Climate-Driven Impacts of Warming and Grazing on Sub-Arctic Coastal Wetlands in Alaska

Climate change is rapidly warming the Arctic, especially at lower latitudes. Warmer temperatures and earlier springs are altering the timing of plants and animals, especially for long-distance migratory herbivores. Changes in the timing of both plants and herbivores have the potential to impact plant productivity and nutrient cycling, while also altering plant community diversity and composition. In chapter 2, I conducted a field experiment to investigate how earlier growing seasons and differences in arrival times of migratory geese influence physical traits of sedge forage species. I found that both an earlier growing season and late grazing by geese had similar effects on plant traits but delays in grazing had a greater effect than a change in spring. In chapter 3, I examined how earlier springs and differences in timing of goose herbivores affect soil nitrogen availability in sedge grazing lawns. I found that both earlier growing season and early grazing by geese increased soil nitrogen, while late grazing decreased soil nitrogen. However, early grazing resulted in a greater increase in soil nitrogen than an earlier growing season. In chapter 4, I investigated how warming and grazing interact to affect plant community diversity and composition in three different coastal wetland plant communities. I found that both warming and grazing increase community diversity but can also interact to mediate or synergistically increase community effects. Grazing decreased dominant grasses but increased low-lying forbs, while warming had little effect on functional groups across different communities