The influence of relief on microclimate and location of the upper tree-limit

Abstract

In the hitherto works concerning the course of the upper tree-limit or mountain pine-limit and their relation with mean annual temperature, the limits of vegetation horizons were determined much more precisely than the location of isotherms - the latter were determined basing on interpolation and extrapolation of data from meteorological stations. Thanks to the application of Onset HOBO data loggers, the measurements of air temperature were carried out in selected sites at the upper tree-limit in Sucha Woda Valley in the Tatra Mountains. The measurements were conducted every hour during 4 months in warm period in 2007. The measurement sites were located in different land reliefs of different exposition. The lowest temperature was recorded in the depression of a channel shape located about 100 m below the other sites. Also in the next site located in a concave land form - the bottom of the Czarny Potok valley, the recorded temperature was lower than in the sites located in non-dismembered area. Despite the fact that the investigations had only a preliminary character, they showed that the upper tree-limit and probably also the mountain pine-limit should not be compared with the course of mean annual temperatures determined basing on interpolation and extrapolation. Only direct measurements of temperature in the field give a true picture of relation between the relief and microclimate and the upper tree-limit.