RKVIEWS 565 



tion of timber that there is grave danger in overgrazing much of our 

 absolute forest land, which will lead to a gradual destruction of the 

 timber now standing and more or less complete elimination of repro- 

 duction following fires and lumbering. 



One of the most important problems dealing with large areas of our 

 absolute forest land is how intensively can it be grazed without serious 

 injury to it as a forest? The many researches conducted by the United 

 States Forest Service and by other agencies in recent years have thrown 

 much light on our grazing problems in their relation to natural repro- 

 duction. Sampson's recent bulletin, dealing entirely with the effect of 

 grazing upon aspen reproduction, clearly shows that great damage to 

 the natural regeneration of this species results from both sheep and 

 cattle grazing, although the regeneration usually appears in dense stands 

 and is almost entirely from root suckers. 



There is little or no aspen reproduction until the stands are severely 

 opened up by lumbering or fire. Fully stocked reproduction is best 

 after clear-cutting. The author's studies appear to show that even 

 where sheep in moderate numbers are permitted to graze on such clear- 

 cut areas the aspen reproduction is often destroyed, almost to the last 

 sprout. The damage done by sheep is much greater than by cattle, and 

 the damage by both depends upon the duration and intensity of the 

 grazing. Sampson's studies extended over a period of five years and 

 were conducted on the Manti National Forest, in central Utah, a region 

 in which pure stands of aspen are of high value and cover considerable 

 areas. Sample plots were established on clear-cut areas, which were 

 studied each year and records made of the reproduction. Some of the 

 plots were lightly grazed, others moderately grazed, and still others 

 heavily grazed. The amount of damage on all plots varied somewhat 

 with the season. The mortality of one-year-old sprouts, even under 

 light grazing, is so high it is reasonably sure to have a determined effect 

 on the stand of timber. 



If the sprouts that appear the first year after clear-cutting are de- 

 stroyed by grazing the sprouts, the succeeding year, are much less vig- 

 orous. Those produced the third season and later are distinctly lacking 

 in vigor and are of little value for regeneration. Aspen sprouts grow 

 rapidly, and at the end of three years they attain a height which ex- 

 empts them from destructive grazing by sheep, and after four or five 

 years are damaged little by cattle. The problem, therefore, seems to 

 be the protection of reproduction for a period of three or five years 

 after clear-cutting, or at least to protect it adequately to assure repro- 

 duction in fully stocked stands. Although the writer believes that very 



