Shrub Height and Snow Depth In The Alaskan Arctic

Deciduous shrubs are predicted to increase in size and abundance in arctic tundra with climate warming. However, one barrier to this increase in shrubs may be exposure of taller stems above the snow pack where winter damage from dessication, abrasion, cold and browsing can occur. We measured shrub height and snow depth along transects at several sites from Atquasuk (70.5 N 157.5 W) and Oumalik north of the Colville River to sites south of the Colville River (Ivotuk) and in the Seward Peninsula (64.9 N 163.7W). We found that, although summer shrub heights are often greater than snow depths, these shrubs are usually snow covered by the Deep Cold stage of winter. One or a combination of two mechanisms account for this:1) 'lay over' of stems pushed over by wind or snow load and 2) buildup of snow around and over shrubs by the trapping of blowing snow by a dense network of branches and shoots. As deciduous shrubs become taller in response to climate warming, these mechanisms may allow them to remain protected in the winter despite an even greater mismatch in shrub height and snow depth.