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lOURNAL <JF I'ORKSTKV 



are also often seen. The one shown in figure i shows clearly the fire 

 origin of the stand, as the old trees are cat-faced, butt-scarred, and oc- 

 casionally show charring. Many other two-aged stands have been in- 

 vestigated and they uniformly show the same conditions. Of course, 

 many old aspen stands exist where no fires have run for a long time, 

 which assume a broken, uneven-aged form. The most "permanent" 

 stands, namely, stands with no coniferous admixture, are very likely 

 to be even-aged, however, showing clearly their fire origin. Since fires 

 almost never run through aspen at the present time, it may appear dif- 



Kic. 2. — Heavy grass cover in aspen stand under light grazing 



ficult to believe that they were frequent not more than 50 years ago. 

 It has not been long since the aspen areas were covered with a dense 

 growth of tall grasses {Brouius and Agropyron), however, such as 

 may still be found in a few areas inaccessible to stock or where stock 

 is excluded, as in figure 2. These grasses grow the best on the deep 

 rich soils of the aspen belt and in moderate shade. Upon rocky out- 

 crops they become sparse and short, and in the deep coniferous shade, 

 as on north slopes, they are absent or fail to develop well. Such 

 grasses form a great mass of inflammable litter that would burn 

 rapidly, killing the young conifers and all or most of the easily in- 



