A Regional GIS-Based Model to Predict Long-Term Responses of Soil and Soil Water Chemistry to Atmospheric Deposition: Initial Results

The aim of this study was to develop GISSMART, a GIS-based model, for estimating relative regional changes in soil andsoil water chemistry for given atmospheric deposition and nutrient uptake scenarios. The regional application was performed by dividing the study area into grid cells, the size and the form of the pixels being determined on the basisof the available GIS data bases of Finnish soil and vegetationtypes. GISSMART is the biogeochemical model SMART, extended forhandling GIS data in space and time. The Kangasvaara catchment(56 ha) in eastern Finland was used as the first test site. Data from four other nearby catchments were also used, togetherwith Multisource National Forest Inventory data (25 × 25 m2) from an area of 10 × 40 km2 for estimating soil chemistry. Multisource forest inventory datafrom the Finnish Forest Research Institute, including tree species, age and growth by tree species was based on LandsatTM-images and field measurements. The same satellite based estimation method was applied to obtain regional soil chemistry input data for GISSMART. Base saturation was the key state variable and nutrient uptake the key driving variablein this application of GISSMART. The results of the model testruns were reasonable. A slight decrease in base saturation waspredicted for the assumed deposition and nutrient uptake scenarios. In future work, the aim is to improve the description of hydrological processes and land use management in the model. This would also enable assessment of the effectsof climate change and land use management scenarios.