arrived in NA planning to make a living as farmers.. The amount of cultivated land soared..Farmers grew abundant wheat and grazed many thousands of cattle, breaking down soil structure.
When the stock market crashed in 1929, a cycle of poverty and land degradation befan. A prolonged drought accelerated the negative impacts of the soil.. strong winds began to carry away millions of tonnes of topsoil, creating dust storms.
(SOLUTIONS) what is crop rotation?
the practice of alternating the kind of crop grown in a particular field from one year to the next. (can return nutrients to the soil, break cycles of disease, minimize erosion)
(SOLUTIONS)what is intercropping? How does this help slow erosion?
Planting different types of crops in alternating bands or other mixed arrangements. This helps slow erosion by providing more ground cover than a single crop does.
What is agroforestry?
When crops are interplanted with trees. More productive than just planting food crops alone.
(SOLUTIONS) What is contour farming?
When furrows are ploughed sideways across a hill perpendicular to its slope to prevent formation of rills and gullies. (furrows follow the nature contours of the land.)
(SOLUTIONS) What is terracing?
Level platforms cut into steep hillsides to contain water from irrigation and precipitation(staircase-like layers). The most effective method for preventing erosion on extremely steep terrain.
(SOLUTIONS) What are shelterbelts(windbreaks)?
Rows of treees or shrubs planted along the edges of fields to slow wind.
What is alley cropping?
When shelterbelts are combined with intercropping
What is tillage erosion?
When soil is loosened due to overturning, making it more likely to move downslope due to gravity
What is irrigation?
Artificially providing water for agriculture
What is waterlogging and how is it harmful?
Waterlogging is the overirrigation of soils, suffocates plant roots
What is salinization?
The buildup of salts in surface soil layers
What is fertilizer?
substances that contain essential nutrients
What is biochar?
Biomass reduced to a black, carbon-rich, charcoal-like residue. Effectively holds on to plant nutrients and heavy metals
about how long does it take for 10 cm of soul to be created?
2000yrs
