JACK PINE. 5 



and gravels), and collected in pockets. There are immense areas 

 barren or valuable only for timber growing. 



Jack pine is distinctly a tree of cold climates. Great variations of 

 temperature take place within its range, and it occui-s, for instance, 

 where the winter temperature is often 60° F. below zero and the 

 summer heat sometimes over 105° F. above. The growing season 

 within its range varies from two to four months. 



The heaviest rainfall of the jack-pine belt is in parts of Nova Scotia 



and New Brunswick, v\dicre it usually amounts to from 20 to 40 inches 



annually. The precipitation in the western portions of its range 



varies from 14 to 29 inches a 3'ear. Although essentially a dry-land 



tree, jack pine demands a climate with a moderate rainfall and 



produces the best stands where the annual precipitation is about 25 



inches. Snowfall is generally abundant throughout its region of 



distribution, and protection is thereby afforded to the ground and 



the young growth. 



FOREST TYPES. 



Jack pine occurs chiefly in the following forest types: (1) In pure 

 stands, on what is known as jack-pine land; (2) in mixture with 

 Norway pine, on Norway pine land; (3) in mixture with white pine 

 and other species, on white pine land; (4) in mixture with poplar 

 (aspen) ; (5) in coniferous swamps and muskegs. The first and the 

 last of these forest types occur throughout the range of the species, 

 while the second and third are limited to the United States «,nd the 

 southern part of Canada. In general, the types in which jack pine 

 occurs are relatively transient ones, as this species perpetuates itself in 

 nature largely through the accidental agency of fire. (See Pis. Ill, 

 IV, and V.) 



JACK PINE LAND. 



Land composed of poor, medium-to-coarse sands or land which is 

 impoverished by fire and on which Norway or white pine does not 

 readily spring up and thrive is the kind on which pure or nearly pure 

 stands of jack pine constitute one of the principal forest types of the 

 North. Even on this land, if for a number of years fires are excluded, 

 soil and humus conditions improve and jack j^ine gradually gives way 

 to the longer-lived and more persistent Norway pine, or in some cases 

 to spruce. In the Lake States this land is usually known as "jack 

 pine plain" because of its comparative!}'' flat topography. In 

 Canada it is usually known as "jack-pine ridge," although often it is 

 only a few feet in elevation above the level of the coniferous swamp or 

 muskeg. In the Lake States the "jack pine plain" in many cases 

 formerly supported a good growth of Norway or white pine and the 

 process of reversion to these species is now going on. On the border 

 of the prairie region in Minnesota and Manitoba, "jack-pine prairies" 

 occur which have only a scattering growth of small jack pine trees. 



