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



young trees made bushy by injuries contribute to the more rapid 

 growth of the main bole. 



PERMANENT EFFECTS. 



It is important to know what becomes of the seriously injured sap- 

 lings. If they recover and become normal trees, then the ultimate 

 effects of such damage are unimportant. But if a considerable por- 

 tion of them die. and if others remain dwarfs or develop into -de- 

 formed trees, then the need for applying protective measures is ap- 

 parent. Owing to the slow growth of yellow pine, effects of grazing 

 injuries upon the later development of reproduction requires a good 

 many years to determine. Observations so far made, however, indi- 

 cate clearly the effects that may be expected where injured reproduc- 

 tion is protected and where it remains subjected to continued severe 

 grazing. 



Observations of a great many trees formerly injured but later pro- 

 tected from grazing indicate conclusively that young injured pines 

 have remarkable recuperative powers. Even though they have been 

 eaten off repeatedly for as long as 10 years, a few years' protection 

 will enable them to recover. Unless the injuries are particularly 

 severe, the subsequent growth is as rapid as in the case of younger 

 uninjured trees of the same height. Ordinarily, trees subjected to 

 repeated grazing develop many laterals capable of supporting vigor- 

 ous height growth at the first opportunity. TThen protection is 

 afforded to such trees, the ultimate effects of the injuries appear to be 

 simply the retardation of growth equivalent to the period of serious 

 injury plus 5 to 10 years required for the plant to regain its normal 

 vitality and to develop a well-defined leader. If. however, the young 

 trees are defoliated, as is characteristic of severe sheep injuries, recu- 

 peration is necessarily very slow. 



The ability of injured trees to recuperate if protected is well illus- 

 trated at the Fort Valley E anger Station pasture. Previous to three 

 years before the observations were made, the pasture had been greatly 

 overstocked with cattle during certain portions of the year, but since 

 that time it has been grazed only moderately. Reproduction is 

 abundant, but during the period of overgrazing the saplings were 

 severely damaged. Practically no damage was done in the three 

 years preceding the observations. A comparison of the last three 

 years' growth of saplings in the pasture previously injured, but 

 showing no damage during this period, and of the growth during 

 the same period of injured saplings just outside the pasture where 

 severe grazing conditions prevailed, gave the results presented in 

 Table IX. Twenty trees in each of four height classes were ex- 

 amined. 



