Animals in Carbon and Nutrient Cycling
Historically, most research in ecosystem ecology and biogeochemistry has focused on the roles of plants and microorganisms in regulating nutrient cycling in ecosystems, as plants take up carbon and nutrients and microbes decompose plant detritus, returning carbon and nutrients to the soil and atmosphere. However, animals can also play important roles in carbon and nutrient cycling by physically disturbing soil, selectively consuming plant matter, and releasing carbon and nutrients through excretion, egestion, and the decomposition of animal bodies. We study the impacts of animals on biogeochemical cycling in diverse ecosystems, from old fields in New England to high-altitude deserts in Argentina to the Arctic tundra.
Zoogeochemical effects of northern ungulates
Large herbivores can have marked effects on carbon and nitrogen cycles, the study of which is termed zoogeochemistry. This is particularly true in northern systems, where nutrient cycling and plant growth is often stymied by a lack of nitrogen. Through processes that result in the deposition of nitrogen, such as waste and carcass deposition animals can contribute large quantities of available nitrogen to ecosystems. Ultimately, these nutrient subsidies can alter nutrient cycling, carbon storage, and plant growth. Spanning several ecosystems, Kristy’s work examines the impact of various northern herbivores, including caribou, elk, white-tailed deer, and mule deer, aiming to untangle the zoogeochemical effects of these large mammals.
Food webs, nutrient cycling, and carbon storage in the High Andes
In the essential ecosystem process of nutrient cycling, plants and microbes are generally considered the main biotic players. Plants, of course, take up carbon from the atmosphere and nutrients from the soil, and microbes decompose decaying plant litter and return nutrients and some carbon to the soil. But what happens in ecosystems with little vegetation and almost no plant litter? Julia's research examines how large animals may play an important role in carbon and nutrient cycling in a barren alpine landscape in the High Andes of Argentina. In a system comprised of vicuñas (herbivores), pumas (predators), and condors (scavengers), Julia hypothesizes that carcasses and latrines (communal vicuña scat piles) provide important nutrient inputs into the soil, and that the trophic interactions within this food web determine the distribution and deposition rate of these inputs. She will combine soil sampling and stable isotope analysis at carcasses and latrines to evaluate the effects of puma predation and vicuña anti-predator behavior on the distribution of nutrients in the landscape.