Site index estimation by means of site properties : Scots pine and Norway spruce in Sweden
Hägglund, Björn; Lundmark, Jan-Erik
The aim of this study is to establish functional relationships between site index (dominant height at a total age of 100 years) and site properties, which can be used for predicting site index in forestry. The functions are derived from a mathematical growth model, assuming that the effects of different growth factors interact in a multiplicative way. Data selected from the National Forest Survey and comprising more than 3 000 plots are used to estimate the parameters of the model by means of regression analysis. In total, 10 functions are constructed-6 for Scots pine and 4 for Norway spruce. These functions are checked by an examination of residuals and by a comparison with data not used for constructing the functions. The checks gave fairly satisfactory results, and the functions seem suitable for their purpose. However, site indices predicted have an accuracy considerably lower than when using site index curves in stands suitable for that method. Hence, the use of the functions should be restricted to situations where site index curves cannot be applied.
site index; Scots pine; Norway spruce; growth model; regression analysis
Studia Forestalia Suecica
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