Falge, E*; Staudt, K; Meixner, FX: Validation of gas exchange models for a Picea abies canopy in the Fichtelgebirge, Germany
Vortrag, Atmospheric Transport and Chemistry in Forest Ecosystems, Thurnau: 05.10.2009 - 08.10.2009

Canopy exchange of water and carbon dioxide in a mountain Norway spruce stand of Central Germany was analyzed with two micrometeorology and gas exchange models, the three dimensional STANDFLUX, and the one dimensional ACASA. The models describe canopy water vapor and carbon dioxide exchange based on rates calculated for individual needles and as affected by local gradients in photon flux density, atmospheric humidity, atmospheric carbon dioxide concentration, and air temperature. The models were used to calculate forest radiation absorption, net photosynthesis and transpiration of the tree canopy. Model parameterization was derived for the Weidenbrunnen site, a 54-year-old Picea abies stand. Parameterization included information on vertical and horizontal leaf area distribution (STANDFLUX and ACASA), tree positions and tree sizes (STANDFLUX). Needle gas exchange in STANDFLUX was modeled using specific sets of physiological parameters for top, middle, and bottom of the canopy measured during two intensive field campaigns (IOP-1&2). For ACASA build-in leaf physiological parameters were adapted to accommodate these measurements. Comparisons of the vertical distribution of modeled branch transpiration with water use estimates from xylem sapflow measurements in the canopy profile provided a test of the models. The validation of the models is an important step toward effective use of IOP-1&2 data from the entire EGER project. While the one dimensional model is best suited for assessing vegetation/atmosphere exchanges of landscapes or regions, STANDFLUX provides a starting point for developing efficient tools for three dimensional simulations of plot-scale vegetation/atmosphere exchange of both, not reactive and reactive chemicals. Model development in the area of in-canopy turbulent transport is viewed as critical over the long-term in order to provide an efficient linkage between studies at the measurement sites and generalization via remote sensing/mesoscale modeling. The results are a contribution to the EGER project (Exchange Processes in Mountainous Regions, Deutsche Forschungsgemeinschaft), which investigates the role of process interactions among different scales of soil, in-canopy and atmospheric processes for mass and energy budgets of vegetated surfaces.

Letzte Änderung 23.10.2009