110 SILVICULTURE METHODS OF NATURAL REPRODUCTION 



necessary to consider is the great risk of windfall in any approach 

 to a selection system of cutting. Experience has shown that once the 

 canopy is considerably broken the danger of windfall is great. The 

 soil is deep and moist, and trees upturn easily. 



Until the last few years the prevailing system has been to cut all 

 merchantable material, leaving a few old defective Douglas firs as 

 seed trees, and then broadcast burn the area. One of the problems 

 of the system has been to burn the area successfully and yet keep the 

 fire under control. The operable portion of the stand does not usually 

 extend more than half way up the side slopes, and it is a very hazard- 

 ous operation to dispose of the slash successfully on the cut-over 

 bottoms and slopes. The upper slope timber can be operated at some 

 future date and is also a big factor in supplying seed for reforesting 

 the cut-over area. A recent departure from the earlier system has 

 been to break up the slash into blocks by leaving wide belts of green 

 timber across the main drainages and so keep the slash fire from get- 

 ting too much of a head; these strips also act as an additional source 

 of seed. If the slash can be properly disposed of and subsequent 

 fires do not occur, satisfactory reproduction is obtained. 



A still more recent system of operation proposed for this type is 

 selective logging. There are, no doubt, certain types of management 

 which will admirably fit into such a scheme, as for instance where 

 pulpwood is the desired product. There are also certain types of 

 Douglas fir stands operated for saw timber to which it can be applied. 

 The scheme is to make a large number of light cuts and so not dis- 

 turb the canopy too abruptly. Whether it can be applied generally 

 to Douglas fir stands is yet to be determined, but it is questionable 

 if it can be without depreciating the quality of the forest. The advent 

 of the tractor and truck has made the application of such a system 

 more feasible, with its proposed frequent returns to the same area. 



Engelmann Spruce Type. Although there are strong indications 

 that Engelmann spruce may become of outstanding importance in 

 the future for pulpwood, to date it has largely been the source of 

 supply for portable sawmill operations cutting to meet local demands. 

 The type usually contains 70 to 80% of Engelmann spruce, the balance 

 of the stand being made up of alpine fir or cork bark fir or both. 

 The type often merges with the lodgepole pine, of which it may con- 

 tain considerable quantities along its margins. The character of the 

 stand varies with site and aspect. In the middle and southern por- 

 tions of its occurrence it can usually be successfully operated on a 

 selection system of cutting, quite a range of age classes being present 

 in the stand. From 30 to 50% of the volume is reserved. The slash 



