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Biosphere

Biosphere . Soils. Soils — properties and formation processes: ♦ properties of podzols, brown earths and gleys — horizons, colour, texture, drainage ♦ the influence of soil-forming processes on profiles as demonstrated by podzolisation, gleying, organic and nutrient movement. SQA.

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Biosphere

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  1. Biosphere Soils Soils — properties and formation processes: ♦ properties of podzols, brown earths and gleys — horizons, colour, texture, drainage ♦ the influence of soil-forming processes on profiles as demonstrated by podzolisation, gleying, organic and nutrient movement SQA

  2. Biosphere Soils Terminology Pedalfer soil: soils where precipitation exceeds evaporation– wet areas. Pedocal soil: soils where evaporation exceeds precipitation – dry areas. mor: acidic humus associated with coniferous forests/tundra areas mull: chemically neutral humus associated with deciduous forests anaerobic: without oxygen gleying: waterlogging eluviation: movement of humus, chemical substances, and mineral particles from the upper layers of a soil to lower layers by the downward movement of water through the soil profile illuviation: Deposition of humus, chemical substances, and fine mineral particles in the lower layers of a soil from upper layers because of the downward movement of water through the soil profile

  3. Biosphere Soils What is soil? Soil is a mixture of weathered rock, decayed organic matter, water and gases. Mineral matter. This consists of minerals from chemical and physical weathering of the parent material. Organic material. Material from decaying plants and organism. Air and water. Ever changing and fills the voids or spaces in the soil.

  4. Biosphere Soils Soil forming processes Relief Vegetation Climate Soil formation Humans Time Soil biota Drainage Parent material

  5. Biosphere Soils Soil forming processes Climate Climate Temperature and precipitation have a major influence on the soil. Higher temperatures encourage soil biota activity whilst the opposite is true. In wetter areas where, precipitation is greater than evaporation, this causes the leaching of the soil and the removal of soluble minerals and humus. However where evaporation is greater than precipitation, water actually moves upwards through the soil, called capillary action, and this brings minerals from deeper down up to the surface.

  6. Biosphere Soils Soil forming processes Relief and drainage Relief and drainage A steep slope will allow water to run-off and increase the chances of soil erosion. Flat land is usually poorly drained and this waterlogging can prevent soil forming properly. Aspect can lead to south-facing slopes being warmer and encouraging biota activity and vegetation more so than in north-facing slopes. The ease with which water can pass through as soil can also affect its development.

  7. Biosphere Soils Soil forming processes Vegetation Vegetation Vegetation provides plenty of humus aiding soil fertility. Soil biota activity is encouraged and these areas are more likely to be warm and moist further improving soil fertility. The type of vegetation present will affect the type of soils that develops.

  8. Biosphere Soils Soil forming processes Humans Humans People increasingly cause change in soils. By clearing woodlands in one area, planting trees in another, growing crops, adding chemicals and fertilisers, draining marshes the soil is altered much more quickly than would occur naturally.

  9. Biosphere Soils Soil forming processes Soil biota Soil biota This is all the animals living in the soil. Bacteria, worms, plants, roots and insects all absorb nitrogen, mix the soil by burrowing through it, and also aerate it (create air pockets that can be filled by water). The decaying humus in the topsoil makes this the most fertile section of any soil.

  10. Biosphere Soils Soil forming processes Parent material Parent material This is the main rock type under the soil, usually the bedrock (regolith). The parent material affects the colour, texture and chemical make-up of the soil. Eg red sandstone bedrock produces red, “sandy” soil.

  11. Biosphere Soils Soil forming processes Time Time Long periods of time are needed for soils to reach maturity by the processes already mentioned (about 1000 years for one cm - in many parts of Britain we have had only 10,000 years since the last Ice Age stripped the original surface soils away). It is thought that 10 000 years are needed for a soil to settle and mature.

  12. Biosphere Soils Soil profiles A soil profile is a vertical section from the surface vegetation to the bedrock. By examining the different layers or horizons it is possible to work out the soil type. A Horizon The A Horizon: This is the main layer and consist of a mixture of organic and inorganic material. This is usually nutrient rich and fine textured. Often referred to as topsoil. Topsoil Subsoil B Horizon Soil profile The B Horizon: This is the subsoil, which contains less organic matter and is coarser in texture, reflecting the importance of weathering.Nutrients may leach out of the A Horizon. Regolith C Horizon The C Horizon: This is the zone of regolith (fragments of rock). Large particles sit on the underlying bedrock. Soil profile can vary in depth. In Britain the average depth is 1.5m

  13. Biosphere Soils Brown Earth forest soils

  14. Biosphere Soils Brown Earth forest soils

  15. Biosphere Soils Brown Earth forest soils Location: Temperate deciduous forests of Central Europe, Russia and North America. Further south than podsols. Climate: Moderate climate. Milder winters, cooler summers and lower precipitation, allowing more rapid decomposition – although it is still exceeds evaporation (pedalfer). Good conditions for vegetation growth/soil biota. Relief & drainage: Gently rolling landscape, allows soil to drain well. The A horizon is greasy due to its high organic content and is a light brown colour due to the humus. Leaching occurs but is less than in other soils from wetter areas, but where it is more pronounced an iron pan may develop in the B horizon. Soil biota: Warmer temperatures encourage soil biota activity, making horizons less distinct. Leaf litter is more rapidly decomposed.

  16. Biosphere Soils Brown Earth forest soils Natural vegetation: Deciduous forests (ash, beech, oak). Plentiful supply of leaf litter. The resulting humus is deep and only slightly acidic (mull). Type of soil: Horizons here a less distinct due to more soil biota activity mixing the layers. A pedalfer soil, but less acidic.more alkaline soil due to leaf litter type. Processes: Climate is less of a negative influence – mixing is promoted vis biota and some gentler leaching may occur, possible leading to the development of an ironpan. Parent material: Weathering of the parent material contributes to the soil forming process here. Human use: More fertile and useful than the other main soil types and populations here are greater. With the addition of manure and fertilisers these soils support grain crops and grazing cattle.

  17. Biosphere Soils Brown earth soils Precipitation = evaporation approx Deciduous trees/ heathers/shallow roots Thick leaf debris Mild acid humus with plant foods A Horizon Brown layer – well aerated Dark brown layer No marked horizons Merging boundary due to mixing by biota B Horizon Lighter brown layer Deep brown layer C Horizon Parent material

  18. Biosphere Soils Podsol soils

  19. Biosphere Soils World biomes - Podsol soils

  20. Biosphere Soils Podsol soils Location: Northern coniferous forests. Climate: Long cool/cold winters and short mild summers. Precipitation can be variable – low to fairly heavy. Considerable snowfall though leading to spring snow-melt.. Leads to low soil biota activity and slow decomposition. Relief & drainage: On mountain sides or tops, up to 350m. Precipitation and drainage leads to rapid leaching of iron and aluminium oxides (eluviation) from the A horizon leaving it rich in silica and ash-grey in colour. The deposition of iron oxides in the B horizon (illuviation) creates a red-brown colouring and may concentrate to forma thin solid layer called an iron pan. This impedes drainage and can cause waterlogging. Soil biota: Not much activity here because of the cold climate and this means that the soil is not mixed, leading to clear horizons developing.

  21. Biosphere Soils Podsol soils Natural vegetation: Coniferous trees (pines, spruces, firs). Produces litter of needles and pines, creating a thin acidic humus (mor). Type of soil: Heavy with aluminium and iron, leading to an acidic pedalfer soil. This soil has clearly defined horizons. Processes: The climate has a strong influence here, ie lack of warmth limits soil biota activity restricts mixing of soil and causes humus to decay slowly; and leaching of iron and aluminium, as spring snow melts, and humus causes an iron pan to develop. Parent material: This only has a small influence with podsols. Human use: Mainly used for commercial forestry plantations (conifers). If lime were added, some cultivation could take place with oats, potatoes or hay. Waterlogging due to the ironpan is a major problem.

  22. Biosphere Soils Podsol soils Layer of needles and cones Raw,black acid humus (mor) A Horizon Ash grey layer Iron pan – impedes drainage B Horizon Reddish brown layer C Horizon Parent material Precipitation > evaporation Coniferous trees/ heathers/shallow roots Sandy texture Denser texture

  23. Biosphere Soils Gley soils

  24. Biosphere Soils Gley soils

  25. Biosphere Soils Gley soils Location: Found in Tundra areas, or in places with poor drainage and low temperatures eg Dartmoor (SW England) Climate: Cold and wet. Summers are mild and brief and severe winters limit soil biota activity. The important factor here is the lack of warmth. The continual process of freezing and thawing, and consequent expansion and contraction, leads to vertical mixing of soil particles and poorly defined horizons. The presence of permafrost impedes drainage. Relief & drainage: Wet and exposed flat regions with very poor drainage - the soil is damp/waterlogged due to the permafrost. The presence of water here causes a lack of oxygen (anaerobic conditions), leading to a gleying of the soil, turning it blue-grey in colour and greasy to the touch. Soil biota: Severely restricted due to extreme cold and waterlogging. Soil is mixed by freeze/thaw action, but very slowly.

  26. Biosphere Soils Gley soils Natural vegetation: Vegetation growth is limited due to lack of warmth and waterlogging. Typically mosses, lichens and marsh vegetation dominate. Larger plants can’t survive due top the shallow soils (permafrost). Produces a dark, acidic humus (mor). Type of soil: Pedalfer soil. Clearly defined horizons. Processes: As the soil is usually waterlogged it is deficient in oxygen, limiting soil biota activity. Litter is broken down very slowly in the cold temperatures. This soil is closely linked to the climate and vegetation. Parental material: Fragments of parent material are moved through this soil by freeze/thaw action. Human response: Limited potential for humans so populations are scarce. By ploughing, liming and fertilising/manuring this soil is still only capable of growing low value crops such as oats or potatoes. These areas are remote from population centres though so profits would be hard to make with such crops.

  27. Biosphere Soils Gley soils Grassy meadowland/small shrubs A Horizon Black with acid humus (mor) B Horizon Waterlogged blue grey gleyed mud Angular rock fragments Permafrost C Horizon Parent material Precipitation > evaporation Mosses and lichens Silty texture Waterlogged Impermeable clay

  28. Biosphere Soils Summary Brown Earth forest soils Summary: • Precipitation is slightly greater than evaporation, leading to a downwards movement of water and moderate leaching. A narrow hard pan can sometimes develop. • Faster decomposition due to warmer temperatures and less water. Lots of soil biota activity – worms, rodents, insects. • Litter is mainly from deciduous leaves, leading to only a mild acid humus. • Clearly defined horizons.

  29. Biosphere Soils Summary Podsol soils Summary: • Precipitation is greater than evaporation, leading to a downwards movement of water and leaching. • An iron/aluminium hardpan is formed which acts as a barrier to drainage. • Low temperatures result in limited biota activity and a slow breakdown/decomposition of litter. • An acidic (mor) humus develops due to the layer of pine needles/fir cones. • Clearly defined horizons.

  30. Biosphere Soils Summary Gley soils Summary: • Damp waterlogged soils. Inadequate drainage. Permafrost layer may be present. • Poorly defined horizons. • Dark, acidic (mor) humus develops from the slowly decaying mosses, lichens and harsh vegetation. • Limited soil biota activity due to waterlogging and low temperatures, so little biological activity. Humus decays very slowly.

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