Skip booklet index and go to page content

COSEWIC assessment and update status report on the Athabasca Thrift, ssp. interior in Canada

Habitat

Habitat Requirements

Armeria maritima subsp. interior occurs primarily on gravel pavements within areas of active sand dunes. These gravel pavements originated through aeolian action on a sandy gravel till. As the sand was winnowed out of the till the surface became covered by a single layer of stones, a lag concentrate, that reduced erosion of sand from the till (Raup & Argus 1982). In time, the pavement stones were eroded sand polished by wind-blown sand into two- or three-faced ventifacts. This habitat is variously described on herbarium labels as gravel barrens, sandy-gravel barrens, or sandy till plains covered with ventifact gravel. This taxon is also known to grow in moist interdunal depressions; both west and east of the William River and south of Yakow Lake (herbarium specimens, Purdy 1995). Its cespitose growth form, however, does not adapt it to withstand burial by sand. As the dune slack is invaded by moving sand these plants will be buried. These populations, therefore, are relatively ephemeral but they may play an important role in survival of the subspecies as sources of seed.


Trends

There is no information on changes in quality or loss of this habitat but it is evidently very fragile. When the area was first visited in 1962 (Argus unpubl.) tracks of a light aircraft, which landed on an area of gravel pavement some 10 or more years earlier, were still very evident. Disturbance of the gravel veneer could increase the rate of surface erosion.


Protection/Ownership

All populations of this subspecies occur within the Athabasca Sand Dunes Wilderness Provincial Park.