154 UNIVERSITY OF COLORADO STUDIES 



sedge zone is very wide. In the filling up of shallow lakes, the shrubs 

 generally enter with the sedges, forming small clumps in the wet meadow 

 thus developed. An excellent illustration of this fact is seen in the 

 meadow just beyond the bounding moraine west of Redrock Lake. 



Shrub Zone 



The shrubs are massed in a narrow zone averaging about two meters 

 (6.5 ft. )wide. Salix chlorophylla is the commonest species. It grows 

 chiefly in the wetter parts and together with Betula glandulosa is advan- 

 cing into the sedge zone. The other three willows are scattered about 

 in clumps, sometimes of a single species, sometimes variously grouped. 

 The birch, which, as has been said, is found in the wettest soil, is also 

 found in other parts of the zone. 



Both willows and birches are true shrubs, in no place trees. The 

 birches, especially, are low, seldom more than one meter tall. It is 

 somewhat remarkable that even with the comparatively unfavorable 

 temperature there should be such a dense growth of these shrubs. 

 Often they form an almost impassable thicket (see Fig. 10). In places 

 individual clumps of shrubs extend to the water's edge and on the 

 southwest shore a considerable number of shrub islands are scattered 

 through an area of sedges (Fig. 1). In addition to the shrubs a few 

 Engelmann spruces occur as wind timber at the east shore of the lake 

 and elsewhere there are individual trees of this species among the shrubs 

 and even in the sedge zone. 



A number of mosses are abundant around the bases of the shrubs. 

 In nearly all places a distinct ledge has been built up by the mosses at 

 the boundary of the zone, next to the sedges. Species of Sphagnum 

 and Polytrichum are the most important of these building mosses. 



Most of the herbaceous plants recorded for this zone are found in 

 openings and not in the shade under the shrubs. Various tongue-like 

 areas of grassland extend radially across the zone or through a part of 

 its width. Sometimes these are distinctly like portions of the sedge 

 zone while elsewhere they are dominated by grasses from the forest. 

 In still other places, while grasses are abundant, there are scattered 

 shrubs of Dasiphora fruticosa. On the whole, however, the shrub zone 



