Role of ice scouring and goose grubbing in marsh plant dynamics
1994
Belanger, L. | Bedard, J.
1. The effects of scouring by ice and of grazing by the greater snow goose (Chen caerulescens atlantica) on the substrate and vegetation of a brackish tidal marsh in the St Lawrence estuary were studied from 1985 to 1987. During spring and fall migratory stopovers, the birds fed mainly on Scirpus americanus rhizomes. 2. The presence of ice-made depressions was related mainly to the physical characteristics of Scirpus marshes. Goose grubbing has no significant effect on the annual dynamics of these depressions. 3. In exclosures, i.e. in the absence of geese, ice drift has little influence on species abundance and net above-ground primary production of the marsh except at high levels of disturbance. 4. In ice-made depressions, goose grazing reduced net primary production by approximately 45% and facilitated colonization by competitive species such as Zizania aquatica, Sagittaria spp. & Scirpus torreyi. History or frequency of disturbance seems to play an important role in this process. 5. By exploiting ice-made depressions, snow geese contribute to an increase in the heterogeneity but a decrease in the primary production of the Scirpus marsh.
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