COsub2/sub fluxes and ecosystem dynamics at five European treeless peatlands – merging data and process oriented modeling

摘要

The carbon dioxide (CO₂) exchange of five different peatland systemsacross Europe with a wide gradient in land use intensity, water table depth,soil fertility and climate was simulated with the process orientedCoupModel. The aim of the study was to find out whether CO₂ fluxes,measured at different sites, can be explained by common processes andparameters or to what extend a site specific configuration is needed. Themodel was calibrated to fit measured CO₂ fluxes, soil temperature, snowdepth and leaf area index (LAI) and resulting differences in modelparameters were analyzed. Finding site independent model parameters wouldmean that differences in the measured fluxes could be explained solely bymodel input data: water table, meteorological data, management and soilinventory data.Seasonal variability in the major fluxes was well captured, when a siteindependent configuration was utilized for most of the parameters.Parameters that differed between sites included the rate of soil organicdecomposition, photosynthetic efficiency, and regulation of the mobilecarbon (C) pool from senescence to shooting in the next year.The largest difference between sites was the rate coefficient forheterotrophic respiration. Setting it to a common value would lead tounderestimation of mean total respiration by a factor of 2.8 up to anoverestimation by a factor of 4. Despite testing a wide range of differentresponses to soil water and temperature, rate coefficients for heterotrophicrespiration were consistently the lowest on formerly drained sites and the higheston the managed sites. Substrate decomposability, pH and vegetationcharacteristics are possible explanations for the differences indecomposition rates.Specific parameter values for the timing of plant shooting and senescence,the photosynthesis response to temperature, litter fall and plantrespiration rates, leaf morphology and allocation fractions of newassimilates, were not needed, even though the gradient in site latituderanged from 48° N (southern Germany) to 68° N (northernFinland) differed largely in their vegetation. This was also true for commonparameters defining the moisture and temperature response for decomposition,leading to the conclusion that a site specific interpretation of theseprocesses is not necessary. In contrast, the rate of soil organicdecomposition, photosynthetic efficiency, and the regulation of the mobilecarbon pool need to be estimated from available information on specificsoil conditions, vegetation and management of the ecosystems, to be able todescribe CO₂ fluxes under different conditions.