Biosphere

What are the six factors in soil formation

• Biota/organisms

• Climate

• Drainage

• Parent material

• Relief

• Vegetation

Parent material

This refers to the underlying rock or sediment which gets broken down due to biological or chemical weathering

Relief

This refers to the height and shape of the land

Drainage

Whether water can or cannot move through the soil easily will affect the development of the soil profile

Climate

This refers to the precipitation and temperature, which can effect the distribution of organisms, vegetation, and the rates of decomposition

Podzol profile

Brown earth profile

Gley profile

State the three main soils in Britian

Podzol, brown earth and gley

Eluviation (E horizon)

Horizons that loose materials, light in colour and has a sandy texture

Illuviation (I horizon)

Horizons that gain materials, dark in colour and has a dense texture

Formation of podzol

• Biota/organisms: few organisms, leading to the formation of distinct horizons

• Climate: northern altitudes have low temperatures which decreases the rate of decomposition, resulting in a thick, black, acidic mor humus

• Drainage: northern altitudes have high precipitation which leads to leaching, creating an iron pan between the A/B horizons which impedes drainage and causes waterlogging

• Parent material: weathered glacial rock

• Relief: steep sleeps, encouraging leaching

• Vegetation: coniferous vegetation has shallow roots which limits the recycling of any nutrients and any absorption of leached minerals

Formation of brown Earth

• Biota/organisms: soil organisms aerate and mix the soil, leading to the formation of indistinct horizons

• Climate: south-facing slopes have higher temperatures which increases the rate of decomposition, resulting in a thick, mildly acidic mull humus layer

• Drainage: the long tree roots penetrate the soil which absorbs nutrients

• Parent material: biologically weathered rock

• Relief: gentle slopes, leading to lower rates of erosion

• Vegetation: deciduous vegetation produces a deep leaf litter

Formation of gley

• Biota/organisms: few organisms due to anaerobic conditions, leading to the formation of distinct horizons

• Climate: low temperatures and high precipitation leads to slow decomposition, creating a thick, black, acidic mor humus layer

• Drainage: impermeable rock impedes drainage and causes waterlogging

• Parent material: thick impermeable rock

• Relief: flat surfaces such as plateaus or at the foot of a slope, meaning that water cannot drain away

• Vegetation: shrubs have shallow roots which limits the recycling of any nutrients

Leeching

When materials and humus move downwards, occurs when precipitation exceeds evaporation

Soil

Soil is the thin layer of loose material which covers most of the Earth’s land surface

Biota/organisms

This refers to the large and small living things which cause a soil to develop, including vegetation. They help the soil develop by breaking down the organic and inorganic matter

Cold climates

Soils will take longer to form as organic decomposition will be slower

Warm climates

Organic material decomposes faster and encourages soil organisms to aerate and mix the soil

Wet climates

This encourages leeching of the soil

Steep slopes

This leads to a faster run-off of water and greater erosion rates which leaves the soil thin and and infertile

Flat slopes

This leads to more leeching and waterlogging. However, this can accumulate soil washed down slopes

Waterlogging

Saturated soil filled with water that creates an anaerobic environment unable to support organisms

Why are organisms important for the formation of soils?

• Concentrate nutrients at the surface of the soil

• Helps aerate and mix the soil

• Leaves behind deposits that adds nutrients to the soil

• Vegetation reduces erosion by binding the roots to the soil

Decomposition by organisms

The breaking down of organic material into smaller parts, especially by the action of decomposers

Leaf litter by organisms

Decomposed dead organic material that creates an organic rich layer called humus on the A0 horizon

Coniferous vegetation

Found in cold climates, this vegetation has needles rather than cones or leaves, which slows humification as they retain their needles and those that are dropped are difficult to decompose, forming an acidic mor humus

Deciduous vegetation

Found in warm climates, this vegetation has an abundance of leaves especially in autumn which decomposes quickly, forming a thick carbon-rich mull humus

Hard rock parent material

This type of rock takes longer to form a soil, making a coarser, more gritter soil

Weathering

The exposure and decomposition of rocks on the surface overtime due to interactions with the atmosphere

Physical weathering

When rocks are broken down into smaller pieces, caused by changes in temperature, freeze-thaw, or effects of water and wind

Chemical weathering

When rocks are chemically altered, occurring when slightly acidic rainwater reacts with mineral grains in rocks to form new minerals and soluble salts

Biological weathering

When organisms, people, and vegetation break down rock into smaller pieces

Capillary action

When nutrients are drawn upwards, occurring when evaporation exceeds precipitation

The A0 horizon

• Closest to the surface

• Consists of organic debris called leaf litter that decomposes to make humus

The A horizon

• Known as topsoil

• Nutrient rich layer with a fine texture

• Consists of a mixture of humus

The B horizon

• Known as subsoil

• Has a coarse texture

• Consists of more mineral matter from weathered parent material

• Soluble organic matter may also be washed down from above by leeching

The C horizon

• Known as parent material

• Consists of weathered bedrock from the parent material and contributes mineral matter to the above horizons

Soil profiles

A vertical cross-section diagram of soil which shoes the soils horizons so it can be examined

Characteristics of podzol

• Coniferous vegetation with shallow roots, cone and needle leaf litter

• A0 horizon: thick, black, acidic mor humus

• A horizon: mineral and organic layer

• E horizon: eluviation leaves an ash-grey horizon with a sandy texture

• Iron pan

• B horizon: illuviation leads to a reddish brown horizon with a dense texture

• C horizon: partially glacial or fluvioglacial weathered parent-material

• Distinct horizons

Humification

A process which transforms raw organic material into humus

Mottling

When iron minerals are exposed to air, they turn a bright orange colour

Translocation

The movement of materials in soil, often by water or organisms

Vegetation

The type and quantity of plant cover will affect the amount of organic material added to the soil

Characteristics of brown earth

• Deciduous vegetation with deep roots, abundant leaf litter

• A0 horizon: thick, mildly acidic mull humus layer

• A horizon: dark-brown horizon with a loamy texture

• B horizon: light-brown horizon with long tree roots extending down

• C horizon: biologically weathered rock

• Indistinct horizons

Characteristics of gley

• Shrubs with shallow roots, grasses, lichens, and mosses are the only vegetation

• A0 horizon: thick, black, acidic mor humus layer

• A horizon: dark-grey horizon as organic matter cannot be broken down

• B horizon: iron changes from red-brown to a blue-grey due to anaerobic conditions, freeze-thaw breaks off angular rock

• C horizon: impermeable rock

• Distinct horizons