A SITE-INDEX MODEL FOR PURE AND MIXED STANDS OF BETULA-PENDULA AND BETULA-PUBESCENS IN SWEDEN

A site-index model was constructed based on stem analysis data for 266 top-height trees of Betula pendula Roth and Betula pubescens Ehrh. gr owing on 155 temporary sample plots and 12 remeasured, permanent sampl e plots in pure and mixed stands scattered throughout Sweden. Differen t growth functions and techniques for modelling the top-height growth over breast-height age were assessed. A difference model based on the Hossfeld IV growth equation performed best, and its practical applicat ion was therefore recommended. For birch stands over 40 yrs of age, to p-height growth predicted by the new model was significantly slower th an that predicted by a site-index model used previously.