vitality transient. Exposed mineral soil as is found after a fire makes a 

 favorable seed bed. The birches also coppice vigorously, but the stumps 

 have only briefly sustained vitality. 



Range. The north and middle Temperate Zone; nearly to moun- 

 tain and Arctic timber lines. 



Soil. Inhabit a wide range of soils from swamps and moist bottom 

 lands to dry ridges. 



Association. Sometimes occur in smal pure stands, and often 

 with poplar after a fire. Generally mixed singly or in small groups. 



General. Nine tree birches grow in the United States and Canada, 

 of which four inhabit the Pacific region. In Canada, the birches stand 

 at the head of the hardwoods in commercial importance, and the bulk 

 of the cut is supplied by yellow birch. In 1912 birch ranked 7th, and 

 formed 2% of the total lumber cut. It supplied 32% of the total hard- 

 wood cut at an average mill price of $16.36 per thousand. 



BETULA PAPYRIFERA, Marsh. 

 Paper Birch. 



Size. 50 to 100 ft. by 1 to 2 ft. 



Growth. Rapid in early life, but only briefly sustained. Short 

 lived. 



Root System. Superficial. 



Bole. Short, medium taper. 



Crown. Medium spreading. 



Toler ance . I n tolerant . 



Wood. Hard, strong, fairly tough, not durable; 37 pounds. 



Reproduction. Reproduces well on burned-over areas and on 

 mineral soils. Seeds annually. Seed light with long, thin, mem- 

 branaceous wings; germination percent medium; vitality transient. 

 Prefers bare mineral soil to humus as a seed bed. Seedlings occur in 

 openings. Flowers in April and May, and sheds seeds in June. 



Range. Long Island to Iowa and Nebraska; from Labrador to the 

 Rockies; and north to the limit of tree growth. Optimum, New 

 Hampshire and central Maine. Medium altitude. 



Climate . Severe . 



Soil. Poor to medium; prefers good soil. Xerophytic to meso- 

 phytic. 



Association. Occurrence determined largely by fire on burned- 

 over areas. Its common associates are gregarious and grouped, 

 spruce, balsam, yellow birch, sugar maple, and beech. 



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