94 FOREST commissioner's REPORT. 



reproduction and in many cases prevents it altogether, since 

 the root system of the young seedlings is decidedly shallow and 

 weak and can not force its way through any thick covering into 

 the mineral soil, so that the tiny rootlet dries up and dies. The 

 shallowness of the root system indicates that the soil must be 

 fairly moist to afiford a good germinating bed. Bare mineral 

 soil, capable of holding at least a moderate amount of water, 

 usually characterizes burned-over areas, and this, with the ab- 

 sence of overhead shade, explains the al)undant and satisfactory 

 reproduction on old burns. 



By Sprouts. 



Up to a certain age paper birch reproduces itself as readily 

 by sprouts as by seed. The stumps send up from the root 

 collar vigorous shoots, which may a rapid growth during their 

 first few years. Sample counts of i -year-old sprouts from 

 stumps of 40 to 50 year old trees in New Hampshire showed 

 an average of 46 sprouts per stump, with an average height of 

 slightly over 2 feet. Alost of these are soon killed off in the 

 struggle for existence, and usually only from 2 to 4 survive to 

 reach maturity. The old stump decays in a few years, but the 

 sprout origin of the trees may be recognized from the way in 

 which they stand in small clumps. Mature or nearly mature 

 birches do not sprout so freely nor so vigorously as when 

 younger, and in old age probably lose their sprouting capacity 

 altogether. This loss in vigor ordinarily begins at from fifty 

 to sixty years. Consequently, if satisfactory sprout reproduc- 

 tion is desired, the trees should be cut not later than this. The 

 same stump will not produce sprouts for any great length of 

 time, since it eventually becomes exhausted. 



As a rule birch stands are composed either entirely of seed- 

 lings or entirely of .sprouts. Occasionally, however, the two 

 forms are found together in practically even-aged stands. In 

 such cases it is probable that the stand was originally composed 

 of seedlings, but early in life was burned over. Some of the 

 trees may have escaped destruction, while those that were 

 burned sent up one or more sprouts. These seedling sprouts, 

 except for the fact that they often occur in groups, have all 

 the characteristics of seedlings and may lie so treated. 



