202 GR.\ZING ON WOODLANDS 



seldom serious to seedlings more than a year old; and even under 

 the worst conditions only about 4 per cent of the stand more 

 than a year old was killed. Very few seedlings were browsed 

 where the bed ground was used for one night only. On bed 

 grounds used for several nights in succession, on the other hand, 

 most of the leafage of the young growth was devoured, and some- 

 times even the bark was gnawed off. Where the range was 

 grazed too closely, and the total quantity of feed was too small 

 for the number of stock handled, considerably more injury both 

 from browsing and from trampling occurred than where the 

 forage was ample. 



Studies in Arizona and New Mexico. — Hill^ made a critical 

 study of the injury caused by the grazing of cattle and sheep to 

 yellow pine reproduction in Arizona and New Mexico in 19 10. 

 The best summer and autumn forage in this region is found in 

 the open stands of yellow pine, mainly at elevations above 6,cxx) 

 feet. This type constitutes about 6 per cent of the total land 

 area of these States. It is a matter of great importance that the 

 forage crop in the yellow pine type be utilized to the greatest 

 extent possible. It is equally important, however, to interfere 

 as little as possible with the yellow pine reproduction, which is 

 the most important timber of the Southwest. 



Average Injury to Reproduction. ■ — Two hundred and fifty 

 representative plots were located on cattle and sheep range, and 

 observations covering a period of three years were made. On 

 these plots 16.7 per cent of the seedlings up to sh feet in height 

 were seriously damaged each year; that is, the seedlings were 

 damaged to the extent of interfering more or less seriously with 

 their growth, or of being actually killed. In addition, 16. i per 

 cent of the entire stand was slightly damaged, and on an aver- 

 age 21 per cent of the seedlings below 6 inches in height were 

 seriously damaged, each year. The injury inflicted gradually 

 decreased with the height growth of the reproduction (Fig. 66). 



Season of Injury. — The least injury to the young timber 



1 Hill, Robert R., "Effects of Grazing upon Western Yellow Pine Reproduction 

 in the National Forests of Arizona and New Mexico." U. S. Dept. of Agr. Bui. 

 580, 191 7. 



