What is the formula of the net primary production (NPP)? How does NPP relate to the energy pyramids?
Net primary production is the gross main productivity less the organic material consumed as energy source in the metabolism of the producers: NPP = GPP - (organic material spent in aerobic respiration). It shows the organic material available in the first trophic level.
The base of the energy pyramids must show the NPP and not the GPP as the idea of these pyramids is to show the available energy in every trophic level of the food chain.