Biosphere Flashcards
How does climate affect soils?
It governs the rate and type of soil formation and is the main thing that determines vegetation distribution. Climate has two components, precipitation and temperature. Temperature influences evaporation. When precipitation is more than evaporation, leaching will occur. Temperature influences rate of reactions.
How do organisms affect soils?
Organisms like bacteria and fungi affect the rate of plant decomposition. This plant litter is also mixed by organisms like worms and beetles. Soil horizons are hard to separate with lots of organism activity. Plants above also influence the soil too. The nature of the humus depends on the cover from vegetation. Roots help to bind soil together and can compress and re-distribute it.
How does relief affect soil?
It influences soil thickness, as slope angle increases so does erosion hazard. It has an effect on climate. Gradient affects run-off, percolation and mass movement.
Relief and drainage are often considered together. Water flows downwards and across slopes but also vertically into the soil. Relief has an effect on the processes of leaching and capillary action. If water does not flow then waterlogged gleys and peaty soils form. Water flows from upper well-drained areas to lower areas where the water, mineral and organic deposits will accumulate.
How does time affect soil?
Soils develop slowly, in the UK it takes 400 years for 10mm of soil to form. Young soils retain many of the characteristics of parent material. Over time they acquire other features resulting from the addition of organic matter and the activity of organisms.
How does parent material affect soil?
Parent material influences colour (red things like iron oxides), texture (sandy soils have larger particles), structure (hard rocks produce thinner soils), mineral composition (granite = acidic) and permeability (fine clay particles impede drainage).
How does human activity affect soil?
Deforestation and heather burning causes soil erosion. Fertilisers, lime and pesticides alter soil chemistry.
What is decomposition?
The breakdown of plant material into its organic constituents. This is accomplished by enzymes, worms and other organisms.
What is humification?
The breakdown of plant remains leading to the formation of different types of humus. It is probably the most important soil process.
What is weathering?
Refers to the breakdown and decomposition of rocks and minerals by air, water, the sun and frost.
What is capillary action?
Process where water and minerals in solution can be drawn upwards when the rate of evaporation exceeds precipitation.
What is leaching?
Removal of soluble minerals, salts and humus which are washed downwards through the soil and may accumulate in what is called the subsoil. This occurs when the rate of precipitation exceeds evaporation.
What are the forming factors for a podzol?
Cool environments where there is more precipitation than evaporation. Cool temperatures slow chemical reactions and precipitation causes leaching. Podzols are found anywhere but are more likely to be found at higher altitudes. Drainage in podzol lead to leaching which helps mix iron chemicals from the A horizon into the soil below creating their distinct reddish brown colour. Acidic rocks are their parent material such as granite. Coniferous woodlands are almost always on podzol soils. The leaf litter is mostly litter so it is hard to break down. Few organisms live in podzol soils so fertilisation isn’t frequent due to climates. This results in little horizon mixing so they are distinct.
What is mull humus?
Humus which develops under deciduous forests.
What is mor humus?
Humus which develops under coniferous forests.
What are the characteristics of a podzol?
Acidic soils, distinct horizons, light colours, eluvial horizons, mor humus, free draining.
