Which of the following best defines Net Primary Productivity?

Net Primary Productivity (NPP) refers to the amount of energy that remains in the form of biomass after accounting for the energy that plants use during respiration. This concept is vital in understanding ecosystems, as NPP indicates the energy available to support the entire food web, particularly the consumers that rely on plants for energy.

In this context, NPP can be calculated by subtracting the energy used in plant respiration from the total energy produced through photosynthesis. Therefore, it accurately reflects the energy that plants convert into new growth, which becomes accessible to herbivores and, subsequently, to higher trophic levels.

The other statements do not encapsulate the essence of NPP. For instance, the total energy produced by photosynthesis describes gross primary productivity, while the energy used in plant reproduction is not directly related to NPP. Although energy stored in plant biomass plays a role in ecosystem dynamics, without considering the energy expended during respiration, it does not provide the complete picture of energy availability for consumers.