The abundance and condition of hedgerow tree standards in Northern Ireland

Abstract

Hedgerows often contain large numbers of tree standards which provide a range of ecosystem services in agricultural landscapes. A stratified random survey indicated that there are ca. 5.3 million hedgerow tree standards in the six counties of Northern Ireland, of which 2.9 million (56.7%) are ash trees (Fraxinus excelsior). Of the six most common hedgerow trees, rowan (Sorbus aucuparia) were in the worst condition, with over 30% of those surveyed showing serious symptoms, while birch trees (Betula spp.) were the healthiest, with only 5.5% showing serious symptoms. Older trees, more isolated single trees and tree standards in hedgerows with a high number of connections to other hedgerows were more likely to display symptoms of disease. Planting trees beside roads and hammered-in fence wire did not make the trees more likely to suffer ill health. It is concluded that: (1) many farmland hedgerow trees are in poor condition, especially ash, which suffers widely from canker; (2) epidemics involving tree pathogens which have high mortality rates will lead to serious loss of ecosystem services provided by hedgerow standards; and (3) increasing abundance, diversity and care of tree standards in hedgerows would mitigate the impact of tree diseases on the ecosystem services provided by hedgerows on farmland.