The amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis.
- It is expressed in terms of weight (g-2) or energy (kcal m-2)
- The rate of biomass production is called productivity.
Gross primary productivity: (GPP) is the rate of production of organic matter during photosynthesis.
Net primary productivity: A considerable amount of energy is utilized by plants in respiration.
Gross primary productivity minus respiration losses (R) is the net primary productivity.
GPP – R = NPP.
Net primary productivity is the available biomass for the consumption to heterotrophs (herbivore and decomposers.
Secondary productivity: is defined as the rate of formation of new organic matter by the consumer.
DECOMPOSITION: Earthworm is said to be ‘friends’ of farmer:
- Breakdown the complex organic matter.
- Loosening of the soil helps in aeration and entry of root.
The decomposers break down complex organic matter into inorganic substances like carbon dioxide, water and nutrients, called decomposition.
Dead plant remains such as leaves, bark, flowers and dead remains of animals, including fecal matter, constitute the detritus.
The process of decomposition completed in following steps:
Fragmentation: Break down of detritus into smaller particles by detritivore (earthworm).
Leaching: Water soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.
Catabolism: Bacterial and fungal enzymes degrade detritus into simple inorganic substances.
Humification: Accumulation of dark coloured amorphous substances called humus.