12 BULLETIN 580, U. S. DEPARTMENT OF AGRICULTURE. 



This suggests the conservative use of forage as a means of preventing 

 excessive injury to reproduction. 



CHAEACTEB OF FOBAGE. 



Observations were made to determine the relative amounts of 

 damage to reproduction in the principal forage types of the yellow- 

 pine belt. 



Two main classes of forage are foimd in the yellow-pine type 

 of the Southwest. These are the mountain bunchgrasses (Jluhlen- 

 hergia gracilis, Festuca arizonica. and Blepharoneuron tricholepis) 

 and blue grama grass (Boutelouu gracilis), which occurs usually on 

 the more level mesas. Both types, with variations, are prominent 

 on the Coconino Forest. The blue grama is very palatable to all 

 classes of stock. The bunchgrasses, though very nutritious, are not 

 generally preferred by any class of stock because of their accumu- 

 lation of coarse, dry foliage. 



The general conclusions regarding the relation of the intensity of 

 grazing to the amount of damage to tree reproduction are believed 

 to apply in the case of the grama range. But in the case of the 

 bunchgrass type, a serious amount of damage occurs on some por- 

 tions, even though the type is not grazed closely. A study was there- 

 fore made to determine which class of stock is responsible for such 

 damage. 



Since no bunchgrass areas are grazed exclusively by sheep, it was 

 necessary, in order to determine the damage done by this class of 

 stock, to compare the amount of damage done on bunchgrass areas 

 by both sheep and cattle with that on similar areas grazed by cattle 

 only. Accordingly 72 plots were selected in the bimchgrass type 

 grazed moderately by both classes of stock. These plots contained 

 2,372 trees subject to grazing. During 1912 and 1913 counts on these 

 plots showed an average of 128 trees injured and 320 trees severely 

 browsed, or a total of 32 per cent which, if present conditions con- 

 tinue, may be expected to become seriously injured. On a number 

 of the plots practically every tree had been killed by grazing. As 

 compared with these figures there were no injuries or severe browses 

 on the 15 plots in this type located on areas grazed closely by cattle 

 only. Of the total of 618 trees only 7 were even moderately browsed. 



The obvious conclusion that sheep are chiefly responsible for the 

 severe damage is substantiated by the fact that the serious damage 

 noted was characteristically that of sheep, that is, the needles were 

 cropped closely along the stems, instead of the end of the shoot 

 being eaten off. 



It is not assumed that the injuries on the sheep-grazed areas are 

 representative of the bunchgrass type as a whole. All of the plots 

 studied were located in the north half of the Forest, where the bunch- 



