Health condition of European ash in young stands of diverse composition
During the recent decades, the ascomycete Hymenoscyphus fraxineus has been spreading across Europe causing dieback of ash and threatening existence of the species. Still, several studies have suggested positive effect of stand diversity on ash health condition. The aim of this study was to evaluate effect of stand composition and structure on ash health condition in young stands in Latvia. Among the tested stand properties, number of shrub species and tree height were the best linear predictors of ash health condition, yet their effect differed between the provenance regions. In the eastern part of Latvia, number of shrub species in stand showed positive relationship with ash health, while taller trees displayed worsening health condition. In the western pat of Latvia, the relationships were inverse. Such differences in biotic relationships might be related to differences in climate, hence development of the pathogen, and/or genetically determined susceptibility of different populations of ash.