2 Forestry Quarterly. 



ward to the coast of Maine and through the Northern States to 

 Minnesota, common and of large size in the region north of Lake 

 Superior. 



Along the southern limit of its range, for instance in Wiscon- 

 sin, it remains a small tree, usually, less than lo" in diameter and 

 below 60' in height. 



It reaches its maximum development north and west of Lake 

 Superior, west of Lake Winnipeg and north of the Saskatchewan 

 River, where it frequently reaches a height of 85' to 90' with a 

 straight trunk, sometimes free of branches for 30 feet, but rarely 

 exceeding 20" in diameter breast high. 



North of Lake Winnipeg it rapidly deteriorates into an inferior 

 tree, seldom exceeding 8" in diameter and 50' high. The trees 

 of larger diameter are normally infected with heart rot. 



In Western Ontario, and elsewhere, the Jack Pine occupies all 

 the poorest sands where White Pine, Red Pine, or even aspen and 

 birch no longer thrive. However, it can and does grow on the 

 better soils, for instance on sandy loam. It never covers large 

 areas in pure stand, but occurs in smaller stands of from five acres 

 to several hundred acres in extent, wherever successive fires have 

 swept over the country and have so reduced the humus contents 

 of the soil that only the hardy Jack Pine can thrive. 



It is normally associated with aspen and White Birch on the 

 burned over areas, and while in the earlier stages of its develop- 

 ment it appears in pure stands, later owing to the open crown 

 conditions, birch, balsam, spruce slowly creep in. In fact the 

 presence of birch is always a sure indication of merchantable Jack 

 Pine. On the ridges and exposed situations where the soil is 

 shallow and poor (causing low water content), Black Spruce 

 enters the mixture to a large extent. 



Typical Jack Pine forest has a characteristic vegetation of its 

 own. Alnus viridis and several species of Vaccinium are more 

 generally found here than elsewhere. The dry soil and maximum 

 light conditions are inducements to the growth of these plants. 

 Other shrubs common to the forests of this region are Mountain 

 Ash, Sorbus americana; Mountain Maple, Acer spicatiim; Hazel, 

 Corylus americana. 



Under young stands of Jack Pine the ground cover is extremely 

 sparse, but it increases when the stand becomes soonewhat open 



