392 Tlie Xew York State College of Forestry 



means the destruction of large areas of pi-imeval forests. Nature 

 sets about it promptly to heal the scars thus resulting, and if 

 left to her own de\dces would ultimately again produce a climax 

 type. But man impedes her at every turn either by preventing 

 reforestation or, where forestry is practiced, by an arbitrary 

 selection of the future forest citizens, that is, the trees. Nature's 

 methods in the production of a climax forest when judged by 

 financial standards, are neither economical or necessarily wise. 



FACTORS GOVEBNING DISTRIBUTION OF FORESTS 



In general trees are impartial to soil unless the soil characters 

 are of an extreme type. Relatively few have arbitrary soil re- 

 quirements and their absence from given localities is not to be 

 construed as resulting from the type of terrain but rather from, 

 competition due to other factors. Those trees which are most 

 happily adjusted to their euAdronments are bound to survive in 

 the warfare of mutual adjustment owing to the advantage accru- 

 ing from better growth conditions. It is only near the limits of 

 its range that a species may become exacting as to soil, for here 

 the balance which means the life or death of the organism is more 

 delicately adjusted and an unfavorable soil may be sufficient to 

 cause the elimination of a species from a given terrain. 



Temperature is the potent factor in controlling tree distribu- 

 tion and results in forest belts which are determined, at least so 

 far as their general contours are concerned, by latitude. No part 

 of the earth is too hot to support forests, other factors being favor- 

 able, while the northern tree limit is believed to be fixed by a 

 normal duration of temperature of 50° Fahr. for at least a month 

 each year.* But the contour lines of forest belts are not of neces- 

 sity east and west contours. Temperature fluctuates with altitude 

 and with proximity to large bodies of water, that is, to oceans and 

 iarge lakes. Mean annual temperature decreases with altitude. 

 Large water areas tend to modify a climate owing to the fact that 

 water cools and warms less rapidly than terrain. Added to the 

 last is the effect of warm or cold ocean currents which sweep 

 along the continental coasts. Doubtless supermaximum tempera- 

 ture fluctuations of brief duration and infrequent interval are 

 jvotent factors in determining the limitations of species. 



While temperature results in broad belts of vegetation of dif- 

 ferent types available moisture (precipitation, humidity, water 



*R. DeC._Ward. Climate, 1908, page 28. 



