Bayreuther Institut für Terrestrische Ökosystemforschung
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Development of physically-based models of forest gas exchange at the catchment scale


From 01/1995 to 12/1997

Principal Investigator: John Tenhunen
Staff: Wolfgang Faltin, Stefan Fleck, Ulrich Joss, Bertram Ostendorf
Grant: 0339476 B Vorhersage und Erklärung des Verhaltens und der Belastbarkeit von Ökosystemen unter veränderten Umweltbedingungen

In the recent years, much effort has been invested at BITÖK in including physiology in stand level gas exchange models for a variety of habitats. One long-term goal of the upscaling efforts and the modelling hierarchies is the spatial simulation at landscape and regional scales of water, carbon and other trace gas fluxes, utilizing geographical information systems (GIS). To achieve this, a stand model that can function as the core of a GIS-based landscape simulator for spatial assessment of canopy gas exchange is used. This pixel model, called PROXEL (Process pixel), considers 4 compartments: the plant canopy, the unsaturated soil zone, the atmosphere and the ground water aquifer. The latter two components act as upper and lower boundaries.The research area is at a scale which is tuned to allow relatively intensive ecosystem experimentation. lt is a section of the Fichtelgebirge region that includes the intensive sites currently studied in the Lehstenbach catchment, extends considerations to include most of the important landscape elements, but restricts landscape size so that it will be possible in the future to examine process coupling and variation along typical toposequences and at transitions between ecosystem types.Available data about structural properties of the forest stands in this area were collected and a database design was evaluated for later retrival of these data in the context of a GIS based modelling approach and to assess the importance of different structural compositions of forest stands on a landscape level.106 A/Ci - curves of photosynthesis of beech-leaves were evaluated to figure out Nitrogen-dependent quantities, that can be represented in the models used. The results show a linear dependence of electron transport capacity (Jmax) and carboxylation capacity (Vcmax) on Nitrogen, which is particularly valid for their temperature dependent maximum value. Activation energies for respiration and carboxylation were dependent on leaf Nitrogen concentrations as well as on specific leaf area (SLA).The common photosynthesis module of STANDFLUX and GASFLUX was then extended to beech as a new species and nitrogen- and SLA-dependencies were introduced into the model and successfully tested against sapflow-data from the Steigerwald research-site.
(final report 1998)

List of publications of this Project

Tenhunen, JD; Matzner, E; Heindl, B; Chiba, R; Manderscheid, B: Assessing environmental influences on ecological function of a spruce forest catchment in the Fichtelgebirge in Beck E., Bendix J, Kottke I, Makeschin F, Mosandl R,: Ecological Studies, Springer Verlag, 147, 357-375 (2001)
Tenhunen, JD; Kabat, P: Integrating hydrology, ecosystem dynamics, and biogeochemistry in complex landscapes in Tenhunen, JD and Kabat, P: Dahlem Workshop Series, Wiley, Chichester, 1-367 (1999) -- Details
Joss, U; Graber, WK: Profiles and Simulated Exchange of H2O, O2, NO2 Between the Atmosphere and the HartX Scots Pine Plantation, Theoretical and Applied Climatology, 53, 157-172 (1996)
Ostendorf, B; Boyns, M: Spatial information system (SIS). Documentation for a C++ toolkit for linking environmental models and GIS in Bayreuther Institut für Terrestrische Ökosystemforschung (BITÖK): Bayreuther Forum Ökologie, Selbstverlag, 26, 1-64 (1995) -- Details
Ostendorf, B: Räumlich-differenzierte Modellierung von Ökosystemen in Bayreuther Institut für Terrestrische Ökosystemforschung (BITÖK): Bayreuther Forum Ökologie, Selbstverlag, 13, 1-140 (1995)
Ostendorf, B: Berechnung der räumlichen Variabilität der Einstrahlungsstärke mit der "Image Processing Workbench" in Bayreuther Institut für Terrestrische Ökosystemforschung (BITÖK): Bayreuther Forum Ökologie, Selbstverlag, 13, 95-104 (1995)
Ostendorf, B; Tenhunen, JD: Möglichkeiten zur räumlich differenzierten Parameterisierung von Bestandesmodellen in Bayreuther Institut für Terrestrische Ökosystemforschung (BITÖK): Bayreuther Forum Ökologie, Selbstverlag, 13, 17-29 (1995)
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