22 BULLETIN 1291, U. S. DEPARTMENT OF AGRICULTURE 
A prominent even-aged understory may also occur where light 
ground fire has killed some of the parent trees, thus opening up 
the canopy, destroying practically all the advance reproduction, 
and stimulating a vigorous sprouting. (PL VI, fig. 2.) A typical 
case of this persistent unsuccessful sprouting in fully stocked 
stands was shown by a permanent sample plot in a practically 
virgin two-aged (110 and 45 years) stand of site quality 2 on the 
Manti National Forest. 
The first year of observation, 55 sprouts were noted, either of 
that or previous years. In the following year there were 2 new 
sprouts, only 33 of the former sprouts remaining. Next year the 
original 55 sprouts had been reduced to 18, although 6 new ones had 
appeared. Four years from the first observation of this sprout 
growth only 11 remained of the first lot, 1 of the second lot, 5 of 
the third, while the last two years of growth had produced addi- 
tional sprouts of which 18 still remained. 
Nisbet (9) states that in England the European aspen (Populus 
tremula), which is silvically equivalent to ours, will send up suck- 
ers from roots that remain alive in the soil long after the parent 
trees are cut out and the stumps have rotted away. From the many 
uneven-aged stands which exist in the Rocky Mountains, pointing 
to repeated regeneration without the agency of fire, it is evident that- 
sprouting can remain sufficiently active to regenerate the stand with 
normal density, even at the maximum ages reached by aspen. In 
forest management on a coppice system, however, the vigor of 
sprouting at different ages frequently assumes considerable impor- 
tance. To determine the effect of age on sprouting, acre plots 
were located in TO-, 90-, and 110-year-old aspen stands. These 
showed conclusively that reproduction after cutting is vigorous at 
any rotation likely to be used in practical management, and suffi- 
cient to restock the area fully. 
From approximately 1,000 trees on each age. plot, more than 110,- 
000 suckers were sent up by the 70-year growth, and more than 
100,000 by the middle group. The trees 110 years of age, under 
somewhat less favorable conditions, sent up niore than 50,000 suck- 
ers. In the fifth year of regeneration, these plots averaged 28,500, 
36,000, and 13,000 shoots per acre, respectively. The 70-year plot 
showed the highest growth, attaining an average of 57.5 inches; the 
middle plot averaged 41.9 inches ; and the oldest, 46.4 inches. 
Root-sucker sprouts are the form most frequently found. An 
examination of 6,724 sprouts showed that 91 per cent were root 
suckers, 8 per cent were from the root collar, and 1 per cent from 
the stump. Although there is little difference in the vigor of these 
sprouts, suckers from small roots tend to be small and weak, and as 
a class, those from the large, firm roots of the root collar seem most 
vigorous. Sprouts on the stump, although usually vigorous in de- 
velopment, are frequently torn loose by the weight of heavy settling 
snow and killed. Occasionally the weight of root suckers will twist 
a small, shallow root which has no strong lateral anchoring roots so 
that sprouts become decumbent shrubs. This is particularly true on 
steep slopes, where the weight of snow is added to that of the sprouts. 
Second only to the question of the age at which stands should be 
cut to get good sprout regeneration, is the question of the season of 
