Vertical profiles of evapotranspiration within a spruce forest canopy
2 Biogeochemistry Department, Max Planck Institute for Chemistry, Mainz
P 1.4 in Funktion von Ökosystemen
The EGER (ExchanGE processes in mountainous Regions) project aims at the detailed quantification of relevant processes within the soil-vegetation-atmosphere system by observing diurnal and annual cycles of energy, water and trace gases. Field experiments were conducted at the Waldstein site in the Fichtelgebirge mountains combining micrometeorological, chemical and biogeochemical measurements, and were complemented by stand scale models.
Latent heat flux within and above the canopy was measured with seven eddy-covariance systems mounted to a slim tower. Branch transpiration was quantified with xylem sapflow measurements at six heights within the canopy. The 1D multilayer canopy-surface-layer model ACASA, which incorporates a third-order closure method to calculate turbulent transfer within the canopy, and the 3D canopy light absorptance model STANDFLUX, provide simulated transpiration profiles. Vertical coupling between the subcanopy, the canopy and the air above the canopy was investigated using the eddy-covariance measurement profiles. Preliminary comparisons of the vertical evapotranspiration profiles from the measurements and model simulations revealed a good agreement for coupled and partly coupled exchange regimes, whereas during decoupled situations modeled and measured values were less consistent.