Life at High Temperatures
by Thomas D. Brock
The upper temperature limit at which higher plants are able to grow and reproduce is about 45 degrees C (113 degrees F), although very few plants are able to grow at such high temperatures. (Desert plants are able to tolerate much higher temperatures, but do not grow at such temperatures.)
Along many hot spring channels one often sees large bright-yellow masses of the monkey flower, Mimulus guttatus, a member of the snapdragon family (photo below). The monkey flower begins to bloom along hot springs in late April, when the adjacent ground is still snow-covered, and is at its peak in mid-June. The warm environment, virtually a tropical climate, allows the plant to grow through the winter along the snow-free hot spring channels. During the winter the stems are short and the leaves grow close to the warm ground. As soon as the weather warms, the stems grow quickly and profuse flowers are formed.
Yellow monkey flower blooming in April near a hot spring
The adaptation of plants to the thermal environment is also seen in areas of hot ground, such as that shown with the buffalo in the photo below. Plant life on such areas often forms characteristic circular patterns with no vegetation in the hot center. Moving outward from the center are mosses, which are most abundant at soil temperatures around 45-50 degrees C (113-122 degrees F). Farther out are grasses, and finally trees. Such concentric patterns trace the upper temperature limits for different kinds of plants.
Circular pattern of vegetation around a thermal area
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