A comparison of the growth responses of three sedges to foraging by lesser snow geese.

Abstract

SUMMARY:

1.The responses to herbivory of above-ground organs of the sedges Carex subspathaces and Carex X flavicans were investigated at La Perouse Bay, Manitoba. Demographic techniques were used to compare the production and turnover of leaves and shoots and the elongation of leaves between plants of swards on which lesser snow Geese fed and plants of swards from which geese were excluded. The effects of herbivory on the shoot demography of carex aquatilis were also studied.

2.Patterns of foraging by the geese varied seasonally. Following their arrival at La Perouse Bay, the geese fed by pulling shoots of carices and by grubbing the roots and rhizomes of graminoids. After the hatch of the goslings, the geese fed by clipping the leaves of grasses and sedges.

3.Within one summer, gazing increased the cumulative production of leaves of Carex subspathaceaand of Carex X flavcas. Though the geese removed few leaves, leaves of shoots of both species in grazed plots had shorter lifespans than leaves of shoots in ungrazed plots. Grazing also increased the total number of leaves per shoot which died during the growing season.

4.The rates of elongation of leaves of shoots of Carex subspathacea and Carex X flavicans in grazed plots did not consistently differ from the rates of elongation of leaves of shoots in ungrazed plots.

5.Herbivory by geese did not consistently alter the production of shoots of Carex aquatilis, Carex subspathacea, or Carex X flavicans.

6.The increased production of leaves is the primary response of above-ground organs of these carices to herbivory by geese. The unresponsiveness of shoot production suggests that these carices are more vulnerable to damage from the loss of shoots than from the clipping of leaves.