Effects of Hedgerow Rejuvenation Management on Invertebrates with Particular Reference to Habitat Structure

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.