SOUTHERN CASCADES (M26ID) 



AND KLAMATH MOUNTAINS 



(M26IA) 



Ecology 



Southwestern Oregon is one of the most di- 

 verse regions in the United States. Geology and 

 soils are extremely varied. Elements of the 

 California, north coast, and eastern Oregon flo- 

 ras combine with many species indigenous 

 only to the Klamath Mountain region. During 

 periods of climate change, plants from as far 

 south as Mexico and as far north as the Arctic 

 established in the area and mixed with en- 

 demic species. Plants and animals continue 

 to migrate north and south along the Cascade/ 

 Sierra and Coast ranges and east and west 

 across links in the ranges. Species such as 

 mountain mahogany, sagebrush, and quaking 

 aspen reflect the area's importance as an east- 

 west axis, and Pacific silver fir and Alaska 

 yellow-cedar reflect north-south movement. 

 Sierran pine and shrub species are also com- 

 mon. The area has been the site of local de- 

 velopment of ancient conifers including yew, 

 cypress, and redwood. 



Forest vegetation in interior valleys of the 

 Rogue and Umpqua rivers and lower elevations 

 of the Cascade Range and the Siskiyou Moun- 

 tains includes drought-tolerant conifers and 

 hardwoods such as ponderosa and sugar 

 pines, California black and Oregon white oaks, 

 and Pacific madrone. Mid elevations include 

 Douglas-fir, white fir, tanoak, and chinkapin. 



Higher elevations are dominated by true firs 

 and mountain hemlock. The Siskiyou Moun- 

 tains also contain large areas of soils that sup- 

 port Jeffrey pine, Port-Orford-cedar, and 

 unique associated flora. 



Southwestern Oregon has a mediterranean 

 climate, with generally mild, wet winters and 

 warm, dry summers. Most precipitation is 

 from November to March. Summer thunder- 

 storms are common. Annual precipitation 

 ranges from slightly less than 20 inches in in- 

 terior valleys to 120 inches at higher elevations. 

 The late 1980s and early 1990s was a period 

 of below-average rainfall. The area has the 

 greatest temperature extremes in western Or- 

 egon. In summer, it is often the warmest part 

 of the state. 



Drought Index 



Rogue/Umpqua Basin 



Year 



Southwestern Oregon has experienced a drought 

 over the past decade. This drought index graph 

 shows years that are drier than average (below 

 zero) and years that are wetter than average 



(above zero). Source: Surface Water Supply Index, Natural 

 Resources Conservation Service. 



All Species 

 Past and present fires irifluence vegeta- 

 tion — Historically, fire has played a critical role 

 in shaping vegetation. At low to mid elevations, 

 frequent, low-intensity ground fires were once 

 common. Fire frequencies ranged from 15 to 

 50 years in the Klamath Mountains. In inte- 

 rior valleys, the fire-return interval was prob- 



Oregon — 39 



