14 BULLETIN 244, U. S. DEPARTMENT OF AGRICULTURE. 



tween the midwinter (January) mean of 26° in northern New Jersey 

 and the midsummer (July) mean of 84° in southeast Texas. Within 

 its geographical range occurs a total temperature range of 134° F., 

 from a minimum of —22° in New Jersey to a maximum of 112° in 

 northern Louisiana. The length of the growing season is indicated 

 approximately by the period during which killing frosts do not occur. 

 In New Jersey this period averages only five months, from May 1 to 

 October 1 ; in northern Louisiana it is a little less than eight months, 

 from March 16 to November 8. There is a variation in snowfall from 

 an average of 40 inches at the north to none whatever over the south- 

 ern range of the species. 



In the northeast, the 45-inch line of annual precipitation closely 

 parallels the northern limit of shortleaf's range, and the line marking 

 an average of 40 inches of precipitation about coincides with its 

 southwestern boundary in Kansas, Oklahoma, and Texas. Shortleaf 

 advances farther into this region of low relative humidity than any 

 other pine, and in its advance into Texas falls behind only cypress 

 and eastern red cedar. The belt of maximum development of 

 shortleaf — northern Louisiana and Arkansas and the southern 

 Piedmont — coincides strikingly with the rainfall zone of 45 to 55 

 inches, or an average of 50 inches. 



In general, shortleaf pine reaches its best development under (1) 

 a mean annual temperature of about 55° F., from a 35° average for 

 the coldest months of the year to a 75° average for the warmest; (2) 

 an annual precipitation of 45 to 55 inches, distributed through at 

 least nine months of the year; and (3) in deep, porous or well-drained, 

 clayey, or gravelly loam. In less favorable conditions, the species 

 shows considerable vigor of growth over regions of wide variation in 

 temperature, atmospheric moisture, soil composition, and, excepting 

 in the heavier, poorly drained soils, soil moisture. In demands upon 

 both moisture and heat, shortleaf is clearly the least exacting of the 

 important southern pines, which may be put in the following order: 

 Slash, longleaf, loblolly, shortleaf. 



LIGHT REQUIREMENTS. 



Shortleaf pine requires an abundance of direct overhead light fof 

 development, yet at the same time it possesses to a remarkable 

 degree both the power to withstand suppression for many years and 

 the capacity of rapid recovery following suppression. The intimate 

 relation between light supply and growth in early life is graphically 

 shown in figure 5, drawn to scale from an 11-year-old crowded short- 

 leaf-pine stand. The adjacent stands cut off all side light and 

 slightly reduce the overhead supply. The height growth increases 

 at an accelerated rate as the distance from the adjacent stand 

 increases, reaching its normal level of 22 feet at a distance approxi- 



