HR: 10:20h
AN: A21F-01    [PDF]
TI: Forest Thinning Dramatically Enhances Ozone Flux due to Reactions With Elevated Emissions of Biogenic Hydrocarbons
AU: * Goldstein, A H
EM: ahg@nature.berkeley.edu
AF: University of California, Department of Environmental Science, Policy, and Management 151 Hilgard Hall, Berkeley, CA 94720-3110 United States
AU: McKay, M
EM: megan@nature.berkeley.edu
AF: University of California, Department of Environmental Science, Policy, and Management 151 Hilgard Hall, Berkeley, CA 94720-3110 United States
AU: Kurpius, M R
EM: Meredith.Kurpius@orst.edu
AF: University of California, Department of Environmental Science, Policy, and Management 151 Hilgard Hall, Berkeley, CA 94720-3110 United States
AU: Kurpius, M R
EM: Meredith.Kurpius@orst.edu
AF: Oregon State University, Department of Oceanic and Atmospheric Science, Corvallis, OR 97331 United States
AU: Schade, G W
EM: gws@iup.physik.uni-bremen.de
AF: University of California, Department of Environmental Science, Policy, and Management 151 Hilgard Hall, Berkeley, CA 94720-3110 United States
AU: Schade, G W
EM: gws@iup.physik.uni-bremen.de
AF: University of Bremen, Institute of Environmental Physics Fachbereich 01 Otto-Hahn-Allee 1 / NWI, Bremen, D-28359 Germany
AB: Forests are routinely managed for timber production and fire suppression by thinning and harvesting. The impact of these activities on biosphere-atmosphere exchange of reactive trace gases is profound, but has rarely been studied in the field. Here we present simultaneous observations of ozone and terpene fluxes before, during, and after pre-commercial thinning of a ponderosa pine plantation at Blodgett Forest (1300 m elevation on the western slope of the Sierra Nevada Mountains, CA). We previously reported that monoterpene emissions increased by an order of magnitude during and following forest thinning (Schade and Goldstein, GRL 2003). We also previously reported that half the daytime ozone flux to this ecosystem under normal summertime conditions (no disturbance) was due to gas-phase chemical loss, and we suggested that this ozone loss was occurring by reactions with biogenically emitted terpenes whose lifetime was short enough that they reacted before escaping the forest canopy (Kurpius and Goldstein, GRL 2003). Here we report that ozone loss was also dramatically enhanced during and following thinning, and we link these observations to confirm that the chemical ozone loss in the canopy was indeed due to reaction with biogenically emitted compounds whose emission was enhanced by disturbance. Based on the magnitudes of ozone flux due to chemical loss and the measured terpene fluxes, we infer that the emissions of previously undetected short-lived terpenes are approximately 15-20 times those of a-pinene during thinning, and 30-50 times those of a-pinene during summer and fall. Since a-pinene accounts for approximately 25% of the total monoterpenes we routinely measure with our automated in-situ GC instrumentation, we conclude that emissions of highly reactive terpenoid compounds could have been drastically under measured in previous field campaigns and that emissions of unidentified reactive terpenes could be 5-10 times larger than emissions of total terpenes documented in previous studies.
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
DE: 0345 Pollution--urban and regional (0305)
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting