This community type is the drier of the two aspen 

 types identified as successional to a climax P. menziesii 

 forest. The vegetation is characterized by the conspicu- 

 ous presence of P. menziesii in the tree layer, absence of 

 a distinct tall shrub stratum, and the prominence of 

 Juniperus communis in the low shrub layer. Occasionally 

 Pinus contorta will also occur in some abundance in the 

 tree layer. Symphoricarpos oreophilus and Berberis 

 repens are frequent and often abundant members of the 

 low shrub layer. The herbaceous stratum usually con- 

 sists of a variable mixture of grasses and forbs. The 

 most consistently occurring grasses are Stipa 

 occidentalis, Agropyron trachycaulum, Poa fendleriana. 

 and Sitanion hystrix. Frequently prominent forbs are 

 Astragalus miser, Fragaria vesca, Lupinus argenteus. 

 and Taraxacum officinale. Species diversity is ordinarily 

 low. 



The type is recognized as a serai stage within the P. 

 menziesii climax forest series. It appears most closely 

 related to the P. menziesii/B. repens and P. menziesii/ 

 S. oreophilus habitat types described by Mauk and 

 Henderson (1984) for northern Utah and by Youngblood 

 and Mauk (1985) for central and southern Utah. 



Heavy Uvestock grazing tends to favor the production 

 of B. repens. A. miser. Fragaria vesca. and T. officinale 

 at the expense of P. fendleriana, S. occidentalis, 

 A. trachycaulum. and S. oreophilus. 



Production was not sampled in this infrequently 

 encountered type. However, production of both trees and 

 undergrowth will probably be somewhat less than in the 

 more moist POTR-PSME/AMAL c.t., which averaged 

 160 ft-/acre (36.7 m-/ha) of tree basal area and 

 748 lb/acre (839 kg/ha) of undergrowth. Composition of 

 the undergrowth indicates moderately good forage suita- 

 bihty for livestock, with 41 percent desirable and 48 

 percent intermediate. Value of the type as wildlife habi- 

 tat is low to moderate, considerably less than in the 

 POTR-PSME/AMAL c.t., because of the absence of a 

 tall shrub layer. 



This serai community type has not been reported to 

 occur elsewhere. 



Populus tremuloides-Pinus ponderosa/ 

 Quercus gambelii Community Type 

 (POTR-PIPO/QUGA c.t.) 



This minor serai community type is in the LaSal and 

 Abajo Mountains, the Aquarius Plateau, and as far 

 north as the southern edge of the Uinta Mountains. The 

 six sampled stands grew at elevations between 7,500 and 

 8,800 ft (2 290 and 2 680 m), primarily on gently sloping, 

 southerly exposures. The majority of stands occurred on 

 soils derived from sandstone parent material, but vol- 

 canic soils also support the type. 



The vegetation of this community type is unique 

 because of the presence of Pinus ponderosa as virtually 

 the sole conifer associated with Populus tremuloides in 

 the tree stratum and the presence of a tall shrub ele- 

 ment in the undergrowth. Quercus gambelii is usually 

 the primary tall shrub species, but Prunus virginiana or 

 Acer grandidentatum may fill this role. Frequently 

 Symphoricarpos oreophilus forms a distinct low shrub 



layer. The herbaceous undergrowth is usually rather 

 sparse and consists of such species as Achillea 

 millefolium, Thermopsis montana, Thalictrum fendleri, 

 Ligusticum porteri, Poa pratensis, and Taraxacum 

 officinale. 



Normal succession in this type slowly leads to 

 P. tremuloides replacement by P. ponderosa. In northern 

 Utah the type is most likely a serai stage with the 

 P. ponderosaJCarex geyeri habitat type (Mauk and 

 Henderson 1984), whereas in central and southern Utah 

 it probably is within either the P. ponderosa.Q. gambelii 

 or P. ponderosaj'S. oreophilus habitat types (Youngblood 

 and Mauk 1985). 



Only a single stand in this type was sampled for 

 proditctivity. Tree basal area was a fairly high 

 170 ft^/acre (39.1 m^/ha), of which 26 percent was 

 conifers. Aspen site index at 80 years was a low 40 ft 

 (12.2 m). Only 567 suckers acre (1 402 ha) were encoun- 

 tered in this stand; a third of these were in the 1- to 

 4.6-ft (0.3- to 1.4-m) size class. Only 13 conifer seed- 

 lings'acre (32/ha) were present, all of which were 

 P. ponderosa in the large size class. 



Production of undergrowth was a low 707 lb acre 

 (794 kg/ha). This was about equally divided between 

 shrubs, forbs. and graminoids. A relatively high 50 per- 

 cent of this was classified as desirable and 42 percent of 

 intermediate forage suitability. The type is considered 

 poor to fair range for Hvestock and at least moderate to 

 good wildUfe habitat. 



This community type has not been identified outside 

 of Utah. 



Populus tremuloides-Pinus ponderosa/ 

 Juniperus communis Community Type 

 (POTR-PIPO/JUCO c.t.) 



The POTR-PIPO/JUCO c.t. is a minor but widely dis- 

 persed type observed along the eastern portion of the 

 Uinta Mountains in northern Utah and on the Markagunt 

 and Aquarius Plateaus in southern Utah. The 14 stands 

 sampled in this type occurred at elevations between 

 7,600 knd 8,900 ft (2 320 and 2 710 m), on gentle slopes, 

 and on soils derived from a wide variety of parent 

 materials. 



This is the most common of the two community types 

 where Pinus ponderosa becomes prominently associated 

 with aspen (fig. 15). The undergrowth in this type is 

 characterized by the virtual absence of tall shrubs and 

 the prominence of Juniperus communis in the low shrub 

 layer. Symphoricarpos oreophilus and Berberis repens 

 frequently accompany J. communis in the low shrub 

 layer. The usually sparse herb stratum consists of a vari- 

 able mixture of such relatively dr\'-site grasses as 

 Sitanion hystrix, Stipa comata. and Poa fendleriana. and 

 such forbs as Astragalus m.iser, Antennaria microphylla, 

 Fragaria vesca, and Taraxacum officinale. None of these 

 herbaceous species has high constancy. 



This aspen-dominated type is considered a serai stage 

 within the P. ponderosa forest series. It appears most 

 closely associated with the P. ponderosa Festuca 

 idahoensis habitat type (Mauk and Henderson 1984) of 

 northern Utah, and possibly the P. ponderosa/ 



38 



