Some Permanent Sample Plot Studies. 



117 



ains at an elevation of about 6,800 feet above the sea level. 

 It is about one mile from Independence Lake, on the head- 

 waters of Sage Hen Creek, a sub-tributary of the Truckee 

 River. The east slope is much steeper than the west because 

 the entire range may be considered as an immense block up- 

 heaved from its eastern margin and tilted westward. The 

 prevailing winds blow landward from the Pacific and as they 

 strike the Sierras they lose a portion of their moisture and are 

 deflected upward.. This causes a sharp diminution in rainfall 

 and snowfall between the crest of the ranges and the eastern 

 foothills. The climate is decidedly local. Observation of the 

 climate of the Sierras 1 for the past thirty years show the fol- 

 lowing results at three different stations in the Tahoe National 

 Forest : 



TABLE 1. 



Taking these stations as being typical for places having 

 the same elevation on the east slope it can be said that at an 

 elevation of 6,800 feet there is a mean annual precipitation of 

 about thirty to thirty-five inches. From seventy to ninety per 

 cent of the total precipitation falls as snow during the winter, 

 which almost completely disappears by the middle of the 

 growing season except at high altitudes where there is per- 

 petual snow. Mean monthly precipitation tables show that 

 less than five per cent of the annual precipitation occurs dur- 

 ing the growing season. A semi-arid condition is the result, 

 especially during the latter part of the season. The rate of 

 growth on the east slope of the Sierras is much less than that 

 on the west side, the timber resembling that in the arid South- 

 west more than the heavy stands of the true Pacific slope. 



The mountains in this part of the Tahoe National Forest 

 are not very rugged. The area has a gentle southeast slope, 

 rising more abruptly to the north and west as the top of the 



1 U. S. Dept. Agri., Weather Bureau, Summary of Climatological 

 Data for U. S., Section 15. 



