History matters: village distances, grazing and grassland species diversity.
Abstract
Temperate semi-natural grasslands are characterized by high levels of species diversity and have a high conservation value. Plant species diversity in grazed semi-natural grasslands is known to be influenced by management intensity and habitat connectivity. Both grazing pressure and between-patch connectivity are expected to depend on the movement patterns of livestock in the landscape. The present study examines associations between fine-scale (within 0.25 m2 plots) plant species diversity in semi-natural grasslands and present grazing intensity, present and historical habitat connectivity, and the (present and historical) distance from the nearest village. The study area was a local (4.5×4.5 km) agricultural landscape on the island of Öland, Sweden. Fine-scale (Shannon) diversity and species richness were unimodally associated with the distance from the nearest historical (AD 1800) village, with maximum values c. 1-1.5 km from villages. These associations suggest that the distance from historical villages behaves as an integrated descriptor of variation in long-term management intensity (livestock movements) and reflects aspects of the functional connectivity between plant communities in semi-natural grasslands. Groups of variables characterizing village distances, grazing pressure and habitat connectivity had overlapping effects on species diversity. Grazing intensity had the largest individual impact on diversity, followed by the distance from the nearest historical village and present-day habitat connectivity. Synthesis and applications. The study indicates the importance of viewing grassland diversity in the context of local landscape history. Unimodal associations between fine-scale plant species diversity and the distance from the nearest village in AD 1800 suggest that information on the proximity to villages in the historical landscape has a potential use in conservation planning - as an indicator of variation in long-term grassland management intensity. Conservation programmes for grazed temperate grasslands should (1) give priority to old grasslands with an uninterrupted history of grazing management, (2) ensure a moderate grazing intensity, (3) avoid overgrazing and/or long breaks in the continuity of grazing management.