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What you should know by the end of this lesson:
What you should know by the end of this lesson:
Factors affecting soil formation
Have a definition of the key terms of this topic
What is the Biosphere?
What is the Biosphere?
The term Biosphere refers to the biotic response to specific climatic and other environmental conditions such as relief and soils, which results in a variety of different types of vegetation. The various plants which exist on the earth’s surface inter-react within a system called an ecosystem.
Soil - Key Terms
Soil - Key Terms
Digital Workbook and Paper Jotter
Take note of all these key terms. They will come up regularly through the topic and should be easily accessible until learn them.
Horizon – a layer of soil within the profile.
Humus – decaying and decomposed vegetation, animals and bacteria. Present at the surface.
Humification – the conversion of plants and animals into humus. Happens faster when it is warmer.
Leaching is the movement of water down through a soil profile, removing nutrients from the topsoil and taking them to the subsoil.
Capillary action/rise - is the upwards movement of water through the soil in areas of high evapotranspiration.
Eluviation – removing minerals from the A horizon.
Illuviation – depositing minerals in the B horizon.
Gleying – is the process of soil becoming waterlogged and losing oxygen.
Mull – slightly acidic humus layer of soil within the profile.
Mor – very acidic humus layer
Percolation – the downward movement of water through the soil
Permafrost – permanently frozen bedrock or subsoil. An impermeable layer which prevents drainage
Anaerobic – When the soil is starved of oxygen making it very unhealthy
Soil Formation Factors
Soil Formation Factors
The 3 soils that you will study are Podzols, Brown Earths and Gley soils.
The key features that you should refer to when describing and explaining how each soil is formed are:
•Climate
•Relief
•Organisms
•Parent Material
•Vegetation
•Time
Digital Workbook and Paper Jotter
Take a note of the title of each formation factor
Read the information below about how each factor affects soil formation
Climate
Climate
This is probably the most important soil formation factor.
Climate determines the rate and type of soil formation and is also the main determinant of vegetation distribution.
Two major components;
1. Precipitation - when precipitation exceeds evaporation, leaching of the soil will occur. If evaporation is greater than precipitation with capillary action will take place.
2. Temperature - determines the rate of reactions; chemical and biological decay and so has an influence on weathering and humification.
In this photograph, soils are thin on the glacially eroded rock outcrops but are much deeper on the raised beach deposits in the foreground.
Relief (shape of the land)
Relief (shape of the land)
This is probably the most important soil formation factor.
Climate determines the rate and type of soil formation and is also the main determinant of vegetation distribution.
Two major components;
1. Precipitation - when precipitation exceeds evaporation, leaching of the soil will occur. If evaporation is greater than precipitation with capillary action will take place.
2. Temperature - determines the rate of reactions; chemical and biological decay and so has an influence on weathering and humification.
Organisms
Organisms
Organisms influencing soil development range from microscopic bacteria to large animals including man. Microorganisms such as bacteria and fungi assist in the decomposition of plant litter. This litter is mixed into the soil by macro-organisms (soil animals) such as worms and beetles.
Soil horizons are less distinct when there is much soil organism activity.
This soil has developed on Old Red Sandstone and so has derived its distinctive colour from its parent material.
Parent Material
Parent Material
This is the material from which the soil has developed and can vary from solid rock to
deposits like alluvium and boulder clay. It has been defined as ‘the initial state of the soil
system’.
The parent material can influence the soil in a number of ways:
colour
texture
structure
mineral composition
permeability/drainage
Vegetation
Vegetation
The nature of the soil humus is determined by the vegetation cover and resultant litter inputs.
Roots contribute dead roots to the soil, bind soil particles together and can redistribute and compress the soil.
Long roots can also draw up minerals that have been leached down through the soil.
Time
Time
•Soils develop very slowly. In Britain, it takes about 400 years for 10mm of soil to develop.
•Young soils retain many of the characteristics of the parent material. Over time they acquire other features resulting from the addition of organic matter and the activity of organisms.
•The soils of Britain are relatively young because they are largely post-glacial.
•An important feature of soils is that they pass through a number of stages as they develop, resulting in a deep profile with many well-differentiated horizons.
Well done you have finished lesson 1 of Biosphere
Well done you have finished lesson 1 of Biosphere
Return to the topic launch page and attempt the lesson quiz
Return to the topic launch page and attempt the lesson quiz
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