Localised damage patterns to oak during severe UK storms in winter 2021

There has been a recent (< 20 years) increase in the recurrence of windstorm disturbances in European forests, likely due to accelerating anthropogenic climate change. Across Europe, there remains a paucity of studies documenting storm damage to trees at a local scale. In the aftermath of two successive 2021 UK winter storms, named Arwen and Barra, a census of storm damage to native UK oak (Quercus robur and Quercus petraea) was carried out across three sites in the North East of England, Great Britain; a region that suffered some of the highest windspeeds in both storms. Native UK oak suffered significant losses, in particular to notable and veteran specimens. This is of great concern, given the species’ ecological and cultural significance. A total of 79 storm damaged oak were recorded across all three ∼ 80 ha study sites. Crown damage was the most documented damage type and was present in 59.5% of the 79 surveyed trees, followed by windsnap, 22.8%, and windthrow, 17.7%. Bark defects were the most frequently encountered point of pre-existing structural weakness, making up 48.3% of all reported defects in damaged trees, followed by weak forks, 40%, and prune wounds, 11.7%. Our findings inform our understanding of storm impacts and further highlight a clear dose/response relationship, whereby storms of greater magnitude caused a greater scale of damage. However, there were several marked differences between our findings and those documented in the aftermath of the Great Storm of 1987 (the most comparable UK storm to Arwen in terms of the scale of damage). Perhaps the most notable difference was that oak in an open parkland or hedgerow setting appeared less storm damaged, in terms of recorded severity. Our study characterises the impacts of the two successive winter storms and stresses the importance of documenting observations of storm damage to oak at a local scale, to facilitate improved modelling of future storm events and inform forest management.