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<br />Environmental Sening
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<br />The BOR is currently creating a new digital land cover/land use database for the Central Platte
<br />Valley study area, using 1 :24,000 color IR aerial photography flown August 21, 1998. The study
<br />area is somewhat larger than the WELUT database, and extends to Lexington. This study
<br />tentatively includes about 39 mapping units, which are generally consistent with but more
<br />detailed than the 24 mapping units used in the WELUT database.
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<br />The vegetation and land cover types used in the WELUT database are described below.
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<br />2.2.1 Croplands
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<br />Based on Currier et aI. (1985), croplands occupy about 62 percent of the study area, including
<br />corn (45.7 percent), other crop (9.1 percent), and alfalfa (7.5 percent). The highest percentages of
<br />com were found in the eastern part of the study area, between Kearney and Chapman. Other
<br />crops include winter wheat, soybeans, sorghum, and fallow fields. The area of alfalfa was
<br />highest in Segments 10 and 1 I. In these segments, alfalfa was grown to supply local dehydration
<br />plants where it is fonned into pellets and sold for feed. There were about 20 dehydration plants
<br />between Kearney and Lexington. Croplands were rarely found inside the floodplain boundary,
<br />but riverine lands have been converted to cropland in a few areas through clearing and leveling.
<br />A minimum mapping area of 10 acres was used for com, alfalfa, and other crops.
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<br />2.2.2 Grasslands
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<br />About 17 percent of the study area is in pasture and hayland including grassland (12.8 percent) ~
<br />and "wet meadow" (4.5 percent) (Currier et aI. 1985). Grasslands were mostly limited to the
<br />highly dissected loess bluffs on the ancient river escarpment 1 to 2 miles from the floodplain.
<br />Most of the wet meadows (bottomland grasslands) were found on large islands in the river
<br />channel, including Mormon Island (Segments 2 and 3), Shoemaker Island (Segment 4), and Fort
<br />Farm Island (Segment 7). Grasslands, including hayed, grazed, and fallow lands, were mapped
<br />with a minimum size of 5 acres, and wet meadows were mapped with a minimum size of 10
<br />acres.
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<br />The principal native grass species of upland native prairie grasslands include the following
<br />(names follow Great Plains Flora Association 1986): big bluestem (Andropogon gerardii), little
<br />bluestem (Andropogon scoparius), sideoats grama (Bouteloua curtipendula), switchgrass
<br />(Panicum virgatum), Indian grass (Sorghastrum nutans), blue grama (Bouteloua gracilis),
<br />western wheatgrass (Agropyron smithii), junegrass (Koeleria pyramidata), and needle-and-thread
<br />(Stipa comata) (Sidle and Faanes no date). Common forbs include scurfpea (Psoralea spp.),
<br />dotted gayfeather (Liatris punctata), false boneset (Kuhnia eupatorioides), Missouri goldenrod
<br />(Solidago missouriensis), purple prairie clover (Dalea purpurea), aster (Aster sp.), and scarlet
<br />globemallow (Sphaeralcea coccinea). Typical shrubs include eastern pricklypear (Opuntia
<br />macrorhiza), lead plant (Amorpha canescens), western snowberry (Symphoricarpos
<br />occidentalis), white coralberry (Symphoricarpos albus), smooth sumac (Rhus glabra), and
<br />soapweed yucca (Yucca glauca).
<br />
<br />Nagel et aI. (] 995) evaluated 279 native prairie sites in the Central Platte Natural Resources
<br />District (NRD) within Buffalo and Dawson Counties. Smooth brome (Bromus inermis) and
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