MODELING INCIDENCE OF ROOT-ROT IN PICEA-ABIES PLANTATIONS IN SOUTHERNSWEDEN

An empirical model is presented to forecast the incidence of root rot at stand level. In addition, the impact of different thinning programm es on the incidence of root rot is evaluated. The model is based on da ta from 152 permanent forest research plots of pure Picea abies in sou thern Sweden, within which the incidence of root rot at stump height i n thinned trees has been recorded after each thinning since 1950. In t otal, about 20 000 stumps have been studied. According to simulations with the model, areas previously used as fields or for grazing are par ticularly susceptible to root rot, while old hardwood sites are less s usceptible. Furthermore, simulations with the model imply that the ear lier, the harder or more often a stand is thinned, the faster will be the development of root rot.