Warunki mikroklimatyczne we wnętrzu boru sosnowego na Mierzei Łebskiej
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Date
2010
Authors
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Publisher
Wydawnictwo Poznańskiego Towarzystwa Przyjaciół Nauk
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Abstract
The observed regularities concerning the differentiation of the temperature of individual layers of
the pine forest point to the assumption by the tree crowns of the role of the active surface, which is served by
the soil surface in the area devoid of vegetation. This is supported among others by the higher values of air
temperature to a height of 6 m above ground level between 12.00–15.00 hours, this means during the maximum
of the intensity of solar radiation (Molga 1970). Moreover the lowest values of air temperature appears
to a bottom part of the pine forest above ground level between 15.00–8.00 hours. The inversion of temperature
near the ground is a natural phenomenon in the night hours, particularly at dawn. If no compact vegetation layer
is present, it comes into being during calm nights and in the predawn hours above the active surface (above
the ground) due to the radiation of heat from the ground zone to higher layers of the atmosphere. Appearance
of the cool layer in the bottom part of pine forest under the hight of 6–8 m above ground level during the points
to the assumption of the role of the active surface by pine crowns at this very height (Molga 1970; Paszyński
et al. 1999).
Differences in temperature between the open area and the forest interior or the layer of air above the forest
point to the differentiation of energy exchange processes, this being dependent on the nature of the active
surface. The forest area is characterised by a clearly lower albedo value than the area of the grey sand dune
upon which the MAWS 201 station is located. In addition, forest areas may accumulate a greater amount of
heat during the day than the sandy soil covered with grassy vegetation. The stored heat, the quantity of which
depends both on the heat capacity and the albedo value, is transferred to the atmosphere in the night. Thus,
the layer of atmosphere above the forest is usually warmer at night than the air located above the ground not
covered with dense and tall vegetation. During the day, the soil is considerably warmer than the active surface
of the forest, which results from the lower heat capacity of the soil. For this reason, a considerably greater
quantity of energy radiates in a longwave form than in the case of the forest, and thus the temperature of air
above the ground during the day is higher (Paszyński et al. 1999). During the day, the interior of the forest is in
turn cooler than the areas devoid of vegetation due to considerably weaker solar radiation reaching the forest
bed. At night, however, due the emission of additional quantities of heat from the tall vegetation and the more
difficult emission of energy from the forest soil to the atmosphere above the forest (due to its absorption by
the vegetation), the temperature of air inside the forest is usually higher than in the area devoid of vegetation
(Geiger 1942; Molga 1970).
The distribution of humidity in individual layers of the researched forest community does not differ considerably
from the results of research carried out on this topic by other authors. The greater content of water
vapour in the air inside the forest in comparison with the open area results directly from the considerable
intensity of evaporation of the lower active surface of the forest. The maintenance of the greatest air humidity
in the lower zone of pine crowns is most probably connected with their additional transpiration (apart from the
transpiration of vegetation of the forest bed) and low wind velocities, which make it possible for water vapour
to gather and remain in this zone (Molga 1970).
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Keywords
Słowiński National Park,e, Pine forest, Microclimate
Citation
Badania Fizjograficzne, Seria A, Tom 61, 2010, s. 157-168
ISBN
978-83-7654-010-8