Journal of Conference Abstracts

Variability of Carbon Dioxide Fluxes over a Growing Season in a Mid-Boreal Headwater Bog, Kenora, Ontario, Canada

Anuraag K. Bhardwaj (anu@mgm.lan.mcgill.ca) & Nigel T. Roulet (roulet@felix.geog.mcgill.ca)

Departmentof Geography, McGill University, Burnside Hall, 805 Sherbrooke St. W.,
Montreal, P.Q., H3A 2K6, Canada.

Net ecosystem exchange (NEE) was monitored for several peatland communities in a mid-boreal, headwater bog at the Experimental Lakes Area (Kenora, Ontario., Canada) throughout the 1995-96 growing seasons. Transparent and opaque chamber systems were used to measure NEE and dark respiration at replicate plots that were clipped and unclipped of vascular vegetation. Carbon dioxide fixation and soil respiration were estimated from the NEE measurements. They were compared within peatland communities over time, and between communities over space. Communities that supported xerophytic vegetation fixed CO₂ at rates that had little temporal variation. The fixation rates were similar in magnitude to those measured for wetter, sedge-dominated communities. Dark respiration from clipped and unclipped plots varied within and between communities across the sampling season, and the variation was associated with differences in ground temperature and water table. By subtracting CO₂ fluxes between clipped and unclipped plots, the contribution of vascular respiration to total CO₂ emissions was estimated to be approximately 75 % of total respiration losses. Large community-specific, and seasonal, variations in vascular respiration, along with strong associations between vascular respiration and ground temperature, were observed.

Upscaling Procedure for the
Dynamic Nutrient Availability Model

Ämer Bilaletdin¹ (emir.bilaletdin@vyh.fi) & Juha Kämäri² (juha.kamari@vyh.fi)

¹ Regional Environmental Agency of Häme, P.O. Box 297, FIN-33101 Tampere, Finland.

² Finnish Environment Institute, P.O. Box 140, FIN-00251 Helsinki, Finland.

The aim of the Finnish upscaling application is to model relative and/or absolute regional changes in nitrogen availability and leaching for given scenarios for climate change, forest cutting and deposition. The model to be used, SMART2, although simple, offers a good basis for scaling up deposition, land use and climate change effects by using GIS information on factors such as soil type, vegetation, evapotranspiration, and soil moisture, as a starting point for deriving model inputs.

The regional applications will be performed by dividing the study area into grid cells, the size and the form of the pixels being determined on the basis of available GIS data bases on Finnish soil and vegetation types. As the output from the regionalised model, relative regional estimates (relative to the base case) for element leaching will be provided.

As the first step, the model will be applied to an extensively studied catchment, Kangasvaara, in Sotkamo, Central Finland. We will assess whether some simplification can be made to the model. First, the model will be calibrated using all available measurement data against all soil and surface water observations before and after the forest cutting (fall 1996). Simultaneously, an independent calibration will be made using only data that are available on a large regional scale in Finland. These include GIS data, transfer functions between GIS data and model inputs, as well as other models relating basic meteorological and vegetation information to model inputs (e.g. uptake model for forest growth uptake, and SVAT model for evapotranspiration). These two calibrations form a site-specific test on whether regional data bases can provide meaningful input values for SMART2. The third application will be on a larger regional scale, to the River Eurajoki basin (615 km²) in south-western Finland. For this basin much of the required GIS data already exist as a result of other Finnish regionalisation projects.