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Effects of simulated and actual caribou grazing on low-arctic tundra vegetation

Pamela, C.O. 2011. Ph.D. thesis. University of British Columbia

Abstract

Barren-ground caribou have been grazing and trampling the tundra for thousands of years. Because the timing of grazing and trampling is episodic, it has been theorized that their impacts at any given site are weak or absent. This study investigated if this could be verified observationally and experimentally. I conducted an experiment to examine the effects of simulated grazing and lichen removal on birch hummock - lichen heath tundra in the low-Arctic. I also examined the effects of trampling and grazing by the Bathurst Caribou Herd on the biomass of three low-Arctic plant communities. In general, the simulated grazing at intermediate and high intensities did not cause changes in vascular plants biomass or species diversity, or carbon dioxide flux. However, lichen removal caused significant reductions in lichen biomass, lichen diversity, and net ecosystem production. Ecosystem respiration rates and biomass were much lower on than off the caribou migratory trails in each of the habitats studied, due to the low amounts of biomass on migratory trails compared to off the trails. These studies show that the effects of grazing were not easily detected, but the migratory trails that have been used by caribou for thousands of years were distinctly different than the surrounding areas. The results indicate that some habitats may be resistant to change, but once they are altered, they may not readily recover