Populus tremuloides-Abies lasiocarpa/ 

 Amelanchier alnifolia Community Type 

 (POTR-ABLA/AMAL c.t.) 



This minor serai community type was encountered 

 principally on the Bear River and Wasatch Ranges in 

 northern Utah. Two stands were observed in the Abajo 

 Mountains of southeastern Utah. The type occurred at 

 the lower edge of the Abies lasiocarpa zone. The north- 

 ern Utah stands were at elevations between 6,300 and 

 7,800 ft (1 920 and 2 380 m), whereas those in the Abajo 

 Mountains were at 8,600 ft (2 620 m). The type occurred 

 most frequently on slopes with northerly and easterly 

 exposures and occupied soils derived from a wide variety 

 of parent materials. 



The POTR-ABLA/AMAL c.t. contains a high degree of 

 both structural and species diversity. The vegetation is 

 comprised of four more or less distinct layers. The tree 

 overstory is dominated by Populus tremuloides but has 

 a substantial amount of A. lasiocarpa that may also be 

 accompanied by other conifers. The tall shrub layer in 

 the undergrowth is typified by the presence of 

 Amelanchier alnifolia, Prunus virginiana, or Acer 

 grandidentatum. A pronounced low shrub layer exists 

 that usually has Symphoricarpos oreophilus as its most 

 abundant constituent. Other frequently abundant shrubs 

 include Pachistima myrsinites, Berberis repens, and Rosa 

 woodsii. The herbaceous layer usually contains a rich 

 mixture of graminoids and forbs. Thalictrum fendleri is 

 usually among the most abundant and may be accompa- 

 nied by such species as Aster engelmannii, Senecio serra. 

 Geranium viscosissimum, Osmorhiza chilensis. Elymus 

 glaucus, and Agropyron trachycaulum. 



The type obviously represents a serai stage within the 

 A. lasiocarpa coniferous forest series, probably within 

 the A. lasiocarpa/Acer glabrum or A. lasiocarpa/ 

 0. chilensis habitat types (Mauk and Henderson 1984). 

 The natural process of succession in this type will lead 

 to overstory dominance by A. lasiocarpa. As conifers 

 become more prevalent, the shrubby and herbaceous 

 undergrowth tends to become less abundant, less 

 diverse, and shift in composition toward the more shade- 

 tolerant species. Heavy grazing in this type tends to 

 suppress the S. oreophilus and A. engelmannii and to 

 favor P. myrsinites and B. repens. If grazed by cattle, 

 composition would additionally tend to shift away from 

 the grasses A. trachycaulum and E. glaucus and toward 

 a greater abundance of T. fendleri and O. chilensis. 

 Heavy sheep grazing, on the other hand, would tend to 

 suppress T. fendleri and O. chilensis and favor the 

 grasses. 



Productivity for trees in this serai aspen type appears 

 relatively moderate. Tree basal area ranged from 53 to 

 288 ft-/acre (12.1 to 66.2 m'-Iha) and averaged 150 ft^/acre 

 (34.4 m^/ha). An average 15 percent of this basal area 

 consisted of conifers and the remainder was aspen. Site 

 index for aspen at 80 years ranged from 47 to 66 ft (14.3 

 to 20.1 m) and averaged 54 ft (16.5 m). Aspen reproduc- 

 tion averaged approximately 1,800 suckers/acre 

 (4 500/ha), about two-thirds of which were in the large 

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

 95 percent of which was A. lasiocarpa, averaged approxi- 



mately 890 stems/acre (2 200/ha). About 20 percent of 

 these were in the large size class. 



The undergrowth is fairly productive for a serai type 

 and contains a high proportion of shrubs. Annual 

 growth ranged from 578 to 1,986 lb/acre (649 to 

 2 229 kg/ha) and averaged a moderate 1,256 lb/acre 

 (1 410 kg/ha). An average 53 percent of this was shrubs, 

 36 percent forbs, and only 11 percent graminoids. A 

 high 62 percent of the undergrowth is of desirable forage 

 suitability. The type is good livestock range, particularly 

 for sheep, if succession has not progressed to the point 

 where conifers are appreciably suppressing the produc- 

 tion of shrubs and herbs. The type is considered excel- 

 lent wildUfe habitat because of the great amount of 

 structural diversity: an overstory consisting of both 

 aspen and conifers, a tall shrub layer, a low shrub layer, 

 and an herb layer of forbs and grasses. 



This serai type has not been identified elsewhere. How- 

 ever, it is beHeved to be a serai stage in the A. lasiocarpa/ 

 O. chilensis habitat type in Utah, and Steele and others 

 (1983) list P. tremuloides as a serai species in the 

 A. lasiocarpa/0. chilensis habitat type in eastern Idaho 

 and western Wyoming. The serai type was not recog- 

 nized per se in that area (Mueggler and Campbell 1982; 

 Youngblood and Mueggler 1981). 



Populus tremuloides-Abies lasiocarpa/ 

 Symphoricarpos oreophilus/ 

 Senecio serra Community Type (POTR- 

 ABLA/SYOR/SESE c.t.) 



The POTR-ABLA/SYOR/SESE c.t. is fairly common 

 in northern Utah and most prominent on the Bear River 

 and Wasatch Ranges and on the west slope of the 

 Uintas. Elsewhere, it is widely scattered, extending 

 southward to occasional occurrences on the high 

 plateaus and mountain ranges in southern Utah. We 

 sampled 48 stands of this type at elevations ranging 

 from 6,800 to 8,900 ft (2 070 to 2 710 m) in northern 

 Utah and between 8,500 and 9,400 ft (2 590 and 2 870 m) 

 in southern Utah. The type occupies all exposures and 

 slopes of varying steepness but usually on concave or 

 undulating topography. The type occurred most fre- 

 quently on soils derived from sandstone and limestone 

 parent materials but was not encountered on volcanic 

 soils. 



The type is characterized by the presence and 

 projected increasing abundance of Abies lasiocarpa in 

 the tree layer, the absence of a distinct tall shrub layer, 

 a low shrub layer dominated by Symphoricarpos 

 oreophilus or Rubus parviflorus, and the prominence of 

 tall forbs or tall grass species in the herbaceous layer. 

 This herb layer usually consists of a rich composite of 

 forbs and grasses. Members of the tall forb group are 

 conspicuous. Although the particular combination of tall 

 forbs present may vary, the most constant are Senecio 

 serra, Rudbeckia occidentalis, Agastache urticifolia, 

 Valeriana occidentalis, Aster engelmannii, Mertensia 

 arizonica. and Delphinium occidentale. Other forbs com- 

 monly present include Thalictrum fendleri, Hackelia 

 floribunda. Geranium viscosissimum, Osmorhiza chilensis, 

 and Vicia americana. The tall grasses Bromus carinatus. 



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