5o6 Forestry Quarterly. 



in the southeast the corn is tall but it is sown in rows and not in 

 hills. 



The data given above would seem to indicate that the main 

 factor in influencing the volume which can be produced on a 

 given area in a given time is the number of individuals. This 

 in turn seems to depend primarily upon the amount of moisture 

 available for vegetative purposes during the growing season pro- 

 vided there is not an excess. In this respect the northeast is 

 more favorably situated than the southeast because its moisture 

 is better conserved. While more precipitation falls in the south- 

 east there is much less evaporation in the northeast, transpiration 

 is less active and the moisture which falls in the winter does not 

 run off but is locked up until the growing season. 



Assuming the annual evaporation from water surfaces in the 

 tropics at 64 inches, the evaporation in the northeast would be 

 approximately one-third of this and midway between for the 

 southeast. These figures will give some notion of the difference 

 in evaporation between the northeast and southeast. It is evident, 

 therefore, that the precipitation in the southeast must be consid- 

 erably greater in order to compensate this single factor of loss 

 from evaporation, if the plants are to be supplied with the same 

 amount of moisture in the two regions. 



The factors which lead to less active transpiration in the north- 

 east are a lower temperature, less sunshine and a shorter growing 

 season. These all tend to conserve the precipitation and give a 

 continuous supply of available moisture during the period of 

 plant growth. 



There is a marked loss of precipitation during an open winter. 

 A cold winter during which nearly all the precipitation occurs 

 in the form of snow furnishes the optimum conditions for the 

 storage of water in natural ground reservoirs. The water from 

 these reservoirs becomes available for vegetative purposes during 

 the growing season instead of running off quickly soon after it 

 falls. 



Another important factor which is a direct result of the larger 

 amount of moisture available during the growing season in the 

 northeast is the greater fertility of the soils in the northern parts 

 of the country. This is due almost wholly to the higher humus 

 content which in turn must be ascribed to the greater rapidity 

 of decay in the southeast. In the northeast a large amount of 



