GRAZING RESPONSE STRATEGIES ALONG A SNOW DEPOSITION GRADIENT - A LABORATORY EXPERIMENT ON 3 GRASS SPECIES FROM SVALBARD

The objective of this study was to determine whether Arctic grasses fr om different sites along a snow deposition gradient respond similarly to grazing. The effects of laboratory simulated grazing (two levels of clipping frequency, clipping height, and nutrition) on accumulated bi omass of different plant parts and number of tillers were measured in the reindeer forage grasses Poa arctica R. Br. from a dry ridge habita t, Festuca rubra L. from a moist lee-side habitat, and Deschampsia alp ina L. from a wet snowbed habitat in Svalbard. Both P. arctica and F. rubra increased the proportion of biomass allocated belowground at the cost of the aboveground structures in response to high clipping frequ ency combined with high clipping height, leaving total accumulated bio mass unchanged. In D. alpina, on the contrary, the percentage of above ground biomass increased at the cost of belowground structures in resp onse to high clipping frequency and low clipping height. This results in higher vulnerability to clipping and reduced total biomass. These t wo contrasting response patterns may reflect differences in adaptation s in the habitats. Stress tolerance is more important on wind-blown ri dges and in lee-side habitats where the grazing season is longer. On t he other hand, rapid growth is more important in the snowbed where the growing season is shorter. These strategies may be of great importanc e in regulating and driving the local foraging patterns of Svalbard re indeer.