i) What is primary productivity? Why does it vary in different types of ecosystem?
ii) State the relation between gross and net primary productivity.

Explanation

i) The amount of biomass produced per unit area in a certain time period by plants through photosynthesis is defined as primary productivity.
It depends upon the type of plant species associated with an ecosytem, photosynthetic capacity of these plants and nutrients availability. This is the reason why it varies in different types of ecosystem.
ii) The relation between the gross and net primary productivity can be shows as:
ii) The relation between the gross and net primary productivity can be shown as:
Pn=Pg-R
Where, Pn=Net primary productivity.
Pg=Gross primary productivity.
R=Respiratory losses.