Fig. 13. The usual order in which coniferous trees are encountered with increasing altitude in eastern Washington and northern Idaho. The horizontal bars indicate the upper and lower limits of the species relative to the climatic gradient. The heavy lines indicate that portion of a species' altitudinal range in which it can maintain a self-reproducing population in the face of intense competition. [After R. Daubenmire, "Vegetation: Identification of Typal Communities," Science 151:291-298, 1966. Copyright © 1966 by the American Association for the Advancement of Science.]