The increasing role of tree disease and decreasing influence of anthropogenic management over 50 years of woodland dynamics

Woodlands are under threat from a variety of global change stressors, and understanding the main effects and interactions between these is critical for their protection. Here, we analyse vegetation change over 50 years within approximately 100 broadleaved woodland sites across Great Britain from 1971 to 2022 and quantify the interactions between management history, deer herbivory and ash dieback. We find an overall trajectory towards a less diverse, more shade-adapted ground flora which has recently been locally disrupted by ash dieback. Plots with evidence of ash dieback have higher forb cover and ground flora richness relative to plots without dieback. However, this effect of ash dieback was shown mainly where there was high grazing risk; the grazing reduces the vigour of generalist understorey shrubs which can also lead to lower tree regeneration. Our results reveal how woodland dynamics have been shaped initially by a response to a reduction in interventionist management and then by disturbance driven by high herbivory risk and a novel tree disease.