|
New tools are needed to assess carbon uptake for different forest management strategies and species composition where other methods, e.g. flux towers, fail due to large spatial integration. Furthermore, the fluxes of the different components in the forest ecosystem need to be assessed, whereof the carbon uptake and transpiration of the trees are of significant importance. The concept of WUE relies on the strong link between plant carbon uptake by photosynthesis and plant water use from transpiration, depending on the common pathway of the two fluxes – through the stomata. On seasonal and annual time scales, WUE is a useful parameter because it appears to be a conservative species property where the variation is largely explained by the air vapor pressure deficit. If the same relationships are valid for instant leaf fluxes, up-scaling from leaf to stand can be estimated from up-scaled sap-flow measurements.
In this project, the suitability for using the concept of WUE as a means of up-scaling carbon fluxes for deciduous forests is evaluated. This is achieved through estimations of transpiration and carbon flux relations at leaf level, including both analysis of earlier measurements on a large number of leaves and new measurements of leaf carbon and water exchange as well as branch sap-flow, and validated against net ecosystem fluxes measured by eddy covariance techniques.
Preliminary results show that leaf WUE is dependent of incoming PAR below 500 μmol m-2 s-1 and, for the full range, dependent on VPD. The relationship is independent of both different levels of the trees and for the variation in environmental parameters. On the basis of these results, future work will include up scaling of carbon and water fluxes from leaf to stand scale using sap flow, the established leaf WUE relationship and the MAESTRA forest stand model. This will be done for different type of forests and climate.
Participants
Resources: WUPC is run under an EU financed Marie Curie Individual Intra-European Fellowship.
Role
Risø is the host of the Fellowship.
Duration: WUPC is funded to run from October 2006 to September 2010.
Employees involved:
Maj-Lena Linderson (head of project, research fellow), Teis Mikkelsen (supervisor, planning and performance of the measurements), Andreas Ibrom (supervisor, biometeorology and modelling), Kim Pilegaard (scientist in charge of the MC EIF)
Student projects
Two student projects have so far been offered and soon finished in connection to the project:
- Lina Olsson, “Influence of weather on the between-tree sap flow variability at the Sorø beech forest, Denmark”, Batchelor thesis, Lund University, Sweden;
- Sonny Nilsson, “Modeling tree net carbon uptake for a beech forest at Sorø, Denmark, using sap flow measurements and WUE relationships”, Master thesis, Lund University, Sweden.
|