HR: 13:55h
AN: B53A-02    [Abstracts]
TI: Including Complexity, Heterogeneity and Vegetation Response Characteristics into Carbon Balance Assessments at Continental Scale: Stepwise Development of a Simulation Framework with the Bottom-Up Core Model PIXGRO
AU: * Tenhunen, J
EM: john.tenhunen@uni-bayreuth.de
AF: Department of Plant Ecology, University of Bayreuth, Bayreuth, 95440 Germany
AU: Geyer, R
B53A-02 AF: Department of Plant Ecology, University of Bayreuth, Bayreuth, 95440 Germany
AU: Owen, K
B53A-02 AF: Department of Plant Ecology, University of Bayreuth, Bayreuth, 95440 Germany
AU: Falge, E
B53A-02 AF: Department of Plant Ecology, University of Bayreuth, Bayreuth, 95440 Germany
AU: Reichstein, M
B53A-02 AF: Potsdam Institute for Climate Impact Research - Natural Systems Department, Telegrafenberg C4, Potsdam, 14473 Germany
AB: The cultural landscapes of the European continent are characterized by highly fragmented land cover, distributed along the gradient from extremely sparse, dry Mediterranean shrublands to sub-arctic wetlands and forests. In addition, several mountain systems, in particular the Alps, modify vegetation and land surface exchange characteristics. In the recently begun CARBOEUROPE project, energy, water and CO2 exchanges of selected ecosystem types are monitored via eddy covariance methods. The model PIXGRO is being developed to help relate measurements at flux tower sites to measurements carried out at larger scale and to CO2 exchange estimates obtained with atmospheric inversion techniques. The main question addressed in this modelling effort is how to efficiently include a spectrum of vegetation characteristics into carbon balance assessments at large scale and in such a way that the influence of local response on regional fluxes may be visualized and analyzed. Furthermore, the modelling attempts to demonstrate both strengths and weaknesses in existing ecosystem process information required to understand carbon balances. The model PIXGRO attempts to define continental distribution and controls on net ecosystem CO2 exchange for ca. 12 ecosystem types, including coniferous forest, deciduous forest, grassland, cropland (assumed dominated by grain crops), northern boreal mixed forest, tundra, wetlands, alpine forest, evergreen forest, evergreen shrubland, and Mediterranean oak woodland. The model uses a single layer canopy with two leaf classes (sun and shade) and a three layered rooting zone to estimate GPP, ecosystem respiration and overall ecosystem gas exchange. Maximum LAI is determined during each year from the MODIS LAI-product. In the case of grassland, crops, tundra and wetlands, classical growth routines estimate dynamic changes in the vegetation canopy. Soil/canopy coupling in response to drought reflects a root system hormonal signalling and is calibrated with observations at flux tower sites during the extremely dry year 2003. PIXGRO is applied over a European grid with 10 km resolution in MODIS sinusoidal projection, where 1 km2 land cover and soils information is used to define average LAI, most frequent soil type and weighting of flux rates in the spatial summary. Phenological influences are based on temperature climate (onset of growth and senescence) and soil water availability (herbaceous dieback and stomatal restrictions). Initial results demonstrate good agreement of the simulations with observations at flux tower sites and year to year variation in the spatial patterns of NEE. These spatial patterns are examined with respect to plausibility, the identification of key factors determining contributions to the overall European flux rates, and future research needs.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0476 Plant ecology (1851)
SC: Biogeosciences [B]
MN: Fall Meeting 2005