Pinus monophylla I p. edulis 



^ 2 4 6 8 10 



SUMMER (JULY-SEPT. ), PRECIPITATION (CM) 



Figure 8. — Relat'lonship of velati-ve Qunipev tree cover to amount of summer preciyl- 

 tation^ derived from Visher (1966). 



CONCLUSIONS 



The map of the pinyon- juniper vegetation type in the Great Basin provided in this 

 study should more accurately depict the location of these woodlands than previously 

 available maps. This increased accuracy is due to this map's small scale and objec- 

 tively derived boundaries based on LANDSAT-1 imagery. The map shows that pinyon- 

 juniper woodlands occupy 17.6 million acres (7.1 million ha) in the study area, about 

 two-thirds of which occur in Nevada. 



A floristic list of 240 positively identified species was obtained from sampling 

 the woodland vegetation on 482 plots on 66 mountain ranges. This list could help 

 other workers begin vegetation studies in Great Basin pinyon- juniper woodlands. 



The proportion of pinyon and the total vegetal cover were found to increase more 

 with elevation than with change in longitude or latitude. Dominance by juniper is 

 associated with lower elevations and with increasing proportions of precipitation 

 coming during the summer. The replacement of single-needle pinyon by double-needle 

 pinyon at higher elevations is also associated with the southeasterly trend toward 

 more summer precipitation. Higher average total vegetal cover is associated with 

 higher altitudes and more northerly latitudes. 



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