Full descriptions of Level 3 ecoregions in Copper River basin
Level 1 Boreal Level 2 Alaska Range Transition
Level 3 Alaska Range
A series of accreted terranes conveyed from the Pacific Ocean fused to form this arcing mountain range. In turn, these towering mountains harbor a complex mix of folded, faulted, deformed metamorphic rocks. Landslides and avalanches frequently sweep the steep, scree-lined slopes. Discontinuous permafrost underlies shallow and rocky soils. Because of the Alaska Range?s height, a cold continental climate prevails and much of the area is barren of vegetation. Occasional streams of Pacific moisture are intercepted by the highest mountains and help feed small icefields and glaciers. At the glacier?s termini, swift glacial streams with heavy sediment loads course down mountain ravines and braid across valley bottoms. Alpine tundra supports populations of Dall sheep and pikas on mid and upper slopes. Shrub communities of willow, birch, and alder occupy lower slopes and valley bottoms. Forests are rare and relegated to the low-elevation drainages. Brown bears, gray wolves, caribou, Dall sheep, and wolverines are common denizens in the Alaska Range.
Level 2 Pacific Mountains Transition
Level 3 Copper River Basin
This mountain basin lies within the former bed of Glacial Lake Ahtna on fine-textured lacustrine deposits ringed by coarse glacial tills. The basin is a large wetland complex underlain by thin to moderately thick permafrost and pockmarked with thaw lakes and ponds. A mix of low shrubs and black spruce forests and woodlands grows in the wet organic soils. Cottonwood, willow, and alder line rivers and streams as they braid or meander across the basin. Spring floods are common along drainages. Arctic grayling, burbot, and anadromous sockeye salmon are common fishes. Black and brown bears, caribou, wolverines, and ruffed grouse are present throughout these wetland habitats. The climate is strongly continental, with steep seasonal temperature variation. The basin acts as a cold-air sink, and winter temperatures can be bitterly cold.
Level 2 Coast Mountains Transition
Level 3 Wrangell Mountains
This volcanic cluster of towering, ice-clad mountains is at the northwest edge of the St. Elias Mountains. This exceedingly steep, rugged terrain is the result of the ongoing collision of the Pacific and North American tectonic plates. Here, relatively recent volcanic flows and debris form a carapace over the Wrangellia terrane. The Wrangell Mountains possess a peculiar mix of climates because of their size and geographic location (i.e., on the Interior-side of the Coastal Mountains). The sheer height of the Wrangell Mountains allows interception of moisture-laden air emanating from the north Pacific Ocean. The abundant maritime snows feed extensive icefields and glaciers interspersed by dull gray ridges draped with rock shard slopes and patches of alpine meadows. The climate grades to dry continental at lower elevations where the Wrangell Mountains abut the cold-air basin of the Copper River. Shrublands of willow and alder with scattered spruce woodlands ring the lower slopes. Spruce and cottonwood grow along larger drainages. The Wrangell Mountains are highly dynamic due to active volcanism, avalanches, landslides, glaciers, and stream erosion. Soils are thin and stony and underlain by discontinuous permafrost. Its best-known denizen, the Dall sheep, roams throughout the area along with mountain goats, brown bears, caribou, wolverines, and gray wolves.
Level 1 Maritime Level 2 Coastal Rainforest
Level 3 Chugach-St. Elias Mountains
Arcing terranes of Pacific origin have been thrust onto the North American continent forming a rugged ice-clad mountain chain surrounding the Gulf of Alaska. This is the largest collection of icefields and glaciers found on the globe outside the polar regions. These towering mountains of faulted and folded sedimentary rocks intercept an abundance of maritime moisture, mainly in the form of snow. Huge icefields, snowfields, and glaciers surround steep angular and cliffy peaks that are mantled with hanging glaciers; isolated small peaks called nunataks poke up sporadically in the middle of the broad glaciers. In the summer, glacial meltwaters form rivulets and plunge down vertical ice shafts called moulins to join vast amounts of water flowing along the base of glaciers. Where they exude onto coastal flats, glaciers spread to form expansive lobes that gush water at their edges. Some glaciers run all the way to tidewater. Ice sheets swelled during past glaciations, inundating surrounding lands along the coast, as well as the Interior. The sheer height of these mountains together with their expansive icefields, forms an effective barrier for Interior species, except along the Alsek and Copper River corridors. Thin and rocky soils exist where mountain summits and slopes are devoid of ice, snow, and active scree. Here, alpine communities of sedges, grasses, and low shrubs grow which, in turn, support Dall sheep, mountain goats, hoary marmots, pikas, and ptarmigans. Glaciers and icefields have receeded, leaving broad U-shaped valleys, many with sinuous lakes. Here, deeper soils have formed in unconsolidated morainal and fluvial deposits underlain by isolated pockets of permafrost. Alder shrublands and mixed forests grow on lower slopes and valley floors where moose and brown and black bears forage.
Level 3 Gulf of Alaska Coast
Lush, lichen-draped temperate rain forests of hemlock and spruce interspersed with open wetlands blanket the shorelines and adjacent mountain slopes along the Gulf of Alaska. A cool, hypermaritime climate dominates with minor seasonal temperature variation and extended periods of overcast clouds, fog, and precipitation. Snow is abundant in the winter and persists for long periods at sea level. Permafrost is absent. Tectonic events have raised and submerged various portions of the coastline through time. Common forest animals include black and brown bears and Sitka black-tailed deer. Bald eagles, common murres, Bonaparte?s gulls, Steller?s sea lions, harbor seals, and sea otters teem along its endless shorelines. Numerous streams and rivers support Dolly Varden, steelhead trout, and all five species of Pacific salmon. Salmon spawning runs deliver tremendous amounts of nutrients to aquatic and terrestrial systems. A fjordal coastline and archipelago exists around Prince William Sound and points west where continental ice sheets repeatedly descended in the past. Here, fjords formed where glacier-carved terrain filled with seawater after deglaciation. At the head of fjords lie broad U-shaped valleys that have steep, deeply incised side walls draped with hanging glacial valleys. A coastal foreland extends from the Copper River Delta southeast to Icy Point, fringed by the slopes and glacier margins of the Chugach-St. Elias Mountains. Here, unconsolidated glacial, alluvial, and marine deposits have been uplifted by tectonics and isostatic rebound to form this relatively flat plain. Because of its geographic position, the foreland is water-drenched through persistent maritime precipitation and overland runoff from the mountains. The organic soils shed water slowly and are blanketed with wetlands among meandering and braided silt-laden streams. Temperate rain forests of hemlock and spruce grow sporadically where soil drainage affords (e.g., moraines, stream levees, and uplifted beach ridges). Rare dusky Canada geese and trumpeter swans nest on these wet flats where brown bears, Sitka black-tailed deer, and moose roam.
Level 1 Level 2 Ecoregion Polar (-like) Arctic Tundra Beaufort Coastal Plain Brooks Foothills Brooks Range Bering Tundra Kotzebue Sound Lowlands Seward Peninsula Bering Sea Islands Boreal (-like) Bering Taiga Nulato Hills Yukon-Kuskokwim Delta Ahklun Mountains Bristol Bay Lowlands Intermontane Boreal Kobuk Ridges and Valleys Ray Mountains Davidson Mountains Yukon-Old Crow Basin North Ogilvie Mountains Yukon-Tanana Uplands Tanana-Kuskokwim Lowlands Yukon River Lowlands Kuskokwim Mountains Alaska Range Transition Lime Hills Alaska Range Cook Inlet Basin Copper River Basin Pacific Mountains Transition Copper River Basin Maritime (-like) Aleutian Meadows Alaska Peninsula Aleutian Islands Coastal Rainforests Alexander Archipelago Boundary Ranges Chugach-St. Elias Mountains Gulf of Alaska Coast Kodiak Island Coast Mountains Transition Wrangell Mountains Kluane Range
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