Górna granica zarośli subalpejskich w wybranych pasmach górskich Europy Środkowej – uwarunkowania i typy ekotonu
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2010
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Polskie Towarzystwo Geograficzne
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Abstract
W artykule dokonano porównania typów górnej granicy zarośli subalpejskich w wybranych pasmach górskich Europy Środkowej (góry Słowacji, Gorgany, Czarnohora, Góry Rodniańskie, Riła, Pirin oraz pasma Alp Wschodnich: Dolomity, Brenta i Alpy Julijskie). Podstawą analizy była typologia górnej granicy kosodrzewiny opracowana przez autora w trakcie szczegółowych badań prowadzonych w Tatrach, na Babiej Górze i w Karkonoszach. Wyróżniono granice orograficzne, edaficzne, morfologiczne, obniżone mechanicznie i antropogeniczne. Wykazano, że mają one swoje odpowiedniki w innych pasmach górskich, przy czym proporcje pomiędzy poszczególnymi typami zależą od budowy geologicznej i rzeźby, a także od stopnia przekształcenia zarośli subalpejskich przez człowieka.The main aim of the study was to compare structure and controls on the krummholzline in the mountains of Central Europe. The krummolz-line is the upper part of the forest-alpine tundra ecotone and usually constitutes wide transitional zone between subalpine thickets and alpine meadows. In the mountains of moderate zone different species of shrubs (pines, junipers, birches, rhododendrons, and alders) could be found in krummholz belt. However, only in the mountains of Central Europe close thickets of mountain pine Pinus mugo (with an addition of green alder Alnus viridis) occur, stretching up to few hundreds meters above timberline. Decomposition of those thickets into patches is controlled by different environmental factors. Thus, five types of krummholzline were distinguished as the result of author’s previous studies in the Tatra Mts., the Babia Góra Massif and the Giant Mts. These are orographic, edaphic, morphological, mechanically lowered and anthropogenic boundaries. It was the basis for further analysis, carried out in selected mountain ranges in Central Europe in 2000–2009. Study area encompassed mountain ranges in the Carpathians (the Nizke Tatry Mts., the Mala Fatra Mts., the Gorgany Mts., the Czernohora and the Munti Rodnei) and in the Eastern Alps (the Julian Alps, the Dolomites, and the Brenta Massif). Furthermore, the literature on the vegetation of the mountains of Balkan Peninsula (the Rila Mts. and the Pirin Mts.), was analysed. Natural environment of the studied mountain ranges is comparable, however there are differences in geology and climate (precipitation and temperature). Since the Middle Ages subalpine thickets have been significantly altered by human activity. The main factor affecting the krummholz-line was the sheep and cattle grazing. Establishing the national parks limited the human impact and enabled the regeneration of krummholz within the abandoned pastures, however the environmental policy significantly differs in the specific countries (krummholz planting vs. clearing). The orographic boundaries, controlled by harsh climatic conditions in the bottom of the U-shaped valleys occur mainly in the Munti Rodnei and the Julian Alps. The main factor controlling edaphic boundaries is discontinuous soil cover on debris slopes. Such boundaries are the dominant type of the ecotone in the Gorgany Mts. In the Eastern Alps as well as in the Pirin Mts. edaphic boundaries occur at the base of limestone and dolomite cliffs. Morphological boundaries are controlled by thick soil cover, resulting from slope inclination. They occur in all studied mountain ranges. The main difference between morphological and edaphic boundaries is a well-developed zone of dispersed krummholz patches. The avalanches and debris flows are the main processes lowering the krummholz-line. Whereas the avalanche-controlled krummholz-line are common in the Carpathians, the debris flows-controlled boundaries are more frequent in the Eastern Alps. Contemporary structure of the anthropogenic krummholz-line has resulted from the intensity and timing of degradation as well as the environmental policy in the 20th century. In sites with intensive reconstruction (mountains in former Czechoslovakia), the krummholz-line has been moved several hundreds meters upslope and now constitutes abrupt transition between mountain-pine thickets and alpine meadows. In the sites located in Ukraine and Romania, where mainly secondary succession occurred, the krummholz- line is characterised by a relatively wide transitional zone with mountain-pine patches of different size and shape. Although the ecotone resembles the structure of natural reaches, it cannot be explained by the impact of climatic, edaphic or geomorphic features. The evidence for its anthropogenic origin is the presence of the alpine juniper Juniperus nana and white bent-grass Nardus stricta communities above krummholz-line as well as the dead mountain-pine individuals among relatively young thickets. The mountain-pine patches tend to merge and gradual advance in altitude of the krummholzline has been observed for the last 50 years. In the Eastern Alps the secondary succession of krummholz is considered to be a threat to biodiversity. Therefore, mountain-pine is cleared in order to protect the alpine meadows.
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Jodłowski M., 2010, Górna granica zarośli subalpejskich w wybranych pasmach górskich Europy Środkowej – uwarunkowania i typy ekotonu, Czasopismo Geograficzne, 81(1–2): 43–59.