COS 68-4 - Forest canopy temperature: A comparison between an isotopic approach, and photosynthesis-weighted air temperature

Tuesday, August 7, 2012: 2:30 PM
Portland Blrm 257, Oregon Convention Center
Dustin Bronson, Biology, University of Pennsylvania, Philadelphia, Xin Song, Department of Biology, University of Pennsylvania, Philadelphia, PA, Michael Goulden, Earth System Science, University of California, Irvine, Irvine, CA, Kenneth L. Clark, Silas Little Experimental Forest, USDA Forest Service, New Lisbon, NJ, Paul Bolstad, Department of Forest Resources, University of Minnesota, St. Paul, MN, Tilden Meyers, Atmospheric Tubulence and Diffusion Division, NOAA, Oak Ridge, TN, Jiquan Chen, Department of Environmental Sciences, University of Toledo, Toledo, OH 43606, Toledo, OH, Asko Noormets, Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC, Danilo Dragoni, Geography, Indiana University, Bloomington, IN, David, Y. Hollinger, Northern Research Station, USDA Forest Service, Durham, NH, J. William Munger, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, Stephen Wofsy, Division of Engineering and Applied Science, Harvard University, Cambridge, MA, Timothy A. Martin, School of Forest Resources and Conservation, University of Florida, Gainesville, FL, Russell K. Monson, Laboratory of Tree Ring Research, University of Arizona, Tucson, AZ, Dennis D. Baldocchi, Environmental Sciences, Policy, and Management, University of California, Berkeley, CA, Ankur R. Desai, Department of Atmospheric and Oceanic Sciences, University of Wisconsin Madison, Madison, WI, Eugenie Euskirchen, Institute of Arctic Biology, University of Alaska-Fairbanks, Fairbanks, AK, William J. Massman, Rocky Mountain Research Station, U.S. Forest Service, Fort Collins, CO and Brent Helliker, Biology, University of Pennsylvania, Philadelphia, PA

We tested the hypothesis that the canopy temperature when weighted by growing season gross primary production (GPP) is approximately 21 °C, for a range of forest types from subtropical to boreal. We used stemwood tree cores from a selection of AmeriFlux sites to calculate a resolved canopy temperature using δ18O of the stemwood cellulose (Tcanδ).  We also used data from the same AmeriFlux sites to calculate an air temperature value weighted by GPP (Tgpp).


Our results confirm that values of Tcanδ are approximately 21 °C for a range of forested ecosystems, similar to previously published data.  Our data also suggest that Tgpp could explain Tcanδ in temperate ecosystems. However, for ecosystems with extremely high or low mean annual temperature the difference between Tgpp and Tcanδ was as much as 8 °C. Prior eco-physiological studies have shown that plant canopy temperature can deviate substantially from air temperature either through convection for heating or transpiration for cooling. Therefore we employed infrared sensors to measure canopy temperature directly and will report these results as they compare to Tgpp, and Tcanδ.