CBSE · Class 12 · Biology · EcosystemExplain the process of decomposition in an ecosystem. Describe the major steps involved in decomposition along with the factors affecting the rate of decomposition.

Definition of Decomposition\nDecomposition is a vital biological and chemical process in which complex organic matter, derived from dead plants and animals (such as leaves, bark, flowers, and dead remains of animals), is broken down into simpler inorganic substances like carbon dioxide, water, and various inorganic nutrients. This process is crucial for the recycling of nutrients within an ecosystem.

Major Steps in Decomposition\nThe process of decomposition involves several sequential steps that often occur simultaneously on the detritus:

1. Fragmentation:

   • Detritivores (such as earthworms) break down detritus into smaller particles.
   • This process increases the surface area of the detritus particles, making them more accessible to microbial action.

2. Leaching:

   • Water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.
   • This prevents these nutrients from being washed away immediately by surface runoff.

3. Catabolism:

   • Bacterial and fungal enzymes degrade detritus into simpler inorganic substances.
   • These enzymes are secreted extracellularly by decomposers directly onto the detritus.

4. Humification:

   • Leads to the accumulation of a dark-colored amorphous substance called humus.
   • Humus is highly resistant to microbial action and undergoes decomposition at an extremely slow rate.
   • It serves as a reservoir of nutrients for plants.

5. Mineralization:

   • The humus is further degraded by some microbes, and inorganic nutrients are released.
   • This makes nutrients fully available for uptake by green plants, completing the nutrient cycle.

Factors Affecting Decomposition Rate

• Chemical Composition of Detritus: Decomposition is rapid if detritus is rich in water-soluble substances like sugars and nitrogen. It is slower if detritus is rich in lignin and chitin.
• Climatic Factors: Temperature and soil moisture are the most important climatic factors. Warm and moist environments favor rapid decomposition, whereas low temperatures and anaerobiosis inhibit it.