75 
Table 1 (continued) 
Ordination rank* 
1235456) 718) 9 OMI A2 SAS Gay 1819) 202122) 23)24-25. 2627.28 
Saxifraga oppositifolia 
Astragalus umbellatus 
Pedicularis capitata 
Parrya nudicaulis 
Cassiope tetragona 
Salix rotundifolia 
Saussurea angustifolia 
Luzula arctica 
Artemisia borealis 
Juncus biglumis 
Cardamine sp. 
Trisetum spicatum 
Minuartia arctica 
Oxyria digyna 
Cerastium beeringianum 
Hierchloe pauciflora 
Braya pilosa 
Carex rupestris 
Kobresia myosuroides 
Oxy tropis nigrescens 
Oxytropis deflexa 
*See text for stand description 
Stands sampled for presence-only were larger 
than those sampled for frequency, and in some 
of the latter stands, which were not sampled for 
presence, some rare species were undoubtedly 
missed in the quadrats. The result is that the 
presence lists for the frequency stands are short- 
er than those for the presence stands. The error 
introduced is probably not great since only rare 
species would be involved, but the lists are not 
entirely comparable. 
Species and Community Patterns 
Subunits recognized in the plains landscape 
are outlined below: 
Simple subunits: of more or less uniform appear- 
ance overall. 
1. Old lake beds: no longer with permanent 
standing water, although small ponds 
might be found in some portions. 
2. Smooth plain, dry, wet or intermediate: 
very uniform in appearance with respect 
to both vegetation and microtopo- 
graphy. 
3. Indistinct old polygons: pattern still dis- 
cernible, but little present microtopo- 
graphic variation. 
4. Patterned plain: vegetational variation 
apparent, but little microtopographic 
variation, and not divisible into one or 
two distinct components. 
Complex subunits: composed of one or two 
fairly discrete communities. 
1. Low-center polygons: depressed wet cen- 
ters with water standing on or very close 
to the surface all season, separated by 
raised ridges covered by dry, springy 
mats of low vegetation. 
2. High-center polygons, with either sand- 
silt or organic surface materials: raised 
centers covered by springy mats of low 
vegetation, separated by troughs 30-60 
cm deep covered by wet sods. 
