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Jwne 1991 Cyp+iu TOC ' Subridrrur F,/fetu on Vcgcution • 1 <br />• runoff is very slow, permeability is modera[ely slow, and available water capacity is high. <br />Effective rooting depth is 60" or greater. <br />Detailed soil descriptions are presented in Eahibit 15, Typid Pedon Descriptions, and Exhibit <br />16, Soil Mapping Unit Descriptions. <br />2.3 EXISTING VEGETATION <br />2.3.1 Blg Sagebrush/Meadow Type <br />Baxd on data prexnted in current permit documents, existing vegetation within the study acct <br />is compoxd primarily of a sagebrush/meadow type [hat oaurs in the lowland areas along Fish <br />Creek. The major speces in this type include Kentucky bluegrus (Poa prateruis) and silver <br />sagebrush (Artemisia cana). Thex two spedes account for 55 percen[ of the cover by all speces <br />in this type. Wetland speaes, like Baltic rush ~uncus arcticus ssp. ater) and species of xdge <br />(Carex scopu/orum and rtrrex praegracilis), also occur and account for 17.3 percent cover in this <br />type. Thex species tend to octvr immediately adjacent to the stream channel, on low terraces <br />adjacent to the stream channel and in low places on the higher terraces where abandoned stream <br />meanders remain. The sagebrush meadow type is restricted to the mapped alluvia] valley floor <br />within the study area. The sagebrush meadow type depends on predpitation, run-on from <br />adjacent uplands, redistributed snow and rub-irrigation u sources of water. Total production <br />(hued on 1984 data) for the sagebtvsh/meadow type wu 248 gams per square meter. Of this <br />total, perennial gruses and grasslike plants accounted for 61 percent of the total, 30 percent of <br />• the total was provided by xdges and rushes, and 8.5 percent of [he total was provided by silver <br />sagebrush. Both cover and production data were collected from [he entire permit area and, <br />therefore, are a reflection of the type u a whole. Field reconnaissance obxrvations in the study <br />area suggest that xdges and rushes are not u prevalent and silver sagebrush is more abundant <br />than in [he type as a whole. <br />Some of the major plant speces that occur in the sagebrush/meadow [ype have water <br />requirements [hat are greater than what can be provided by predpi[ation only (Table 1). <br />Supplemental moisture for thex speces is provided by rub-irrigation, runoff from adjacent <br />uplands and redistributed snow that tends to collect on the valley floor. Of the speces listed <br />in Table 1, the sedges (Carex spp.), Baltic rush, Sulalcea neomexirnna, and shrubby dnquefoil <br />(Potenti/la fruiuosa) are speces that are most dependent on and indiative of sub-irrigation and <br />usually occur on si[es where the capillary fringe reaches the soil rurface. If the apillary fringe <br />does not extend into the rooting zone for thex species, they will not persist. Spedes like silver <br />sagebrush and Ren[ucky bluegrass, which require rupplemen[al moisture, may have roo[s <br />extending into the capillary fringe, but do not depend to any significant extent on sub-irrigation <br />as a source of additional water. Thex species make ux of other forms of moisture subsidies, <br />like runoff from upland areas and redistributed snow. Obxrvations from a site just upstream <br />from the study area, where the stream channel has recently cut to a depth of 12 to 15 feet below <br />existing stands of silver sagebrush and Kentucky bluegrus, suggest that even when the stream <br />channel is lowered significantly, these vegetation types persist. <br />2.3.2 Blg Sagebrush/Shrubland Type <br />. Upland area adjacen[ to the bottom-land sagebrush/meadow type support a sagebrush shrubland <br />type in which big bluegrass (Pact ampla) and a species of sagebrush (Artemisla arbusculaJ occur <br />u dominant species. Three speces of sagebrush account for approximately 29 percent of the <br />ACZ fu. • P.O. Box 771018 • Suambaar Spnngr, Colorado 80/77 '(303)8796160 <br />