HR: 0830h
AN: B31D-0328    [PDF]
TI: Tree-ring Indices and Isotope Signatures of Pinus ponderosa Related to Historic Ozone Changes Outside Los Angeles
AU: * Gregg, J W
EM: jwg1@cornell.edu
AF: Oregon State University, Department of Forest Science, Corvallis, OR 97333 United States
AU: Brooks, J R
EM: Brooks.reneej@epa.gov
AF: US Environmental Protection Agency, 200 SW 35th st, Corvallis, OR 97333 United States
AU: Lee, E H
EM: Lee.ehenry@epa.gov
AF: US Environmental Protection Agency, 200 SW 35th st, Corvallis, OR 97333 United States
AU: Grulke, N E
EM: ngrulke@fs.fed.us
AF: USDA Forest Service Pacific Southwest Research Station, 4955 Canyon Crest Drive, Riverside, CA 92507 United States
AB: Ozone concentrations in the Los Angeles (LA) basin were at historic highs in the late 1970s. Since that time Clean Air regulations have helped lower ozone, but little is known of the long-term vegetation responses. Extensive research has used tree-ring indices together with the physiological and environmental information stored in the $\delta^{18}$C and $\delta^{18}$O signatures of tree-ring cellulose to understand past climates. Here, we used the forty-year ozone record from Camp Paivika, CA, the site in the San Bernardino mountains of the LA basin with both the longest record and the highest values, to determine climate versus ozone impacts on basal area increment and $\delta^{13}$C and $\delta^{18}$O signatures for Ponderosa Pine. Annual growth increment was significantly related to ozone and temperature but not precipitation. $\delta^{13}$C showed the typical climatic pattern of becoming more enriched in warm dry years, but was more strongly related to ozone independent of climate effects. $\delta^{18}$O was also enriched in warm, dry years, but was most strongly related to annual growth increment and showed no relationship with ozone. The relationship between $\delta^{18}$O and growth is likely due to alterations in evaporative enrichment within the foliar tissues. Our results will be discussed in light of physiological processes and environmental variation responsible for alterations in $\delta^{13}$C and $\delta^{18}$O signatures.
DE: 1610 Atmosphere (0315, 0325)
DE: 1615 Biogeochemical processes (4805)
DE: 1620 Climate dynamics (3309)
DE: 1655 Water cycles (1836)
SC: Biogeosciences [B]
MN: 2003 Fall Meeting