30 Forest Club Annual 



black, gravelly loam which had washed in from the adjoining 

 -slopes. Although of sufficient fertility, these valleys are too high 

 for successful agriculture. 



The precipitation varies greatly with general altitude and 

 exposure. Over the entire western slope the rainfall is very 

 heavy, and the records at Summit, where the Southern Pacific 

 Railway crosses the divide, may be considered representative. 

 The records, which give 46.58 inches annual precipitation at 

 this place, also show that over 40 inches of this amount is snow- 

 fall, totaling 37.1 feet in depth. At Truckee, only seven miles 

 east of the divide and about 1,400 feet lower in altitude, the 

 precipitation is but 26.98 inches, and from this place eastward 

 the precipitation rapidly diminishes until at a distance of fifteen 

 miles from the divide a desert climate is found. 



This region is well drained by the highly developed trunk- 

 streams and their tributaries. The Feather, Yuba and American 

 river systems drain the well watered western slope. The east 

 slope, since precipitation is rather low, has but a single main 

 stream, the Truckee River. From the northwest part of 

 Lake Tahoe, the river flows almost due north through the 

 Truckee Canyon to Truckee, thence pursuing a northeasterly 

 course to the desert, where it is used for irrigation and finally 

 lost. Lake Tahoe drains a large area but the river itself has 

 very few tributaries, most of these draining the region lying to 

 the northwest. Nearly every stream of either slope has its 

 origin in some lake or in the springs of some intermontane 

 meadow, the two noteworthy examples of this feature being 

 Lake Tahoe and the Sierra Valley. Besides these, the ranges 

 are dotted with numerous lakes and meadows of lesser size and 

 importance. 



A clear cut classification into forest types is difficult in this 

 region. A constant transition from one type to another, rather 

 than a constant type over a considerable area, is almost uni- 

 versally the case. Since a definite line cannot readily be drawn, 

 only those types which are easily determined are considered. 

 These are : 



1. Jeffrey Pine Type. 



2. California Red Fir Type. 



3. White Fir Type. 



4. Brush Type. 



JEFFREY PINE TYPE. 



The Jeffrey Pine Type covers most of the slopes below 

 6,500 feet. In the basin of the Truckee River, however, the 



