BIOSPHERE Summary of What You Must Know You should be able to:

BIOSPHERE

Summary of What You Must Know

You should be able to:

describe and explain the effect of physical factors – climate, relief, drainage, parent material, soil biota and vegetation on soil formation.

draw annotated diagrams to describe the properties of podzols, brown earth soils and gley soils, referring to horizons, colour and texture.

recognise the type of soil shown in a profile diagram, and describe the features which help to identify the soil type.

compare and contrast the appearance and soil forming factors of two of the three soil types.

explain the series of soils found in a soil catena.

explain fully what is meant by the term climax vegetation.

describe and explain the changes in the types of plants (succession) to be found across a coastal sand dune transect, referring to the names of specific plants.

explain the changing environmental factors that they must adapt to.

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The Biosphere

The Living environment

This consists of plants, animals, insects, micro-organisms and people.

The Non-living environment

This consists of

Water (rain or stored in the soil). Air – provides oxygen and carbon dioxide which is essential for life. Solar energy – provides heat and light. Rocks – the lithosphere – provides nutrients Soil – varies in depth, acidity, nutrients and fertility

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The Biosphere – where life is found 3m below to 30m above the ground. It comprises water areas, both salt and fresh and all land. An Ecosystem – a natural system in which life of plants and animals are clearly linked to one another and to the non-living environment through food chains.

Ecosystems vary in size from extensive areas of rainforest to a micro system under a stone.

All ecosystems depend on two basic processes:

• A flow of energy (heat and light)• The recycling of nutrients within the system

Ecosystems will remain in balance unless conditions change such as climate or through human interference.

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Soils

Soil is the function of climate (water and temperature), organisms (bacteria, insects, plants etc.), parent material (rock under the soil), relief (steepness) and time.

Factors affecting soil formation

Soil Formation

Climate

Drainage

Relief

Vegetation

Soil Biota

Parent Material

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Classification of soils:

When precipitation exceeds evaporation water washes down through the soils carrying minerals with it. These soils are called pedalfers and include podzols and brown earth soils.

Hard pan – a resistant layer in the soil at or below the surface. Usually caused by illuviation (deposition of minerals, humus and other materials) after leaching of the upper horizons. Hard pans can be formed of clay humus or a compound of Calcium, iron and silicon.

Soil formation – a profile

A

B

C

Horizons

Organic matter Humus

Translocation

Hard pan

Bed rock

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When describing any soil you must mention the impact of climate, vegetation, parent material, soil biota, drainage and relief on its development

Brown Forest Soils

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Plentiful supply of deciduous vegetation – mildly acidic humus.

Moderate leaching occurs leading to a thin iron pan whenever leaching is more active.

Warm temperatures lead to more biotic activity and decomposition. This makes the horizons merge more gradually.

Soil is free draining so there is less likelihood of a hard pan layer.

Gentle sloping land has good drainage and moderate leaching.

This is the most fertile of the three soils we study and it can support agriculture which allows greater human development and higher population density.

Podzol Slide 32

High levels of precipitation plus spring snowmelts leads to a great deal of water flushing through the soil causing rapid leaching of minerals and the formation of a thick iron pan.

The Iron pan impedes drainage.

Pine cones and needles result in very acidic humus.

Soil horizons more clearly defined as there is little mixing due to restricted action of soil biota (this is a result of the cold climate).

Cold climate also leads to slow breakdown of plant materials.

Highlands: High precipitation and short growing season.

Steep slopes – downward movement of water increases leaching and iron pan formation.

Tundra/Gley Soils

Slide 33

Gleys have damp waterlogged soils due to inadequate drainage resulting from permafrost layer found below the surface. Because there is waterlogging there is a lack of oxygen in the soil.

There is a lot of partially decomposed material due to the restricted level of biotic action. This is the result of a very short summer with low temperatures and the waterlogged soils.

Horizons are poorly defined due the movement caused by constant freezing and thawing.

Parent material is obvious within the B horizon. The vegetation is dominated by mosses and lichens

which produce acidic humus. Large areas of flat land increase the drainage problems.REMINDER:

When describing any soil you must mention the climate, vegetation, soil biota, relief and the impact of each on

the development of the soil.

Soil catena showing variations in soil processes and effects along a slope

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Brown EarthBrown Earth Podzol Podzol GleyGley

Climate Climate Milder warmer Milder warmer climate leads to climate leads to increased biotic increased biotic activity and activity and decomposition.decomposition.

Moderate Moderate leaching occurs leaching occurs leading to thin iron leading to thin iron pan in some pan in some places where places where leaching is more leaching is more active.active.

High levels of High levels of precipitation and precipitation and spring snow melt spring snow melt leads to downward leads to downward movement of water movement of water and consequent and consequent leaching of mineralsleaching of minerals

Hard iron pan forms Hard iron pan forms and impedes and impedes drainage.drainage.

Cold temps. result Cold temps. result in slow breakdown of in slow breakdown of plant materials and plant materials and leads to a thick black leads to a thick black humus. humus.

Soils are damp and Soils are damp and waterlogged due to waterlogged due to inadequate drainage inadequate drainage resulting from resulting from permafrost. permafrost. Waterlogging leads to Waterlogging leads to lack of oxygen in soils.lack of oxygen in soils.

Constant freeze thaw Constant freeze thaw means horizons are means horizons are poorly defined and poorly defined and parent material is found parent material is found in the B horizon. in the B horizon.

VegetationVegetation A plentiful supply A plentiful supply of plant material of plant material (esp. from (esp. from deciduous leaves) deciduous leaves) leads to slightly leads to slightly acidic humus acidic humus

Acidic humus Acidic humus caused by nature caused by nature of the needles and of the needles and cones from pine cones from pine trees. trees.

Mosses and lichens Mosses and lichens dominate vegetation dominate vegetation leading to acidic humus leading to acidic humus

Biosphere: Summary Notes

Brown EarthBrown Earth Podzol Podzol GleyGley

Bio activity Bio activity (organisms) (organisms)

Horizons merge Horizons merge more gradually due more gradually due to increased action to increased action of biota.of biota.

Climate severely Climate severely limits soil bio limits soil bio activity so horizons activity so horizons are clearly defined are clearly defined

Because summer Because summer is so short and cold is so short and cold there is a very there is a very restricted biotic restricted biotic action. This results action. This results in lots of partially in lots of partially decomposed decomposed material in the soil. material in the soil.

Relief and Relief and drainagedrainage

Gentle slopes Gentle slopes lead to good lead to good drainage and drainage and restricts leaching.restricts leaching.

Less likelihood of Less likelihood of hard pan so soil is hard pan so soil is free draining free draining

Higher areas have Higher areas have more precipitation more precipitation and a shorter and a shorter growing season.growing season.

Steep slopes Steep slopes cause downward cause downward flushing of water flushing of water and increases and increases leaching and hard leaching and hard pan formation. pan formation.

Much flat land Much flat land which increases which increases drainage problems. drainage problems.

Summary Notes

Ecosystems

The non-living environment includes:

Water: rain or water stored in the soilAir: provide oxygen and carbon dioxide which are essential for life.Rocks: provide the nutrients for the soil.Soil: these vary in depth, nutrients and fertility.Solar energy: the sun is the earth’s primary source of energy and provides light and heat.

Controls on ecosystems

The organism within an ecosystem are controlled by two main factors:

1. Environmental factors (non-living environment)2. Competition (from other plants)

Succession

The change of community (plants and animals) and habitat over the years as a result of changing environmental conditions often brought about by the community. Slide 20

Environmental conditions

Each species has its own preferred set of environmental conditions. Under these conditions the species will flourish. Obviously if these conditions differ markedly from the optimum the species will be unable to survive and will be replaced (competition).

Competition

Ecosystems are rarely composed of single species. The number and variety present is determined by the suitability of the environmental conditions, species diversification and the ability of species to compete for energy and nutrients.

The Nutrient Cycle

Soil

Nutrients lost through leaching (down) or capillary action (up)

Nutrients added by weathering of parent rock

Litter: surface layer of

vegetation

Biomass = weight of living material (plants

and organisms)

Nutrients taken up by plants and organisms

Nutrients released as plants and leaves

decompose

Trees and animals die

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All ecosystems go through stages or seres when a different set of plants grow in thearea. A sere is a process of succession.

Climax vegetation

An empty area of ground will always be colonised by plant species. The plants arriveas seeds or spores.

The arrival and development of the vegetation is influenced by:

1. Climatic factors2. Soil type3. Biota4. Time5. Competition from other plants

The first set of plants to arrive is the pioneer community. These first colonisers tend to

be simple, hardy, low lying, lacking in diversity and unable to compete with otherspecies as the ecosystem develops.

Over the years the pioneer community is succeeded by other plants more suited tothe new environment (natural selection). After many years climax vegetation isreached.

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Climax vegetation

Climax vegetation is the final stage in the possible development of natural vegetation of a region or area. This is when the composition of the plant community is relatively stable and in balance with the existing environmental conditions which are normally determined by climate and soil. In sand dunes the climax vegetation is made up of pine and oak trees and flowering plants.

Sand Dune Succession: psammosere

Stage 1: At and behind the strandline, sea couch and sea rocket colonise. These are pioneer plants. It is a hostile environment (saline and strong winds) in which few plants can survive.An embryo gradually forms as the vegetation semi-stabilises the sand (through roots etc) and encourages a slight build up to form a dune.

Stage 2: 20 metres or so from the strandline are the yellow dunes (formerly embryo dunes). Here the marram grass grows as it has adapted to harsh conditions and salinity. The marram grass stabilises the dunes which continues to grow higher. The marram grass roots go deep to reach the water table.

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Stage 3: As the marram grass begins to die (conditions have become less suitable for marram) and a humus forms. Therefore soils begin to form. Conditions have become suitable for plants like dandelions.

Stage 4: Soil becomes richer in nutrients and plants such as birdsfoot trefoil colonise the fixed dune. The dune succession now reaches its climax vegetation with flowering plants, pine and oak trees growing.

Stage 5: Between some of the dunes ridges are low lying depressions called dune slacks. They are often covered in water from October till April submerging plants and creating very wet conditions. Rushes and sedges grow here.

Factors which affect changes in the soil

The embryo and yellow dune soils have a higher salt content and are therefore more alkaline.

The sandy texture of the soil means rapid drainage therefore there is a lot of leaching. Rainwater will remove the salt in the soil in the semi – fixed and fixed dunes (further away from sea spray). pH gets more acidic so different plants can now colonise.

With the addition of humus water retention will improve further away from the coast so the soil is wetter. The Humus encourages a decrease in pH.

Vegetation type depends on calcium carbonate. Where sand and shell fragments are found in high proportion rich grasslands flourish.

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Mineral matter (inorganic): minerals derived from parent material by physical and chemical weathering. Usually dissolved by water in the soil.

Organic material (humus): derived from decaying roots, leaves, needles and remains of dead animals.

Air and Water: co-exist and occupy the spaces in the soil called voids.

Organisms: the life in the soil. Living organisms include worms, fungi and bacteria, called biota. They assist in the decay of plants and they mix the soil by their movement.

Types of parent material

• Solid bedrock

• Alluvium

• River terrace gravel

• Wind blown sand (loess)

• Glacial till

What does soil contain?

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(Inorganic)

Ecosystems can vary enormously in scale:

Ecosystems can vary enormously in scale:

• Small, or micro scale, e.g. under a leaf or stone

• Medium scale, e.g.. a woodland, a sand dune, a salt marsh

• Large, or global scale, e.g.. Tropical rainforests, hot deserts

Slide 13

Ecosystems depend upon two basic processes:Ecosystems depend upon two basic processes:1. A continuous flow of energy, the main source being sunlight.

• Sunlight is taken in by the green leaves of plants.

• It is then converted, by a process known as photosynthesis, into a form of energy which can pass through the ecosystem in the food chain.

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The food chain

Snowy Owl

Lemming

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2.The recycling of nutrients: carbon, nitrogen, phosphorus and potassium.

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As they burrow through the soil, earthworms drag dead leaves and other organic matter down to the

lower levels, and break them down into humus

This earwig and her babies are among the thousands of insects and other

small animals that live in soil.

Dung beetle feeding on animal dung and so help to

break down plant and animal matter.

Slide 2

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Soil

TIME

• 400 yrs for 10mm of soil to form

• 1000 yrs for 1mm in extreme conditions

• 3,000 – 12,000 yrs for farming soil

• Horizons develop when soil reaches maturity

PARENT MATERIAL

• Depth

• Texture (coarse or fine)

• Drainage (permeability)

• Nutrient content

• Colour

CLIMATE

• Determines rate of weathering

• Precipitation affect type of vegetation

• Dictates leaching or capillary action

• Temperature determines length of growing season and humus supply

SOIL BIOTA

• Nutrient cycle/recycling

• Bacteria and fungi decompose dead plants and animals

• Worms and termites aerate the soil

RELIEF/TOPOGRAPHY

• Altitude: soils are thinner higher up

• Aspect: Northern Hemisphere south-facing slopes are warmer and drier.

• Slope angle affects drainage and soil depth

HUMAN INFLUENCE

Affects soil development by

• Adding fertiliser

• Breaking up horizons by ploughing, draining or irrigating land

• Accelerating or controlling soil erosion

determines soil

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Slide 1

Equator

Tropic of Cancer

Tropic of Capricorn

Arctic Circle

Podzol

Podzol

Brown Earth Brown Earth

Gley Soil Gley Soil

Distribution of 3 Major Soil Types: Brown Earths, Podzols and Gleys.

Slide 1

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Brown Earth Profile

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Podzol Profile

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Gley Soil Profile

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Gley Soil Profile

Waterlogged Tundra in summer

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AB

C

Which soil type is which?

Simplified stages in

soil formation

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HYPOTHESES: The sequence of soil profiles found in western Britain

1. Soil depth will decrease as gradient increases.

2. Soil moisture will decrease as gradient increases.

3. Soil acidity will be highest where gradient is lowest and leaching predominates.

4. Soil texture will be sandier where slope gradient is greatest and clay particles have been washed down-slope.

5. Organic content will be highest where slope gradient is lowest and soil depth greatest.

6. Soil acidity will be positively related to vegetation density.

Slide 10

Pioneer community (first plants to colonise an area)

Climax vegetation ( final stage in the

succession)

The complete process, from bare ground to climax vegetation, is called a plant succession or sere

Slide 16

Vegetation succession across a Coastal Sand Dune - psammosere

Vegetation across a grey dune and a dune slackEmbryo and fore-

dunes

Slide 17

Lime grass

Sea rocket

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Marram grass

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How Marram Grass stabilises sand dunes Slide 17

Birdsfoot trefoil

Cotton Grass

Spruce

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