Colorado Plateau Life Zones
Plant and animal communities change as elevation increases.
The concept of life zones arose on the Colorado Plateau in the late 1800s. C. Hart Merriam studied the distribution of plants and animals from the Grand Canyon to the San Francisco Mountains. Across the gradient, he identified life zones based on the effects of elevation on temperature and moisture (or vice versa) and, in turn, on plants and animals. Scientists today recognize that additional factors contribute to the makeup of life zones, among them soil type, underlying rock, and past fires. Yet Merriam's concept for the arid southwest's life zones is still generally applicable.