31 



in height at the expense of diameter. Diameter growth is greater in 

 more open stands, owing to lessened competition for soil moisture as 

 well as light. Xo experiments to determine the effect of thinnings on 

 growth rate have been made, but it is probable that judicious thin- 

 ninirs made from time to time in crowded stands would result in in- 

 creased growth, both in diameter and in height. 



MANAGEMENT. 



No hard and fast rules can be formulated for the management of 

 Douglas fir in anv of its silvical remons. A few broad rules can, 



C5 .^ O 7 



however, be outlined for each of these extended regions, which, 

 though lacking in detail, will suit the general conditions prevailing 

 over the whole region, and can, by modification, be used as a basis 

 for more detailed silviculture on limited areas. 



The universal aim of silviculture is to get the most and the best 

 timber per unit area in the shortest possible time. On the humid 

 mountain slopes of Washington and Oregon no tree is better fitted 

 to achieve this ideal than Douglas fir. Its rapid growth, the density 

 of its stands, and the high qualitj^ of its lumber give it preference in 

 suitable situations over all other species. Besides this it reproduces 

 itself abundant^, and a second crop is relatively eas}^ to secure. In 

 the southern parts of its range, however, other trees often excel it in 

 value, and in such cases the object of management must be to reduce 

 the proportion of fir and encourage a predominance of the more 

 valuable species. 



The successful silvicultural management of a virgin forest should 

 result in a complete and even restocking of cut-over areas with young 

 growth of the best species which the situation is capable of producing. 

 In practice this result is sought by rules planned to secure a suitable 

 seed bed for the desired species and an abundant supply of the riglit 

 kind of seed. Since Douglas fir needs mineral soil to germinate and 

 requires plenty of light afterwards, the first object is achieved for 

 this tree by clean cutting or by thinning heavily enough to admit an 

 abundance of light, and hj burning away the humous layer which 

 covers the mineral soil. To insure a sufficient seed supply, enough 

 trees must be left on each acre of ground to scatter seed evenly over 

 all parts of it. The manner of thinning, disposal of brush, and the 

 number and distribution of seed trees are details which vary with the 

 different silvical regions in the range of Douglas fir and with local 

 conditions in each. 



KORTH COAST REGION. 



In the forests of western Washington and Oregon, where Douglas 

 fir is by far the most abundant tree and often forms vast, nearlj^ pure, 

 even-aged stands, its management is comparatively simple. The chief 



[Cir. 150] 



