Air temperature as a determinant of the forest line in the Tatras

The forest line has been widely studied by a number of scientists representing various research disciplines. Changes in its position are an indicator of climate change. However, despite numerous studies, it is not always known what has the greatest influence on the position of the forest line. In the Tatras, which are Alpine moun-tains, the position of the forest line in places not disturbed by human activity or slope processes mainly depends on the annual mean air temperature and the number of days with negative temperature and its value in the warm season. The most unfavourable thermal conditions are found at the bottoms of concave landforms, just above the forest line. This thermal barrier effectively limits the upward movement of the forest line, even if the average annual temperature increases. Small concave landforms may have a higher vertical temperature gradient and lower air temperature values at their bottoms than larger and higher-lying forms.