354 FOREST INDICATORS. 



dominant with the greatest requirements is the subclimax. This is in accord 

 with the occurrence of lodgepole as the characteristic burn community in the 

 northern Rocky Mountains, aspen in the southern, and scrub in the Southwest 

 and in California. As burn indicators, they have several features in common, 

 in spite of their differences in life-form. They not only indicate the possibil- 

 ity of reestablishing the climax by preventing fire in some cases or by planting 

 in others where the original climax dominants have disappeared. But they 

 also make it clear that artificial means and fire especially must be resorted 

 to in areas where it is desirable to maintain the subclimax as a relatively 

 permanent type (plate 87). 



The importance of burn subclimaxes has been emphasized by Clements 

 (1910: 56) in the case of the lodgepole pine: 



"The lodgepole forest is the key to the silvicultural treatment of the forests 

 of the eastern Rocky Mountains, especially in Colorado and Wyoming. Its 

 position in a zone between Douglas fir and yellow pine below, and Engelmann 

 spruce and alpine fir above gives the forester a peculiar advantage. Its 

 enormous seed-production, the power of the seeds to remain viable in the 

 cones for years, its preference for soils of moderate water-content, the de- 

 pendence of reproduction upon sunlight, and its rapid growth are all points 

 of the greatest value in enabling the forester to accomplish his results. And 

 it is by means of fire properly developed into a silvicultural method that the 

 forester will be able to extend or restrict lodgepole reproduction and lodgepole 

 forests at will. " 



The relation of aspen to lodgepole in burn subseres and its role as a tem- 

 porary type have been dealt with in the same study (20, 47). The significance 

 of aspen as a burn subclimax and its importance as a temporary type have 

 been discussed by Pearson (1914: 249), Sampson (1916:86), and Baker (1918: 

 294, 389). In the Northwest where Pseudotsuga forms a remarkably per- 

 manent subclimax in burns of enormous extent, Hofmann (1917:23) has 

 reached the following conclusions: 



"The study of burns and cut-over areas in the Douglas-fir region of the 

 Pacific Northwest has brought out the following facts : The distance to which 

 seed trees are capable of restocking the ground is limited to from 150 to 300 

 feet. They can not, therefore, account for the restocking of the large burned 

 areas. The irregular dense stands of young growth are due to seed stored in 

 the forest floor or in cones. This seed retains its viability through the fire 

 and is responsible for the dense reproduction that springs up after the first 

 fire. The even-aged stands of reproduction immediately following a fire, 

 regardless of location of remaining seed-trees, the irregular alternation _ of 

 dense stands of reproduction with grass areas, and the failure of reproduction 

 on areas burned over by a second fire before the stand reaches seeding age, or 

 by consuming all of the duff and precluding any possibility of seed remaining 

 after the fire, all point to the seed stored in the duff as the principal source of 

 seed responsible for the restocking. 



"Since the seed must be produced by the stand before it is destroyed, the 

 age at which the different species begin to produce seed is of the utmost im- 

 portance. It varies greatly, and this variation alone is often the controlling 

 factor in determining the composition of the second growth. For example, 

 when western white pine, Douglas fir, and knobcone pine (Pinus attenuata) 

 appear in a mixed stand which is destroyed by fire, all of these species may 

 again appear in the next stand; but if this second growth is destroyed by fire 



