The role of mammalian herbivores in primary succession on the Tanana River floodplain, interior Alaska

Abstract

I compared willow (Salix) communities along the Tanana River exposed to varying levels of herbivory to examine how herbivory influences the landscape distribution of vegetation. Moose (Alces alces) and snowshoe hare (Lepus americanus) herbivory decreased plant biomass and canopy height and increased the proportion of dead stems in willow communities. Herbivory also shifted the age distribution of plants in willow communities towards younger age classes, and also decreased the number of communities dominated by willow on the landscape. A frame-based simulation model was built to incorporate the effects of herbivory and river fluvial dynamics on plant succession. My results show that herbivory, erosion and accretion are all necessary components to accurately model the landscape distribution of vegetation communities. Erosion/accretion had a major role in landscape vegetation patterns shifting the landscape toward earlier successional communities, while herbivory had a minor role, shifting the landscape towards later successional communities. The interactions among these biotic and abiotic processes account for the empirically observed landscape vegetation patterns.