High-Arctic Plant—Herbivore Interactions under Climate Influence

Publisher Summary This chapter focuses on a 10‐year data series from Zackenberg on the trophic interactions between two characteristic arctic plant species, arctic willow Salix arctica and mountain avens Dryas octopetala , and three herbivore species covering the very scale of size present at Zackenberg, namely, the moth Sympistis zetterstedtii , the collared lemming Dicrostonyx groenlandicus and the musk ox Ovibos moschatus . Beside the impact of predation, climate in terms of timing and duration of the snow‐cover is one of the most important variables affecting the plant–herbivore system. Positive winter temperatures that create thawing events with ice horizons in the snow and icing on bare ground can have catastrophic effects on both vegetation and herbivores. Data from Zackenberg show that timing of snowmelt, the length of the growing season and summer temperature are the basic variables that determine the phenology of flowering and primary production upon which the herbivores depend, and snow may be the most important climatic factor affecting the different trophic levels and the interactions between them. Hence, the spatio‐temporal distribution of snow, as well as thawing events during winter, may have considerable effects on the herbivores by influencing their access to forage in winter.