Analysis of the ecological principles underpinning forest landscape restoration: a case study of wood cricket (Nemobius sylvestris) on the Isle of Wight (UK).

Abstract

Current woodland restoration programs are increasingly focussing on the creation of habitat networks in order to increase woodland cover and connectivity. However, the basic assumptions underpinning such strategies are largely untested for species associated with woodland habitat. For many woodland invertebrate species, local scale processes are potentially more important than processes operating at the landscape scale in terms of species persistence, especially for those species that show high dependence on woodland habitat conditions and have limited dispersal ability. The applicability of landscape-scale approaches to woodland restoration therefore needed to be evaluated in relation to the ecological characteristics of invertebrates. This thesis examines these issues and provides a quantitative analysis of the factors influencing presence of wood cricket (Nemobius sylvestris) at multiple scales within the landscape. The investigation was conducted in woodland habitats on the Isle of Wight in the south of the United Kingdom. A landscape-scale survey indicated that wood cricket was found predominantly in large woodland fragments situated in close proximity to each other, with ancient woodland characteristics and with a high amount of edge habitat. The current pattern of distribution of wood cricket suggested that most woodland fragments in the agricultural matrix are effectively isolated from each other, indicating the importance of maintaining a high level of connectivity between habitats for this invertebrate species. An investigation within woodlands indicated that locations with permanent low cover of ground vegetation, low canopy closure and high availability of leaf litter were the preferred habitat conditions for wood cricket. Ride and track edges, woodland peripheries and open areas created and maintained by management activities were found to be the main habitat locations for wood cricket. It was further found that wood cricket was mainly present at permanent edges or in close proximity to these locations, indicating the importance of maintaining these habitat features for this species. The mean dispersal rate for dispersing wood cricket obtained from a series of field experiments was found to be similar to that of other ground-dwelling invertebrate species that were strongly associated with woodland. This level of habitat specialism was consistent with the habitat preferences found for wood cricket, and therefore wood cricket can be seen as representative of this particular group of wood land-associated invertebrates. Comparable to wood cricket, the dispersal ability for species of this group was found to be limited. Few individuals of nymph (i. e. juvenile) and adult wood cricket populations were found to disperse. Wood cricket was found able to disperse up to 55 m into non-woodland habitat and mature habitat corridors were found to be used by wood cricket, but not new immature woodland plantings. The results of this investigation indicate that the overall success of woodland conservation for woodland invertebrates lies in adopting a multi-scale and multimanagement strategic approach. The current initiatives focussing on restoration and re-instatement of traditional management activities within existing woodlands were found to be highly beneficial for wood cricket. Corridors were found to facilitate movement if suitable woodland habitat conditions were provided. Creation of woodland habitat networks might therefore be beneficial for wood cricket if given enough time to develop.