Alvar

The word Alvar designated in Old Swedish as in today's Swedish treeless, unsuitable for agriculture land with a thin layer of vegetation on rocky limestone bedrock. The scientific and now internationally accepted definition adds that the limestone rock has been planed more or less flat from the ice of the ice age and that Alvar areas have a dry summer, hemiboreales climate. An Alvar is a unique, differentiated in itself biotope with a characteristic flora and fauna.

Geographical distribution

Most impressively, the Alvar landscape is marked on the Ordovician limestone bedrock of the Swedish Baltic island of Öland. In the southern part of an area of ​​about 255 square kilometers, is named Alvar ( Great Alvar ). It has been explained together with the adjacent rural landscape by UNESCO in 2000 as " agricultural landscape Südölands " World Heritage Site.

Alvar Smaller areas are found in the central Swedish province of Västergötland, northern Öland, and on the Silurian limestone of the neighboring island of Gotland. Of the approximately 995 km ² Alvar on Earth are about 665 km ² in Sweden. The 160 km ² Alvar in Estonia are mainly due to the Silurkalk islands of Saaremaa ( Osel dt ), Hiiumaa ( Dago dt ) and Muhu. In Russia there is a small area south-west of Saint Petersburg. The about 110 square kilometers in North America can be found in the Ordovician - Silurian arc south of the Canadian Shield bedrock in the Great Lakes region in Ontario, Michigan, Ohio, and New York.

Therefore the size information may already be approximate, because the Alvar landscape is constantly changing, which are partly natural and partly of human origin. In Estonia, about 270 km ² Alvar are since 1930 by government- planned reclamation projects related to the collectivization of agriculture lost. But also to itself, the Alvar landscapes would constantly change through natural processes, that is, bushes spreading, until the first trees to take root. Thus, the Alvar would eventually become forest, if it were not exposed to the constant interference by man. Alvar has been preserved since the Middle Ages centuries in his character by means of extensive farming.

Vegetation

Example Alvar of Öland

The uniqueness of alvar vegetation is caused by the action of specific climatic conditions on the rocky limestone bedrock. A Winter with a long frost and strong winds follow in the spring of relatively low rainfall; the summer is hot and dry; to autumn brings unproductive rain.

Many Alvar species are about thanks to increased photosynthesis, the short time -effective customized growth and reproduction conditions, so that they have already matured to the early onset of the dry season its seeds. A striking result is huddled on a few weeks in spring colored flower period of many species over wide areas in the Great Alvar, for example, the chives (Allium schoenoprasum var oelandicum ), forms the magenta lawn; the little white meadowsweet ( Filipendula vulgaris ); the yellow sharps Stonecrop (Sedum acre) and the White Stonecrop (Sedum album), a number of orchid species, among which the yellow and red mixed stocks of elder boys Krauts ( Dactylorhiza sambucina, Swedish Adam och Eva ) are a tourist attraction.

Another consequence of the interaction of climate and soil in Alvar is the close juxtaposition of different habitats. Even on the seemingly bare horizontal slabs live almost invisible blue-green algae ( cyanobacteria ) species ( eg Gloeocapsa spec.) And up to one hundred lichen species. In the gaping gaps, however, of which the plates are passed through and that collects Verwitterungsgrus and humus, up to 51 species were found of higher plants per square meter. At short distances, the degree of weathering of the rock ground between gravel, coarse-grained and fine Grus or the typical Kalkverwitterung almost coal-black humus changes. According varies the strength of the cover of the rock ground a few millimeters to several decimeters. As long as the bottom layer is thin on the rock, it is moved not only from the summer heat dried out, but in the winter due to frost and to some extent put through its paces, so that there are hump - or wave-like deformations of the soil. This process is a further stress factor to which the species that live on such thin layers of soil, are adjusted.

Another, everywhere varying parameter is the water permeability of the soil. In karst underground rainwater seeps quickly and leaves the surface fast drying. Elsewhere, water can not penetrate deeper into the soil is prevented even on horizontal drainage by residues of silicate moraines. So wet spots result with lush grass and bush vegetation, Kalksümpfe with muddy lawn of moss Scorpidium scorpioides and pseudo Calliergon turgescens on the base as well as large stocks of sedges (eg stiff sedge ( Carex elata ) ), common reed (Phragmites australis) and bins cutting ( Cladium mariscus ), even shallow lakes as Moeckel Mossen between Resmo and Stenåsa or Knisa mosse at Sandvik. In the summer, such wetlands are smaller, but all do not dry out completely, unless in the disaster summers that come about every seven to ten years. They are often breeding grounds for sea and shore birds and resting places for cranes.

Along the parameters of depth and penetration of the soil settle most diverse group of species with different survival strategies against competitors, stress factors (temperature extremes, nutrient deficiency, dehydration ) and the action of man, such as grazing or deforestation.

The interaction of the Alvar typical climate ( harsh winters, moderate rainfall, hot dry summers ) with the outlined geological factors is geobotanisch striking phenomena, namely the increased occurrence of endemic species ( occurring only here ) and relict species (ie species which were widespread at the end of the Ice Age and postglacial heat periods, but now widely isolated only in Alvar be found from its current reserves are ). The list of these species is remarkable.

Endemic species

The abbreviations " E " and "G" following the species names in the following list of endemic species characterize the various sites on Öland and / or Gotland.

• Allium schoenoprasum var alvarense ( E, G)
• Anemone pulsatilla ssp. gotlandica (G)
• Arenaria gothica (G )
• Artemisia oelandica ( Ö)
• Crepis tectorum ssp. pumila ( E, G)
• Eleocharis uniglumis ssp. sterneri ( E, G)
• Festuca rubra ssp. oelandica ( E, G)
• Galium oelandicum ( Ö)
• Helianthemum oelandicum var oelandicum ( Ö)
• Helianthemum oelandicum var canescens ( Ö)
• Lychnis alpina var oelandica ( Ö)
• Senecio jacobaea ssp. gotlandicus ( E, G)
• Silene uniflora ssp. petraea ( E, G)

Relict species

The abbreviations " E " and "G" following the species names in the following list relict species characterize the various sites on Öland and / or Gotland.

Arctic- alpine:

• Asplenium viride ( Ö)
• Draba incana ( E, G)
• Lychnis alpina ( Ö)
• Poa alpina ( E, G)
• Potentilla crantzii ( E, G)
• Thamnolia vermicularis ( E, G)

West European:

• Baldellia ranunculoides ( E, G)
• Globularia vulgaris ( E, G)
• Plantago uniflora ( = Littorella uniflora ) ( E, G)
• Teesdalia nudicaulis ( E, G)

Mediterranean:

• Anthericum ramosum ( E, G)
• Anthericum liliago ( Ö)
• Apera interrupta ( E, G)
• Fumana procumbens ( E, G)
• Hippocrepis emerus ( E, G)
• Hornungia petraea ( E, G)
• Orobanche alba ( E, G)
• Petrorhagia prolifera ( E, G)
• Sisymbrium supinum ( E, G)
• Tragopogon crocifolius (G)
• Veronica praecox ( E, G)

Southeast European:

• Allium linear ( Ö)
• Anemone pratensis ( E, G)
• Asperula tinctoria ( E, G)
• Aster linosyris ( E, G)
• Gypsophila fastigiata ( E, G)
• Inula ensifolia (G )
• Plantago tenuiflora ( Ö)
• Polygala comosa ( E, G)
• Prunella grandiflora ( E, G)
• Ranunculus illyricus ( Ö)
• Vincetoxicum hirundinaria ( E, G)
• Viola pumila ( E, G)

Continental / siberian:

• Artemisia rupestris ( E, G)
• Oxytropis campestris ssp. campestris ( E, G)

Circumpolar:

• Carex obtusata ( Ö)
• Dasiphora fruticosa ( Potentilla fruticosa = ) ( E, G)
• Sanguisorba officinalis (G )

Fauna

With the Alvar Special Flora lives an equally special insect fauna together.

Sociological aspects of vegetation history

Today's image of Alvar is a dynamic that is hidden to the eye and in their levels only reveals itself to the historical view. In the 19th century, the Alvar was almost without bushes and trees. Because not only the extensive grazing was to blame. Another factor was the poverty of the landless cottagers that derived from non- inheriting sons of the village peasants, in ever increasing numbers on the edge of the village in a kind of slum (Swedish: malm ) led a poor life. For heats of primitive huts and cooking their meager food they depended on what day -length collection hikes could bring to the Alvar also: proper in luck firewood from a leftover tree, but usually only fagots and yet to be dried cow dung.

With the turn of the 20th century changed all that Part of the Malm - residents found work in the emerging industry on the mainland; many went away with the great wave of emigration to America. A little later sat in agriculture mechanization and intensification. But they made only in marginal strip of Alvar's trying to do there land arable with the new methods. The actual Alvar became more and more left to themselves, so initially the rise of the equally aggressive and tough juniper, the increasingly dense shrub encroachment and the eventual emergence of forest.

In the second half of the 20th century, the conservation commanded such trends, which threatened to reduce the biodiversity of the Alvars. As an effective means Alvar restore back to its open state, controlled forest fires proved ( this means it takes but only in North America ) and Entbuschungsprojekte and state grazing premiums, ie the farmers are paid to keep cattle on the Alvar.

UNESCO World Heritage

Efforts to Alvarschutz extra motivation since 2000 and intensified by the fact that the villages at Stora Alvar along with this as " agricultural landscape Südölands " (or " farmlands Southern Öland " ) were awarded the World Heritage seal of UNESCO. The brief justification for the award shows that UNESCO recognizes the worth preserving in this piece of earth in his character as a cultural ( and not as a man of relatively unspoiled natural) heritage:

The Alvar appears here as an integral part of an ensemble that is built around the linear villages on the western and the eastern edge of the Alvars. These impress with great simple, solid, oxblood colored painted wooden farm buildings. Beyond this down to the west to the Kalmar sloping fertile farmland on the other side of the island first farmland, then the profitable pastures of flat expiring in the Baltic Sea Seewiesen ( sjömarker ). These are highly valued by the ornithologists bird sanctuary, monitored by the Ornithological Ottenby at the southern tip of the island. It is exceptionally rich in species as the Alvar of plants to birds.

This ensemble has a very old cultural history. As early as the Stone Age ( about 3000 BC ) agriculture was practiced here, as impressive remains of refuges and settlements in and around the Alvar testify. The districts of linear villages were established mainly during the Middle Ages. Today, the ensemble of Alvar, Seewiesen, farmland and large rural villages is a perfect example of how stylish one understands in Sweden to supplement an old rural tradition full of simple dignity with a discreet elegant, efficient modernity.