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. Slide 25 Slide 30

The Living environment The Biosphere Core 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 Slide 19

All ecosystems depend on two basic processes: 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. Slide 20

Factors affecting soil formation 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 Relief Climate Vegetation Soil Formation Drainage Soil Biota Parent Material Slide 28

A B C Soil formation – a profile Horizons Organic matter Humus Translocation B Hard pan C Bed rock 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.

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 Slide 31

Natural vegetation — deciduous forest vegetation provides deep leaf litter, which is broken down rapidly in mild/warm climate. Trees have roots which penetrate deep into the soil, ensuring the recycling of minerals back to the vegetation. Moderate leaching occurs leading to a thin iron pan whenever leaching is more active. In lower rainfall areas no iron pan can form. soil biota break down leaf litter producing mildly acidic mull humus. They also ensure the mixing of the soil, and preventing the formation of distinct layers within the soil.

South-facing slopes with a greater amount of sunshine and higher temperatures increase the rate of humus production. Soil colour varies from dark brown in A horizon to lighter brown in B horizon where humus content is less obvious. Texture is loamy and well-aerated in the A horizon but lighter in the B horizon. The C horizon is derived from a range of parent material, with limestone producing lighter-coloured alkaline soils, clay dark coloured soils. 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. Yellowish/ grey colour to top soil due to leaching and a the lack of minerals from the parent material. The Iron pan impedes drainage causing waterlogging and reduced bioactivity in the top soil. Pine cones and needles and a lack of other vegetation result in a thin very acidic humus (mor). 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, thin acidic humus.

Steep slopes – downward movement of water increases leaching and iron pan formation. Highlands: High precipitation and short growing season restricts the bioactivity to a short period of the year. Parent material – may be fluvioglacial sands or till or acidic parent rock which determines the nature of the C horizon

Tundra/Gley Soils Slide 33

Gleys have damp waterlogged soils due to inadequate drainage resulting from permafrost layer found below the surface. Because of this waterlogging there is a lack of oxygen in the soil leading to a lack of Soil Biota. 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 due to the freeze thaw action of ice. The vegetation is dominated by mosses and lichens which produce acidic humus. Large areas of flat land in addition to the permafrost increase the drainage problems and form large tundra ponds in summer . 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 Slide 36

Climate Vegetation Brown Earth Podzol Gley Milder warmer climate leads to increased biotic activity and decomposition. Moderate leaching occurs leading to thin iron pan in some places where leaching is more active. High levels of precipitation and spring snow melt leads to downward movement of water and consequent leaching of minerals Hard iron pan forms and impedes drainage. Cold temps. result in slow breakdown of plant materials and leads to a thin black humus. Soils are waterlogged due to inadequate drainage resulting from permafrost. Waterlogging leads to lack of oxygen in soils. Constant freeze thaw means horizons are poorly defined and parent material is found in the B horizon. Vegetation A plentiful supply of plant material (esp. from deciduous leaves) leads to slightly acidic humus Acidic humus caused by nature of the needles and cones from pine trees. Mosses and lichens dominate vegetation leading to acidic humus

Bio activity (organisms) Summary Notes Brown Earth Podzol Gley Bio activity (organisms) Horizons merge more gradually due to increased action of biota. Leads to a thick humus and more minerals brought from the parent material. Climate severely limits soil bio activity so horizons are clearly defined. Little influence of parent material. Because summer is so short and cold there is a very restricted biotic action. This results in lots of partially decomposed material in the soil. Relief and drainage Gentle slopes lead to good drainage and restricts leaching. Less likelihood of hard pan so soil is free draining Higher areas have more precipitation and a shorter growing season. Steep slopes cause downward flushing of water and increases leaching and hard pan formation. Much flat land which increases drainage problems.