HR: 1340h
AN: PP53A-1384    [Abstracts]
TI: Differential Response in Plant Taxa Morphology and Physiology During Increases in Late-Quaternary Atmospheric CO$_{2}$ Concentrations Affect Plant-Climate Interactions.
AU: * Van de Water, P K
EM: pvandewater@usgs.gov
AF: U.S. Geological Survey, 200 SW 35th St., Corvallis, OR 97333 United States
AU: Barnum, E
EM: lizbarnum@yahoo.com
AF: Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97333 United States
AB: The effects of changing atmospheric CO$_{2}$ on plant physiology mediate vegetation response to climate change. For example, growth chamber studies on short-lived plants show significant changes in plant morphology and physiological parameters such as changes in biomass and water-use efficiency (WUE; the amount of carbon assimilated to plant water-loss) as atmospheric CO$_{2}$ concentrations increases from $\sim$200 p.p.m. to modern concentrations and beyond. Many modern studies show WUE increases linearly with rising atmospheric CO$_{2}$ meaning that less water is expended for each unit of carbon assimilated. To test for the consistency of these findings with past, long-lived plants and in past communities growing under a similar range of atmospheric CO$_{2}$ levels, macrofossils of select species were analyzed from packrat ({\it Neotoma} sp.) midden chronologies gathered throughout western North America. Measurement of and analysis for the stable isotope content of these macrofossils shows greater morphological and eco-physiological differences between species than expected from study results using growth chambers. For example, isotopic analysis shows long-standing associates, {\it Pinus edulis} and {\it Juniperus} spp. have significantly different WUE during the transition from the Pleistocene to the Holocene. The WUE in {\it Pinus edulis} matches changes in atmospheric CO$_{2}$ whereas {\it Juniperus} spp. does not. Yet over the same period, changes observed in {\it Pinus flexilis} needles from trees growing in cooler habitats above the pinyon-juniper woodlands are more similar to {\itJuniperus} spp. changes compared against trends in the more closely related {\it Pinus edulis}. Morphology changes occurring during this period include increased biomass and reduced stomata. These results show taxonomic differences in the morphological and physiological adaptation to changing CO$_{2}$ concentrations. These responses need further assessment especially in light of their direct affect on plant-climate interactions.
DE: 1615 Biogeochemical processes (4805)
DE: 1620 Climate dynamics (3309)
DE: 0315 Biosphere/atmosphere interactions
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting