In order to detect possible differences between dead and control trees, individual tree and environmental variables were analyzed. The analyzed variables were: 

Overall, environmental variables seemed to have a rather weak influence on oak mortality in this study. There were, however, some significant results found. When pooling all sites or studying Tinnerö exclusively, the size distribution (DBH) differentiated between the dead and the control trees, with the dead trees being more concentrated to the central part of the size span. In particular, the dead oaks exhibited fewer small sized trees, eg. trees with a DBH of 25-40 cm. Analyses of the depth of the bark crevices confirmed this general pattern. The amount of bare rock enclosing the oak did not affect the vitality of the tree, and neither did the soil type when pooling all sites. In Tinnerö, however, a somewhat higher frequency of dead oaks grew on non-clay soils. The impact of soil moisture differentiated among the sites. In Tinnerö, there was a higher frequency of dead oaks growing on moist soils, while most of the dead oaks in Sturefors grew on mesic soils. No significant trend was detected when pooling all sites. Dead oaks were more likely to have shelf fungus (Polyporus spp.) and holes when pooling all sites. There was a higher occurrence of shelf fungus on dead oaks in Tinnerö and holes on dead oaks in Sturefors. Compared with the other sites, oaks in Sturefors generally grew under more closed conditions. The dead oaks at this site were exposed to less sunshine and had more closed crown silhouettes than the control trees.