Alvar Vegetation of Öland—Changes, Monitoring and Restoration

Abstract

Alvars are habitats characterised by thin soils on limestone bedrock. The largest alvar area in the world is the Stora Alvaret, Oland (25,500 hectares), which is characterised by the presence of several plant communities of high conservation value. Emigration at the end of the nineteenth century reduced land-use intensity resulting in scrub encroachment, mainly by Juniperus communis L. This later accelerated, leading to abandonment because grazing in the low-productivity pastures was uneconomic. Monitoring in permanent plots over a twenty-year period (1971-91) showed an increase in juniper cover over time and a clear correlation with a decline of other vascular plant species. This resulted in a gradual loss of both a valuable mosaic structure and a high level of bio-diversity in the landscape. An EU funded LIFE project (1996-99), which examined the effects of grazing and scrub clearance, is outlined. Various management techniques were tested and evaluated, providing valuable information for the present large-scale restoration and management programme supported by the European Union agri-environment schemes. In 1994 less than 60% of the Stora Alvaret was grazed. By 2005 this had increased to 98%. The reintroduction of grazing has resulted in a significant increase in the abundance of twelve out of 72 vascular species in permanent plots (1997-2001). Sheep and cattle numbers increased in Oland during the last decade, whereas they decreased in Sweden as a whole over the same period. Sixteen nature reserves have been established in Stora Alvaret, and a functioning alvar pasture landscape has been re-established. Almost all alvars in Oland have been designated as Natura 2000 areas. Ejvind Ros?n (e-mail: eje.rosen? ebc.uu.se), Uppsala University, Plant Ecology, Evolutionary Biology Centre, Villav?gen 14, SE-752 36 Uppsala, Sweden. INTRODUCTION This paper gives an overview of the vegetation and land-use history of limestone areas, called alvars, on the island of ?land. The word alvar refers to large areas with various thin deposits of soils, both calcareous and silicious, overlying the bedrock. With a few exceptions these areas are not suitable for cultivation but have been used as pasture for thousands of years. Alvars are mainly located on the Swedish islands of ?land (Rosen 1982; Bengtsson et al. 1988) and Gotland in the Baltic (Ekstam and Forshed 2002), but they also occur in Estonia and western Russia (Partei et al. 1999; Znamenskiy et al. 2006). Similar alvar landscapes occur in the Great Lakes region of Canada and the USA (Catling and Brownell 1995; Stark et al. 2003). *As an abbreviation in the text Stora Alvaret is referred to as Alvar, while alvar is used as a general term. Most attention will be given to the largest area, Stora Alvaret (The Great Alvar)*, covering 25,500ha, located in the southern part of the island. It occupies about half the area of the World Heritage Area known as 'The Agricultural Landscape of Southern Oland'. A total of c. 35,000ha are classified as alvars, however, including smaller areas in the eastern and northern parts of the island (Fig. 1). Alvars on the eastern side are usually part of the more productive grasslands in the coastal zone, while alvars in the north are mostly small and isolated. The latter are mainly located on the western side of the island, which is higher and drier than in the east, but with moist to wet areas occurring in depressions in the bedrock. Interspersed sand and gravel deposits often support small woodlands. Until the 1820s Stora Alvaret was a large commonage. After land reform, nearby villages received their own share of alvar land, which was then usually separated by stone walls. Since then almost all land has been privately owned. Recent land use changes, e.g. overgrazing, abandonment of Biology and Environment: Proceedings of the Royal Irish Academy, Vol. 106B, No. 2, 387-399 (2006). ? Royal Irish Academy 387 This content downloaded from 157.55.39.164 on Thu, 07 Jul 2016 04:43:22 UTC All use subject to http://about.jstor.org/terms Biology and Environment Fig. 1 ? The location of alvars on ?land, with Stora Alvaret in the southern part. Inset shows the location of ?land in the SW part of the Baltic. ?land is part of Kalmar county. grazing, scrub encroachment, etc. have resulted in major changes in landscape dynamics and loss of valuable habitats. The results of different restoration methods and their impact on conservation, as well as monitoring, are presented. BACKGROUND TO THE ECOLOGY OF OLAND