Net Primary Production

Net primary production is the amount of chemical energy that plants, algae, or other producers keep after they have paid the cost of their own metabolism. Gross primary production is the total energy captured by photosynthesis, and respiration is the portion the organism uses to stay alive, so subtracting respiration gives the energy left for growth, storage, and for the rest of the food web. This works because all energy fixed by producers is first captured in GPP, then some is immediately lost back to the environment as heat through respiration.

Use this formula when you need to find how much biomass or usable energy producers add to an ecosystem over a period of time. It is common in ecology, agriculture, and carbon-cycle studies when comparing plant productivity in different habitats.

• Subtracting NPP from GPP instead of subtracting respiration from GPP
• Using consumer respiration values instead of producer respiration
• Forgetting that NPP is the energy remaining for growth and storage, not the total energy captured