File:Brigham Young University science bulletin (1955) (20228435359).jpg

Title: Brigham Young University science bulletin
Identifier: brighamyounguniv14brig (find matches)
Year: 1955 (1950s)
Authors: Brigham Young University
Subjects: Biology -- Periodicals
Publisher: Provo, Utah : Brigham Young University
Contributing Library: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library
Digitizing Sponsor: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library

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Biological Series, Vol. 14, No. 2 Reconnais.sance of Northern Yukon VEGETATION 15 The general aspect of northern Yukon is dominated by vegetation of low relief, i.e., tun- dra. The hills and valleys have the look of a well-tended golf course (Fig. 11). The vegeta- tion is not unifonn, however, it varies in cover and in composition. The major vegetative con- trol appears to be the amount of moisture that is available. Substrate differences appear to influ- ence the water supplv directlv, and thus the plant cover indirectly. The limestone, shale, sandstone, and siliceous conglomerates, slates, and schists of the lower, rounded mountains gen- erally lack the more lush vegetation of the ba- jada.s, wet meadows, and stream courses of lower elevations. Rock stripes, boulder patches, and rock outcrops appear at first glance to be barren of higher plants. They are vegetated by a sparse cover of plants widely spaced. Even the lowlands display a mosaic pattern in the green mantle of the land. Frost-heaved patches of gravel of ir- regular shape produce a varied pattern in the tundra. The swales where water drains slowly over the surface are bright green compared to the slopes alongside them. Polygonal patterns ap- pear here and there in the tundra, apparently always associated with poorly drained sites. The lower trenches of most polygons are moist or have standing water in them and frequently are more lushly vegetated than the surrounding area. Tall vegetation is present only along the streams, \\'here willows and an occasional cottonwood stand a few feet above the surface. Southward along the upper reaches of the drainage of the Old Crow and rarely in the headwaters of the streams which drain to the Arctic Sea, there oc- curs a depauperate assemblage of the Boreal Forest, chiefly along stream courses, and along some south facing slopes. This forest extends to about 69° 15' N'^ along the Firth River, at ap- proximately 140° 25' W. Eastward, however, the forest does not extend that far north, reacliing only to about 68° 39' N along Spruce Creek, a tributary of the Canoe River, at approximately 1.38° 43' W. The trees reach their best develop- ment in the mountain system on south facing slopes near the bases of low rounded hills. In the Old Crow Flats there has developed a parkland tundra or taiga, the interspaces of which is dom- inated by a heathland of dwarf birch, willows, and other shrubs. In some places the woodland is really quite dense, the trees reaching a height of up to 25-30 feet and a few inches in diameter.
Text Appearing After Image:
\' 'I v-^i,,-^ ,. Fig. 11. Northwestward from apprcximately 58°32' N; 1.38°27' W, along westward dipping cue.stas of Li.sbume Limestone, at the northwest edge of the Ban) Mountains, in the headwaters of Wood Creek. Low vegetated valleys are in the Kayak .shale, in part in fault-repeated sections. Tussock and alpine tundra and heathlands.

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