8 forestry Quarterly. 



tree with excessive taper, and is very limby, never growing much 

 more than lo inches in diameter and 60 feet high. 



Compared with its associates it will withstand considerable 

 drought and frost and it is altogether peculiarly adapted to thriv- 

 ing under xerophytic conditions. 



Jack Pine is a comparatively deep rooted tree; where spruce 

 and balsam fir are blown down by the hundreds, Jack Pine 

 easily holds its own. The tendency under average conditions is 

 to develop strong laterals, rather than tap root, thus securing 

 maximum food materials and optimum moisture. These laterals 

 ramify in all directions 12" to 24" beneath the surface. 



Up to ninety years of age wind has practically no effect on the 

 tree, but as it becomes over-ripe and its vitality is reduced it is 

 more susceptible to wind action, and much valuable timber blows 

 down before it is noticeably deteriorated. Where there is excess 

 of water content in the soil the roots of the Jack Pine are forced 

 to grow closer to the surface, the windfall is more frequent, but 

 as the species here never reaches an average size which would 

 permit of harvesting for tie, or saw material, the increased damage 

 due to windfall is of small import. 



Tolerance. — Jack Pine is most intolerant of shade at all ages. 

 This intolerance accounts in part for its presence in pine islands 

 during the younger stages, where, by the exclusion of quick grow- 

 ing broad-leaved species, it secures the optimum amount of light 

 necessary for its existence. 



For reproduction the optimum seemingly is sunlight. Under 

 mature forest the average density is such that the light admitted 

 is below the minimum necessary for the young tree, so that seed- 

 ling growth is very rarely found under mature stands. 



During the seedling stage the Jack Pine can hold burned over 

 land, provided it can secure complete possession of the ground 

 from the beginning, but if the faster growing Aspen enters into 

 competition with it, it quickly succumbs to the broad leaved tree. 

 In later life the open symmetrical head of the Jack Pine admits 

 the maximum amount of light to the growing crown. 



Owing to the inabiHty of Jack Pine to endure even its own 

 shade, in the transitional change it gives way to other trees which 

 are capable of growing under less favorable light conditions, e. g. 

 spruce, balsam. White Pine. 



Seed Production. — With the optimum amount of light, cones 



