Aspen Bibliography

Soil-forest types of the Yukon and Tanana valleys in subarctic Alaska

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Journal of Soil Science





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The region consists of flood plains, river terraces, low mountains, and dissected plateaux. Much of the area is covered with wind-blown, micaceous silt and fine sand. The summer temperature of nearly 100° F. drops in winter to - 70°. The mean annual precipitation is about 12 in. The important types of forest soils include lithosols and regosols, alluvial soils, melanized raw-humus soils, micro-podzols, half–bog soils, lowmoor peat, highmoor bog soils, and tundra-forest soils. Forest cover consists of white and black spruce, tamarack, paper birch, aspen, and tacamahaca poplar, accompanied by Sitka alder, willows, Alaska rose, highbush cranberry, many heath shrubs of both American and Eurasian origin, mosses (largely of Sphagnum and Hylocomium genera), and lichens.

Spruce stands on productive loessial uplands and permafrost-free terraces yield as much as 15 Mbf. per acre. A comparatively rapid growth of trees on lithosols and regosols, attaining 0.3 cords per acre per year, is attributed to large differences between the day and night temperatures resulting in condensation of water on fissures and fragments of rocks. Highmoors, covering slopes up to 45°, and some half-bog soils support sporadic cover of dwarfed trees; these otherwise unproductive sites provide food and shelter for wildlife, an important item in Alaska's economy.

The immediate neighbourhood of highmoor peat and alkali solonchak soils, as well as the development of non-podzolic, melanized soils covered with thick raw humus, are among many paradoxes of the Alaskan environment.