Upper Treeline and Alpine Tundra - Mountains and Plains: The Ecology of Wyoming Landscapes - page 242

tolerate the subalpine forest ecosystem as they move
from one alpine zone to another. Populations of the
same species farther north, where there is more tundra
because treelines are lower, may have a greater chance
of surviving.
Such discussions invariably consider the plight of
the American pika, a small mammal in the rabbit fam-
ily that essentially is restricted to alpine tundra (see
fig. 14.7). it nests in the crevices of boulder fields and
frequently is seen scurrying from one rock to another,
often stopping to bark along the way. if the forest mar-
gin continues to move upward because of global warm-
ing, pika habitat will be squeezed into smaller and
smaller patches. At present, the alpine treeline appears
to be moving upward very slowly, if at all, and pikas are

able to survive below treeline where subalpine meadows
and talus slopes are in close proximity.

overall, sorting out the causes of shifting treelines
and nutrient enrichment is a challenge that requires
an understanding of microclimate; wind; soil; cryo-
turbation; the effect of cold night skies; the chemistry of
the atmosphere and soil; the various factors that influ-
ence streamwater chemistry; and the adaptations of the
plants, animals, and microorganisms found on land
and in water. treelines are likely to expand upward,
slowly at first. the alpine tundra, though far removed
from urban-industrial developments at low elevations,
is nevertheless another bellwether of changes under
way throughout the region.