greater intensity of shading and competition. The type 

 most likely represents a serai stage within either the 



A. concolor/J. communis or perhaps the P. pungens/ 

 J. communis habitat types that occur in central and 

 southern Utah (Youngblood and Mauk^ 1985). 



Heavy livestock use may lead to an increase in 

 J. communis and Berberis repens in the shrub stratum, 

 and an increase in S. hystrix, A. miser, A. millefolium, 

 and F. uesca in the herbaceous layer. Poa pratensis and 

 Taraxacum officinale are also likely to increase under 

 abusive grazing. 



Production was not sampled in this minor aspen type. 

 Production of wood, however, is probably somewhat less 

 than the 177 ft-/acre (40.7 m^/ha) basal area measured in 

 the more moist POTR-ABCO/SYOR c.t. Undergrowth 

 production is probably less than the low 422 lb/acre 

 (473 kg/ha) measured for the POTR-ABCO/SYOR type. 

 Composition of the undergrowth indicates moderately 

 good forage suitability with 41 percent of the under- 

 growth cover in the desirable class. Lack of overall 

 production makes this type rather poor livestock range. 

 The type is of only moderate value as wildlife habitat. 



This serai community type has not been noted outside 

 of Utah. 



Populus tremuloides-Pseudotsuga 

 menziesii/Amelanchier alnifolia 

 Community Type (POTR-PSME/AMAL c.t.) 



This is a fairly local serai community type in the Bear 

 River and Wasatch Rjmges of northern Utah. One stand, 

 however, was sampled in the LaSal Mountains of south- 

 eastern Utah. The type occurs at relatively low eleva- 

 tions. The northern Utah stands were at elevations 

 between 6,000 and 7,850 ft (1 830 and 2 390 m). The 

 stands occupied primarily steep, north-facing or east- 

 facing slopes. They were on soils derived from sand- 

 stone, limestone, or quartzite parent materials. 



The vegetation of this type consists of a complex, 

 multilayered assemblage of species. The Populus 

 tremuloides-dominated tree stratum includes 

 Pseudotsuga menziesii as a prominent conifer constitu- 

 ent. A tall shrub element is generally dominated by 

 Amelanchier alnifolia, Prunus virginiana, or Acer 

 grandidentatum. A distinct low shrub layer also exists in 

 which Symphoricarpos oreophilus is the usual dominant, 

 but which also frequently contains Pachistima 

 myrsinites, Rosa woodsii, and Berberis repens. The her- 

 baceous stratum contains a wide and variable assort- 

 ment of species. Potentially prominent grasses are 

 Bromus carinatus, Elymus glaucus, and Agropyron 

 trachycaulum. Occasionally the sedge Carex geyeri is 

 abundant. The most constant and abundant forbs are 

 Osmorhiza chilensis, Thalictrum fendleri, Geranium 

 viscosissimum, Lathyrus spp., and Smilacina racemosa. 



This type is a successional stage leading to a 

 P. menziesii forest climax. Undergrowth species similari- 

 ties suggest the type represents a serai stage within 

 several different habitat types described by Mauk and 

 Henderson (1984). These include the P. menziesii/ 

 O. chilensis, P. menziesii/Acer glabrum, and P. menziesii/ 



B. repens habitat types. 



Heavy livestock use is likely to cause a decrease in 

 abundance of S. oreophilus and A. alnifolia and an 

 increase in less palatable species such as B. repens, 

 Achillea millefolium, and G. viscosissimum. In addition, 

 heavy use by sheep will tend to suppress O. chilensis, 

 T. fendleri, and Lathyrus spp. to the benefit of B. carinatus, 

 E. glaucus, and C. geyeri. On the other hand, heavy cat- 

 tle use will tend to suppress the graminoids and favor 

 the forbs. 



The type appears to be moderately productive for 

 trees. Basal area averaged 160 ft^/acre (36.7 m^/ha) and 

 ranged between 105 and 283 ft^/acre (24.2 and 

 64.9 m^/ha). An average 14 percent of this basal area 

 consisted of conifers. Site index at 80 years for aspen 

 ranged between 50 and 66 ft (15.2 and 20.1 m) and aver- 

 aged a relatively high 60 ft (18.3 m). Aspen reproduction 

 in these stands averaged a moderate 2,900 suckers/acre 

 (7 200/ha), about half of which were in the 1- to 4.6-ft 

 (0.3- to 1.4-m) size class. Conifer regeneration was not 

 great. Only 338 stems/acre (836/ha) were recorded, and 

 only 13 percent of these were in the large size class. 



Undergrowth is not very productive in this type. It 

 ranged between 561 and 994 lb/acre (630 and 

 1 115 kg/ha) and averaged a low to moderate 748 lb/acre 

 (839 kg/ha). This production was well distributed among 

 the various vegetation classes: 38 percent shrubs, 41 per- 

 cent forbs, and 21 percent graminoids. Of the under- 

 growth, 45 percent was desirable forage and 47 percent 

 of intermediate suitability. Thus, the type is rather 

 mediocre range for livestock. However, it is considered 

 good habitat for wildlife because of the great amount of 

 vegetation diversity. The tree layer consists of both 

 aspen and conifers, while the undergrowth is composed 

 of tall shrubs, low shrubs, forbs, and graminoids. 



Similar aspen communities serai to P. menziesii- 

 dominated forests have been noted in Idaho and 

 Wyoming. Mueggler and Campbell (1982) identified a 

 similar P. tremuloides-P. menziesii/P. virginiana c.t. on 

 the Caribou and Targhee National Forests. Youngblood 

 and Mueggler (1981) observed a somewhat similar 

 P. tremuloides-P. menziesii/Spiraea betulifolia type in 

 eastern Wyoming; unlike the Utah type, however, theirs 

 had an abundance of Spiraea. In addition, P. tremuloides 

 was recognized by Steele and others (1983) as a major 

 serai tree in both the P. menziesii/0. chilensis and 

 P. menziesii/B. repens habitat types in eastern Idaho and 

 western Wyoming. 



Populus tremuloides-Pseudotsuga 

 menziesii/ Juniperus communis 

 Community Type (POTR-PSME/JUCO c.t.) 



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

 distributed serai type. Five of the eight stands sampled 

 were on the south slope of the Uinta Mountains in 

 northern Utah. The remainder were on the Markagunt 

 and Aquarius Plateaus in southern Utah. The type 

 inhabits the upper elevation portion of the Pseudotsuga 

 menziesii zone, with three-fourths of the stands at eleva- 

 tions exceeding 8,000 ft (2 440 m). The stands were 

 primarily on relatively gentle slopes and on soils derived 

 from either sedimentary or volcanic parent materials. 



37 



