The geologic composition of the Centennial Valley floor is 

 Quaternary alluvium which resulted from the erosional breakdown 

 of the surrounding mountains (Taylor and Ashley 1990) . 



Climate 



The Centennial Region is characterized by long cold winters 

 and short cool summers. The average annual precipitation is 20 

 inches (1961-1991) . 



Average snowfall during the winter months is 150 inches. 

 Snowfall during every month of the year is not uncommon. 



The mean annual temperature is 34.9 F. During extreme cold 

 periods, air temperatures commonly drop to the -3 0°F to -4 0°F 

 range. The summer maximum temperature rarely exceeds 90 F. 



Although frost occasionally occurs during every month of the 

 year, the average length of the frost-free season is 

 approximately 51 days. This season extends from mid-June to mid- 

 August (MAPS 1990) . 



Soils 



The soils of the western portion of the Centennial Mountains 

 (east of Odell Creek) consist of rock outcrops and talus slopes 

 at higher elevations and mollisols on the benches and terraces. 

 The soils of the Centennial Mountains west of Odell Creek, north 

 and south of the Red Rock River basin, are inceptisols-alf isols. 

 The parent materials are colluvium, igneous rock, and 

 sedimentary. The Red Rock River drainage contains characteristic 

 mollisols from a cold, wet basin who are derived from the parent 

 material alluvium. The soils surrounding the Lima Reservoir are 

 aridisols-mollisols that are calcareous from the parent materials 

 of alluvium and colluvium (MAPS 1990) . 



Soils of the Centennial Valley are in the process of being 

 mapped by the Soil Conservation Service (Gomez personal 

 communication) . 



Vegetation 



Vegetation of the Centennial Mountains is diverse and varies 

 with elevation, hydrology, substrate and microhabitat . It is 

 predominately coniferous forest dominated by Douglas fir 

 ( Pseudotsuqa menziesii ) and lodgepole pine f Pinus contorta ) . 

 The streams and higher cool slopes are characterized by the 

 spruce ( Picea enqelmannii ) and horsetail ( Equisetum arvense ) 

 association (DeVelice 1992) . Whitebark pine ( Pinus albicaulis ) 

 and subalpine fir ( Abies lasiocarpa ) dominate in the subalpine 

 region with occasional stands of limber pine ( Pinus flexilis ) 

 (DeVelice 1992) . The lower elevations along the foothills are 

 dominated by big sagebrush ( Artemisia tridentata ) , three-part 

 sagebrush ( A. tripartita ) and rabbit brush ( Chrysothamnus 

 nauseosus) . The upper wetlands are dominated by shrubby 

 cinquefoil ( Potentilla fruticosa ) and Idaho fescue (Festuca 

 idahoensis ) . The lower, wetter meadows are dominated by tufted 

 hairgrass ( Deschampsia cespitosa ) , sedges (Carex spp.) and rushes 

 ( Juncus spp. ) . The swamps and drainages are dominated by willows 

 ( Salix spp) . The Centennial Sandhills consist dominated by 

 thickspike wheat grass ( Agropyron dasystachyum ) , silverleaf 



