HR: 1340h
AN: B13B-1197    [Abstracts]
TI: Influence of Tree Height on the Carbon Isotopic Discrimination of Canopy Photosynthesis in Southeastern Pine Forest Ecosystems
AU: Mortazavi, B
EM: mortazavi@ocean.fsu.edu
AF: Florida State University, Department of Oceanography, Tallahassee, FL 32306-4320, United States
AU: Chanton, J
EM: chanton@ocean.fsu.edu
AF: Florida State University, Department of Oceanography, Tallahassee, FL 32306-4320, United States
AU: * Conte, M
EM: mconte@mbl.edu
AF: Marine Biological Laboratory, Ecosystems Center 7 MBL Street, Woods Hole, MA 02543, United States
AU: Martin, T
EM: tamartin@ufl.edu
AF: University of Florida, School of Forest Resources and Conservation 359 Newins-Ziegler Hall P.O. Box 110410, Gainesville, FL 32611-0410, United States
AB: Intensive investigations of carbon and water exchange in highly productive pine forests in the Southeastern US are restricted to a limited numbers of locations that are equipped with eddy covariance towers. These towers are mostly located within homogenous stands. However, the southeastern pine forests are composed of plantations of different ages/heights that are interlaced with hardwood forests. We have measured variability in photosynthetic parameters, and the ¹³C of ecosystem, foliage and soil respired CO₂ over a 3-yr period at the Ameriflux tower site in Gainesville, FL, a slash pine ecosystem. Additionally we examined trends in canopy foliage bulk organic matter ¹³C, leaf wax ¹³C and the ¹³C of foliage respired CO₂ as a function of tree height. Sampled tree heights ranged from 5 to 25 meters along the transect, characteristic of pine plantations within this region. A highly significant positive correlation was observed between tree height and the ¹³C of foliage bulk organic matter. Leaf wax ¹³C mirrored the trend observed in foliage respired CO₂ and bulk organic matter, with approximately a –3 ‰ offset from foliage respired CO₂. Point measurements of upper-crown light-saturated net photosynthesis rate were not correlated with height, but were likely confounded by water stress effects. Research in other forest ecosystems has demonstrated tree height effects on hydraulics and leaf gas exchange, but these effects have not been explored in southern pines. These data suggest that southern pine hydraulics and leaf gas exchange may be influenced by tree height, and that scaling of isotopic data in these forests will require careful consideration of age and height variation.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting