What is the difference between gross and net primary productivity?

Question

What is the difference between gross and net primary productivity?

Answer 1

Gross primary production (GPP) is the rate at which an ecosystem's producers capture and store a given amount of chemical energy as biomass in a given length of time. Some fraction of this fixed energy is used by primary producers for cellular respiration and maintenance of existing tissues. The remaining fixed energy is referred to as net primary production (NPP).

Answer 2

Gross Primary Production, GPP, is the total amount of CO2 that is fixed by the plant in photosynthesis.

Respiration, R, is the amount of CO2 that is lost from an organism or system from metabolic activity. Respiration can be further divided into components that reflect the source of the CO2.  

Rp =Respiration by Plants

Rh = Respiration by Heterotrophs

Rd = Respiration by Decomposers (the microbes)

Net Primary Production, NPP, is the net amount of primary production after the costs of plant respiration are included.

Therefore, NPP = GPP - R