442 THE INVESTIGATION OP SUCCESSION. 



evidence from fire scars and from annual rings can not eliminate the possibility 

 of an error of one year in determining the date of a fire. This is because the 

 time of the growing season at which a fire occiu-s determines whether growth or 

 germination may begin that year. With scars and root suckers on trees which 

 remain alive, it is probable that growth begins the year of the fire, unless it 

 occurred in the fall or early winter. On the other hand, it is equally probable 

 that seeds remain dormant until the following year, ualess the fire occurs in 

 spring or early summer. The majority of fires occur after midsummer. If 

 the growing season is not over, scars and root suckers will show one more ring 

 than the pines and perennial herbs which appear the next year. If it is after 

 growth ceases, scars, root sprouts, pine seedlings, and perennials will agree in 

 the number of rings. In most of the biu-ns studied, scars formed the first ring 

 the year of the fire, while the pine seed did not germinate until the next spring. 

 In the bum of 1905 the aspen-root sprouts followed the fire immediately, but 

 in the bums of 1901 and 1878 aspens and pines appeared together the year 

 after the fire. Therefore the following simple rule was used to determine the 

 year of a fire: Subtract the niunber of rings of a scar, or the number of rings 

 plus one of a seedling or tree, from the year in which the count is made. Tins 

 mle assumes that the tnmk is cut sufl&ciently low to show the first year's 

 growth. With lodgepole it was necessary to cut the trunk at the surface of 

 he ground, or on slopes, below the surface." 



