Reaktion von Weisstannen auf ein- bis mehrmaligen Verbiss entlang von Lichtgradienten

Abstract

Browsing of silver fir (Abies alba) saplings by ungulates is one of the most important issues concerning decreasing regeneration of this tree species. In addition to genetic drivers, environmental factors such as light availability play an important role for the response of a browsed tree. Using an experimental design with fences, we investigated the influence of natural browsing on tree growth along a light gradient. The few fir saplings that responded by flagging up a lateral shoot compensated the browsing induced height difference compared to unbrowsed trees within four vegetation periods. Most firs however reacted with new shoots and remained smaller than unbrowsed ones. The more often a fir sapling was damaged on its terminal shoot, the smaller the tree remained. A positive relation between tree height and light was found only up to a canopy openness of 11%. Mortality over the whole five years was high in low light (<10%) and in forest gaps (>15%), due to desiccation, competition with other plants or browsing (50% of total mortality). We recommend regenerating firs under moderately shaded conditions.