Climate Warming Alters Caribou Forage Quality in Northern Alaska
Abstract
Warming in the Arctic may affect forage quality characteristics of vegetation, potentially resulting in nutritional consequences for thousands of arctic caribou. Caribou are highly dependent on summer forage to obtain adequate nutrition for the remainder of the year; consequently, even slight changes in forage quality during summer can have large impacts on caribou survival during winter. We examined temperature effects on total leaf nitrogen and dry matter digestibility (DMD) of 3 plant species commonly consumed by caribou (Betula nana, Salix pulchra, and Eriophorum vaginatum). All work took place at Toolik Lake Field Station in northern Alaska in 2018. Three approaches to warming effects on forage quality were used: A) a short-term warming experiment (1 month of passive open-topped chambers), B) a long-term warming experiment (25 years of passive open-topped chambers), and C) a landscape study comparing south vs. north-facing slopes whereby the south-facing slopes were naturally warmer. Leaves from the warming experiment were sampled in June and July, and leaves from the landscape study were sampled in August. We used acid detergent fiber (ADF) and neutral detergent fiber (NDF) methods in filter bags to determine DMD, and an elemental analyzer to determine nitrogen content (% N), a key forage quality trait. There were 4 main findings: A) both DMD and % N were higher in June than in July for all 3 species; B) warming had a greater effect in June than in July on S. pulchra DMD and on B. nana % N, where S. pulchra DMD experienced a greater decrease between June and July samples in the warming plots than in the control plots, and B. nana % N experienced a smaller decrease; C) B. nana DMD and E. vaginatum DMD were higher on the south slopes than the north slopes, but S. pulchra DMD was lower; D) % N was lower on the south slopes in all 3 species. Our results suggest that experimental warming has a greater effect on the rate of the natural decline of B. nana and S. pulchra forage quality early in the growing season, and the shrub species respond differently to warming. The contrasting results of our landscape study to our warming experiment could be due to other factors that may vary with aspect, such as winter snow depth, soil moisture, and soil and nutrient deposition.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B23K2472B
- Keywords:
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- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 0475 Permafrost;
- cryosphere;
- and high-latitude processes;
- BIOGEOSCIENCES