A Regional Model for General Stress Resistance of Norway Spruce Stands

Ojansuu, R. (1989). A Regional Model for General Stress Resistance of Norway Spruce Stands. IIASA Working Paper. IIASA, Laxenburg, Austria: WP-89-022

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Abstract

The Growth Efficiency Index (GEI) is used to indicate stand resistance for environmental stress. GEI denotes the annual growth of stem wood per leaf area. Stands under different climates are compared by Stress Resistance Index (SRI), defined as the ratio between GEI and the length of growing season.

The driving variables of the model are environmental variables (1) effective temperature sum, (2) length of the growing season and stand variables, (3) stand age, and (4) ratio of actual to potential basal area. Site productivity is depicted by site index as a function of effective temperature sum. The standard forestry variables are modeled from yield tables as functions of driving variables. Leaf area is approximated with the basal area at crown base. The relationship between basal area at crown base and the standard forestry variables has been developed from forest inventory data.

The model can be used to compare stress resistance of stands at different locations, ages and densities in ordinary scale. The regional implications of the model can be illustrated by mapping the results over Europe using the computerized grid system of the RAINS (Regional Acidification INformation and Simulation) model. The environmental factors incorporated in the model can be estimated to every grid element using a spatial interpolation method. The consequences of different silvicultural policies to the general stress resistance can be presented in form of maps.

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