Floristic Composition and Structure of Two Dry Sand Prairies at Sand Ridge State Forest, Mason County, Illinois

Burns and Quiver prairies, located about 3 km apart, are dry sand prairies in small forest openings on ridges and swales of large stabilized dunes at Sand Ridge State Forest, Mason County, Illinois. Dominant species were nearly identical on both prairies. Schizachyrium scoparium (little bluestem) had an importance value of 40.1 on Quiver Prairie and 35.7 on Burns Prairie. Tephrosia virginiana (goat’s-rue), Opuntia humifusa (common prickly pear), and Ambrosia psilostachya (western ragweed) were among the top five species on both prairies. Other common grasses were Dichanthelium villosissimum (hairy panic grass) on both prairies and D. depauperatum (panic grass) on Quiver Prairie. Both prairies, less than 5 ha in size, are situated in forest openings and are subjected to extensive woody encroachment. The C-value and FQI for all native species for Burns Prairie was 3.93 and 35.8 respectively with 13 species having a CC of 7 or greater. For Quiver Prairie the C-value was 4.25 and the FQI was 38.0 with 15 species having a CC of 7 or more. Prescribed burns at irregular intervals have reduced woody encroachment, but more effort is needed as trees species, particularly oaks and Junperus virginiana (red cedar) are becoming more common.