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7uly 1993 -22- 923-2515 • <br />increase in production of about one half ton (Fulton 1993) per acre would not justify the expense <br />of constructing a dam and ancillary fiood irrigation facilities. <br />5.1.6 Wetlands <br />A narrow band of wetlands occurs in the inundated and saturated soils along Grassy Creek <br />(Figure 2). These wetlands generally occur in soils (Silas loam, Silas Variant loam) mapped by <br />the SCS (1991) as having a hydric component. Most wetlands are periodically inundated by high <br />water during spring and following intense precipitation events during the summer. <br />The vegetation of these wetlands is diverse and related to surface water and soil moisture <br />conditions. Wetlands with standing water or a water table near the surface area are dominated <br />by cattail (7ypha latifolia), an obligate wetland plant. Areas bordering the stream with moist <br />soil due to a high water table aze dominated by herbaceous plants and often have individuals and <br />clumps of willows (Salix bebbiana, S. exigua, and S. monticola). The degree of soil saturation <br />in this habitat is variable and related [o soil texture, topography and the volume of water flowing <br />in the stream. Obligate sedges like Nebraska sedge (Carex nebrascensis) and beaked sedge <br />(Carex utricu[ata) and grasses such as shortawn foxtail (Alopecurus aequalis), reed mannagrass <br />(Glyceria grandis) and nuttall alkaligrass (Puccinellia airoides) dominate the wettest habitats. <br />Facultative wetlands grasses such as redtop (Agrostis alba), spike bentgtass (Agrostis exarata), <br />and tall fescue (Festuca arundinacea), along with Baltic rush (Juncos arcticus ssp. arer), and <br />Torrey's rush (Juncos torreyt) occur in sites with less soil moisture. Upland species such as <br />quackgrass (Agropyron repens), orchard grass (Dacrylis glomerata), agassiz bluegrass (Poa <br />agassizensis), timothy, and meadow fescue (Festuca pratensis) are present in the driest habitats <br />of these wetlands. Table 5.18 provides a list of the major plants' observed in the wetlands <br />communities. <br />• <br />Golder Associates <br />