ALNUS OREGON A: ITS VALUE AS A FOREST TYPE ON 

 THE SIUSLAW NATIONAL FOREST 



By Herman M. Johnson 

 Forest Examiner, Forest Service 



INTRODUCTION 



The genus Alntis comprises many species scattered on both sides of 

 the equator in various parts of the world, but occurs chiefly in the 

 northern hemisphere. Many of them are only shrubs, but there are six 

 species in the United States that belong to the tree class. The different 

 species cover much of this country and there are few large areas upon 

 which one or more are not present. The alders are old inhabitants of 

 the earth. They occurred in the Eocene and Miocene forests of the 

 old and new world and have held their own throughout the ages. Ap- 

 parently, they have neither gained nor lost in extent of range during 

 the hundreds of thousands of years which measure their tenancy upon 

 the earth. 



The Oregon or red alder is the largest of the alder group in this 

 country and occurs only on the Pacific Coast. The red alder is so 

 named because newly cut wood rapidly turns a reddish brown. This 

 applies only to the sapwood ; but since the trunk is largely sapwood it 

 is an important matter. This coloring is probably due to some chem- 

 ical change in the sap when exposed to the air. 



SILVICAL CHARACTERISTICS 



The Alntis oregona, or red alder, as it is commonly called, belongs 

 to the birch family, Betulacese. It is the largest and most important of 

 the alder group in this country. It extends from southern Alaska to 

 southern California, a north and south range of over 2,000 miles. Its 

 altitudinal limit is 7,000 feet. 



It is a tree of moist situations, hence occurs mainly along streams 

 and in river bottoms. Normally it occurs in mixture with the other 

 moisture-loving species, but frequently forms pure stands. 



The red alder, although the most tolerant of this genus, when com- 

 pared with its associated broadleaf species it is below the average in 

 this regard. In pure stands the density of its crown canopy is less 

 than 0.75. 



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