Buchkogel (Plabutsch)

About

The Buchkogel, at 656 meters above sea level, is a hill in the Austrian state of Styria. It is located in the southern part of the Grazer Bergland in the west of the state capital Graz. The mixed forests within the Plabutsch ridge serve as a popular recreation area. Parts of the karstified hill were settled back in the Chalcolithic period and served for limonite mining during the Middle Ages and World War II. On the top there is the historical Kronprinz Rufolf observation tower built in 1879. The name Buchkogel is either derived from a lost castle (German Burg) or the extensive beech (German Buche) population.

The mostly forest-covered hill is situated near the western border of the 16th city district Straßgang. It is part of the Plabutsch ridge which borders the wide Mur valley (Grazer Feld) in the west. On an eastern spur of Buchkogel St. Martin's château and church can be found, a smaller church consecrated to John and Paul is located on the hill ridge about a mile northeast of the summit. While the whole hill is part of a landscape protection area the south-eastern slopes (Kehlberg) are partially being cultivated as vineyards.

Buchkogel, like the rest of the hill ridge, is built from mid-Devonian limestones and dolomite rocks which are part of the Graz Paleozoic. Underneath lie dolomite sandstones, diabase tuffs and fossil-rich limestones. A local specialty is the occurrence of grey and brown Rauchwacken, yellow and brown, mostly mylonitic limestones and brown clay-slates that all together form a layer up to 100 meters thick. Anton Schäfer dubbed this lithology Braungesteine because of its characteristic brown weathering. The approximately north–south-striking Devonian layer package falls on average 30 degrees to the west and is determined by a fracture tectonic with the main direction east–west. The hill ridge is divided into individual blocks with different strike directions, some of which also vary within these units. The largely thick-stratified carbonate rocks reacted to the tectonic stress by breaking.

In the course of these processes profound joints were created that made the development of caves and sinkholes possible. Following the miocene karstification, the ridge was buried under loose sediments. The removal of these sediments during the Riss/Würm interglacial period happened asymmetrical because of the mighty down-cutting of the Mur river. As a result, the eastern slope of the Buchkogel shows a concave profile. On the western side a blind valley with numerous sinkholes and little poljes was formed. The sparse creeks run through a ponor into the mountain and emerge from the Eisbründlhöhle, a small cave about 70 meters below on the eastern foot of the hill. At that sea level the Devonian rocks meet the loamy and thus water-damming sediments of the Riss terrace. The subsurface connection at the narrowest part of the hill ridge could be scientifically verified in the 1950s via dye tracing. This means that the hill has its own closed karst water system which is not connected to the Mur valley's groundwater body.

The Buchkogel which is mainly owned by the Gebäude- und Baumanagement (building and construction management) GmbH Graz is covered by thermophilic deciduous and mixed forests. The dominant tree species is Fagus sylvatica or common beech (German Rotbuche) that possibly led to the hill's name. Other species at the dry warm locations are Acer campestre, Quercus petraea, Sorbus aucuparia, Tilia cordata and Viburnum lantana. Reforested spruce trees, pretty common in the surroundings, are rather rare to be found. The forests on the western city border of Graz not only serve as recreation area, but also make an important contribution to the urban climate, especially regarding the air quality. Along with the rest of the ridge Buchkogel serves as habitat for the chamois. The total number of chamois within the Graz city borders has been estimated at 50 to 70 individuals by September 2018. The area north of the Buchkogel has been called ornithologically significant after a breeding bird survey in 2000/01. The observed species include Grey-headed woodpecker, Green woodpecker, Stock dove, Black woodpecker, Black stork and Eurasian sparrowhawk, all protected under the Council Directive 92/43/EEC on the Conservation of natural habitats and of wild fauna and flora. In the area of the blind valley Lesser spotted woodpecker and Red-backed shrike also occur as breeding birds. Four of them (Green woodpecker, Stock dove, Eurasian sparrowhawk and Lesser spotted woodpecker) are included on the IUCN Red List.

Adapted from Wikipedia (CC BY-SA). Photography via Wikimedia Commons.