Biometric techniques were used to measure net ecosystem production (NEP) across three climatically distinct forest chronosequences in Oregon. NEP was highly negative immediately following stand-replacing disturbance in all forests and recovered to positive values by 10, 20, and 30 years of age for the mild and mesic Coast Range, mesic West Cascades, and semi-arid East Cascades, respectively. The response of stand-level NEP to individual disturbance events is greater than that attributable to edaphoclimatic differences between forest type. However, regional age class distributions are such that the variability in landscape-level NEP attributable to disturbance regimes is equivalent to that attributable to regional edaphoclimatic differences between forest types. Simulations of age class distribution under varying disturbance frequencies suggest that the sensitivity of landscape-level NEP to changes in disturbance regime varies among forest types and is linked to both remnant detritus and photosynthetic recovery rate that are partly a function of edaphoclimatic differences.
