Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Natural Resource Management

First Advisor

Alan J. Leffer


Arctic, caribou, digestibility, forage, protein, tundra


Caribou (Rangifer tarandus) rely on the short growing season for much of their annual nutrition, making them susceptible to even small changes in forage quantity and quality. Body condition in the summer and fall is linked to winter survival rates and fecundity in cows, critical factors in the robustness of caribou populations. Due to a warmer, wetter climate, snowfall is predicted to increase over Alaska’s North Slope in the next several decades. Deeper snow results in higher soil temperatures, allowing microbial mineralization of nitrogen to continue throughout the winter and increasing the availability of nitrogen for plants in spring and summer; however, deeper snow can also delay the onset of spring and initial plant growth. These biophysical changes may impact the quantity, quality, and seasonality of caribou forage. I used a 20+ year snow manipulation to evaluate how a set of winter climate change scenarios may affect tussock tundra vegetation community composition and forage quality in northern Alaska. I sampled leaf tissue of six plant species (Salix pulchra, Betula nana, Rhododendron tomentosum, Vaccinium vitis-idaea, Carex bigelowii, and Eriophorum vaginatum) weekly between leaf-out and senescence in two consecutive years in areas of ambient, reduced, and added snow. Leaf tissue was analyzed for %N, dry matter digestibility, and digestible protein to quantify temporal changes in nutrition as well as differences between species and among functional groups (deciduous shrubs, evergreen dwarf shrubs, andgraminoids). Deeper snow increased leaf %N and digestible protein in the two deciduous shrubs and graminoids, but not the evergreen shrubs. Dry matter digestibility varied between species with small differences associated with divergent winter snow depths. Deeper snow also increased the duration of higher-protein forage by as much as 25 days in S. pulchra and 6-9 days in B. nana and C. bigelowii. Consequently, predicted increases in winter snow over the North Slope by the end of the century may enhance both summer and autumn forage quality and availability for caribou. Through multiplier effects of increased nutrition on body condition, survivorship, and fecundity, better forage conditions may improve the health and welfare of caribou in northern Alaska.

Library of Congress Subject Headings

Caribou -- Food -- Alaska.
Caribou -- Wintering -- Alaska.
Climatic changes -- Alaska.
Snow -- Alaska.
Tundra ecology.



Number of Pages



South Dakota State University



Rights Statement

In Copyright