As ecosystem scientists, we consider the exchange of carbon into the system through
photosynthesis to be a positive flux and respiration to represent a loss to the atmosphere.
Atmospheric scientists would consider the signs to be reversed. Net ecosystem exchange
(NEE) measured during the daylight hours includes gross photosynthesis (Pg or GPP),
photorespiration (Rp), maintenance respiration (Rm), and synthesis (growth) respiration (Rs)
of autotrophic plants, as well as heterotrophic respiration (Rh) by animals and microbes: