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r~ .. zo viability. Furthermore alteration of hydrologic regimes, possibly due to factors beyond the control of DOE, may lead to associated changes in vegetation throughout the drainage, potentially degrading Preble's meadow jumping mouse habitat on the site. Any proposed activities on this site that would significantly alter the existing hydrology should be considered a serious threat to the survival of Preble's meadow jumping mouse. Xeric tallgtass prairie management recommendations: The existence of this increasingly rare xeric tallgrass prairie as a natural area could be a valuable education tool while contributing to conservation. The area should be managed as a tallgrass prairie site. 'The greatest threat to this community on the buffer zone is invasion by exotic plant .species. Further increase of exotic species may decrease the biodiversiry significance of the site by altering the native floral and faunal species composition (Bock and Bock 1988, West 1993). .Several exotic species occur in the community in various quantities. These species include cheatgrass, Japanese brome, musk thistle (Carduus nutans), Kentucky bluegrass, toadflax (Linaria dalmatica), alyssum (Alyssum minus), and knapweed. Of these :species, musk thistle, toadflax, alyssum, and knapweed present the greatest threat of increasing invasion of the grassland. Other species mentioned above appear to be present in small disturbed patches but do not seem to spread into undisturbed areas. l~lusk [histle, toadflax, and alyssum are common in areas with little recent disturbance. Krtapweed is common to dense along gravel access roads throughout the area and has spread from the roads a shoe distance into the relatively undisturbed prairie (S. Kehler personal observation). It is no[ known if this species will spread further into the prairie over the course of time. Knapweed seems to be aggressively expanding in the area around the Front Range of Colorado (CNHP unpublished data). We observed that :significant sources for several weeds are on the adjacent mining sites as well as within the Rocky Flats Environmental Technology Site. To adequately protect this ecosystem ~Nill require continued partnerships with the adjacent landowners and managers, particularly to manage weeds and restore gravel mining sites and other significant areas. Aggressive management (herbicide application, manual cutting, etc.) may be necessary to control these species. Early season grazing, burning, or mowing may be affective management tools to control many of the cool season exotic plants and favor warm season dominant native plants. Ecological Monitoring Program sire TRO1 (U. S. Dept. of Energy 1994a) would be considered a good baseline monitoring site because of its location in a relatively pristine part of the xeric tallgrass prairie. More species- s:pecific management techniques are no[ presented in this report since relevant information already exists in the Weed Control Program described in the Watershed Irlanagement Plan for Rocky Flats (U. S. Dept. of Energy 1993). (treat Plains Riparian Woodland and Shrubland Management Recommendations: Exotic <_.pecies heavily dominate the understory in the mosaic of plant associations that make ttp this commurtiry and have severely degraded the community. It is suspected that