limited variety of other species such as Berberis repens, 

 Rosa woodsii, Osmorhiza chilensis, Lupinus argenteus, 

 Astragalus miser, and Vicia americana may be irregu- 

 larly present in lesser amounts. 



A variety of conifers may occur in this type as 

 incidentals, but the aspen overstory appears to be sta- 

 ble. The undergrowth, however, reflects a long history of 

 overgrazing of what probably was once either a 

 POTR/CAGE or a POTR/SYOR/CAGE cUmax commu- 

 nity type. The dominant P. pratensis and T. officinale 

 are palatable to both cattle and sheep. Their growth 

 form enables them to withstand grazing and increase in 

 amount as competition from the more grazing-sensitive 

 species is reduced. Continued heavy grazing probably 

 will not further alter the undergrowth appreciably, at 

 least until the aspen overstory begins to break up with 

 old age and browsing suppresses aspen sucker regenera- 

 tion. If this should happen, the aspen stand will eventu- 

 ally be lost. 



This type is generally only moderately productive for 

 growth of trees. Tree basal area ranged from 71 to 

 193 ft^/acre '16. 3 to 44.3 mVha) and averaged 126 ft-/acre 

 (28.9 m^/ha). All but 1 percent of this was aspen. Site 

 index at 80 years ranged from 30 to 70 ft (9.1 to 21.3 m) 

 and averaged a moderate 53 ft (16.1 m). Aspen regenera- 

 tion was a moderate 1,900 suckers/acre (4 700/ha). 

 Slightly more than half of these were in the 1- to 4.6-ft 

 (0.3- to 1.4-m) height class. 



Forage production on this grazing-altered type gener- 

 ally appears to be considerably less than the potential 

 for the site. Not only has heavy grazing changed under- 

 growth composition but may have reduced its total 

 biomass as well. Undergrowth production varied from 

 303 to 1,287 lb/acre (340 to 1 445 kg/ha) and averaged a 

 low to moderate 780 lb/acre (876 kg/ha). This was com- 

 posed of 58 percent forbs, 37 percent graminoids, and 5 

 percent shrubs. Only 29 percent of the vegetation was 

 desirable forage; 69 percent was of intermediate forage 

 suitability. This contrasts markedly with 57 percent in 

 the desirable category for the successionally related 

 POTR/CAGE c.t., and 51 percent desirable in the related 

 POTR/SYOR/CAGE c.t. Therefore, the POTR/POPR 

 type should be considered relatively poor livestock range 

 that has considerable potential for improvement. The 

 simplicity of vegetation structure and species composi- 

 tion detracts considerably from the value of this type as 

 wildlife habitat. It and the POTR/SIHY c.t. are probably 

 among the poorest of the aspen types for this use. 



A similar P. tremuloides/P. pratensis serai type has 

 been identified in southeastern Idaho (Mueggler and 

 Campbell 1982). Although not reported elsewhere, simi- 

 lar communities likely occur in Wyoming and Colorado. 

 The type is probably a grazing-induced serai stage of the 

 POTR/CAGE and POTR/SYOR/CAGE types, which 

 apparently do occur in these states (Hoffman and 

 Alexander 1983). 



Populus tremuloides-Ahies lasiocarpa/ 

 Vaccinium caespitosum Community 

 Type (POTR-ABLA/VACA c.t.) 



This infrequent community type is primarily res- 

 tricted to the Uinta Mountains. We sampled only four 

 stands at approximately 9,000 ft (2 740 m) elevation on 

 moderately steep slopes with concave or undulating 

 topography. They occupied soils principally derived from 

 quartzite parent materials. 



The POTR-ABLA/VACA c.t. is a serai type that is 

 rapidly succeeding to conifers. Both Abies lasiocarpa 

 and Pinus contorta are replacing Populus tremuloides in 

 the overstory. A low shrub layer consisting primarily of 

 either Vaccinium caespitosum or Vaccinium scoparium 

 dominates the undergrowth. Herbaceous cover is gener- 

 ally sparse, with Arnica latifolia usually being most 

 abundant. 



Apparently, the type is a serai stage within the 

 A. lasiocarpa/V. caespitosum or possibly the 

 A. lasiocarpa/V. scoparium habitat types (Mauk and 

 Henderson 1984). Populus tremuloides is intolerant of 

 shade and is subject to rapid replacement by 

 A. lasiocarpa, barring fire or other disturbance that 

 would retard the conifers. As the conifer cover increases, 

 the undergrowth will become even more depauperate. An 

 aspen stand can only be maintained here by periodic 

 clearcutting, burning, or other disturbance that kills the 

 conifers and stimulates aspen suckering. 



Neither tree nor undergrowth productivity were sam- 

 pled in this type. However, tree basal area, primarily 

 conifers, averaged 170 ft-/acre (39 m-/ha) in the succes- 

 sionally related Abies lasiocarpaJVaccinium caespitosum 

 habitat type, and 178 ft^/acre (41 m-/ha) in the possibly 

 related A. lasiocarpa/V. scoparium habitat type (Mauk 

 and Henderson 1984). 



Annual undergrowth production within this serai type 

 depends, to a great extent, upon the amount of conifers 

 present. Typically, as the proportion of conifers 

 increases, undergrowth decreases. The somewhat similar 

 POTR-ABLA/CAGE c.t., with an average 20 percent 

 conifers in the overstory, produced approximately 270 

 lb/acre (300 kg/ha) undergrowth. Production within the 

 POTR-ABLA/VACA c.t. probably averages about this 

 amount. Judging from species composition of the under- 

 growth, approximately a third of this is in the desirable 

 and two-thirds is in the intermediate forage suitability 

 class. Thus, the type is poor livestock range and proba- 

 bly not more than moderate wildlife habitat. 



This serai type has not been specifically identified as 

 occurring outside of Utah. However, it or a similar serai 

 type may be present at least in northwestern Colorado. 

 Hoffman and Alexander (1980, 1983) indicate that 

 P. tremuloides is a serai species in the A. lasiocarpa/ 

 V. scoparium habitat type found there. 



30 



