NEP=GPP-ER
where \(ER\) is ecosystem respiration.
Operational definition
Ecosystem balance.
The difference between gross primary production and total ecosystem respiration over the stated interval:
A positive value indicates net accumulation of organic carbon within the defined accounting system before any omitted lateral exports are considered. A negative value indicates net consumption of previously stored or imported organic carbon.
Net ecosystem exchange may use an opposite atmospheric sign convention, so the variable being reported must be named explicitly.