(1) Primary Productivity : The rate of generation of biomass in an ecosystem which is expressed in units of mass per unit surface (or volume) per unit time, for instance grams per square metre per day (g/m²/day) is called primary productivity.
(2) Primary productivity is described as gross primary productivity (GPP) and net primary productivity (NPP).
(3) The rate of production of organic matter during photosynthesis is called gross primary productivity of an ecosystem. Of this the amount of energy lost through respiration of plants is called respiratory losses.
(4) Gross primary productivity minus respiratory losses gives the net primary productivity (NPP).
(5) Net primary productivity is the available biomass for the consumption to heterotrophs (herbivores, carnivores and decomposers).
(6) Factors affecting primary productivity: Gross primary productivity (GPP) depends on the following factors:
- Plant species inhabiting a particular area.
- Variety of environmental factors such as temperature, sunlight, salinity, oxygen and carbon dioxide content, etc.
- Availability of nutrients and
- Photosynthetic capacity of plants.
