Anthropogenic effects on vegetation structure of the boreal forest in Estonia

During the past few decades a wide range of structural and compositional indicators has been developed for the assessment of forest natural status. In many cases the indicators have been chosen on empirical bases without testing their predictive power. This study describes a number of structural and compositional parameters in Vaccinium vitis-idaea pine forest over a wide range of stand age and management intensity values. A robust index was developed to describe management intensity: area-weighted sum of anthropogenic activities, based on the forest management database. After the removal of forest age effect, forest management intensity had a negative influence on spruce abundance, number of diameter classes, basal area and number of decay classes of dead wood. Stepwise logistic regression analysis produced the optimal set of indicators for the evaluation of dry boreal forest naturalness: basal area of lying dead wood, structural variation of the tree layer, herb-layer species composition and presence/absence of woodpeckers.