Colorado contain the tall forb and grass components 

 similar to our POTR/SESE c.t. Their P. tremuloides/ 

 T. fendleri type appears to be primarily a more general- 

 ized combination of our POTR/SESE and POTR/CAGE 

 types. Aspen communities similar to the Utah 

 POTR/SESE c.t. have also been noted in northeastern 

 Nevada (Lewis 1975). 



Populus tremuloides/Carex geyeri 

 Community Type (POTR/CAGE c.t.) 



This is a relatively common community type widely 

 distributed in the higher mountains throughout Utah, 

 with 90 percent of the 49 sampled stands at elevations 

 over 8,000 ft (2 440 m). The type was found on all 

 exposures, on shallow to steep slopes, and on a wide 

 variety of soil parent materials. The type occurred most 

 frequently on soils derived from sandstone, volcanics, 

 and granite. 



The vegetation of this type bears considerable resem- 

 blance to that of the POTR/SYOR/CAGE community 

 types except for the lesser amounts of the key shrubs. 

 Symphoricarpos oreophilus or Juniperus communis or 

 both are frequently part of the undergrowth in the 

 POTR/CAGE c.t., but not in such amounts that form a 

 distinct shrub stratum. Vegetation structure, therefore, 

 consists essentially of only two layers: the Populus 

 tremuloides dominated overstory and the herbaceous 

 undergrowth (fig. 9). Abies lasiocarpa and Picea 

 engelmannii occasionally accompany P. tremuloides in 

 the tree layer but only as incidental species. Berberis 

 repens at times provides considerable ground cover. The 

 undergrowth typically consists of substantial amounts of 

 one or more of the following graminoids: Carex geyeri, 

 Carex rossii, Stipa occidentalism and Calamagrostis 

 rubescens. These species are considered more or less eco- 

 logical equivalents in this classification (see the 

 POTR/SYOR/CAGE c.t. section). Carex geyeri and C. 

 rubescens are most frequently encountered in northern 

 Utah, whereas S. occidentalis and C. rossii appear more 

 widely distributed. Frequently Ag^ropyron trachycaulum 



is also abundant. The most common forbs in this com- 

 munity type are Achillea millefolium, Astragalus miser. 

 Geranium viscosissimum, and Taraxacum officinale. Con- 

 siderable amounts of Lathyrus spp. may also be present 

 in some stands. 



We believe that the POTR/CAGE is primarily a climax 

 community type. In those cases where A. lasiocarpa 

 appears able to actively invade and replace 

 P. tremuloides, the stand might be considered a serai 

 stage within an A. lasiocarpa/B. repens habitat type 

 (Mauk and Henderson 1984). Heavy, prolonged grazing 

 of this type will probably shift undergrowth composition 

 toward greater abundance of A. miser, T. officinale, and 

 Poa pratensis as the less grazing-tolerant forage species 

 are reduced. 



Although tree basal area is relatively high in this type, 

 growth rate is only moderate. Tree basal area on the 24 

 stands sampled for production ranged from 89 to 

 322 ft^/acre (20.5 to 73.9 m^/ha) and averaged 171 ft^/acre 

 (39.2 m^/ha). Aspen constituted 99 percent of this. Site 

 index of aspen at 80 years ranged from 32 to 77 ft (9.8 

 to 23.5 m) and averaged a modest 52 ft (15.7 m). Aspen 

 reproduction averaged a moderate 2,200 suckers/acre 

 (5 500/ha) about half of these in the 1- to 4.6-ft (0.3- to 

 1.4-m) height class. 



Annual production of undergrowth usually is fairly 

 low. Although it ranged from 78 to 1,289 lb/acre (88 to 

 1 447 kg/ha) across 23 stands, it averaged a rather mea- 

 ger 665 lb/acre (746 kg/ha). This production was about 

 equally divided between forbs and graminoids, with less 

 than 5 percent in the shrub category. Of the under- 

 growth, 93 percent was classified in the desirable and 

 intermediate forage suitabihty classes. The high percent- 

 age of graminoids makes this type better suited for cattle 

 than for sheep. Low productivity, however, limits its 

 value as livestock range. The type is not good wildlife 

 habitat because of its lack of diversity in both vegeta- 

 tion structure and species composition. 



This relatively common Utah type occurs also in 

 Idaho, Wyoming, and Colorado. Mueggler and Campbell 

 (1982) identified a P. tremuloides/C. rubescens c.t. in 



Figure 9.— The Populus 

 tremuloides/Carex geyeri c.t., 

 widely distributed 

 throughout the higher 

 mountains and plateaus of 

 Utah, has a relatively simple 

 undergrowth dominated by 

 such graminoids as C. geyeri, 

 Carex rossii, or Stipa 

 occidentalis. Common forbs 

 include Achillea millifolium, 

 Geranium viscosissimum, 

 and Astragalus miser. 



26 



