AOBPreview originally published online on June 30, 2009
Annals of Botany 2009 104(4):775-784; doi:10.1093/aob/mcp156
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Simulating carbon dioxide exchange rates of deciduous tree species: evidence for a general pattern in biochemical changes and water stress response
1 Department of Horticulture
2 Department of Applied Economics and Statistics, Clemson University, Clemson, SC 29634, USA
3 Department of Horticulture & Landscape Architecture, Colorado State University, Fort Collins, CO 80523-1173, USA
4 Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA
* For correspondence. E-mail bauerle{at}colostate.edu
Received: 9 March 2009 Returned for revision: 21 April 2009 Accepted: 21 May 2009 Published electronically: 30 June 2009
Background and Aims: Deciduous trees have a seasonal carbon dioxide exchange pattern that is attributed to changes in leaf biochemical properties. However, it is not known if the pattern in leaf biochemical properties – maximum Rubisco carboxylation (Vcmax) and electron transport (Jmax) – differ between species. This study explored whether a general pattern of changes in Vcmax, Jmax, and a standardized soil moisture response accounted for carbon dioxide exchange of deciduous trees throughout the growing season.
Methods: The model MAESTRA was used to examine Vcmax and Jmax of leaves of five deciduous trees, Acer rubrum ‘Summer Red’, Betula nigra, Quercus nuttallii, Quercus phellos and Paulownia elongata, and their response to soil moisture. MAESTRA was parameterized using data from in situ measurements on organs. Linking the changes in biochemical properties of leaves to the whole tree, MAESTRA integrated the general pattern in Vcmax and Jmax from gas exchange parameters of leaves with a standardized soil moisture response to describe carbon dioxide exchange throughout the growing season. The model estimates were tested against measurements made on the five species under both irrigated and water-stressed conditions.
Key Results: Measurements and modelling demonstrate that the seasonal pattern of biochemical activity in leaves and soil moisture response can be parameterized with straightforward general relationships. Over the course of the season, differences in carbon exchange between measured and modelled values were within 6–12 % under well-watered conditions and 2–25 % under water stress conditions. Hence, a generalized seasonal pattern in the leaf-level physiological change of Vcmax and Jmax, and a standardized response to soil moisture was sufficient to parameterize carbon dioxide exchange for large-scale evaluations.
Conclusions: Simplification in parameterization of the seasonal pattern of leaf biochemical activity and soil moisture response of deciduous forest species is demonstrated. This allows reliable modelling of carbon exchange for deciduous trees, thus circumventing the need for extensive gas exchange experiments on different species.
Key words: Carbon budget, deciduous trees, modelling, MAESTRA, soil moisture, species response, transpiration, Acer rubrum, Betula nigra, Quercus nuttallii, Q. phellos, Paulownia elongata