HR: 17:30h
AN: B12G-07    [PDF]
TI: Disturbance and Net Ecosystem Production Across Three Climatically-Distinct Forest Landscapes
AU: * Campbell, J L
EM: john.campbell@orst.edu
AF: Dept. of Forest Science, Oregon State University, Corvallis, OR 97331 United States
AU: Sun, O J
EM: osbert.sun@oregonstate.edu
AF: Dept. of Forest Science, Oregon State University, Corvallis, OR 97331 United States
AU: Law, B E
EM: bev.law@oregonstate.edu
AF: Dept. of Forest Science, Oregon State University, Corvallis, OR 97331 United States
AB: To assess the relative influence of mesoclimate stand replacing disturbance on the NEP (Net Ecosystem Production) of Oregon forests, we used biometric techniques to measure NEP at 36 independent forest plots arranged as three replicates of four age classes in each of three climatically-distinct ecoregions. Among hemlock-spruce forests growing in the coastal fog belt, NEP ranged from 200 to 600 gCm$^{-2}$y$^{-1}$ with the highest rates occurring in the youngest age classes (10-20 years following disturbance) and the lowest rates occurring in the oldest age classes ($>$100 years following disturbance). Among Douglas fir forests growing in the W. Cascades, NEP ranged from -200 to 500 gCm$^{-2}$y$^{-1}$ with the highest rates occurring in the intermediate age classes (50-150 years following disturbance) and the lowest rates occurring in the oldest age classes ($>$400 years following disturbance). Among ponderosa pine forests growing in the semiarid plateau of the E. Cascades, NEP ranged from -200 to 200 gCm$^{-2}$y$^{-1}$ with the highest rates occurring in the intermediate age classes (50-150 years following disturbance) and the lowest rates occurring in the oldest age classes ($>$200 years following disturbance). For the most part, heterotrophic respiration remain similar across age classes. As such, successional trends in NEP are driven primarily by net primary production and in particular, wood production. Among stands of the same age, Oregon's edaphoclimatic gradient causes NEP to vary 90% of the regional mean. Among stands in the same ecoregion, NEP varies 140% over development following stand replacing disturbance. However, disturbance history and recovery rates on this landscape are such that some developmental stages occur less frequently than others. Consequently, the regional variation in NEP attributable to disturbance is only 60% of the mean. Simulations of age class distribution under varying disturbance frequencies suggest that the sensitivity of landscape-level NEP to disturbance regime change is highest in the W. Cascades, lowest in the E. Cascades and intermediate in the Coast Range.
DE: 0400 Biogeosciences
DE: 1650 Solar variability
SC: Biogeosciences [B]
MN: 2003 Fall Meeting