76 



Indiana Their results are combined and summarized m Figure 5. 

 This diagram shows the relative evaporation near the surface of the 

 soil, the standard of comparison being the evaporation ma maple- 

 beech climax forest, where evaporation is relatively low. Ihe aver- 

 age daily amount, in c.c, shows that there is a progressive increase in 

 evaporation as follows: 8.1 c.c. in a maple-beech forest, 9-35 c.c. in 

 the oak-hickory upland forest, 10.3 c.c. in an oak dune forest, 11. 3 c x^ 

 in a pine dune forest, and an increase to 21.1 c.c, on the cottonwood 

 dunes This expressed on a percentage basis is, m inverse order, re- 

 spectively 260 per cent, in the cottonwoods, 140 per cent, m the pmes, 

 127 per cent, in the oak dunes, 115 per cent, m the oak-hickory for- 

 est, and 100 per cent, in the maple-beech forest. 



Intensity of evaporation 



Sta. A. Cottonwood dunes 



Sta. B. Pine dune 



Sta. C. Oak dune 



Sta. D. Oak-hickory 



Sta. E. Maple-beach forest 



Fig 5 Diao-ram showing the relative rate of evaporation in different kinds of 

 foreslxn nortS Illinois and Indiana. [Data from Fuller ('11) and McINutt and 

 Fuller ('12).] 



Shimek ('10 '11) has made valuable observations on the relative 

 rate of evaporation on the prairie of western Iowa. He used the open- 

 pan method in four representative habitats. His results show very 

 clearly that the rate of evaporation is much greater m exposed places 

 than where there is shelter from the sun and wind. I have put his 

 data in a form comparable with those which have just been discussed 

 r Fio- 6) and have made the cleared field area. Station 4, the^ stanclard 

 of c'omp^rison, as it more nearly approaches the standard used at 

 Charles on and by others. Station 3 is on a high bluff, exposed to the 



Intensity of evaporation 



Sta. 3. Open, much exposed prairie 

 vegetation 



Sta. 1. Open, exposed slope of bluff, 

 prairie 



Sta. 4. Open, cleared area, partly pro- 

 tected 



Sta. 2. Bur-oak grove, protected 



2'/. 



5tandaf*d 



Fig. 6. Diagram of relative evaporation in prairie and forest habitats, in western 

 Iowa. (Data from Shimek.) 



