What does net primary production refer to?

Net primary production (NPP) refers to the amount of organic matter or biomass produced by photosynthetic organisms, after accounting for the energy used in respiration. It is a crucial measure in ecology, as it indicates the energy available to support herbivores and higher trophic levels in an ecosystem. NPP is typically expressed in units of mass per area per time, such as grams of carbon per square meter per year. Understanding NPP helps assess ecosystem health and productivity.