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JOURNAL OF FORESTRY 



Vol. XV MAY, 1917 No. 5 



TREE GROWTH AND CLIMATE IN THE UNITED STATES 



By K. W. Woodward 



Professor of Forestry, Durham, N. H. 



The purpose of this paper is to summarize the available informa- 

 tion with regard to forest yields in the United States and attempt to 

 determine the relation of these yields to climate and soil In the dis- 

 cussion which is to follow the following forest types will be recognized : 



I, spruce type; 2, northern hardwood type; 3, white pine type; 4, 

 southern hardwood cove type ; 5, southern hardwood slope type ; 6, 

 southern hardwood ridge type ; 7, southern pine type ; 8, southern bot- 

 tom land type ; 9, western yellow pine type ; 10, lodgepole pine type ; 



II, Engelmann spruce type; 12, silver pine type; 13, sugar pine type; 

 14, sequoia type; 15, Douglas fir type. In differentiating these types 

 an attempt has been made to segregate the areas of tree growth which 

 have similar climatic and soil characteristics and tend toward an 

 ultimate stand of the same composition. 



Spruce type 



The spruce type which is found in New England, Michigan, Wis- 

 consin, Minnesota, and New York, and in scattered islands southward 

 in the southern Appalachians to North Carolina, is characterized by a 

 relatively short growing season, not more than four months, a total 

 annual precipitation of at least 35 inches, medium run-off on account of 

 the long winter season, and slow evaporation by reason of the low tem- 

 peratures. As a consequence there is a relatively large amount of 

 available moisture present for tree growth. This is true in spite of 

 the fact that the cold winters necessitate foliage which is adapted to 

 the dry conditions prevailing under low temperatures. 



The characteristic species of this type are red spruce, balsam fir, 

 tamarack, and paper birch. Using a rotation of 100 years as a stand- 

 ard, spruce will attain a diameter, breast high, of 10 inches, and a 



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