10 
Thus it will be seen that the great wheat-growing district of the 
valley of the Red River of the North has a precipitation practically 
identical with that of western Kansas, and shghtly less than the 
Staked Plains of Texas. The southern region, however, has more 
wind, higher temperature, greatly increased evaporation, and a more 
uneven distribution of rainfall. These are adverse conditions for 
planting and growing trees, and to overcome them requires an intel- 
ligent selection of species and a system of cultivation which reduces 
the evaporation of soil moisture to a minimum.? 
EFFECT OF FORESTS ON CLIMATE. 
Many of the residents of the Plains region believe that increased 
cultivation of the soil, forest planting, and the building of reservoirs 
to catch storm waters will cause a permanent increase in the precipi- 
tation. But this theory is unsupported by proof. The records that 
have been kept long enough to warrant any general conclusions indi- 
cate simply wet and dry periods of variable length, which result in a 
fixed average precipitation. Much has been said concerning the 
effect of forests on climate, but little is known exactly, and most of 
what is known contradicts the popular beliefs. The most that can 
be said from the facts at hand is that an increase of precipitation by 
forests is not demonstrated. Even were it otherwise, planting suf- 
ficient to affect general climatic conditions would need to be on so 
large a scale as to be wholly impracticable. 
On the other hand, observations show that within the forest ex- 
tremes of both heat and cold are modified and that the evaporation 
from a water surface is less than one-half that in the open, while 
the evaporation from soil covered with forest litter 1s about one- 
eighth that from bare fields. Forests check the run-off to a great 
extent. The amount of water transpired by a forest is considerably 
less than that given off by a similar area of ordinary agricultural 
crops. 
These facts point to conclusions about which there is no doubt. 
Forests are conservers of moisture. They are the best natural means 
of saving the water that falls, and are of great utility for this rea- 
son, regardless of their problematical effect upon the amount of 
precipitation. 
The principal effect of tree planting on the climate of western 
KKansas will be to check the winds and lessen evaporation in the 1m- 
mediate vicinity of the plantation. 
“For a detailed discussion of the climate and geology, the reader is referred 
to publications of the U. S. Weather Bureau, and the paper, ‘“‘ The High Plains 
and Their Utilization,’ in Vol. IV of the Twenty-first Annual Report of the 
U. S. Geological Survey. 
[Cir. 161.] 
