Plant beta‐diversity is enhanced around grassland–forest edges within a traditional agricultural landscape

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AbstractQuestionsAre there positive edge effects on beta‐ and alpha‐diversity of plant species across semi‐natural grassland–secondary forest gradients located within a traditional agricultural landscape? Is beta‐diversity (dissimilarity in plant species composition between two given plots) well explained by environmental differences for both grasslands and forests? Do gradients of environmental factors created by forest edges influence spatial variation in alpha‐diversity from edges to grasslands and forests?LocationSemi‐natural grasslands and secondary forests (or conifer plantation) around paddy fields in a traditional agricultural landscape, western Japan.MethodsVegetation survey and environmental (soil water content and sunlight) measurements were conducted on 11 transects passing through grassland–forest ecosystems. Spatial variations in plant beta‐ and alpha‐diversity and environmental variables and their relationships were examined.ResultsWe quantitatively demonstrated common positive edge effects on beta‐diversity in both grasslands and forests. Our results suggest that among‐edge variations in light conditions, which likely depend on edge aspect and forest type, promote high grassland plant beta‐diversity in the vicinity of edges. However, the high beta‐diversity of forest floor communities in the proximity of edges cannot be explained by this mechanism. Alpha‐diversity tended to be lower within grassland plots located around edges than in grassland interiors, while the richness of the forest community increased toward the edge. This alpha‐diversity pattern was suggested to be attributable to resource gradients created by the forest edges.ConclusionsAlthough plant alpha‐diversity may not be consistently high in the vicinity of edges, beta‐diversity in the communities bordering grassland–forest edges will generally be high in the traditional agricultural landscape. Thus, maintenance of environmental heterogeneity among grassland–forest edges in agricultural ecosystems should be prioritized for local biodiversity conservation.