Interactions among herbivory, climate, topography, and plant age shape riparian willow dynamics in northern Yellowstone National Park, USA

Understanding how the environmental context modifies the strength of trophic interactions within food webs forms a central challenge in community ecology. Here, we demonstrate the necessity of considering the influence of climate, landscape heterogeneity and demographics for understanding trophic interactions in a well-studied food web in Yellowstone National Park, USA. We studied riparian willow (Salix spp.) establishment and stem growth reconstructed from tree rings on the northern range of Yellowstone over a 30-year period that included the reintroduction of a top-predator, the gray wolf (Canis lupus). We used climate variables (annual precipitation, stream flow, and growing season length), herbivore abundance, and landscape descriptors (elevation and topographic wetness index) to predict establishment and growth processes through time before and after the introduction of wolves. We fitted Bayesian hierarchical models to establishment data and time series of individual stem heights f...