| Summary: | Small mammals play an integral role in their ecosystems. This is especially true in northern ecosystems, where small mammals represent both top-down and bottom-up forces and can have strong effects on ecosystem function through affecting biogeochemical cycling. Despite these important effects, the role of small mammals in influencing biogeochemical cycling has been largely underappreciated in the understanding of arctic ecosystems, leading to a call to better understand how small mammal herbivores impact ecosystem processes including carbon cycling. The overarching goal of this dissertation is to assess how biogeochemical cycling is affected by small mammal herbivore presence, behavior, and population dynamics in the arctic tundra of northern Alaska, USA. To achieve this, I present four chapters that examine the different ways that small mammals can influence arctic biogeochemical cycling. In the first chapter, I differentiate the roles of small mammal and large mammal herbivores in affecting above- and below-ground responses in arctic tundra after 20 years of exclusion. In Chapter 2, I explore how structure building activities of small mammals can influence soils and plants. I then discuss how small mammal population cycles may in impact ecosystem function in Chapter 4. Finally, in the last data chapter, I examine how changes in animal density and diet during different phases of the small mammal population cycle may affect nutrient limitation in tundra systems. This dissertation provides a more comprehensive analysis of the different ways that small mammals influence arctic ecosystems and updates the understanding of their roles in contemporary tundra environments. Furthermore, this dissertation contributes to a growing interest in linking multiple ecological levels and can be used to better understand the future of ecological conditions in the Arctic.
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