The complexity of forest borders determines the understorey vegetation

Questions What are the most important drivers of plant species richness (γ-diversity) and species turnover (β-diversity) in the field layer of a forest edge? Does the tree and shrub species richness structure and complexity affect the richness of forest and grassland specialist species? Location South-eastern Sweden. Methods We sampled 50 forest edges with different levels of structural complexity in agricultural landscapes. In each border we recorded trees, shrubs and herb layer species in a 50 m transect parallel with the forest. We investigated species composition and species turnover in relationship to the proportions of gaps the border, the diversity of trees and shrubs and distance to semi-natural grasslands. Results Total plant species richness in the field layer was mainly explained by the proportion of gaps to areas with full canopy cover, and tree diversity. Increasing number of gaps promoted higher diversity of grassland specialist species within the field layer, resulting in open forest borders with the highest overall species richness. Gaps did however have a negative impact on forest species richness. Conversely, increasing forest species richness was positively related to tree diversity but number of grassland specialist species was negatively affected by tree diversity. Conclusions Managing forest borders, and therefore increasing the area of semi-open habitats in fragmented agricultural landscapes, gives future opportunities to create a network of suitable habitats for both grassland and deciduous forest specialist species. Such measures therefore have the potential to increase functional connectivity and support dispersal of species in homogeneous forest/agriculture landscapes. This article is protected by copyright. All rights reserved.