Guano Creek-Sink Lakes RNA

Sink Lakes-Guano Creek Research Natural Area (RNA) was established to represent the Wyoming big sagebrush/needle-and-thread (Artemisia tridentata ssp. wyomingensis/Hesperostipa comata) and Thurbers needlegrass (Achnatherum thurberianum) communities. The RNA includes three vernal lakes (including Billy Burr Lake) which are dry playas in drought years and vernal pools during wet years. Tertiary-age basalt flows are dissected by the Eugene-Denio Lineament, giving rise to numerous faults that create a series of northwest-southeast trending grabens containing intermittent lakes. The playas are ringed by silver sagebrush/Nevada bluegrass (Artemisia cana/Poa nevadensis) and the surrounding uplands are dominated by Sandberg bluegrass (Poa secunda), Wheeler bluegrass (Poa nervosa), and Thurbers needlegrass (Achnatherum thurberianum). Tansy-leaf evening primrose (Camissonia tanacetifolia) dominates dry lakebeds while willow, basin wildrye (Leymus cinereus) and sedges dominate the borders of Guano Creek. Two Bureau sensitive plant species, grimy ivesia (Ivesia rhypara var. rhypara) and Crosby's buckwheat (Eriogonum crosbyae) grow on special soils of welded ash and tuffaceous sandstone.