Abstract
West of the Cascades, broadleafs comprise about 6% of the number of trees but yield<0.01% of the timber. Their present minor rank is not explainable on present climatic or edaphic conditions. Glacial climatic conditions there were unfavorable to broadleafs, leading to the extermination of various biotypes. Relief has interfered with migration of suitable broadleafs into the area since the climate became again favorable to them. The occupation of much of the better ground by conifers is also significant.

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