Geoecology - Soil Flashcards
What is soil
The layer of natural material on the earths surface that is capable of supporting plant growth
How much of earth surface is made up of soil
25%
How much of the earths soil can support the growth of food
10%
What is the study of soil called
Pedology
What are the 5 component of soil
Mineral matter (45%) Air (25%) Water (25%) (Living organisms Humus) = organic matter (5%)
What is mineral matter made up of
Small pieces of rock broken down by weathering and Erosion
What two components of air are essential for plants and microorganism living in soil
Oxygen
Nitrogen
What does water have to benefit plants
Nutrients
Examples of living organisms in soil
Earthworms, slugs, Woodlice
Microorganisms eg bacteria and fungi
Function of organisms in soil
Break down dead plants to create humus
Help mix humus into soil particles by loving and loosening soil particles enabling water to get through
What is humus
Decaying organic matter eg plants, animals, leaves, grass
Function of humus
Provides nutrients to soil
What plays role in creating soil
CLIMATE
vegetation
Time
What is a soil profile
A section of soil extending from the surface to the bedrock
What are the different layers called in a soil profile
Horizon
What are the horizons
O horizon (organic matter, plant litter, animals, humus) A horizon (topsoil, humus, organisms) B horizon (subsoil, where rainwater percolates) C horizon (large clumps or partially weathered roock) R horizon (bedrock, undisturbed parent rock)
Which horizon do organism live
A
6 characteristics of soil
Colour Texture Structure Humus content Ph value Water content
What might affect colour of soil
Rock it developed from
Processes that have occurred eg Leaching
What gives soils their darker colour
Humus
Why might soils be grey
Washed out by rain, lacking nutrients
Soil structure refers to soil …
Peds
Good soil structure allows movement of …
Water and air
3 Ped types
Crumb
Blocky
Platy
Describe crumb soil
Small rounded grains
Near surface
Excellent for water movement
Example of crumb soil
Loam soil
Describe blocky soil
Cube shaped particles that fit tightly together
Few pores
Example of blocky soil
Sandy soils
Describe platy soils
Thin flat plates that overlap
Compact
Hold up water movemeg
Example of platy soils
Clays
Texture of soil is determined by amount of
Sand
Silt
Clay
Texture of clay soils
Wet and waterlogged in winter
Dry and cracked in summer
(Sticky and smooth)
Texture of silt soils
Powdery
Stick together when wet but won’t hold shape when dry
Do clay soils get waterlogged
Yes
Do silty soils get waterlogged
No
Sandy soil texture
Gritty
Don’t stick together when wet
Do Sandy soils get waterlogged
No free draining
Loam soil texture
Contains equal amounts of sand, silt and clay so feels crumbly and moist
How does humus affect soil
Adds nutrients
Binds soil tighter
increases ability to hold water
Give colour
What is ph of soil affected by
Rock it formed from eg alkaline soils from alkaline rock like limestone
Desired ph for most plants
6.5
Slightly acidic
An extremely acidic soil
Peat, little living things
Neutral soils are ideal for
Bacteria
Why is water important to a plant
Enables plant to absorb nutrient through water
Ena ale survival of microorganisms responsible for humus formation
Reduces soil erosion by wind
8 processes affecting soil characteristics
Weathering Humification Leaching Podzolisation Gleying Laterisation Salinisation Calcification
Types of weathering creating smaller pieces for mineral matter of soil
Freeze thaw Exfoliation Carbonation Hydrolysis Oxidation
Does physical weathering change mineral make up
No
Chemical does
Soil formed from carbonation
Dark brown alkaline soil rich in calcium
Hydrolysis forms what soil
Feldspar in rock changes to clay
Oxidation causes what soil
Reddish brown
What is humification
Method by which dead organic matter is converted into hummus by the action of fungi and bacteria
Humification occurs best in
Humid hot conditions
What is leaching
Removal of nutrients from soil by water.
Rainwater washes soluble substances through soil. It builds up in a layer in the soil
Where is leaching most common
Slopes
Areas with heavy rainfall eg mountains -relief rain
What is poszolisation
An extreme type of leaching that occurs when rainwater is acidic
How does rainwater build up acidity for podzolisation
As coniferous forests die and decompose, they add acidity to the rainwater
What mineral does acidic rainwater not dissolve
Quartz
Colour of top layer of podzol
Ash Grey
What is gleying
When soils become waterlogged and lacks oxygen
Is there much living things in gley soils
Can’t grow in wet conditions
Little oxygen
Colour of gley soils and why
Slightly blue/grey due to lack of oxygen
What is laterisation
Severe chemical weathering
All minerals are dissolved out of the soil except iron and aluminium oxides
Giving red colour
What is salinisation
The accumulation of mineral salts close to the surface of soil
Where does salinisation occur
Hot desert regions
Precipitation is low and evaporation is high
Groundwater is high in salt and as it evaporates salt is left
What is calcification
Calcium carbonate is concentrated near the surface of soil (horizon A)
Zonal soil in Ireland
Brown earth soil
Intrazonal soils in Ireland
Gley
Peaty
Describe soil profile of brown earth soils
No distinct horizons as living things have mixed the soil up
Factors influencing BES in Ireland
Climate Relief Living organisms and vegetation Parent material Time
How does Irish climate influence brown earth soil
Temp; 15°c in July and 6°c in January. Good for keeping microorganisms alive year round
Rain; 1500mm year round
Long growing season
How does relief affect BES in Ireland
Temp; higher ground is colder than lowlands because temps decrease by 1° for every 100m climb, less animal activity and less humification
South facing slopes warmer than north.
Living organism and vegetation on BES
Deciduous forest (oak, ash, chestnut, bitch) provide plant litter for humification
Fungi and bacteria
Badgers, rabbits, foxes and hedgehogs churn soil
Parent material of most brown earth soils
Boulder clay deposited in last ice age
Parent material of acidic BES
Granite, schist or sandstone
Parent material of shallow BES (rendzina soil)
Limestone
Parent material of podzolised BES
In lowlands where glaciers deposited their load
How long ago did Irish BES soil
10,000 years ago in last ice age
Irish BES colour
Brown
Presence of humus makes darker
Leaching washes out nutrients making lighter
Ph of BES
Slightly alkaline due to temp and parent material
Livy g things strive in thus pH
Is BES rich in humus
Yes
Trees loose their leaves each autumn adding to amount of litter available for humification
Structure of Irish BES
Crumb
Use of Irish BES
Tillage
Pasture
Texture of Irish Bes
Loam
Water content of BES
Depends on local conditions
Not too wet not too dry
Water content encourages plant growth
Is leaching common in Irish BES
It’s moderate
It washes nutrients into soil
Badly drained areas cause gley soils as BES is leached
natural causes of soil erosion
Rain
Wind
How does rain cause soil erosion
Force and impact of rain breaks soil grains
Soil becomes saturated
Water starts to float on top
Rainwater carries away soil
How does wind cause soil erosion
Blowing dry and exposed soil away
3 types of wind movement
Saltation - medium particles carried short distances
Suspension - fine particles carried long distances
Surface creep - large particles move along surface
Human causes of soil erosion
Farming (over grazing, over cropping)
Deforestation
Tourism in mountain areas
Quad biking
Characteristic and composition of brown earth soil essay 3 aspects
Texture and structure
Humus content and colour
pH
What is desertification
The reas of desert into new lands, Turing productive land into wasteland
What is overgrazing
Overgrazing occurs when farmers let their animals feed on all the vegetation in the area, removing the protective layer of vegetation and leaving soil exposed
What is overcropping
When land is used for vegetation over and over and is not left to recover
What is monoculture
The same crop is planted in the same field year after year
What is a fallow year
A year to recover fro, growing
What is deforestation
The large scale clearing of forests and using the land for non forest purposes
Where is the Sahel
4000km east to west Africa including niger, Mali, Chad, Sudan and Ethiopia
Sabel population change pattern
Doubles every 20 years
Desert conditions advancing into Sahel at rate of
5-10km a year
In Chad how many people are food insecure
3.5 million
Example of crop monocultured in Africa
Cotton
Ways humans positively interact with soil imnsahel
The great green wall —- agroforestry
Low tech/low cost soil conservation:
Stone bunds
Zai holes
How wide was great green wall
15km
Why did great green wall fail
Little effort to involve local farmers in planting or maintaining
Exotic species planted
Not enough funding
What is agroforestry
Growing trees but also using the land to grow crops and/or rear animals
Why did agroforestry succeed
Native species used
Trees producing food were used
Trees increased soil fertility and reduce soil erosion
More funding (from global climate summit)
What are stone bunds
Bunds are a method of soil conservation where small stones are placed across the land to trap rainfall and encourage it to seep into the soil
What are zai holes
Holes that catch rainfall to stop if running off
Soil is too alkaline, how do I make it acidic
Crushed lime
An example of how weathering effects ph of soil
Carbonation
Making it more alkaline
Eg rendzina soils
Sandstone produces soil of what a)colour and b)ph
Pale
Acidic
Limestone as a parent material produces soil of what a)colour and b)ph
Dark
Alkaline (calcium carbonate)
