The Effect of Exposure on Alpine Treeline Position: a Case Study from the High Sudetes, Czech Republic

Abstract

Using the High Sudetes as an example, we examined whether the position of the alpine treeline is in fact related to the heat load of the site, and whether the temperatures of the air and soil change along slopes with differing exposure to solar radiation. We hypothesized that if there are really strong exposure effects they must be expressed both in significant correlations between treeline elevation and heat load of respective sites and in distinct differences in root zone and tree top temperatures. We found that the highest positions of the alpine treeline were situated in places with the potentially highest heat load. Nevertheless, only weak exposure effects on the soil temperatures during the growing season were detected, both in the closed forest and in the tree groups. Further, air temperatures near the terminal shoots varied significantly less than soil temperatures; however, the margins of the closed forest were especially more favorable at the south-facing slopes. Winter soil temperatures did not seem to be generally more advantageous on sites with high heat load. Direct temperature measurements thus indicated that established positions of the alpine treeline are just slightly influenced by differences in heat load.