THE RÔLE OF SEDGES IN SOME COLORADO PLANT COMMUNITIES

Abstract

Every botanist is well aware of the large part taken by sedges in the vegetation of lake shores and swampy areas. For the eastern United States the species involved are well known, as also their relative importance in different stages of succession. Sedges of lake shores in the Rocky Mountains have been referred to by Clements (i), Ramaley and Robbins (7), Ramaley (4), and Robbins (9). In the present paper additional facts are given as to sedges of pondsides together with a series of observations on sedges of mesophytic and xerophytic habitats. This paper is based upon studies carried on largely from the University of Colorado Mountain Laboratory at Tolland, Colorado. Statements in the paper apply chiefly to the northern part of the state and to the mountain districts rather than to the plains. All species mentioned are well-known constituents of the Colorado flora. The nomenclature employed is that of Rydberg's Flora of the Rocky Mountains and the Adjacent Plains (New York, I9I7). The various life zones are given the following names in accordance with customary usage: Plains, Foothill, Montane, Subalpine, Alpine (4). Sedges exist chiefly in primitive communities or unstable situations. An area in a region that is climatically mesophytic becomes eventually either forest or grassland in which sedges have a very small place. So also, a climatically xerophytic area grows poor in sedges as the ultimate type of vegetation appears. Most sedges are aquatics or marsh plants or else they are xerophytes. Only a few are true mesophytes, and even these are likely to become crowded out by grasses and herbaceous dicotyledons in a meadow which has developed from marsh. Meadow or prairie of xerarch origin is also typically without sedges, the xerophytic sedges of more primitive stages disappearing before the meadow stage is reached. In the following systematic account the various genera of Cyperaceae are briefly considered, but chief attention is given to Carex.