23 



from open-gro"SYn trees on level land is 100 or 200 yards; on exposed 

 ridges and mountain slope?j it may be much greater, and in closed 

 stands and in narrow ravines much less. In marking timber over 

 a rugged country, a judicious regard for the exposure and prevailing 

 wind will enable a few seed trees to do the work Avhicli would other- 

 wise require a large number. 



Keproduction is, of course, apt to be most dense and even-aged 

 near the mother trees, and to decrease in regularity and abundance 

 with distance from the source of seed. With w^ell-distributed seed 

 trees a fully stocked second growth may cften be established in one 

 generation, When seed trees are scarce or poorly distributed, com- 

 plete restocking ma}^ require two or three generations and result in 

 an all-aged forest or in a mixture with other species, possibly w^orth- 

 less, which have come in in the meantime. 



The seeds will germinate and produce seedlings, especially in the 

 Eock}^ Mountain region, in mildly humous soils, but the most suc- 

 cessful reproduction is to be found on fresh mineral soil. Almost 

 any kind of mineral soil that contains a little moisture and is not 

 too cold will afford a good seed bed. In good, deep, fresh, but well- 

 drained soil the seedlings grow rapidly and are usually able to keep 

 ahead of the competing species. Light is not an essential for germi- 

 nation, but becomes a ver}^ vital factor in the growth of the seedling 

 as soon as the seed sprouts. Under moderate shade, such as that of 

 mature lodgepole and white fir, the seedlings do not receive enough 

 light for rapid growth, but are able to groAV slowly for a long time. 

 Aspen stands usually afford ideal protection and light conditions for 

 good development. 



One of the most striking silvical differences between the two forms 

 of Douglas fir is their behavior in restocking burned-over areas. In 

 the coast region dense stands of Douglas fir reproduction often cover 

 extensive areas of burned land, and these result later in the homoge- 

 neous, even-aged fir forests typical of this region. Among the Rocky 

 Mountains, on the other hand, large burns are rarely restocked with 

 pure Douglas fir reproduction, and the proportion of other species in 

 mixture is usuall}^ large. In the southern Rocky Mountains the 

 scarcity of Douglas fir in the reproduction which comes in on burns 

 is particularly striking. The principal causes for the smaller pro- 

 portion of reproduction in the Rocky Mountain region probably are 

 (1) the much less abundant seed supply, (2) the less hospitable soil 

 conditions for germination, and (3) the presence of the aggressive 

 lodgepole pine, which monopolizes burns to the exclusion of Douglas 

 fir, just as the coast form of Douglas fir excludes western hemlock, 

 giant arborvitse, and Sitka spruce. Forest fires are the chief allies 

 of lodgepole pine in its competition with Douglas fir. The thick, 



[Cir. 150] 



