Effects of goose grazing on the quality of Scirpus americanus rhizomes

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Abstract
We investigated whether repeated intensive grazing of rhizomes of three-square bulrush (Scirpus americanus) by greater snow geese (Chen caerulescens atlantica) staging in a tidal brackish marsh along the St. Lawrence River in Quebec can induce changes in the nutritional value and structural characteristics of the rhizomes. We compared rhizomes growing on heavily used sites with those growing in ungrazed sites (exclosures) for 3 years. The belowground standing crop of S. americanus was greater in ungrazed than in grazed plots, but no difference was observed in the nutritional constituents (nitrogen and fiber) of rhizomes between the two types of plot. Moreover, S. americanus did not increase the deposition of phenolics (chemical defense) in its rhizomes following grazing. Our results lead us to conclude that goose grubbing decreases quantity without affecting quality of S. americanus rhizomes.