ROLE OF SEDGES IN COLORADO PLANT COMMUNITIES 125 
aurea, C. paupercula. In the Suhalpine Society there are subsidiary species 
as follows: Carex scopulorum, C. nigricans, C. paupercula, C. phaeocephala, 
C. illota, C. alhonigra. 
(c) Alpine Sedge Moor Association: Carex scopulorum, C. nigricans, C. 
nelsonii, C. chalciolepis, C. capillaris. — Carex scopulorum and C. nigricans 
are common around springs and in seepage areas everywhere near the top 
of the Continental Divide. 
{d) Snow-Patch Sedge Association. — In the subalpine and alpine zones 
snow drifts often remain on the ground until midsummer. In such places, 
if there is some accumulation of fine-grained soil, Carex nigricans is likely 
to form an almost pure stand. The snow accumulates year after year at 
the same point, and the very short period each year in which the ground 
is free from snov\^ does not permit the establishment of many plant species. 
A typical area of snow-patch sedge association is made up almost wholly of 
Carex nigricans. A few subordinate species are represented by scattered 
individuals in very small amount. These are Carex scopulorum, Ranun- 
culus adoneus, Sihhaldia procumbens, Caltha rotundifolia, Trollius albiflorus, 
Polytrichum and other mosses. The general appearance is quite different 
from that of ordinary sedge moor because of the low stature and broad 
leaves, widely spreading, of the dominant species. The snow-patch sedge 
association is interesting as being a rather primitive community and at the 
same time an ultimate one. The edaphic conditions are such that no suc- 
cessional stage can develop, at least so long as the mountains stand and snow 
continues to fall and to drift each winter. 
Meadow Association Type 
Meadow, as here understood, comprises all mesophytic grassland, but 
does not include anything that could be called sedge moor or marsh. 
Meadow grassland at lower altitudes in Colorado occurs in rather small 
strips where edaphic conditions are favorable to its development. The 
plains and foothill regions are too dry to support meadow on level ground 
or on south-facing slopes. Alluvial fans of fine-grained black soil support 
a mesophytic grassland designated by Vestal (10) as the Western Meso- 
phytic Prairie Grass Association. Fringes of meadow occur along water 
courses, especially at bends of streams, and also next to {i.e., in drier soil 
than) the sedge moor or willow thicket of mountain lakes. Hillside mead- 
ows, sometimes of considerable extent, occur in the montane zone. The 
higher rainfall and lower temperature of the subalpine and alpine zones are 
suitable for meadow development, and the association is often well devel- 
oped. Lack of humus in the soil is, however, a limiting factor of impor- 
tance. 
A number of species of Carex occur in meadows, but only a few are 
abundant. The most important one is Carex festivella. It extends through 
