UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 580 



Contribution from the Forest Service 

 HENRY S. GRAVES, Forester 



Washington, D. C. PROFESSIONAL PAPER December 21, 1917 



EFFECTS OF GRAZING UPON WESTERN YELLOW-PINE 

 REPRODUCTION IN THE NATIONAL FORESTS OF ARI- 

 ZONA AND NEW MEXICO. 



By ROBERT R. HILL, Grazing Examiner. 



CONTENTS. 



Page. 

 Importance of protecting pine reproduction . . 1 



Scope and method of study 2 



Extent of damage to western yellow-pine 



reproducf'on from grazing 4 



Factors influencing damage 9 



Page. 



Effects of grazing injuries upon western yel- 

 low-pine reproduction 16 



Summary 23 



Application of results to range management 

 in the Southwest 25 



IMPORTANCE OF PROTECTING PINE REPRODUCTION. 



The best summer forage in Arizona and Xew Mexico is found 

 among the open stands of yellow pine, mainly at elevations above 

 6,000 feet, and covering more than 8,800,000 acres, or 6 per cent of 

 the total area of the two States. (See map, fig. 1.) Every economic 

 consideration requires that this forage, one of the region's most 

 important resources, should be converted into meat. At the same 

 time, it is important that this should be done with the least possible 

 injury to the yellow pine, which is by far the most important timber 

 of the Southwest. In many places the tree is not reproducing satis- 

 factorily, hence it is very necessary to protect the young growth 

 (which in any event has to contend with severe winters, dry springs, 

 and parasites and insects) from damage by stock. 



The problem is especially important in the Xational Forests, 

 which are created primarily to conserve the timber supply and to 

 protect the vegetative cover on the watersheds. *In the Forests is 

 the bulk of the yellow pine in Arizona and Xew Mexico, and on the 

 Xational Forest range are grazed approximately 30 per cent of all 

 the range stock in the two States. Stock use the Forest range mainly 

 during the summer, from April to Xovember. 



This bulletin presents the results of a study to determine the 

 character and extent of the damage to young growth of western 

 yellow pine in the Southwest from the grazing of live stock, and to 

 find out the best means of keeping such damage at a minimum while 

 permitting proper utilization of the range. 



4205 17 Bull. 580 1 



