Arctic vegetation: an introduction
The type of vegetation in Arctic National Wildlife Refuge (ANWR) is mainly
characterized as “tundra”, meaning barren land. Contradictory to its literal
name, vegetation on the arctic tundra is highly diverse. The types of vegetation
found depends on numerous factors such as the terrain, local climate, permafrost
and active layer depths, precipitation and water availability and drainage,
nutrient availability and cycling. The shrub tundras are dominated
by deciduous vascular plants. Slightly warmer soil temperatures, deeper
thaw, and more rapid nitrogen mineralization associated with the high water
flow rate in water track and river bar localities cause denser canopies and
higher total foliar nitrogen.
The differences in canopy structure between the graminoid-dominated wetland
tundras and the mixed tussock tundra communities are probably related to
drainage characteristics and their effects on nutrient availability. The
highly heterogeneous nature of the heath sites is probably determined by
their different degrees of exposure on ridge and hill tops. Microtopography
affects the growth and structure of heath, with sheltered hollows causing
denser vegetation and ridge tops causing sparse canopies. (Shaver et al.,
1996)
The arctic coastal tundra consists of thaw lakes and wetlands near the Beaufort
Sea coast and along river deltas. The foothills tundra, a transition between
this and the Brooks Range, is dominated by sedge tussock (Eriophorum vaginatum),
which provides the lush, new growth needed to feed caribou calves and energize
staging snow geese. Riparian areas have willow shrubs that are important nesting
habitat for migratory birds. (World Wide Fund for Nature, 2000)
Diverse vegetation in Arctic National Wildlife Refuge
Photo: Subhankar Banerjee
The tundra plants are usually less than 1 foot high. Tall plants are restricted
to the southern slopes of ANWR. The tundra plants belong to five main groups:
1. Lichens, either on rocks or in mats on the ground
2. Bryophytes (commonly known as mosses)
3. Grasses and grass-like herbs, including mainly sedges
and willows
4. Cushion plants
5. Dwarf shrubs
(Patrick D. Baird, 1964; Janet C. Jorgenson, Peter C. Joria, and David
C. Douglas, 2002)
In ANWR, the following four types of plants are particularly important:
1. Sedges, especially tussock cottongrass
2. Willows, especially diamond-leaf willows
3. Mosses, especially Sphagnum spp.
4. Lichens, of various types
The first two is highly nutritious for herbivores to feed on as a food source,
particularly during the growing seasons, while the latter two help maintain
the ecosystems in other ways and provide food during winter.
Map showing vegetation pattern of ANWR
(Map: http://www.absc.usgs.gov/1002/section2.htm)
Reference:
1. Williams, M.; Rastetter, E. (1999). Vegetation characteristics
and primary productivity along an arctic transect: implication for scaling-up.
Journal of Ecology 1999, 87: 885-898.
2. World Wide Fund for Nature. (2000). Protection of
the Artic National Wildlife Refuge: Key to Managing one of the World's Most
Biologically Valuable Ecoregions, the Arctic Coastal Tundra, http://www.worldwildlife.org/arctic-refuge/anwr_position.pdf
3. Janet C. Jorgenson, Peter C. Joria, and David C. Douglas.
(2002). Arctic Refuge Coastal Plain Terrestrial Wildlife Research Summaries. http://www.absc.usgs.gov/1002/section2.htm
4. Patrick D. Baird. (1964). The Polar World.