116 THE PRINCIPLES OF HANDLING WOODLANDS 



cutting, with oak, maple, and other hardwoods. If the 

 original stand was a mixture of white pine and hard- 

 woods, many of the latter send up vigorous sprouts, 

 which practically maintain the proportion of hardwoods 

 in the future stand, and it becomes difficult to increase 

 the proportion of pine. In pure white-pine stands there 

 is also a tendency toward a replacement by hardwoods 

 because of the great abundance of seed on the ground, 

 and of young seedlings already started under the pines. 

 This tendency can partly be overcome by burning over 

 the ground. Where, however, the hardwoods are estab- 

 lished as the principal growth, pine creeps in underneath 

 them in a few years, provided there are trees to furnish 

 the seed. 



The system of scattered seed-trees is applicable also 

 to the second-growth stands of loblolly and other yel- 

 low pines in the South; in certain instances to second- 

 growth Douglas fir stands on the Pacific Coast; and, 

 where the conditions of moisture are favorable, to cer- 

 tain stands of pure Western yellow pine. 



It is a system more commonly applicable in second 

 growth than in a virgin forest, because in the former the 

 investment in securing reproduction may be brought 

 within a reasonable amount, while in the virgin forest it 

 is difficult to find seed-trees of the right character which 

 do not represent so great an investment as to make the 

 system impracticable. 



Reserving Groups of Seed-Trees. — In exposed sites it 

 is often not practicable to leave isolated seed-trees, because 



