Dead hedge

Abstract: Hedgerows are an important semi-natural habitat for invertebrates and other wildlife within agricultural landscapes. Hedgerow quality can be greatly affected either by over- or under-management. Neglect of hedgerows is an increasingly important issue as traditional management techniques such as hedgelaying become economically unviable. In the UK, funding for hedge management is available under agrienvironment schemes but relatively little is known about how this impacts on wider biodiversity. This thesis describes a randomised block experiment used to investigate how habitat structural change, arising from a range of techniques to rejuvenate hedgerows (including more economic/mechanised alternatives to traditional hedgelaying) affected invertebrate abundance and diversity throughout the year. A novel technique of digital image analysis was combined with estimates of foliage biomass and quality, hedge dimensions and microclimate at the base of the hedge to show which aspects of hedge structure were affected by the rejuvenation treatments. All investigated aspects of habitat structure varied considerably with management type. For example, treatments where the hedge was laid all increased foliage biomass but resulted in differing widths of hedge, and those subjected to more intensive cutting resulted in a lower foliage C:N ratio. For invertebrates utilising the canopy from spring-autumn, the abundance of herbivores and predators was affected primarily by foliage density, with which there was a positive correlation, whilst detritivore abundance was most strongly correlated (negatively) with variation in hedge gap size. For invertebrates overwintering in the soil beneath the hedge, herbivore abundance was positively correlated the maximum temperature at ground level which itself was affected by hedge density, though structural measures did not directly relate to invertebrate parameters. The results suggest that habitat structure is an important organising force in invertebrate community interactions and that management technique may affect trophic groups differently. Specifically, this thesis shows that alternative methods of hedgerow rejuvenation could support abundances of invertebrates comparable or even higher than traditional hedgelaying, with positive implications for the restoration of a larger area of hedgerow habitat on a limited budget.

Abstract: The woody component along field edges often provides the only permanent elements of structural and biological diversity in landscapes that have lost much of their naturalness to agriculture and urban use The main aims of this study were (i) to investigate how four hedge stand types, ie, systems of management distinguished on the basis of the natural and managed growth forms of trees and shrubs (low single-storied, high single-storied, two-storied and multi-storied), differ in their biometric parameters and (ii) to identify the primary management-related determinants of native woody species richness The study used a large dataset of hedgerows (n=538) sampled in seven sites in Northern Italy The four hedge stand types exhibited highly significant differences in size and biometric parameters The multi-storied hedges, associated with the highest stand structural diversity index values, supported the highest number of tree species, followed by high single-storied hedges The low single-storied hedge stand type contained the lowest number of species We found a positive effect of hedge area as well as a marginal negative effect of basal area on native woody species richness The management implications addressed by our study include conversion of single-storied into two- or multi-storied types, increasing hedge size and controlling hedge stand basal area

Abstract: Agricultural intensification often leads to fragmentation of natural habitats, such as forests, and thereby negatively affects forest specialist species. However, human introduced habitats, such as hedges, may counteract negative effects of forest fragmentation and increase dispersal, particularly of forest specialists. We studied effects of habitat type (forest edge versus hedge) and hedge isolation from forests (connected versus isolated hedge) in agricultural landscapes on abundance, species richness and community composition of mice, voles and shrews in forest edges and hedges. Simultaneously to these effects of forest edge/hedge type we analysed impacts of habitat structure, namely percentage of bare ground and forest edge/hedge width, on abundance, species richness and community composition of small mammals. Total abundance and forest specialist abundance (both driven by the most abundant species Myodes glareolus, bank vole) were higher in forest edges than in hedges, while hedge isolation had no ef...