third axes are shown (Figure 5), the high elevation Pinus 

 albicaulis - Abies lasiocarpa community type joins the riparian types 

 as an outlier. The Picea enaelmannii/Equisetum arvense , the Salix 

 exiqua , the Phalaris arundinacea , the Populus trichocarpa/Cornus 

 stolonifera . and the Elymus cinereus community types are the most 

 extreme outliers, highlighting their unique vegetation composition 

 among the community types sampled. 



Ordination of the 4 3 non-riparian and non Pinus albicaulis - 

 Abies lasiocarpa sample plots along the first and second axes is 

 shown in Figure 6. The vertical axis appears to follow a soil 

 disturbance gradient with the Aqropyron dasvstachyum/Phacelia 

 hastata sand dune type and the Aqropyron spicatum and Atriplex 

 nuttallii/Oryzopsis hymenoides badlands types on one end of the 

 axis relative to sites on less erosive substrates. The horizontal 

 axis basically follows a gradient of increasing slope steepness, 

 soil coarse fragment content, and probability of limestone occur- 

 rence from left to right. The five Cercocarpus ledifolius domi- 

 nated or co-dominated types (20 plots) are clustered together in 

 the right half of the second axis. 



Ordination of the 20 Cercocarpus ledifolius dominated or co- 

 dominated sample plots along the first and second axes is shown in 

 Figure 7. Considerable similarity in vegetation composition occurs 

 among the five community types identified as suggested by the 

 single C^ ledifolius cluster in Figure 6 and the overlap among four 

 of the five types in Figure 7. Only the single C^ ledifolius/ 

 Festuca idahoensis occurrence does not overlap with the other 

 community types (Figure 7) . The primary distinguishing feature in 

 composition among the C_^ ledifolius types is the presence (often 

 with less than 5% canopy cover) or absence of a coniferous tree 

 species. Environmentally, occurrences in the upper left hand 

 quarter of the ordination are predominantly found on limestone 

 derived substrates. Other locations within the ordination space 

 have a lower probability of limestone occurrence. 



Community Type Descriptions 



1. Pinus albicaulis - Abies lasiocarpa Type 



(PINALB-ABILAS; whitebark pine-subalpine fir; G5 S5) 



Vegetation. — Pinus albicaulis , Abies lasiocarpa , Picea engel- 

 mannii . and occasionally Pseudotsuqa menziesii occur in 

 varying amounts in the often open, stunted, and wind-deformed 

 tree layer. The undergrowth is highly variable in composition 

 and few individual species ever exceed 5% cover. 



Physical Setting. — The type occurs on glaciated mountain 

 ridges and upper slopes at elevations above 8900 feet. The 

 total cover of soil, gravel, and rock exceeds 50%. The soil 

 surface is often unstable because of a lack of adequate vege- 

 tation cover. 



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