AIPMT Biology Aspirants, read out the next topic AIPMT Biology Study material/ Notes of Decomposition in Ecosystem, important for AIPMT Biology.

Decomposition is the process of breaking down complex organic matter into inorganic substances like carbon dioxide, water and nutrients. Decomposition is done by decomposers.

• Dead plant remains such as leaves, bark, flowers and dead remains of animals, including fecal matter, constitute detritus, which is the raw material for decomposition.
• Earthworm acts as decomposer by helping in the breakdown of complex organic matter as well as in loosening of the soil so called as farmer’s ‘friend’.
• Important steps in the process of decomposition are  Fragmentation, Catabolism, Leaching, Humification, and Mineralisation.

All the above steps in decomposition operate simultaneously on the detritus, and not in the sequence listed.

Decomposition Cycle

• Fragmentation: Break down of detritus into smaller particles is called as fragmentation. Earthworm is Detritivores, so help in fragmentation.
• Catabolism: In this step of decomposition, bacterial and fungal enzymes degrade detritus into simpler inorganic substances.
• Leaching: Water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts by the process of leaching.
• Humification: It leads to accumulation of a dark coloured amorphous substance called humus. Humus is highly resistant to microbial action and undergoes decomposition at an extremely slow rate. Being colloidal in nature it serves as a reservoir of nutrients.
• Mineralization: Humus is further degraded by some microbes and inorganic nutrients get released in the soil by the process of mineralization.

Humification and mineralization occur during decomposition in the soil.

Decomposition is largely an oxygen-requiring process. The rate of decomposition is controlled by chemical composition of detritus and climatic factors.

• Decomposition rate is slower if detritus is rich in lignin and chitin, and quicker, if detritus is rich in nitrogen and water-soluble substances like sugars.
• Temperature and soil moisture are the most important climatic factors that regulate decomposition through their effects on the activities of soil microbes.
• Warm and moist environment favour decomposition whereas low temperature and anaerobic conditions inhibit decomposition resulting in build up of organic materials.