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  • Thumbnail for Relict tallgrass prairie of the Upper Black Squirrel Creek drainage, El Paso County, Colorado : change since the 1940's
    Relict tallgrass prairie of the Upper Black Squirrel Creek drainage, El Paso County, Colorado : change since the 1940's by Tsocanos, Sebastian A. E.

    In the mid 1940s remnant tallgrass prairie near Colorado Springs was recognized in vegetation studies on the plains. Tallgrass prairie is unusual in the arid Great Plains, and is of significant conservation value, particularly given the past and present pressures of urban expansion, intense grazing, and water development. Our study examined the question of whether this community type still exists in the region, if the extent of the community type has changed since then, and whether the species composition has changed. We found that while true tallgrass prairie vegetation is no longer dominant at many of the sites used in the original studies, patches of true tallgrass prairie still occur in the area. The extent of tallgrass prairie in the vicinity has clearly declined over the past 70 years. The vegetation of remaining patches is composed of very similar species to those originally documented. We found that the dominant vegetation is still characteristic of true tallgrass prairie. Among the important grasses were prairie dropseed, indian grass, little bluestem), and big bluestem. Important widespread forbs indicative of true tallgrass prairie included american licorice (Glycyrrhiza lepidota), stiff goldenrod (Oligoneuron rigidum), white heath aster (Symphyotrichum ericoides), and purple prairie clover (Dalea purpurea) among many others. We determined that overall precipitation and temperature in the locality has not changed dramatically since the 1940’s. The alluvial aquifer across much of the area is evidently little changed, but hydrology on a site-by-site basis is poorly understood. While the continued existence of some true tallgrass prairie communities here is reassuring, their diminished extent is cause for concern, especially given increasing pressure from urban expansion, livestock grazing, invasive species, and water development. The uncertain status of future temperature and precipitation, as well as the maintenance of critical surface and subsurface hydrologic regimes is also of concern.