Productivity and Decomposition

Productivity

Ø A constant supply of sunlight is required for the proper functioning of any ecosystem.

Ø The amount of biomass produced per unit area over a time period by plants during photosynthesis is defined as the primary productivity.

Ø It is expressed as weight (g⁻²) or energy (Kcal m⁻²).

Ø Productivity can be mainly divided into gross primary productivity (GPP) and net primary productivity (NPP). GPP is the rate of production of organic matter during photosynthesis.

NPP = GPP − Respiratory losses (R)

Ø Secondary productivity is defined as the rate of formation of new organic matter by consumers.

Ø Primary productivity depends upon

o type of plant species inhabiting a particular area

o photosynthetic capacity of plants

o nutrient availability

Ø Annual net productivity for whole biosphere is about 170 b tons of organic matter.

Decomposition

Ø It is the process of breakdown of complex organic matter into inorganic substances such as carbon dioxide, water, nutrients, etc.

Ø Fragmentation − Breaking down of detritus (dead plant and animal remains, faecal matter) into smaller particles by detritivores (decomposers)

Ø Leaching - Process by which these inorganic matters enter the soil

Ø Catabolism − Process by which detritus is degraded into simpler inorganic substances by bacterial and fungal enzymes

Ø Humification − Accumulation of humus in the soil.

Ø Humus is resistant to microbial action and decomposes at an extremely slow rate. It acts as a reservoir of nutrients.

Ø Mineralization − Process by which humus further degrades to release minerals into the soil

Ø It is an oxygen consuming process and is controlled by the chemical composition of detritus and climatic conditions.

Decomposition cycle in a terrestrial ecosystem