Condensation bog
Condensation peat bogs are a special type of bog in which the water does not come from the soil or from precipitation, but from condensed humidity.
The formation of a condensation bog requires a block pile with a gradient of more than 33 ° and a large difference in height. When there is strong sunlight, a wind tunnel effect occurs here : At the foot of the heap, the air warms up and rises; the air inside the block pile is protected from solar radiation and therefore remains cool. As a result, it flows out of openings in the ground at the lower end of the heap, whereby considerable pressure can build up. When the cool pile air flows out, it expands suddenly at the opening and cools down even further. Mixing with the ambient air cools the entire area around the discharge opening. Cold air holds less moisture than warm air, so air moisture condenses in the area around the opening. Inside the opening, the cooling can even be so strong that the air humidity is reflected as a massive block of ice. The outflow openings in a condensation bog are known as cold air holes.
The cooling effect is self-reinforcing: air flowing downhill through the heap leads to the evaporation of soil moisture; The evaporation cools it down further, making it heavier and flowing even faster. As a result, an even greater pressure builds up at the bottom of the stockpile, and the air - which is already additionally cooled anyway - expands as it flows out and forms even more condensation. However, all of the processes mentioned can only be observed in sunny weather. When the sky is overcast, there is no warming of the ambient air to drive the entire process.
According to the specific landscape conditions for the formation of a condensation bog, this type of bog is extremely rare. According to Steiner (1992), only six condensation bogs are known to date, all of which are located in the Austrian Alps, for example in the Schladminger Tauern or on the Hochschwab .
The vegetation of condensation bogs is similar to that of raised bogs, as the condensation water is as poor in nutrients as rainwater. Due to the steep slope, however, there is a lack of open water areas and thus also extremely wet-loving species. In contrast to raised bogs, the boundary to the surrounding vegetation is also far less sharp. Typically, typical bog plants such as peat moss ( Sphagnum ) or sundew ( Drosera ) are mainly found in the immediate vicinity of the cold air holes. Here, but also between the cold air holes or in the wider area, other species grow that are resistant to moisture and nutrient deficiencies, but do not necessarily have to be restricted to bogs, such as blueberries ( Vaccinium myrtillus ), lingonberries ( Vaccinium vitis-idaea ) or mountain pines ( Pinus mugo ). The transition to "normal" (zonal) plant communities , such as a montane spruce forest, is mostly fluid, since the precipitation of condensation water gradually decreases with increasing distance from the cold air hole. In some particularly well-developed condensation bogs, the bog vegetation can also form a closed blanket between the individual cold air holes.
Due to the strong growth of peat moss and other bog plants, condensation bogs often show a special dynamic: old cold air holes grow increasingly closed and clogged, but new holes break open again due to the internal pressure of the dump air.
The cushions of peat moss and other vegetation are saturated with moisture, which means that peat can form from the dead plant parts . However, the peat layer is always thin and has only a very small area, so that mining is out of the question.
literature
- T. Ellmauer: Vegetation-ecological studies on a condensation bog in Tragöß (Styria) . Diploma thesis, University of Vienna, 1989
- H. Schaeftlein: A peculiar high moor in the Schladminger Tauern . Mitt. Naturwiss. Ver. Styria 92, 104-199
- GM Steiner: Austrian Moor Protection Catalog . Styria Medienservice, Ulrich Mosser Verlag, Vienna 1992
- GM Steiner (ed.): Moors from Siberia to Tierra del Fuego . Biology Center of the Upper Austrian State Museums, Linz 2005, ISBN 3-85474-146-4