What is the primary productivity? Give the brief description of factors that affect primary productivity.

• The rate of biomass production is called productivity.
• It is expressed in terms of $g^{-2}-y{r}^{-1}$ or $(Kcal-m^{-2})$ $y{r}^{-1}$ to compare the productivity of ecosystems.
• It can be divided into Gross Primary Productivity (GPP) and Net Primary Productivity (NPP).
• Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis. A considerable amount of GPP is utilised by plants in respiration.
• Gross primary productivity minus respiration losses (R), is the net primary productivity (NPP).

GPP - R = NPP

Primary productivity depends on
(i) the plant species inhabiting a particular area.
(ii) the environmental factors.
(iii) availability of nutrients.
(iv) photosynthetic capacity of plants.