Silvicultural strategies for Fraxinus excelsior in response to dieback caused by Hymenoscyphus fraxineus

Abstract

Ash dieback caused by the invasive alien fungal pathogen Hymenoscyphus fraxineus often has devastating consequences for the survival, growth and wood quality of Fraxinus excelsior. We analyse the silvicultural implications of ash dieback in forest stands in Europe and review the advice on how to modify management accordingly. We draw on literature as well as unpublished observations and personal experience. The relevant strategy depends on the management objective, the site type (moist or dry), the stand type (pure or mixed stands, even-aged or uneven-aged stands), the age and the degree of dieback. Generally, the strategy should be conservative and trees that are healthy or slightly damaged may be marked and retained. Where dieback is severe, the suggested approach is to harvest remaining commercial timber before value depreciation and to regenerate or replant the area with other tree species. In forests of high value for habitat conservation, it may be advisable to let natural succession proceed unhindered. In all situations, forestry practice plays a key role in implementing in situ and ex situ conservation strategies for ash by preserving trees with low damage levels in all phases of stand development. Wherever there are infected ash trees, risks for operational staff, forest visitors and infrastructure posed by damaged, destabilized ash trees must be minimized.