Table 3. (Con.) 



2. Not as above Unclassified type 



F. (Populus tremuloides-Pinus contorta cover type) 



1 Vaccinium scoparium or Vaccinium caespitosum abundant, 



usually exceeding 10% canopy cover Populus tremuloides-Pinus contorta/Vaccinium 



scoparium c.t. (p. 39) 



1. V. scoparium and V. caespitosum absent, or present in only 



trace amounts 2 



2. Juniperus communis present, usually accompanied by 

 either Carex geyeri. Carex rossii, Carex obtusata. Stipa 



occidentalis. or Festuca idahoensis Populus tremuloides-Pinus contorta/Juniperus 



communis c.t. (p. 40) 



2. Not as above Unclassified type 



TYPE DESCRIPTIONS 



Populus tremuloides/Acer 



gran diden ta t um/Pteridium a q uilin um 



Community Type (POTR/ACGR/PTAQ c.t.) 



This minor community type was identified on the 

 basis of 11 stands primarily along the Wasatch Range in 

 northern Utah. A single example was encountered in the 

 Uinta Mountains just northwest of Vernal and another 

 in the Pine Valley Mountains in southwestern Utah. The 

 Uinta stand lacked Acer grandidentatum but possessed 

 a tall shrub layer dominated by Amelanchier alnifolia. 

 The type appeared to favor northerly and easterly 

 exposures at the lower elevations between 5,800 and 

 7,500 ft (1 770 and 2 290 m). It was usually found on 

 soils derived from sandstones and at the lower toe-slope 

 topographic positions. 



The vegetation of this type is characterized by the vir- 

 tual absence of conifers, a distinct tall shrub layer, and 

 dominance of the herbaceous layer by Pteridium aquilinum. 

 Occasional Abies concolor or Abies lasiocarpa may be 

 present in the tree layer or as reproduction, but not in 

 such abundance to indicate eventual replacement of 

 aspen dominance in the overstory. A tall shrub layer 

 consisting of either Acer grandidentatum, Prunus 

 virginiana, Amelanchier alnifolia, or a combination of 

 these shrubs, distinguishes the type from the closely 

 associated POTR/PTAQ c.t., which lacks this shrub 

 layer. The low shrubs Symphoricarpos oreophilus, Rosa 

 woodsii, and Berberis repens are also frequently present. 

 In addition to the conspicuous dominance of P. aquilinum in 

 the undergrowth, other frequently abundant forbs 

 include Srnilacina stellata, Osmorhiza chilensis, and 

 Aster engelmannii. The grasses Elymus glaucus and 

 Bromus carinatus also frequently provide substantial 

 amounts of cover. 



The successional status of this type is uncertain, 

 except that it is unlikely to succeed to conifers. The type 

 may be a grazing-degraded form of the 

 POTR/PRVI/SESE c.t. with which it has many species 

 in common. P. aquilinum is not only unpalatable to live- 

 stock, it can be poisonous to cattle when eaten in quan- 

 tity. This unpadatability combined with its ability to 

 spread by creeping rhizomes suggests that it is likely to 

 increase greatly in abundance if its palatable associates 

 are depleted by prolonged excessive grazing. On the 

 other hand, seldom if ever does P. aquilinum occur as a 

 minor member of a community. It either tends to domi- 



nate the undergrowth or it is absent. This restricted dis- 

 tribution combined with abundance where it does occur 

 suggests that it may have rather specific, and as yet 

 undefined, environmental requirements and represents a 

 distinct climax community type. 



Tree productivity in this type generally appears to be 

 moderate to relatively high when compared to other 

 aspen communities. Basal area of aspen ranged from 113 

 to 174 ft^/acre (25.8 to 40.0 m^/ha), and averaged 

 136 ft-/acre (31.2 m'/ha). Site index at 80 years ranged 

 from 45 to 69 ft (13.7 to 21.0 m), and averaged 59 ft 

 (18 m). Conifer production was negUgible. Aspen sucker- 

 ing beneath the mature overstory was highly variable 

 but averaged a moderate 1,900/acre (4 700/ha); only one- 

 third of these were in the 1- to 4.6-ft (0.3- to 1.4-m) size 

 class. 



Undergrowth productivity also varies widely but 

 appears to be generally high. Forage productivity, how- 

 ever, may be low to moderate. A substantial portion of 

 the undergrowth usually consists of the unpalatable fern, 

 P. aquilinum. Annual production of undergrowth in the 

 five stands sampled ranged from 836 to 3,792 lb/acre 

 (938 to 4 256 kg/ha) and averaged 2,068 lb/acre 

 (2 320 kg/ha). Over 85 percent of this consisted of forbs 

 (including P. aquilinum), with the remainder divided 

 between the shrubs and graminoid vegetation classes. 

 About a third of this undergrowth comprised desirable 

 forage species, a third intermediate, and a third was 

 classified as least desirable. Although the type may have 

 considerable wildlife habitat benefits because of its mul- 

 tilayered cover of trees, tedl shrubs, and herbs, livestock 

 grazing values may be only moderate because of the 

 amount of unpalatable species. 



Aspen communities containing an abundance of 

 P. aquilinum in the undergrowth have also been identi- 

 fied in northwestern Colorado on the west slope of the 

 Park Range by Bunin (1975) and on the White River 

 National Forest by Hoffman and Alexander (1983); nei- 

 ther of these reports indicated the presence of a tall 

 shrub stratum. Hoffman and Alexander (1980), however, 

 describe a P. tremuloides/P. aquilinum habitat type for 

 the Routt National Forest in which almost half of the 

 stands contain a tall shrub stratum consisting of 

 A. alnifolia or P. virginiana or both, a low shrub layer, 

 and a herb layer containing species typical of our 

 POTR/ACGR/PTAQ c.t. The most conspicuous differ- 

 ence was the abundance of Carex geyeri in their stands 

 and the absence of this sedge in ours. 



13 



