FORESTS OF ROCKY MOUNTAINS FOREST RESERVE 4l 



are not aggressive enough in natural reproduction to bring about much practical 

 benefit. 



Limber pine, under favourable conditions, reaches a size of 18 inches diameter 

 and 60 feet in height, but even then is very subject to having forked tops and 

 crooked boles. Most of the limber, however, and all of the white-bark pine are 

 stunted, and on exposed sites are reduced almost to creeping shrubs. The root 

 system is rather shallow and the trees are subject to wind-fall, although mainly on 

 account of the shallow soil and exposed site which they habitually occupy. Their 

 capacity for resistance to climatic extremes is very great, as they are nearly always 

 subjected to frequent frosts, and severe storms. Their tolerance is small, and prob- 

 ably less than that of lodgepole pine, and this factor is to a considerable degree 

 responsible for their not extending their range to lower sites. The amount of cone 

 production is very small in this region and is the main reason for the small number 

 of trees of these species. As the seeds are large, they will germinate on a moderately 

 thick humus as well as on mineral soil. 



LYALI/S OR ALPINE LARCH. 



This species is confined very closely to the area next to timber-line, although 

 sporadic individuals may be found in mixed stands lower down. The largest tree 

 observed was 17 inches in diameter by 90 feet in height. Usually it is of stunted 

 growth, reaching a diameter of 7 to 8 inches and a height of 40 feet. The presence 

 even of a single tree is made conspicuous by its light-coloured foliage. It never 

 forms stands of any large extent and is worthy of only casual interest. The bark 

 is very thick, approaching, in this respect, Douglas fir. On a 17 inch tree it was 14 

 inches thick. When it develops to timber size it has a long, clear bole and short 

 crown. It is rather deeply rooted. It is the most intolerant of the conifers, which 

 makes reproduction of the scattered individuals in dense mixed stands difficult. 

 Reproduction of the trees near timber-line is also poor on account of the severity 

 of the climate and the raw humus covering the soil, which is unfavourable to the 

 germination of the small larch seeds. 



BALSAM POPLAR. 



Tins is the largest hardwood of the region. It grows only near creeks and on 

 moist flats, and is usually associated with spruce. It reaches a diameter of 30 

 inches and a height of 90 feet, but the large trees are nearly always rotten at the 

 heart, so that the tree is little thought of from the standpoint of wood production. 

 It has a clean bole, broad spreading crown, and shallow root-system. It is intolerant, 

 but less so than aspen, and on account of its rapid juvenile height-growth is able 

 to hold its place when starting with spruce. It reproduces only on moist, bare or 

 lightly-covered soil, and the only condition under which widespread reproduction 

 may take place, is after a fire on a moist spruce site when it may seed in on an 

 area previously unoccupied by it. Its frequent occurrence at the edges of streams 

 is probably due in part to the excessive washing of the soil there which exposes 

 patches of mineral soil that have the requisite amount of moisture for the develop- 

 ment of poplar seedlings. 



ASPEN. 



Unlike balsam poplar, aspen is found mainly on dry slopes, especially on the 

 edge of the prairie where repeated fires have destroyed the coniferous growth. Aspen 

 owes its occupancy of these areas to its rapid growth as a seedling, which lets it 

 compete with grass, and to its sprouting capacity, which provides for a new growth 





