208 FORESTS OF NORTH CAROLINA. 



on the best soils attain a height of 90 feet, and on the poorer a 



height not exceeding 70 feet ; and many of the soils, on account 



of their poorness, are much more suited for a growth of pine than 



of more exacting broad-leaf trees. The white and chestnut oaks 



grown on the crests of the hills will make trees large enough for 



railway ties and tan-bark but scarcely larger ; on the moister 



upper slopes the black and white oaks attain sizes which make 



them suitable for milling-timber; on the cooler and moister lower 



slopes the white oak, northern red oak and yellow poplar attain 



moderately large dimensions and form good timber. The Spanish 



oak generally reaches only a small size and is often defective; 



and the same is true of the scarlet oak. Sourwood large enough 



to be of value commercially is usually defective. The white pine 



will certainly do fairly well in a few localities along the western 



limits of the division, and though at this low elevation it fails to 



clear the stocks, at least in the forest specimens, as it does at a 



higher elevation, it is worthy of being protected on account of its 



rapid growth. Thickets of pure growth will probably form 



cleaner shafts than where single specimens appear in mixed woods. 



The broad-leaf trees require such care as was 'indicated for 



those of the compact red loams (p. 198). The white pine can be 



treated in the same way as will be given for the groves of that 



tree occurring in the high mountains (p. 218). 



FORESTS OF THE MOUNTAIN REGION. 



The differences in the character of the forests of the mountain 

 region are not determined so largely either by the kind of soil or 

 by the amount of moisture contained in it as are those of the 

 Piedmont plateau and coastal region. Within short distances 

 among the mountains there are wide variations in elevation. 

 With increased elevation a rapid lowering of the average annual 

 temperature takes place, and a proportional shortening in the 

 growing-season ; increase in the rain-fall and relative humidity, 

 and a decrease in evaporation both directly from the soil and 

 through transpiration. The effect of these factors in limiting the 

 distribution of certain species is more evident than that of the 

 soils ; though, between certain limits of elevation, changes in the 



