Winter is changing: Trophic interactions under altered snow regimes

Shifts in abiotic conditions can strongly influence not only the demography, ecology, and evolution of individual species, but also the networks of interactions that structure communities and ecosystems. Though many studies have addressed how changes in mean temperature or rainfall patterns will affect ecosystems, there has been far less attention on the impact of changing snow regimes. As climate change alters the abundance and persistence of snowpack in temperate and polar regions of the globe, novel reductions or accumulations of snow may dramatically impact the nature of interactions between organisms in these ecosystems. In this review, we focus on four major mechanisms by which snow cover affects food webs, by (1) generating an insulated subniveal environment, (2) providing a physical or visual refuge from consumption, (3) affecting movement of animals across landscapes, and (4) driving phenology. For each of these mechanisms, we explore examples of observational and experimental studies that have addressed the role of changing snow conditions on food web processes. Then we highlight open questions regarding the influence of changing snow cover on trophic interactions, and suggest types of experiments and tools that could advance this field of research. We conclude that more experimental work is needed to understand the net effects of altered snow cover on food webs, particularly because snow cover may simultaneously affect multiple trophic levels through different mechanisms.