Higher Temperatures Have Contrasting Effects on Different Components of Forage Quality for Caribou in Northern Alaska
Thesis - Open Access
Master of Science (MS)
Department / School
Natural Resource Management
A. Joshua Leffler
arctic, climate change, North Slope, plants, tundra, ungulate
Rising temperatures in the Arctic may affect vegetation, which in turn can affect herbivores, such as caribou, that rely on these plants for forage. Several plant traits contribute to forage quality, including digestibility, nitrogen content, and antiherbivory secondary compounds, but the effect of temperature on these traits individually and combined is unclear. I conducted a three-component study on the effect of higher temperatures on the forage quality of graminoids, deciduous shrubs, and evergreen dwarf shrubs on the North Slope of Alaska. The components included: 1) short and long-term experimental warming, 2) natural temperature variation between south and north-facing slopes, and 3) natural temperature variation along a latitudinal gradient. Metrics measured were dry matter digestibility (DMD), leaf nitrogen concentration (N), and protein-precipitating capacity (PPC) of plant secondary compounds. Leaf N and PPC were integrated to calculate digestible protein (DP) available to caribou. In the warming experiment, DMD in June was higher while DP was lower under short-term warming compared to other treatments in Betula nana and Salix pulchra (deciduous shrubs). Conversely, Eriophorum vaginatum (graminoid) experienced lower DMD but higher leaf N in June under short-term warming. These contrasting metric responses suggest that higher temperatures may mitigate overall effects on forage quality early in the growing season. There was no difference in E. vaginatum DMD or N in either long-term warming plots compared to ambient plots, suggesting long-term acclimation to higher temperatures. In deciduous shrubs, DP was higher in July under long-term warming compared to other treatments, and on south-facing slopes compared to north-facing slopes in July 2019, indicating that many summers of warming may improve deciduous shrub forage quality in late summer. However, different responses in the slope aspect study between 2018 and 2019 may reflect differences in winter snow rather than summer temperature. In the latitudinal temperature gradient study, leaf N varied greatly among species, and no patterns were detected. Overall, responses differed among species and between summer months. Deciduous shrubs, which are preferred by caribou, are becoming increasingly abundant and may experience improved forage quality in late summer under long-term warming, which will further benefit caribou.
Library of Congress Subject Headings
Caribou -- Climatic factors -- Alaska.
Caribou -- Food -- Climatic factors -- Alaska.
Forage plants -- Climatic factors -- Alaska.
Climatic changes -- Alaska.
Number of Pages
South Dakota State University
Becker, Heidi, "Higher Temperatures Have Contrasting Effects on Different Components of Forage Quality for Caribou in Northern Alaska" (2020). Electronic Theses and Dissertations. 4997.