
Title: The woody species diversity of hedges in relation to environment, landscape, history, management and structure in Northern Ireland
Author: McCann, Thomas
Awarding Body: University of Ulster
Current Institution: Ulster University
Date of Award: 2012
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The Northern Ireland landscape was stratified random sampled by 288 25 ha squares, within which hedges and other field boundaries were mapped and surveyed to estimate extent and change between 1998 and 2007. The woody species composition in a 30 m length of each hedge was also recorded to determine the ecological structure of the hedges and to monitor change. The species composition of hedges was assessed against variables describing the physical environment, landscape structure and land use history. Hedges have an estimated length of 113648 km, the result of a net decrease of -4.6% between 1998 and 2007, as losses (mainly due to building construction or field enlargement, and hedges subsumed within woodland planting or scrub habitat development), exceeded gains (mainly due to hedge creation by management or planting). These hedge transitions also affected the mean number of woody species per 30 m which decreased slightly to 4.73. Hedges with higher woody species diversity are: town land boundaries; in smaller townlands with a higher perimeter-area ratio; sinuous in shape; at lower elevation; closer to ancient woodland and to raths; on soil groups classified as moderate to poor quality agricultural land; and have associated species-rich herbaceous ground layers, wet ditches or earth banks. Hedges with lower diversity are: closer to buildings; more intensively managed (flat-topped); on better quality agricultural land. No significant difference in road-side and internal field boundary hedge diversity was found. Native woody species are associated with variables related to higher diversity, e.g. hazel (Gory/us avellana) is more frequent in townland boundary hedges. The opposite is the case for non-native species. These occur in 30% of hedge 30 m lengths and in ca. 90% of sites with hedges, indicating a potential for further expansion. The research highlights the interconnectedness of ecological and historical variables and related landscape metrics which affect patterns of hedge woody species diversity in agricultural landscapes. This has important implications for landscape-level management and planning policies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available