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 Makgadikgadi landscape of northern Botswana 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.
Animal-driven soil biogeochemistry under climate variability
Animals respond to climate variability and uncertainty in different functional ways that are dependent on the degree of that variability. For example, some may shift their behavior to cope with temperature extremes, while others may shift their physiology. The functional differences in coping strategies has ramifications for animal controls on soil biogeochemical cycles. Nat's research leverages a latitudinal gradient of old-field ecosystems to study how soil carbon and nitrogen is impacted by animal populations. She also focuses on capturing pre-existing heterogeneity in soil processes to better estimate animal effects across time and space.
Animal-mediated carbon storage
Restoring ecosystems through trophic rewilding has been acknowledged as a climate change mitigation strategy; however, animal effects on carbon balance involve complex feedbacks and are not yet well understood. As livestock also continue to replace megaherbivores across vast wild landscapes, particularly in Africa, knowledge of how grazing and species functional types affect soil carbon can help to inform grassland management. Urmila’s research examines how animal-mediated soil carbon storage differs across a gradient of livestock and wildlife in the Makgadikgadi landscape of northern Botswana. Her work addresses conservation concerns in an area of human-livestock-wildlife coexistence and intends to provide additional incentive to incorporate carbon sequestration goals into wildlife conservation and livestock management strategies.