Inter- and intraspecific variation in the resistance of winter-dormant birch (Betula spp.) against browsing by the mountain hare

The palatability of saplings of several different species, geographic origins and F₂-families of Betula spp. to the mountain hare was tested in feeding trials with captive and free-ranging animals. Significant variation in the palatability was detected among species and among conspecifics representing different origins and families. The results show that the combination of genetic and environmental factors determines the resistance of individual plants to mammals. Saplings that were stressed by severe competition from surrounding weeds were more resistant than saplings of the same age grown under optimal conditions. One-yr-old seedlings were more resistant than 7-yr-old saplings of the same origin. Some of the exotic species tested were extremely resistant, whereas others were highly palatable. The most resistant species and origins came from Asia and Alaska.