life zone

The summit life zone in the Rocky Mountains not only sweeps up to exceptionally high altitudes, but it embraces vast territory.

The valleys of the west side are within an entirely different plant life zone, typified by dense climax forests.

In the chaparral of the Transition Life-zone, basin sagebrush and snowbrush grow in extensive patches in clearings in the timber.

The major part of this biotic area lies within the Lower Sonoran Life-zone.

Farther south still, in the Tropical Life-zone, seasonal difference in color was not detected in the material studied.