VEGETATION AND VASCULAR FLORA OF TALLGRASS PRAIRIE AND WETLANDS, BLACK SQUIRREL CREEK DRAINAGE, SOUTH-CENTRAL COLORADO: PERSPECTIVES FROM THE 1940s AND 2011.

We examined a tallgrass prairie-wetland complex of the Black Squirrel Creek drainage in south-central Colorado to compare the current grassland composition to its documentation by Robert Livingston in the early 1940s. Livingston considered these grasslands as probable Pleistocene relicts analogous to Midwestern tallgrass prairie with respect to dominant grasses and forbs. Using Livingston's methodology, we assessed an area near his original plots to determine whether the dominant grass species had changed in their contributions to cover or frequency. We found an almost identical suite of species to those documented in the 1940s, with modest differences in frequency and relative contribution to cover by the key grasses. We also characterized wetland habitats occurring within the grassland matrix, documented the vascular flora of mesic and hydric habitats, and analyzed the extent to which they contain species of conservation concern, Midwest prairie elements, or montane species typically occurring regionally at higher elevations. The tallgrass communities here differ from others in Colorado and the Midwest in having a lower abundance of Andropogon gerardii, and being dominated by Sporobolus heterolepis along with xeric species like Bouteloua gracilis and Calamovilfa longifolia, and montane species like Muhlenbergia montana. Although the structure of the extant vegetation remains similar to what existed in the 1940s and continues to be supported by ample groundwater, these grasslands are now reduced in extent. The vegetation mosaic of tallgrass prairie and wetlands holds a rich flora with numerous elements of phytogeographic and conservation interest. [ABSTRACT FROM AUTHOR]