Grazing response strategies along a snow deposition gradient: a laboratory experiment on three grass species from Svalbard

The objective of this study was to determine whether Arctic grasses from 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 biomass of different plant parts and number of tillers were measured in the reindeer forage grasses Poa arctica R. Br. from a dry ridge habitat, Festuca rubra L. from a moist lee-side habitat, and Deschampsia alpina 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 frequency combined with high clipping height, leaving total accumulated biomass unchanged. In D. alpina, on the contrary, the percentage of aboveground biomass increased at the cost of belowground structures in response to high clipping frequency and low clipping height. This results in higher vulnerability to clipping and reduced total biomass. These two contrasting response patterns may reflect differences in adaptations in the habitats. Stress tolerance is more important on wind-blown ridges and in lee-side habitats where the grazing season is longer. On the other hand, rapid growth is more important in the snowbed where the growing season is shorter. These strategies may be of great importance in regulating and driving the local foraging patterns of Svalbard reindeer.