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I I I I I, I' I I, I I I , I I I I l II l, ...,,~,~.,) r..)'....;,_)...J. ... SECTIONTWO Environmental SlUing Kentucky bluegrass (Poa pratensis) were invading species prevalent on 40 percent of the sites. In comparison with reference areas, most of the upland sites rated poor to fair condition. In addition, most of the upland sites had lost their tallgrass species and much of their native forb component, especially legumes. Wet meadows were defined by Currier et al. (1985) as areas of grassland within the floodplain which had interspersed emergents or open water. Detailed information about bottomland grasslands is provided in Section 2.7. The grasslands typically consist of grazed pastures with ribbons of palustrine emergent vegetation in depressions that follow the natural drainage patterns. This mapping unit includes three of the meadow vegetation types described by Currier (1982) in his phytosociological analysis of the floodplain vegetation of the Platte River. Wetland meadows are present along intermittently flooded river channels and other lowland areas within open grasslands and woodland. Dominant species include American bulrush (Scirpus americanus), sedges (Carex spp.), spikerush (Eleocharis palustris), fog fruit (Phyla lanceolata), switchgrass, and lady's thumb (Polygonum persicaria). Lowland grazed meadows occur in areas which are too wet to plow or cut for hay. Dominant species include common ragweed (Ambrosia artemisiifolia), Kentucky bluegrass, redtop (Agrostis stolonifera), sedges, and red clover (Trifolium pratense). Lowland prairiefhayfield is dominated by native non-wetland grass species, especially big bluestetn and little bluestem, but also including needle and thread, Indian grass, hairy grama (Bouteloua hirsuta), and sideoats grama. 2.2.3 Riverine Cover Types Riverine cover types include channel, exposed sandbar (beachlbar), herbaceous, shrub, and woody (Currier et al. 1985). Wet meadows were considered to be both a riverine and an agricultural type. Riverine types (excluding wet meadow) occupied about 10 percent of the study area, with the largest types being woody (5.6 percent) and channel (1.6 percent). Channel was defined as the bank to bank inundated channel. The area of channel was greatest in the segments with the least woody vegetation (Segments 1 to 8). The percentage of open water channel ranged between 0.8 percent in Segments 9 and 10 to 2.5 percent in Segment 1. Beachlbar is an ephemeral habitat type that decreases in area with high flows and increases with low flows. Beachlbar was greatest in Segments 9 to 11 (1.1 to 1.5 percent) and was somewhat less in Segments I to 8 (0.2 to 0.8 percent). Areas identified as beachlbar consisted of unvegetated sandbars. These are areas adjacent or within the river channel which are exposed during the summer as river levels decline. Higher river levels during spring cause scouring of the sandbars and removal of short-lived plant species. Herbaceous included herbs and woody seedlings under 3.3 feet tall inside the floodplain. The vegetation includes annuals and biennials that can become established quickly following high water, such as lovegrass (Eragrostis pectinacea), nutsedges (Cyperus spp.), cocklebur (Xanthium strUmarium), barnyard grass (Echinochloa crusgal/i), and sand dropseed (Sporobolus cryptandrus) (Currier 1982). Slightly more elevated areas which are exposed earlier and for a longer period of time develop a modest cover of perennial vegetation, including willow (Salix spp.) and cottonwood (Populus deltoides) saplings, spikerush, purple loosestrife (Lythrum salicaria), prairie cordgrass (Spartina pectinata), and American bulrush. UIIS B1eiDer Mbolfh-ant t:I1* ~Sl:r-.At:es "'0097,","""".doc S/2/1999(9'S2AMl/URSGWC'S>2 2-3