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SECTIOHTWO Environmental Setting j I ,I ,I I 'I I J I , I \1 Shrub was defined as woody vegetation 3.3 to 13 feet tall in the floodplain. Shrub vegetation gradually increases from Overton to Chapman. This cover type includes five shrub communities representing various topographic positions (Currier 1982). Common species include coyote willow (Salix exigua), false indigo (Amorpha fruticosa), diamond willow (Salix rigida) and cottonwood, with red-osier dogwood (Comus stolonifera) being locally abundant and rough- leaved dogwood (c. drummondii) on drier sites. Woody was defined as woody vegetation over 13 feet tall and consists of riparian woodland and forest. The highest concentration of woody vegetation occurs in Segments 8 to 11, between Kearney and Overton. Currier (1982) identified nine distinct forest vegetation types, all of which are dominated by cottonwood, but which are separated by understory tree, shrub, or herbaceous composition. Other prevalent tree and shrub species in riparian forests include green ash (Fraxinus americana), rough-leaved dogwood, diamond willow, red cedar (Juniperus virginiana) Russian olive (Elaeagnus angustifolia), American elm (Ulmus americana), red mulberry (Morus rubra), false indigo, and hackberry (Celtis occidentalis). 2.2.4 Other Types Other types include upland woods, emergent vegetation, and open water. Most of the woodlands along the Platte River Valley consist of woodlots and shelterbelts around homesteads and range from 1.0 to 2.8 percent of segments (Currier et aL 1985). Common species include cottonwood, red cedar, Russian olive, green ash, American elm, slippery elm red mulberry, box elder (Acer negundo), silver maple (Acer saccharoides), hackberry and Siberian elm (Ulmus pumila) (Sidle and Faanes no date). The ground layer is usually poorly developed, consisting of various grasses including Kentucky bluegrass and timothy. Woodlands were mapped at a minimum of 05 acres. Emergents primarily occur in association with large grassland complexes outside the floodplain (Currier et aJ. 1985). South of the Platte there are extensive wet meadow/emergent communities in Segments 1, 6, and 7. There are also some emergent communities north of the river in Segment 6. Emergent vegetation includes species such as cattail (1yPha spp.), hardstem buirush (Scirpus acutus), American bulrush, spikerush, water sedge (Carex aquatilis), and various species of smartweeds (Polygonum spp.). The major type of open water is lakes formed as a result of sand and gravel operations. Along 1- 80, there are a number of interstate lakes that were created during construction of the highway in the 1960s. 2.2.5 Development Development cover classes include urban and commercial developments, single dwellings, roads, bridges, powerlines, railroads, and gravel operations (Currier et al. 1985). The minimum polygon size used in the development classification was 0.5 acres. Developments occupied about 8 percent of the study area, with the largest types being roads (3.3 percent), commercial/urban (2.1 percent), and single dwelling (0.9 percent). Segment 3 has a larger 24 68FOD9nB6CXlh1.l:Ioc 6I211999(9:52AM}/URSGWCFS/2 I1RS BleilEr ~1f "JdlI FedeI'aI StIrrIt:u