﻿8 BULLETIN 11, IT. S. DEPARTMENT OF AGRICULTURE. 



usually takes place in spite of any impeding forest floor. On dry 

 sites the seedling requires a good deal more light for its develop- 

 ment or existence even than on moist to. wet situations, which is 

 one of the main reasons for the lack of loblolly reproduction under 

 the shade of large trees, where the soil is not moist. For this reason 

 lumbering as a rule improves the seed-bed conditions for loblolly pine 

 and increases its reproduction, provided seed trees of the species are 

 left. The abundance of direct sunlight let in by cutting of the forest 

 also causes the impeding forest floor to decompose rapidly, so that the 

 roots of the seedlings can more readily reach the soil. Another 

 great hindrance to germination and growth of loblolly-pine seed 

 which falls after lumbering, in addition to that of a thick undecom- 

 posed forest floor, is a luxuriant growth of ground cover and under- 

 brush, including hardwood sprouts and seedlings, which in places 

 may be so dense as to preclude pine reproduction entirely. 



Seedling Development. 



The growth in height of loblolly seedlings for the first two years is 

 slow, but during this period there is vigorous root development. 

 Under average conditions seedlings in the open reach a height of from 

 2 to 6 inches the first and from 6 to 12 inches the second season. 

 After this there sets in a rapid height growth of from 1 to 3 feet a 

 year, which continues for from 30 to 50 years before beginning to 

 fall off. 



SUSCEPTIBILITY TO INJURY. 



Wind. 



Loblolly pine is usually windfirm, since it grows mainly on soils 

 conducive to the development of a deep taproot with strong laterals. 

 It is only where there is an impenetrable subsoil that it develops a 

 shallow, flat root system and is easily wind- thrown. It seldom suffers 

 much damage from windbreak, and where broken off will usually 

 show that it has first been killed or weakened by fire, insects, or 

 fungi. 



Fire. 



The thick bark of loblolly pine gives it unusually good protection 

 from damage by surface fires. Table 3 shows the average thickness of 

 bark for trees of different diameters and heights 20 to 50 years old, 

 which indicates their relative susceptibility to damage. 



