Elymus glaucus, and Agropyron trachycaulum are also 

 frequently present. 



The POTR-ABLA/SYOR/SESE c.t. represents a serai 

 stage in the A. lasiocarpa coniferous forest climax series, 

 probably within the A. lasiocarpa/0. chilensis habitat 

 type (Mauk and Henderson 1984). As A. lasiocarpa gains 

 overstory dominance, shading intensity increases, Populus 

 tremuloides degenerates and fails to sucker, and the 

 highly productive and diverse undergrowth changes to a 

 less complex and productive assemblage of species. The 

 tall forbs, grasses, and shrubs will decrease in impor- 

 tance, whereas O. chilensis, T. fendleri, and Stellaria 

 jamesiana will become increasingly prominent. 



Heavy grazing in this type usually will lead to a 

 decrease of many of the tall forbs, especially 

 A. urticifolia, A. engelmannii, and -S. serra. and an 

 increase in R. occidentalis, H. floribunda, S. jamesiana, 

 Achillea millefolium, and possibly Lathyrus spp. 

 Prolonged abusive grazing can lead to a substantial 

 increase in Poa pratensis and Taraxacum officinale, or 

 even replacement of perennial species with annuals such 

 as Nemophila breviflora, Polygonum douglasii, and 

 Collomia linearis. 



Tree production on these sites is slightly better than 

 average. Basal area ranged from 74 to 249 ft'^/acre (17.0 

 to 57.3 m^/ha) and averaged a high-moderate 165 ft^/acre 

 (38 m^/ha). Conifers made up 13 percent of this, mostly 

 A. lasiocarpa. Aspen site index at 80 years ranged from 

 33 to 74 ft (10.1 to 22.6 m) and averaged a moderate 

 54 ft (16.6 m). Aspen regeneration was relatively low in 

 these serai stands, averaging slightly over 800 

 suckers/acre (2 000/ha), of which about half were in the 

 1- to 4.6-ft (0.3- to 1.4-m) size class. Conifer reproduction 

 averaged approximately 240 stems/acre (600/ha), and 80 

 percent of this was A. lasiocarpa. Slightly less than half 

 were in the large reproduction size class. 



Undergrowth, though highly variable, is moderately 

 abundant. Annual production for 13 sampled stands 

 ranged between 202 and 2,121 lb/acre (227 and 

 2 380 kg/ha) and averaged 1,004 lb/acre (1 127 kg/ha). 

 Shrubs were 23 percent and graminoids 18 percent of 

 this, whereas forbs dominated at 59 percent. The vegeta- 

 tion appeared well suited to livestock, with 54 percent in 

 the desirable forage category. The type consequently is 

 fairly good range for Hvestock, especially in early succes- 

 sional stages before conifers begin to appreciably reduce 

 undergrowth production. The type is also considered 

 good habitat for wildlife because of the relatively high 

 level of vegetation diversity. 



The P. tremuloides-A. lasiocarpaJS. oreophilus type 

 described by Mueggler and Campbell (1982) for eastern 

 Idaho contains stands similar to this type. Steele and 

 others (1983) indicate that P. tremuloides is a major 

 serai species in the A. lasiocarpa/0. chilensis habitat 

 type in eastern Idaho and western Wyoming. Because 

 the POTR-ABLA/SYOR/SESE c.t. is believed to be a 

 serai stage in the A. lasiocarpa/0. chilensis habitat type 

 in Utah, it is probably farther north as well. 



Populus tremuloides-Abies lasiocarpa/ 

 Symphoricarpos oreophilus/Carex geyeri 

 Community Type (POTR-ABLA/ 

 SYOR/CAGE c.t.) 



This infrequent but widespread serai community type 

 was encountered from the Bear River Range in the north 

 to the Aquarius Plateau in the south. Of the 14 sampled 

 stands, we encountered five in the LaSal Mountains. 

 Sampled stands occurred at elevations ranging from 

 7,500 ft (2 290 m) in northern Utah to 9,600 ft (2 930 m) 

 in the south. These stands were most frequently on shal- 

 low slopes of less than 25-percent steepness. They did 

 not appear restricted by either slope exposure or soil 

 parent material. 



The vegetation of the POTR-ABLA/SYOR/CAGE c.t. 

 consists of three distinct structural layers: a tree layer 

 of mixed Populus tremuloides and conifers, a low shrub 

 layer dominated by Symphoricarpos oreophilus, and an 

 herbaceous layer with a high proportion of graminoids. 

 Although Abies lasiocarpa is the most common conifer 

 invading the aspen community, Picea engelmannii and 

 Pseudotsuga menziesii may also be conspicuous. The 

 undergrowth composition of this tj^e is fairly similar to 

 that of the POTR/SYOR/CAGE c.t. The low "shrub layer 

 is consistently dominated by S. oreophilus, but Berberis 

 repens and Rosa woodsii may also be prominent in this 

 stratum. The herbaceous layer is usually dominated by 

 grasses and sedges. Carex geyeri is the most constant 

 and abundant of these, but Stipa occidentalis or Carex 

 rossii may occasionally replace C. geyeri as the dominant 

 graminoid. The forbs most common to this type are 

 Thalictrum fendleri and Achillea millefolium. At times, 

 Lathyrus spp., Lupinus argenteus, or Astragalus miser 

 are abundant. 



This is a serai community type within the 



A. lasiocarpa coniferous forest series. Most likely it 

 represents a serai stage within either the A. lasiocarpa/ 



B. repens or A. lasiocarpa/C. geyeri habitat types (Mauk 

 and Henderson 1984; Youngblood and Mauk 1985). As 

 the aspen overstory is gradually replaced by conifers 

 during the natural course of succession, the abundance 

 of undergrowth vegetation will tend to decrease. Heavy 

 livestock grazing in this type will probably lead to 

 increased abundance of A. miser. Taraxacum officinale, 

 and Poa pratensis at the expense of those species less 

 able to withstand the effects of heavy use. In some 

 stands a large amount of Lathyrus spp. or Lupinus 

 spp. may result from heavy cattle grazing. 



Tree productivity within the type is low. Basal area 

 ranged from 67 to 144 ft^/acre (15.5 to 33.0 m-/ha) and 

 averaged only 109 ft^/acre (25 m^/ha). Of this basal area, 

 17 percent was conifers and the remainder was aspen. 

 Site index at 80 years for aspen was also low, ranging 

 from 30 to 45 ft (9.1 to 13.7 m) and averaging only 38 ft 

 (11.5 m). Aspen reproduction averaged a low 890 

 suckers/acre (2 200/ha), 75 percent of which were in the 

 large 1- to 4.6-ft (0.3- to 1.4-m) size class. Conifer 

 regeneration averaged sUghtly over 120 stems/acre 

 (300/ha), of which 93 percent were A. lasiocarpa and less 

 than 20 percent of these were in the large size class. 



32 



