HOW FORESTS FEED CLOUDS 213 



the rainfall of the State of Missouri and the discharge 

 of the Mississippi River at St. Louis, Mo., and Car- 

 rollton, La.* 



FOREST THE GREATEST EVAPORATOR OF WATER. 

 What are the sources from which the evaporation on 

 land is the greatest? The evaporation from a moist 

 bare soil is on the whole greater than from a water sur- 

 face, especially during the warm season of the year when 

 the surface of the soil is heated. A soil with a living 

 vegetative cover loses moisture, both through direct 

 evaporation and through absorption by its vegetation, 

 much faster than bare, moist soil and still more than 

 free water surface. The more developed the vegetative 

 cover, the faster is moisture extracted from the soil and 

 given off into the air. The forest in this respect is the 

 greatest desiccator of water in the ground. Numerous 

 experiments in Europe in the level and slightly hilly 

 forest regions have shown that the forest, on account 

 of its excessive transpiration, consumes more moisture, 

 all other conditions being equal, than a similar area 

 bare of vegetation or covered with some herbaceous 

 vegetation. The amount of water consumed by forests 

 is nearly equal to the total annual precipitation. In 

 cold and humid regions it is somewhat below this 

 amount and in warm and dry regions it is above it. 

 The ground water table under forests was found in- 

 variably to be lower than in the adjoining open fields. 



*Francis E. Nipher: "Report on Missouri Rainfall, with Averages for 

 Ten Years ending December, 1887." Transactions of the Academy of Science 

 of St. Louis, Vol. V, p. 383. Geo. A. Lindsay: "The Annual Rainfall and 

 Temperature of the United States." Transactions of the Academy of Scienct 

 oj St. Louis, June, 1912. 



