Hedgerows as habitat for woodland plants

For hedgerows to act as corridors for woodland plants they must provide habitat conditions to suit species' autecological requirements. This supposition was tested by examining differences in the habitat and autecological characteristics of woodland plants according to their relative frequency in hedgerows and woodlands using a novel Habitat Preference Index (HPI). Indicator values for habitat and autecological characteristics of plant species were derived from Ellenberg and other published sources. Analyses were done separately for three main types of landscape in which hedgerows are found in Britain: (1) Lowland Arable; (2) Lowland Pastural; and (3) Marginal Upland. The relative frequency of plant species across all three landscape types was similar and significant differences between HPIs and environmental indicators were found for all three landscape types. Plants more frequently found in hedgerows had significantly higher indicator scores for soil fertility, temperature, continentality together with reduced soil acidity, in comparison to those species more frequent in woodlands. Analyses of autecological indicators failed to show similar consistent trends across landscape types except for the number of woodland types of the National Vegetation Classification (NVC) in which species occur. Plants more frequently found in hedgerows were associated with fewer woodland communities suggesting that hedgerows contain only a narrow range of recognised woodland NVC stand types. Also, a significantly higher proportion of ancient woodland indicators were found in the group of plants that were more frequent in woodlands. Overall, results suggested that the environments of hedgerows are more similar to woodland edges than interiors. Qualitative differences between the environmental characteristics of hedgerows and woodlands are such that certain woodland plant species are highly likely to be limited in their capacity to use hedgerow networks. Implications for conservation of biodiversity are considered. (C) 2000 Academic Press.