Ti, 
Table 2 (continued) 
Ordination rank* 1 2 4 6 
Parrya nudicaulis 
Cassiope tetragona 
Salix rotundifolia 
Saussurea angustifolia 
Luzula arctica 
Artemisia borealis 
Juncus biglumis 
Minuartia arctica 
Oxyria digyna 
Hierchloe pauciflora 
Braya pilosa 
Carex rupestris 
Kobresia myosuroides 
Oxy tropis nigrescens 
Oxytropis deflexa 
*See text for stand description 
3. Ridged plain, wet or dry: similar to 
either wet or dry smooth plain, but with 
the surface interrupted by _ irregular 
ridges and hummocks of 10-15 cm in 
height. 
“Wet" or “‘dry”’ designations refer to apparent 
surface moisture during the period of the study. 
Each subdivision includes only stands that are 
relatively extreme in appearance. Many areas did 
not fit into this classification and did not appear 
to be simple intergrades between the recognized 
subunits. 
The array of species and stands on the basis 
of presence is shown in Table 1. Species fre- 
quency values, with species and stands in the 
order developed and displayed in Table 1, are 
shown in Table 2. Neither species nor stands 
would be expected to show an entirely compact 
arrangement on a one-dimensional array, but the 
fact that these are as compact as they were 
found to be suggests that one major environ- 
mental gradient exerts strong influence on these 
patterns. In both tables, the rank numbers repre- 
sent the following site types: (1) the centers of 
low-center polygons; (2) flat areas of ridged wet 
plain; (3) flat areas of ridged wet plain; (4) 
seasonal high water area surrounding a lake; (5) 
flat areas of ridged wet plain; (6) seasonal high 
water area around a lake; (7) smooth wet plain; 
17 
35 40 
5 S&S pie oO, Ba 
33 Ul 
7 17 
10 
5 ad. 3 
5 isp 23 i 0 
7 
7 
10 
57 
3 
43 
(8) centers of low-center polygons; (9) seasonal 
high water area around a lake; (10) seasonal high 
water area around a lake; (11) ridges of low- 
center polygons; (12) intermediate smooth 
plain; (13) intermediate smooth plain; (14) 
ridges of low-center polygons; (15) dry smooth 
plain; (16) indistinct old polygons; (17) smooth 
dry plain; (18) smooth dry plain; (19) ridges of 
low-center polygons, now flooded by waters 
backed up by a gravel road; (20) centers of 
high-center polygons with organic surface; (21) 
dry smooth plain; (22) dry smooth plain; (23) 
dry smooth plain; (24) centers of high-center 
polygons with sand-silt surface; (25) centers of 
high-center polygons with sand-silt surface; (26) 
dry patterned plain; (27) ridges of ridged wet 
plain; (28) ridges of ridged wet plain. 
The basic array shown in Table 1 clearly 
corresponds with general gradients of apparent 
microtopographic relief and surface moisture 
(from low to high and wet to dry, respectively, 
as the array is numbered). Since both are com- 
plex environmental features, the specific ‘‘caus- 
al’ factors may well vary along these gradients. 
The extreme community types are conspicuous 
in the field: (1) a low wet type that was 
consistently greener in color than any of the 
more raised areas and was characterized by an 
open stand of rhizomatous sedges, chiefly Carex 
