Prediction of changes in the occurrence of forest herbs in hedgerow networks along a climate gradient in north-western Europe

Abstract

Many herbaceous forest plant species are endangered and suffer from habitat loss and fragmentation, especially in agricultural landscapes. Hedgerow networks represent a forested habitat that may serve as a refuge for forest herbs, even though also hedges have recently been strongly reduced in number and size. It is yet disputed to which extent hedgerows offer a suitable environment for forest herbs and which environmental factors may affect the frequency of these species in hedgerows. To develop an effective conservation strategy for forest herbs in hedgerows on a larger spatial scale, we aimed to combine a set of ecological and life history traits for predicting the frequency of these species in a local data set. A literature data set was used to examine the regional differences in the species composition of forest herbs and environmental conditions in hedgerows along a climate gradient across north-western Europe. Contrary to our expectations, the chosen set of variables in combination had a lower ability of predicting the local frequency of forest herbs in hedgerows than the single variable light availability. An ordination of species lists in the literature data set showed pronounced regional differences in the species pools of forest herbs in hedgerows, the floristic gradient being closely related to climatic continentality. Hedgerows in more continental regions had lower proportions of chamaephytes and, according to an indicator species analysis, drier and less acid soils.