article id 473,
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                        Research article
                    
        
                                    
                                    
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                            The aim of this study was to analyze the occurrence of butt rot damage  to Norway spruce in different parts of southern Finland and to quantify  the associated loss of quality. The data used in the study are from the  9th National Forest Inventory and consist of 5998 sample plots and 8007  spruce sample trees of saw-timber size. To predict the probability of  damage to stands and trees, logistic regression models were constructed.  Separate models were made for the whole study area, for the area where  the general risk of Heterobasidion root and butt rot damage is high and  for the area where the damage frequency is relatively low. In the  high-risk area, the probability of damage decreased with increasing  elevation and increased with increasing temperature sum. In addition,  damage was more common on fertile sites and less common on peatlands;  and thick peat layer decreased the risk of damage. The probability of  damage was also higher in stands where special or selective cuttings had  been carried out. In the sample tree data, the probability of damage  increased slightly with increasing diameter and age of the tree. In the  low-risk areas, elevation was the only variable that explained the  probability of damage to a spruce tree. Site fertility and previous  cuttings (more than ten years ago) explained the probability of damage  to stands only weakly. For spruce damaged by butt rot, the saw-timber  volume was reduced, on average, by 60% both in the high-risk area and in  the low-risk area.
                        
                
                                            - 
                            Mattila,
                            The Finnish Forest Research Institute, Joensuu Unit, P.O. Box 68, FI-80101 Joensuu, Finland
                                                        E-mail:
                                                            um@nn.fi
                                                                                        
                                                     
                                            - 
                            Nuutinen,
                            The Finnish Forest Research Institute, Joensuu Unit, P.O. Box 68, FI-80101 Joensuu, Finland
                                                        E-mail:
                                                            tn@nn.fi