18 DIMINISHED FLOW OF BOCK BIVEB. 



leaves and branchlets form u perpetual reservoir for the storage of a 



large amount of moisture, which is allowed to drain off gradually 

 instead of flowing rapidly into the valleys. Not only does moisture 

 evaporate slowly from the matted leaves lying closely packed in hori- 

 zontal layer.-, but the leave- also clothe and protect the underlying- 

 soil, which is crumbly and porous and is thus capable of holding a 

 large supply of water. Part of this water is gradually given off' to 

 the lower layers of the soil; another part is taken up by the trees to 

 serve in the processes of growth, some of it being ultimately given 

 back to the air by transpiration through the leaves: the remaining 

 part of the original supply is evaporated from the soil and mold. 

 Water distribution, as well as evaporation, has therefore been affected 

 by the reduction of forest areas in southeastern Wisconsin. 



EFFECT- OF CHANGE.- EN THE CHARACTER OF THE FOREST. 



The change- that have taken place in the character and composition 

 of the forests that remain standing at the present day have likewise 

 had an effect upon the water now. Nearly all of the present wood- 

 land- have been culled over and are often entirely of second growth. 

 so that their crown cover is probably more open now than it was under 

 primitive forest condition^: while the mold, which ha- been exposed 

 to wind. rain, and sun. i- -cant and thin a- compared with the former 

 rich, dee}) -nil cover. In the more open -pace.- of the forest grass 

 and weeds have replaced the protective mantle of shrubbery and sap- 

 ling-, and the soil beneath ha- lost its porous, crumbly consistency. 

 and has become more compact. 



A large proportion of the -mailer woodlots are kept in this open 

 condition as a result of pasturing. It is difficult for the rain to pene- 

 trate the dense, intricate root system of this new surface growth and 

 to enter the compacted -oil. Much of the rain is caught in the grass 

 and herbage and afterward- evaporates, while the vegetation absorbs 

 with avidity what moisture it finds in the upper layers of the soil. 

 The forest suffer- under these adverse conditions: the trees begin to 

 dry at the top and prematurely die. (PI. V, rig-. 1 and 2. | 



In a rugged, mountainous region it may well be that a grass surface 

 cover is preferable to no cover at all. because it helps to avert washes 

 and floods, bat it is nevertheless an established fact that the soil 

 beneath such a cover below the uppermost layers is usually a very 

 dry one. A- a great deal of the cultivated area of the region under 

 discussion is pasture land, the effect- ascribed to wood pastures can 



«E. Raman ti, in Forstliehe Bodenkunde and Standortslehre. an authority on this 

 subject. says, p. 356: '-The matted root system of these grasses dries the soil to a 

 considerable depth and interferes with the entrance of the rain water. It has been 

 found that even after prolonged rains the underlying soil often remains absolutely 

 dry." 



