Descriptions of Vegetation Types 



Tree-dominated Types 



Abies lasiocarpa/Arnica cordifolia plant association 



(ABILAS/ARNCOR; subalpine fir/heartleaf arnica; MTNHP rank G5/S5; 1 plot) 



Environment: ABILAS/ARNCOR was sampled once on a relatively steep north facing slope 

 near the crest of the Ruby Range at the head of Laurin Canyon. It is a minor type in the Ruby 

 Range but is common elsewhere in semi-arid mountain ranges of southwestern Montana, usually 

 on calcareous substrates. Vegetation nearby with similar aspects and positions with Picea rather 

 than Abies lasiocarpa potential are classified as Picea/Senecio streptanthifolius. Downliill 

 slopes are Psendotsuga menziesii/Arnica cordifolia. 



Soils: The plot lies close to the edge of the Wliitore rock outcrop complex and Shadow complex 

 soil mapping units (USDA Soil Conservation Service 1989). The soils are most likely similar to 

 those of the Whitore series derived from limestone, or inclusions within the Shadow complex at 

 high elevations on north slopes which support subalpine fir. Soils of both series are deep, well 

 drained Cryochepts. The ground surface of the plot has about 40% cover by litter with somewhat 

 over 20% exposed bare substrate, mostly gravel and some rock. 



Vegetation: The plot is in an open stand of low growing, old, stunted trees dominated by Picea 

 (ca. 30% cover) \N\\h Abies lasiocarpa, the indicated climax species, and Pinus flexilis well 

 represented (ca. 10% cover each). Juniperus communis is the only shrub and Poa secunda is the 

 only graminoid, both present in only trace amounts. The plot has total cover by forbs of about 

 10%, with Antennaria microphylla and Antennaria racemosa being the most common species. 

 The indicator forb Arnica cordifolia is absent but is replaced by Arnica latifolia and Arnica 

 rybergii. Ground cover by mosses is significant (ca. 30%). 



Comments: It is instructive to note here that Abies lasiocarpa is very poorly represented in the 

 Ruby Range, confined to high-elevation north slopes, reflecting the aridity of this range. The 

 study area plot varies from descriptions of the type in the literature (Pfister et al. 1977, Cooper et 

 al. 1995) by having a serai component of Pinus flexilis and Picea rather than the usual Pinus 

 contorta and Pseudotsuga menziesii, and having Arnica latifolia and Arnica rydbergii rather than 

 Arnica cordifolia. These differences are probably due to relatively high elevation, steep slopes, 

 aridity of the range and also possibly the calcareous substrate. Note that this is the only default 

 habitat type defined in Pfister et al. (1977), i.e. A. cordifolia need not be present for the type to 

 be identified, stands simply fall out of the key as ABILAS/ARNCOR, if "none of the above" 

 conditions specified in the key are satisfied. 



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