Conservation Service 1989), a major type in the range with soils derived from limestone 

 colluvium. Whitore soils are deep, well drained stony and channery loams typically covered by 

 about 2" of forest duff They are classified as Cryochrepts. Two of the study area plots have a 

 high fraction of exposed gravel and rock. 



Vegetation: The sampled stands are relatively open (30-70% total tree canopy cover) reflecting 

 both their relative youth and site water stress and are dominated or codominated by serai Pinus 

 flexilis and/or Pseudotsuga menziesii, with Picea slow to gain dominance. Abies lasiocarpa is 

 present in one plot. Slirub cover is low, Juniperus communis being the only well represented 

 species. There is also little grass cover, but Elymus efymoides (syn. Sitanion hystrix) is present in 

 three of the plots. Total forb cover ranges from 3% to around 20% with the indicator Senecio 

 streptanthifolius constant but never well represented. The forbs Agoseris glauca. Delphinium 

 glaucum, Solidago multiradiata and Valeriana dioica have high constancy (75%). Two plots 

 have significant (>20%) ground cover by mosses. 



Comments: Timber productivity is the lowest of all Picea types in Montana (Pfister et al. 1977), 

 and is probably extremely low in the Ruby Range judging from low canopy cover and slow pace 

 of succession. 



Pseudotsuga menziesii/Arnica cordifolia plant association 



(PSEMEN/ARNCOR; Douglas-fir/heartleaf arnica; MTNHP rank G4/S4; 3 plots) 



Environment: PSEMEN/ARNCOR is probably the most extensive forest type in the Ruby 

 Mountains. It was sampled by tliree plots on the east, west, and south flanks of the northern part 

 of the range, where it occupied middle to upperslope positions with cool northeasterly aspects at 

 6,900 to 7,900 feet elevation. It was found on both limestone and granitic substrates, but 

 limestone is more extensive in the range. Adjacent habitats are narrow Picea stringers on cooler, 

 wetter toe slopes and canyon bottoms, Abies lasiocarpa types on cooler granitic slopes, and other 

 Pseudotsuga menziesii types on dryer, warmer aspects. 



Soils: The tliree plots are within the Wliitore-rock outcrop complex mapping unit (USDA Soil 

 Conservation Service 1989), a major type in the Ruby Range with soils derived from limestone 

 colluvium. However, the plot in Laurin Canyon was on granitic substrate, probably a small 

 intrusion overlooked by the scale of soil mapping. Elsewhere, PSEMEN/ARNCOR is reported as 

 common on both calcareous (Cooper et al. 1995) and non-calcareous substrates (Pfister et al 

 1977). Wliitore soils are deep, well drained stony and channery loams typically covered by about 

 2" of forest duff. They are classified as Cryochrepts. 



Vegetation: Pseudotsuga menziesii is the dominant conifer with cover ranging from around 40% 

 to over 70% in the plots. Pinus contorta is abundant in the plots on granitic substrates. Abies 

 lasiocarpa, Picea, and Pinus flexilis are poorly represented. Mahonia repens (syn. Berberis 

 repens) and Juniperus communis are the only well represented slirubs, with the latter occurring in 

 all tliree plots. Cover by grasses is low but, Poa nervosa is constant. Cover by forbs ranges from 

 low to very high, with Arnica cordifolia and Astragalus miser constant and dominant. There is 

 significant ground cover by mosses in one plot. 



17 



