Responses to simulated grazing and browsing of vegetation available to caribou in the Arctic

• Published in: Canadian Journal of Zoology
• Main Authors: Ouellet, Jean-Pierre, Boutin, Stan, Heard, Doug C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1994
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Arctic; Northwest Territories; Canada; Southampton Island; caribou; Cassiope tetragona; Salix lanata
• Online Access: http://dx.doi.org/10.1139/z94-189; http://www.nrcresearchpress.com/doi/pdf/10.1139/z94-189

We investigated the consequences of simulated grazing and browsing on net primary production and chemical composition (nutrients, fiber, and total nonstructural carbohydrates) of some plant types available to caribou on Southampton Island, Northwest Territories, Canada. Clipping experiments were conducted in three large exclosures (22 × 22 m) on one deciduous (Salix lanata), one evergreen (Cassiope tetragona), and one semi-evergreen (Dryas integrifolia) shrub species and two types of sedges (Carex scirpoidea and wet-meadow sedges). The impact of various clipping regimes was analyzed in the growing season during which the treatments were applied and at the end of the following growing season. Clipping, for the most part, reduced plant net production. Responses differed among and within plant types according to the timing and intensity of clipping. In some cases maximum net production of plants was not restored during the recovery year, although grazing and browsing pressure was lifted. Clipping modified the chemical composition of S. lanata, D. integrifolia, and the two types of sedges investigated. In clipped sedges, nitrogen, magnesium, potassium, and phosphorus levels in regrowth were above the maximum obtained from controls at any point during the growing season. These chemical changes possibly enhanced the quality of these plants as food for herbivores. Because plant types that showed a high degree of compensatory growth also showed an increase in quality following clipping, herbivores might benefit if they reselect these plants over the course of the growing season. Growth of S. lanata is negatively affected by clipping and represents an important component of the caribou's summer diet, therefore willows are expected to decrease in abundance as the caribou population increases. The decrease in abundance of deciduous shrubs may have important consequences for the caribou's range use and population dynamics.