title: Evidence that higher [CO2] increases tree growth sensitivity to temperature: a comparison of modern and paleo oaks.
abstract: To test tree growth sensitivity to temperature under different ambient CO2concentrations, we determined stem radial growth rates as they relate to variation in temperature during the last deglacial period, and compare these to modern tree growth rates as they relate to spatial variation in temperature across the modern species distributional range. Paleo oaks were sampled from Northern Missouri, USA and compared to a pollen-based, high-resolution paleo temperature reconstruction from Northern Illinois, USA. Growth data were from 53 paleo bur oak log cross sections collected in Missouri. These oaks were preserved in river and stream sediments and were radiocarbon-dated to a period of rapid climate change during the last deglaciation (10.5 and 13.3 cal kyr BP). Growth data from modern bur oaks were obtained from increment core collections paired with USDA Forest Service Forest Inventory and Analysis data collected across the Great Plains, Midwest, and Upper Great Lakes regions. For modern oaks growing at an average [CO2] of 330 ppm, growth sensitivity to temperature (i.e., the slope of growth rate versus temperature) was about twice that of paleo oaks growing at an average [CO2] of 230 ppm. These data help to confirm that leaf-level predictions that photosynthesis and thus growth will be more sensitive to temperature at higher [CO2] in mature trees-suggesting that tree growth forest productivity will be increasingly sensitive to temperature under projected global warming and high-[CO2] conditions.
authors.affiliation: Department of Plants, Soils and Climate, Utah State University, Logan, UT, 84322, USA. dr.s.voelker@gmail.com.
authors.forename: Steven L
authors.initials: SL
authors.lastname: Voelker
authors.affiliation: Department of Forestry, University of Missouri, 203ABNR Building, Columbia, MO, 65211, USA.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Stambaugh
authors.affiliation: National Health and Environmental Effects Research Laboratory (NHEERL), Western Ecology Division, U.S. Environmental Protection Agency, 200 SW 35th Street, Corvallis, OR, 97333, USA.
authors.forename: J
authors.initials: J
authors.lastname: Renée Brooks
authors.affiliation: Pacific Northwest Research Station, U.S.D.A. Forest Service, 3200 Jefferson Way, Corvallis, OR, 97330, USA.
authors.forename: Frederick C
authors.initials: FC
authors.lastname: Meinzer
authors.affiliation: Department of Forest Ecosystems, Society, Oregon State University, Corvallis, OR, 97330, USA.
authors.forename: Barbara
authors.initials: B
authors.lastname: Lachenbruch
authors.affiliation: Department of Forestry, University of Missouri, 203ABNR Building, Columbia, MO, 65211, USA.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Guyette
mesh_terms: D002245:Carbon Dioxide; D057231:Climate Change; D029963:Quercus; D013696:Temperature; D014197:Trees
chemical_list: D002245:Carbon Dioxide
keywords: Carbon dioxide; Forest productivity; GPP; NPP; Photosynthesis