Plant Community Changes Following Closure of Artesian Wells in Great Sand Dunes National Park, Colorado

Artificial artesian wells have existed in the San Luis Valley of south central Colorado for over 100 years, and they are an important source of water for livestock and wildlife. When Great Sand Dunes National Park and Preserve (GRSA) expanded its boundaries in 2000, ten of these wells were within the new park boundary. Because the habitat surrounding the wells was so severely disturbed by cattle and wildlife trampling, the National Park Service capped the wells in 2010 to promote restoration of the areas to a more natural state. To study changes after well-capping, we compared the plant communities in 2011 and 2012. We measured and compared plant cover, species frequency, and species diversity at recently capped wells on GRSA, at flowing wells (i.e., with water) on adjacent private lands of The Nature Conservancy, and at reference sites. In general, there was little difference in percentage of plant cover and species diversity between well types. For percent cover, annual variation and distance from wellheads were the best predictors for the native and exotic plant species, respectively. Plant species composition varied by well type, with reference sites having the greatest frequency of native plants per site and capped well sites having the greatest frequency of exotic plants per site. For native plants, reference sites had the highest species diversity, while capped wells had the highest community evenness. Overall, our results suggest that in the short term, native plant populations have changed little after well-capping, but the frequency of exotic plants has increased at capped well sites relative to reference sites.