1. ST. ANDREW’S HIGH SCHOOL GEOGRAPHY Mrs Carruthers, Miss Curley and Ms Lynas "Working together to acheive our best" www.sahsgeo.wikispaces.com

2. BIOSPHERE Properties and formation processes of podzol, brown earth and gley soils.

3. What this topic will cover 1. Soil Profiles and horizons 2. Soil Forming Factors 3. Soil Processes 4. Soil Texture and colour 5. Brown Earth, Podzol and Gley soil profiles 6. Soil Cantena

4. By the end of this topic you should be able to: draw annotated diagrams to describe the properties of podsols, brown forest soils, and gley soils, referring to horizons, colour and texture recognise and describe the properties of soils from a soil profile describe and explain the effects of climate, relief and drainage on the formation of podsols, brown forest soils, and gley soils GMTs describe and analyse podsol, brown earth and gley profile describe and analyse data from soil surveys shown e.g. on a soil catena comment on the accuracy of statements which describe soil and patterns shown on maps etc.

5. Definition of Biosphere The biosphere is made up of the parts of Earth where life exists. The biosphere extends from the deepest root systems of trees, to the dark environment of ocean trenches, to lush rain forests and high mountaintops. Scientists describe the Earth in terms of spheres. The solid surface layer of the Earth is the lithosphere. The atmosphereis the layer of air that stretches above the lithosphere. The Earth’s water—on the surface, in the ground, and in the air—makes up the hydrosphere. Since life exists on the ground, in the air, and in the water, the biosphere overlaps all these spheres. Although the biosphere measures about 20 kilometers (12 miles) from top to bottom, almost all life exists between about 500 meters (1,640 feet) below the ocean’s surface to about 6 kilometers (3.75 miles) above sea level.

6. Soil: Some definitions Soil can be defined as the solid material on the Earth’s surface that results from the interaction of weathering and biological activity on the parent material or underlying hard rock. The study of soils as naturally occurring phenomena is called pedology (from the Greek word pedon, meaning soil or earth). Pedology takes into account: factors and processes of soil formation soil characteristics distribution of soil types

7. Soil is made up of four components Mineral mater is the product of weathering and comes from rocks. Air in the soil carries gases to and from the plant roots and animals. It is in the pore spaces when water is not. Water is held in the pore spaces and carries dissolved salts – plant food. Organic matter is the largest fraction. It comes from plant and animal remains that are gradually broken down into a brown material called humus. It is the major source of the three main plant foods – nitrogen, sulphur and phosphorus. It holds water, improves soil structure and provides the energy for plant (and animal) growth.

8. Soil Creation As soon as a barren surface like lava flow, glacial outwash plain or a beach begins to be colonised by flora and fauna, soil development is said to have begun. Organic debris decays and is mixed with the inorganic mineral matter by living organisms. The amount of mixing varies with depth, and this creates layers called horizons. The whole vertical section is called a profile. There are four terms regarding soil layers that you need to be familiar with: Leaf litter: decomposing but recognizable leaves and other debris forming a layer on top of the soil, especially in forests. Fermentation layer: the lower layer of the litter where decomposition is in progress. Regolith: the layer of loose solid material covering the bedrock of a planet. Humus layer: Humus is dark, organic material that forms in soil when plant and animal matter decays.

9. Soil Profiles TOPSOIL, upper or A horizon SUBSOIL, middle or B horizon PARENT MATERIAL, lower or C horizon This diagram shows simplified soil horizons A soil profile is a vertical cross- section of a soil. It is divided into a number of distinct layers, referred to as horizons. The horizons are normally designated by symbols and letters. The presence or absence of particular horizons allows pedologists (soil scientists) to classify the soil. In addition, the organic or O horizon can form above the mineral soil- commonly in forested areas, resulting from the dead plant and animal remains.

10. Soil Horizons The horizons may be further subdivided. For example, in this soil profile the A horizon has been divided into 4 further pedological horizons: (L) leaf litter (F) fermenting leaf litter (H) humus (E) eluvial These lie above the (B) or illuvial horizon. Fresh vegetation Dead vegetation- Litter (L) Fermenting litter (F) Humus (H) Eluvial horizon (E) Illuvial horizon (B) A horizon

11. Soil Profiles Ground surface with living vegetation Litter___________________________________________________ Fermentation______________________________________________ Humus___________________________________________________ A horizon upper and lower parts B horizon possible iron pan C horizon weathered parent rock D horizon unchanged parent rock

12. Soil Forming Factors Soils develop as a result of the interplay of 5 factors: Parent material Organisms: vegetation, fauna and soil biota Relief (landforms and topography) ClimateTime SOIL FORMING FACTORS

13. 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’. Jenny H (1941) Factors of soil formation. McGraw-Hill Book Co Inc pp281. The parent material can influence the soil in a number of ways: colour texture structure mineral composition permeability/drainage This soil has developed on Old Red Sandstone and so has derived its distinctive colour from its parent material

14. Climate This is probably the most important factor (soils produced from the same parent material under different climates contrast). Climate governs the rate and type of soil formation and is also the main determinant of vegetation distribution. Soil climate has two major components; moisture (precipitation) and temperature, influencing evaporation. When precipitation exceeds evaporation, leaching of the soil will occur. Temperature determines the rate of reactions; chemical and biological decay and so has an influence on weathering and humification.

15. Organisms: Vegetation, Fauna and Soil Microbes Organisms influencing soil development range form microscopic bacteria to large animals including man. Micro organisms 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. Higher plants influence the soil in many ways. 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 soil.

16. Relief Relief is not static; it is a dynamic system (its study is called geomorphology). Relief influences soil formation in several ways: It influences soil profile thickness i.e. as angle of slope increases so does the erosion hazard it has an effect on climate which is also a soil forming factor gradient affects run-off, percolation and mass movement it influences aspect which creates microclimatic conditions In this photograph soils are thin on the glacially eroded rock outcrops but are much deeper on the raised beach deposits in the foreground.

17. Time This soil profile shows a recent soil in Culbin Forest which has formed on sand overlying an ancient buried profile Recent soil Buried soil 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.

18. Soil Forming Factors Decomposition and Humification Capillary action Translocation Weathering Leaching Soils are complex and dynamic systems, in which many processes are taking place. SOIL PROCESSES

19. Weathering Chemical weathering involves alteration of the chemical composition of rock minerals. This refers to the breakdown and decomposition of rocks and minerals by factors including air, water, sun and frost. Physical weathering involves continual breakdown or rocks into smaller and smaller particles.

20. Decomposition and Humification Decomposition is the breakdown of plant derived material into its simpler organic constituents. This is accomplished by enzymes, earthworms, mites and other organisms. MOR humus usually develops beneath coniferous woodland or heather moorland, under cool, wet climatic conditions. Breakdown is slow due to the absence of soil biota. Humification is the breakdown of plant remains- leading to the formation of different types of humus. It is probably the most important biological process taking place in soils. MULL humus develops under deciduous woodland, where base-rich plant remains are actively broken down by a prolific soil biota. MODER humus is intermediate between mor and mull.

21. Humus Formation Living vegetation Raw litter - acid (mor) and less acid (mull) Fermentation (decomposing) layer Humus – totally decomposed plant material

22. Capillary Action In Britain precipitation generally exceeds evaporation. As a result capillary action in British soils rarely occurs, apart from in very sandy soils. Where evaporation exceeds precipitation, moisture moves upwards within the soil profile by capillary action. It is therefore in the reverse direction to leaching.

23. Leaching Leaching is most active in sandy soils with high porosity and is least in fine-textured soils such as clays which have restricted pore spaces. A soil with small soil peds or crumbs and high porosity leading to free drainage and active leaching Wherever rainfall exceeds evaporation and there is free downward movement of water through the soil pore system, soluble minerals are leached or removed from the soil profile. Continual leaching tends to impoverish the upper mineral horizons by removal of basic cations (cations are ions having a a positive electrical charge e.g. Ca 2+ ).

24. Translocation The lower horizon gaining the material is the ILLUVIAL horizon (often a subsoil or B horizon) (from the latin words il, meaning in, and luv, meaning washed). This is the zone of maximum accumulation. The movement of material in solution or suspension from one horizon to another is referred to as translocation. The upper mineral horizon losing the material is the ELUVIAL or E horizon. This is where maximum leaching or eluviation (from the Latin word ex or e meaning out, and luv meaning washed) takes place. The E horizon near the surface of a podzol is a good example of an eluvial horizon.

25. Soil Colour Such colours are the result of oxidation-reduction; iron is the main substance affected by these processes- when it enters an aerobic atmosphere it is oxidised to the ferric state, then to crystalline goethite/hematite. If the iron is released in an anaerobic environment, then it stays in the ferrous state giving it the grey blue colour of waterlogged soils. Soils with periodic waterlogging are imperfectly drained and are often highly mottled with blotches of colour different from the predominant soil colour. MOTTLES are often rusty in colour and are due to iron concentration.

26. Soil Colour Generally, the soil colour is determined by the amount of organic matter and the state of the iron. Soil colour is also related in part to soil drainage, with free draining, well AERATED soils (with pore space dominated by oxygen) having rich brown colours. In contrast, poorly draining soils, often referred to as gleys, develop under ANAEROBIC conditions (the pore space dominated by water) and have grey or blue-grey colours.

27. Soil Texture Soil texture is a term used to describe the distribution of the different sizes of mineral particles in a soil. Textures range from clay, sand, and silt at the extremes, to a loam which has all three sized fractions present. The main influence of texture is on permeability which generally decreases with decreasing particle size. Soil high in silt and clay with compact subsoil lacking in pore spaces Soil clod on right (above) is dense with a poor texture and leads to a poor structure if badly managed. Due to continual compaction it is blue-grey in colour due to low oxygen conditions. It is a poor environment for root development. Soil clod on left has been well managed and is relatively loose with ample pore space for good, healthy root development.

28. Three Types of Soil The 3 types of soil studied as part of the Higher Geography course are: Gleys Podzols Brown Earths

29. Characteristics of Brown Earth Soil Free draining Brown/reddish brown Deciduous woodland Litter rich in nutrients Intense biological activity e.g. earthworms Mull humus

30. Brown Earth Profile Ah-topsoil dark coloured enriched with mull humus, variable depth B - subsoil with distinctive brown/red brown colours Lightening in colour as organic matter/iron content decreases with depth

31. Brown Earth: Soil forming factors

32. Organisms in Brown Earths Organisms in brown earth soil help create a good and well aggregated, aerated and fertile crumb structured soil. Thin section of soil showing enchytraeid (potworm) faecal material False colour SEM of mixture of soil fungi and bacteria. Earthworm activity is important in soil mixing

33. Uses of Brown Earths o Amongst the most fertile soils in Scotland o Used extensively for agriculture e.g. winter vegetables. o Fertilisers required to maintain nutrient levels under agriculture. o Occurring on gently undulating terrain - used extensively for settlement and industry. o Sheltered sites suit growth of trees.

34. Characteritics of Podzol Podzol - from the Russian words; pod = under zola = ash Extensive group of leached, acidic soils Distinctive light coloured horizon found immediately below organic debris - eluvial horizon formed due to loss of iron/aluminium by leaching Mor humus with no recognisable plant remains Brightly coloured zone of iron/aluminium deposition - illuvial horizon Darker zone of organic deposition Relatively unaltered C horizon at variable depth Most podzols are free draining

35. Podzol Profile A horizon L - fresh annually supplied acidic plant material LF - partially decomposed organic debris H - mor humus E - eluvial horizon loss of Fe/Al oxides Bh - illuvial horizon- deposition of Fe/Al oxides Hardpan - zone of induration

36. Podzol: Soil forming factors FactorDescription Parent materialAcid rocks, often from granite or schist ClimateCool Precipitation Greater than evaporation Vegetation/ Organisms Coniferous woodland/ heather moorland Slow breakdown, limited or no mixing TopographyStable site from sea level to mountain summits TimeSince end of last ice age 10,000 years

37. Organisms in podzols – Organic matter breakdown

38. Alpine Podzol Shallow podzol found in high altitudes

39. Uses of podzols Generally infertile, non-productive Principally used for forestry and recreation (e.g. forestry plantations, grouse moors). In Scotland also used for grass production and stock rearing Where used for agriculture the top soil is often limed (to decrease acidity) and artificially fertilised (to increase nutrient status) Continual fertilisation and liming necessary to maintain adequate yields

40. Characterisitcs of Gley Soils Gley-from the Russian word; glei= compact bluish grey Poorly drained Periodic or permanent waterlogging Lack of oxygen in pore space = anaerobic conditions Chemical reduction occurs prior to translocation Grey or bluish grey colour to subsoil Where gleying is intermittent, orange/yellow coloured mottling can occur Horizons generally rich in organic matter intergrading into peat deposits - peaty gley to peat

41. Gley Profile Cg - C horizon with evidence of gleying O - organic layer Bg - B horizon with evidence of gleying

42. Gley: Soil forming factors Soil Forming FactorsDescription Parent MaterialVariable costal sand to glacial till ClimateRelatively warm Precipitation greater than evaporation - leaching Vegetation/ OrganismsAnaerobic organisms found TopographyWhere ground water high/ impermeable layer below TimeSince the end of the last ice age 10,000 years

43. Anaerobic organisms in gleys

44. Uses of Gleys When drained, the better gley soils can be used for agriculture; usually productive grassland for dairy or beef cattle. In their natural state they support wet plant species and are used for rough grazing and forestry

45. Mottling Block of gleyed soil with distinct mottles – grey colours denote gradual depletion of iron because of reducing conditions, “rusty” mottles depict zones enriched with ferric compounds within well-areated pathways such as old root channels or distinct pores.

46. Soil Catena In Scotland, in general, podzols are found in the north east and brown earths in the east and south east. However, there can be huge variations in soil types across a small area. This can be seen through a section diagram across an altitude range - called a ‘catena’. In a catena, the sequence of soil profiles which develop down the slope relate to the relief and altitude of the land. Changing slope alters drainage, and the leaching and gleying processes, whilst altitude strongly influences the climatic effects in soil formation.

47. Soil Catena

48. Soil Parent Material Bedrock

49. Soil Catena – Gley Soil Soil Parent Material Bedrock Gley Soils (NOT TUNDRA) See page 11 of the summary notes on information for the gley soil. A gley forms at the bottom of the slope because the area is waterlogged. This is because there is flat land and the water collects here from higher altitudes. This happens as long as the rock is impermeable. There is little humification as there is very few soil biota in the waterlogged conditions. The soil is quite shallow as weathering is slow.

50. Soil Catena – Brown Earth Soil Soil Parent Material Bedrock Brown Earth A brown earth forms on lower slopes as it is the zonal soil for this climate and vegetation. Some humification takes place as the climate is still quite mild and wet and the mild climate aids decomposition. Leaching takes place as precipitation exceeds evaporation – the higher you go the more rain received. Horizons are mixed because soil biota mix the soil.

51. Soil Catena - Podzol Soil Soil Parent Material Podzol Soil At the highest altitude we find podzol soil as it is coldest here and particularly wet. The weathering of the soil is slow due to the cold climate and humification is slow as few biota live in the cold conditions. There are distinct layers because of a lack of mixing by the biota. Leaching and podsolization occurs because precipitation exceeds evaporation. An iron pan caused by re-deposited iron impedes drainage. Sometimes the soil is waterlogged as a result of this, and the flatter/gently sloping relief.

53. [a] Annotate the three soil profiles to show the main characteristics of the soil. [b] For each of the soils explain the processes which have created this soil profile.

55. GLEY – MARKING SCHEME  Horizons – well defined Ao, A and B horizons.  Colour – A horizon, dark brown/grey colour – B horizon, blue-grey with red mottling (iron compounds).  Soil biota – lack of soil biota.  Texture – A – silty, B – clayey – angular rocks frost heaved up into B horizon.  Drainage – waterlogged, giving anaerobic conditions.  Short roots of grasses/shrubs.