| Summary: | Northern red-backed vole populations peak two to three years after snowshoe hare populations peak. Snowshoe hares cycle on a 9 to 11 year cycle and produced a large quantity of fecal pellets in their peak years. The fecal nutrient enrichment hypothesis surmises nitrogen (N) that is released from these pellets is captured by shrubs whose berries are critical food sources for the red-backed voles. These shrubs use the N to produce a large crop of berries that will provide an overwintering food supply for the voles, and reduce their overwintering mortality, resulting in an increase in red-backed vole densities in the spring. To simulate N levels provided by hare pellets I added 0.5, 1.0, 2.0, 4.0 and 17.5 g N/m² to 60 plots each of Empetrum nigrum, Arctostaphylos rubra, Arctostaphylos uva-ursi, Shepherdia canadensis, and Geocaulon lividum in 2004 and 2005 to determine if I could produce an abundant berry crop in 2005. Only E. nigrum had a significant increase in berry production at 1.0 g N/m². Weather conditions in 2005 were probably responsible for the lack of significant response in the other plants. Data from 9 years of berry production indices and northern red-backed vole numbers indicate a strong positive correlation (r = 0.92) between the combined berry production of E. nigrum, S. canadensis and A. rubra and vole densities in the following years. Science, Faculty of Zoology, Department of Graduate
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