Upper Treeline and Alpine Tundra - Mountains and Plains: The Ecology of Wyoming Landscapes - page 236

most of their lives—and under snow for much of the
year—they avoid bone-chilling winds and the coldest
temperatures. 30

Tundra Mosaic, Frost, and Burrowing Mammals

the plant communities of alpine tundra can be easily
classified into one of the following categories: fellfields,
alpine turf, wet meadows, and willow thickets. 31 there
are also snow-beds, talus slopes, and boulder fields,
all of which have little or no plant growth. Lakes and
streams are common, with associated wetland vegeta-
tion that includes sedge-dominated wetlands as well as
willow thickets (see chapter 5).
Alpine tundra is commonly discussed at three spa-
tial scales. At the scale of tens of miles, variation is
caused by differences in local climate. 32 the tundra of
the Southern Rockies is different from that of the cen-
tral and northern Rockies. in contrast, at the scale of a
few feet, abrupt differences can be caused by the pres-
ence of boulders, which absorb and store considerable
heat from the intense sunlight at high elevations, and
then release the heat at night to the benefit of plants
growing nearby. Also, snow accumulates on the lee side
of boulders, and water from rain and condensation
drains rapidly to the soil below the boulders, where it
is less likely to evaporate. Because of these influences,
boulders provide warmer, wetter microenvironments

Fig. 14.6. the big flowers of this 6-inch-tall alpine tundra
plant, known as alpine sunflower or old-man-of-the-moun-
tain, attract pollinating insects during the short cool summer.

environment (fig. 14.6). 27 Because pollination often
does not occur during the short summer, a high per-
centage of alpine plants are capable of producing seeds
without fertilization, a process known as apomixis.
Animals have equally interesting adaptations. Aside
from fish, all vertebrates in the alpine zone are warm-
blooded endotherms, which is adaptive as long as they
have the food required to maintain body temperature.
no alpine amphibians or reptiles have been found.
Some animals migrate up and down the mountain to
find food and shelter. During the winter, a few species
of birds leave the region altogether, like the American
pipit. other animals have the extraordinary ability
to stop eating while they hibernate, such as the mar-
mot. Mice, voles, and pocket gophers consume roots
and other accessible plant materials in their burrows,
even under the snow, whereas the pika works all sum-
mer long to create a cache of food deep in the boulder
fields and talus slopes where it lives (fig. 14.7). Known
as haypiles and composed largely of alpine avens and
other forbs, these caches are quite large, weighing on
average about 60 pounds in the colorado alpine. For
comparison, each pika weighs less than 7 ounces. 28
there can be six to eight pikas per acre, each one feed-
ing outward from its nest . 29 through their burrowing,
all small mammals contribute to soil development and
have effects on the vegetation where they live. tons
of soil are aerated. By living in soil or under rocks for

Fig. 14.7. the American pika, 6-8 inches long, lives in alpine
boulder fields and talus slopes, where it creates “haypiles” for
warmth and food during the winter. it does not hibernate.
copyright Wendy Shattil / Bob Rozinski.