Merriam's Life Zones of North America

Abstract

Forty years ago C. H. Merriam divided North America into 7 life zones. He explained the distribution of these zones on the basis of temp, variations during the period of growth and reproduction. His methods and concepts exerted wide influence and his theory was widely accepted. Recently, however, his work has been much questioned: the boundaries of his zones have had to be altered, the causal factor is not the simple unit factor he supposed, and certain technical errors have had to be corrected.