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i DECOMPOSLLION aaa, , It is physical and chemical breakdown of complex organic remains with the help of, organisms called decomposers. In terrestrial ecosystem, upper layer of soil is the main site, of decomposition. Organic remains (dead plant parts, animal remains and excretions) are, also called detritus. It is of two types— above-ground detritus (leaf litter, dried plant, parts, remains of animals, their droppings and-excretions) and below-ground detritus, , (mainly dead roots, also underground.dead animals)., , Decomposition Processes, Decomposition completely disposes off the whole detritus. It helps in recycling of, biogeochemicals and creating space for newer generations of organisms. A number of, processes are involved in decomposition. They are grouped into three categories, all of which, operate simultaneously. (i) Fragmentation of Detritus. Detrivores (e.g., termites, carrion, beetles, earthworms) feed on larger pieces. The smaller fragments are left. Pulverisation, occurs in the digestive tract of detrivores as a part of detritus comes out undigested. The, part digested by deterivores is immobilized. Due to fragmentation, left-over detritus comes, to have large surface area. Earthworms are-called farmer’s friends because they help in
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ecosvsrin (99 Us, on of detritus and loosening of soil. (ii) Catabolism, The decomposers (¢, fragmentalo 4) excrete digestive enzymes over the detritus. It changes insolube con a, ic stances into simple and soluble organic compounds and inorganic substances, ae, f the broken down food is taken up by decomposers and immobilised. (iii) Leaching., gubstances formed during decomposition are subjected to leaching or Passage to, deepet layers of soil/ground water by percolating water., , Decomposition process gives vise (a Ee products, humus and inorganic nutrients, = minerals): Processes involved in their formation are called humification and mineralisation, t pectvel Humification is the process of formation of humus from detritus or organic, remains. Humus is dark coloured amorphous organic matter rich in lignin and cellulose. It, is quite resistant to microbial action, a reservoir of nutrients and helpful in maintenance of, soil moisture as well as aeration. Itis colloidal in nature, Nutrients are released slowly as the, humus is slowly decomposed. Mineralisation is the ip leas of inorganic substances, both, non-mineral (¢.8-» CO>, H,0) and minerals (2.8.5 Ca**, Mg”*, K*, NH,*) from organic, matter. The process 1s slow because of trapping in humus and immobilisation in decomposersidetrivores. It prevents their washing out or leaching. Nutrients immobilised in decomposer microbes and detrivores are again exposed to humification and mineralisation after the, , death of these organisms., , 0!, soluble, , , , , , = HUMIFICATION, ENVIRONMENTAL., CONDITIONS =, , FRAGMENTATION, =, LEACHING, CATABOLISM MINERALISATION, , , , , , | DETRITUS |, , , , , , , , , , , , , , , , , , , , , , , , , , mineralisation of organic matter,, mples. Pseudomonas, Slime Moulds., , , , , , , , , , , , oe Rate of decomposition of detritus depends upon chemical quality of. detritus,, dtkomn ure, soil moisture and soil pH. The last three influence activity of detrivores and, Somme microbes. (i) Temperature. A soil temperature of 25°C and more hastens, , hiniteercs taking from a few weeks to a few months for complete mineralisation and, of less ae Humus also does not persist beyond a couple of months. A low temperature, degitus - 10°C reduces rate of decomposition. As a result in many temperate a, compen r es UP at the ground level. (ii) Moisture. It is essential for decomposition. DePosition rate is very low in tropical deserts despite presence of favourable temperature.
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Excessive moisture also impedes decomposition probably due to anaerobiosis. (iii) pu. ie,, and slightly alkaline soils are rich in detrivores, earthworms and decomposer micro, ‘al, Acidity decreases the number of detrivores and earthworms, Decomposer microbes Wi 3, in slightly acidic soils but with the rise in acidity, their number begins to fall, As Ur, decomposition of detritus is quite slow in acidic soils. (iv) Composition. Chitin ang, are very slow to get decomposed. Cellulose decomposition takes time, Therefore, q, with small amount of lignin/chitin/cellulose which is rich in nitrogen and water $, Substances (like sugars) decomposes rapidly. (v) Aerobiosis. Aerobic conditions, Sential for activity of decomposer organisms because decomposition is Oxygen re, Process. Anaerobiosis reduces decomposition and causes piling up of detritus,, , Ctr; itus, , lube, ae gg, , Wing, , Differences between Production and Decomposition, , , , , , APA Ce eee: Decomposition, , , , 1, It is the process of synthesis of organic 1. It is the process of breakin, ._. compounds/biomass from inorganic matter substance/waste biomass into, using sunlight by producers (plants). parts by decomposers (bacteri, , 2. It traps energy. It releases energy., , 3. It builds up biomass from inorganic It. releases inorganic * nutrients from the, nutrients. __ biomass,, , 8 down of g, its constituent, a, fungi),, , wb, , , , , , , , , , , , A tree grows, in the son Some are eaten by insects, and other animals. Nutrients, , and energy enter, , tI, , , , , , - _ Agreen leaf falls ~, to the ground., , Leaves partially consumed by, decomposers such as fungi and, bacteria. They begin to lose form, , and become ae, ic, , Further decomposition by :, earthworms, bacteria, soil,, mites, fungi, etc., , leach into soil by, hemical reaction., , , , , , , , ORGANIC ~, -RICH.SOIL:, , , , Minera, , , , , , Fig. 14.2. Schematic representation of decomposition cycle in a terrestrial ecosystem., , , , pice a Dest eeyes i
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Differences between Detritus and Litter, , , , , , , , , , , ape, , It 4 remains of plants and animals i.e., itis | 1. Litter is mostly dried fallen plant matter., freshly deposited organic matter. lies casi ;, be . It is of two types, above ground and below. | 2.. Itis above ground., , __ ground., , Hick, , 4:, , PR
