95 



Summary op Environmental Features of the Peairib and the Deciduous Torest 

 — Temperature, Humidity, and Evaporation — during the Growing Season 



Prairie 



Above the Vegetation 



In sun, maximum heated stratum. 



Cooler above and below this stratum. 

 Absolute humidity less than in or over 



forest. 



Forest 



Above crown, in sun, maximum heated 

 stratum. A thin layer. Cooler above 

 and below this stratum. 



Absolute humidity greater than .in the 

 open. 



Prairie 



Among the V-egetation 



Temperature lower and higher than in 



the forest — ^more extreme. 

 Temperature lower toward the soil, and 



warmer than in the forest. 

 Absolute humidity progressively increases 



toward the soil. 

 Eelative evaporation decreases toward the 



soil; greater than in the forest. 



Forest 



Temperature moderated — not as low or 



as high as on the prairie. 

 Temperature lower toward the soil, and 



cooler than in the open. 

 Absolute humidity progressively increases 



toward the soil. 

 Eelative evaporation decreases toward the 



soil; less than in the open. 



In the Soil 



Prairie 



Temperature averaging warmer than 

 forest, warmer near surface in sum- 

 mer, and cooler in winter. "Warmer in 

 sun and cooler at night than in forest. 



Temperature progressively more stable 

 downward. Soil moisture increases 

 downward. 



Forest 



Temperature cooler on the average and 

 in summer, and warmer in winter, near 

 the surface, than in the open. Cooler 

 in sun and warmer at night than in 

 the open. 



Temperature progressively more stable 

 downward. Soil moisture, below the 

 surface layer, increases downward. 



The conditions on the prairie and in the forest may be graphically 

 shown as in the following diagrams, Figure 14 showing the tempera- 

 ture relations, and Figure 15 showing the relative evaporating power 

 of the. air. 



