Expert models for bilberry and cowberry yields in Finnish forests

In Finland, yields of forest berries are a way of measuring the forest's value as a recreation environment. Berry picking is also an activity of direct economic value. When planning forest management, the effect of silvicultural treatment on berry yields should also be assessed. With the assistance of current forest planning methods, the best method for this assessment is to apply numerical models. This study utilised expert modelling in order to determine the dependence of cowberry and bilberry yields on the characteristics of the site and the tree stand. The modelling technique applied uses the results of paired comparisons of stands, with respect to berry yields, as the dependent variable, and measurable site and stand characteristics as independent variables. Compared to the Analytic Hierarchy Process, the method does not require a complete set of paired comparisons of stands, which means that many stands can be evaluated without unreasonable efforts. The predictions correlated logically with site and stand characteristics and were in line with earlier models. 2002 Elsevier Science B.V. All rights reserved.