904 JOURNAL OF FORESTRY 



In what formerly was a hardwood stand, the ground is now covered 

 with raspberry and maple brush, but interspersed through this is found 

 some fir that is overtopping the brush ; also, throughout the rasp- 

 berry growth, young fir is coming through with 6-inch leaders for this 

 year's growth. These undoubtedly will overtop the brush. The repro- 

 duction in this hardwood type is not as dense as desirable, but is much 

 denser than where the hardwoods are left standing. 



On the areas where the spruce and hardwoods were mixed, contain- 

 ing 30 per cent or more softwoods, the reproduction is good and a 

 fair percentage of the new growth will be softwood. Perhaps it will 

 not be as rich in softwood as was the original stand, but the resulting 

 forest will be hardwoods, fir, and spruce and not almost pure hard- 

 woods, as in regions where the spruce and fir only were removed. 



Cordzvood Cuttings — Gates Hill, Berlin, N. H. 



About seven years ago the cordwood and softwood on CateS Hill 

 was cut at the same time. Result : Scattered through the open spaces, 

 where the light is good, young fir 3 to 6 feet in height can be seen 

 pushing through the brush. As in the case of the other lands described, 

 where the hardwoods have been removed, the reproduction of fir, while 

 not completely taking over the land, is coming in very well, and the 

 future growth will be a mixed forest. 



FACTORS INLUFNCING TREE GROWTH 



Why the spruce and fir reproduction comes in and thrives on hard- 

 wood lands that have been logged over for both softwoods and hard- 

 woods better than on lands that have been logged only for softwood 

 depends on several factors, not the least being the changed light condi- 

 tions. Zon and Graves, in Bulletin 92, Forest Service, make some perti- 

 nent statements under the title "Factors Influencing Tree Growth." 



''Tolerance varies not only with species, but even within the same species, 

 according to conditions under which the tree is growing. These variations are 

 due largely to changes in the structure of the leaves, brought about by changes 

 in transpiration. Among the important factors influencing transpiration, and 

 therefore tolerance, are climate, altitude, moisture, and nourishment in the soil, 

 age of tree, and vigor and origin of the individual. 



"Plants need less light the higher the temperature and more light the lower 

 the temperature. Consequently, the higher the temperature of a given locality 

 the more shade a tree can stand." 



The above applies to mature trees in different regions, but it can be 

 applied to reproduction locally as well. The shading of the ground by 



