52 THE AMES FORESTER 



tent of sunshine each day are recorded. A correlation between 

 these factors and plant growth may then be drawn. 



The San Pete valley, into which Ephraim canyon opens, is de- 

 pendent for its water supply, to grow its crops, upon the water 

 that flows down from the mountains above. A large part of 

 this moisture comes from the snow, which melts off slowly dur- 

 ing the summer and maintains a constant supply. The success 

 of the farm crops is dependent upon a plentiful supply of moisture 

 during their growing period. Wherever a forest cover is re- 

 moved from a steep slope the result will be heavy erosion and 

 frequent floods. The removal* of the forest cover allows the 

 moisture to run off rapidly and very little of it is able to find 

 its way into the soil. A vegetative cover will tend to check 

 erosion in the same manner as does the humus and litter in a 

 forest floor. Overgrazing will cause a less dense vegetative 

 ground cover. 



In order to afford a comparison between the amount of run-off 

 and erosion upon a grazed and ungrazed area, experimental 

 plots, typical of the locality, are grazed for a number of years. 

 During that time a complete record is kept of total precipita- 

 tion, rain and snow, and the amount of run-off and erosion. All 

 the precipitation that falls on these experimental areas flows 

 over a weir where it is recorded by means of a float and gage. 

 The sediment settles to the bottom of receiving tanks where it is 

 measured. At the end of a certain interval the area will be 

 closed from grazing and the records continued. A compari- 

 son of the results secured will show the value of a vegetative 

 cover in preventing erosion and heavy floods. 



About all the timber in this region important from an economic 

 standpoint is found between 5,500 to 9,000 feet in elevation. 

 Between these elevations are included three of Merriam's climatic 

 zones; namely the Upper Sonoran zone, the Transition zone 

 and the Canadian zone. 



The Upper Sonoran zone (Pinon cedar type) extends from 

 5,540 to 6,500 feet in elevation. The characteristic flora of this 

 type is pinon pine (Pinus edulis), western yellow pine (Pinus 

 ponderosa) found along the stream courses, single leaf pinon. 

 (Pinus monophylla), two junipers (Juniperus utahensis) (Juni- 

 perus scopulorum), narrow leaf cottonwood (Populus angusti- 

 folia), scrub oak, (Quercus Gambellii), sagebrush (Artemesia 

 tridentata) , rabbit brush (Chrysothamnus nauseosus). 



The Transition zone (Oak type) extends from 6,500 to 7,500 

 feet. The important species are western yellow pine, Colorado 

 blue spruce (Picea Parryana), Douglas fir (Pseudotsuga taxi- 

 folia), white fir (Abies concolor), Rocky Mountain birch (Betula 

 fontinalis), maple (Acer grandidentatum) , scrub oak, bitter brush 



