Influence of abiotic soil characteristics/factors on the distribution of soil flora and fauna

Soil temperature:
– most living organism thrive only within a narrow temperature range
– due to the limit within which biochemical/physiological processes can proceed efficiently
– usual temperature ranges between 25-35°C
– at low extremes, biochemical processes slow down
– at a higher extreme, enzymes are denatured
– organisms therefore remain within this range
– some are adapted to extreme conditions
– soil temperature influence vegetation cover and humus content
– it also affects soil oil and moisture content.
Soil moisture:
– influenced by soil texture and crumb structure/pore space
– occurs as a liquid, vapour or ice(solid)
– Most available as liquid
– all living organisms require moisture
– for hydration of enzymes during physiological reaction
– soil at field capacity most suitable for soil organisms
– water logging of soil expels air from soil
– detrimental to the growth of aerobic organisms
– few anaerobic organisms are adapted to water logged soil
– e.g sulphur bacteria and denitrifying bacteria
– complete absence of soil water is also detrimental
– does not permit physiological processes
– few organism survive by going in to suspended metabolism/aestivation
soil air:
– influenced by soil texture and crumb structure/pore space
– also influenced by soil moisture content
– it’s composed mainly of oxygen and carbon (iv) oxide
– low concentration of other gases may also be present depending on soil condition
– most soil organism are aerobic
– soil oxygen is therefore very crucial to their metabolism
– some may be anaerobes e.g sulphur bacteria
– soil carbon (iv) oxide is important for photosynthetic organism e.g algae
– soil carbon (iv) oxide may sometimes be greater than found in atmosphere
soil pH
– important for many organisms
– influence soil moisture tension
– affect availability of mineral nutrient
– some organisms e.g bacteria are more tolerant to low pH
– others e.g fungi are less tolerant
– affect soil structure/pore space
– soil pH affect uptake of water by plant root
– alkaline soil is unfavorable for most plant
– determined by presence of unchangeable cations
Soil nutrients:
– mineral element for plant processes
– humus content
– complete absence of soil water is also detrimental
– does not permit physiological processes
– pure organisms survive by going into suspended metabolism.

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