Status Report: 1982-2005 Prairie Community Monitoring Herbert Hoover National Historic Site
Williams M. 2006. Status Report: 1982-2005 Prairie Community Monitoring Herbert Hoover National Historic Site
A result of 22 years of annual prairie inventories and over 26,000 plant observations by Dr. Christiansen has documented a total 212 taxa. Seventy-two percent are native and include warm season grasses such as big bluestem, indian grass, and switchgrass and the ubiquitous herbs common goldenrod, prairie ragwort, and tall lettuce. Common non-native grasses include Kentucky bluegrass and foxtail and common herbs include Canada thistle, dandelion, and wild parsnip. Species richness (number of native and non-native species) increased annually with the highest levels occurring in 1995 after five successive years of prescribed fire. Richness fluctuated during the first ten years of inventories and, after three successive years of fire, dramatically increased. Native species richness decreased after the prescribed fires of 1984 and 1985, increased during the early 1990's with the reintroduction of fire, and has since remained steady. The annual exotic ratio (number of exotic species/total number of species) experienced its lowest ratio in 1992 following three successive years of prescribed fire and has remained steady during the last few years of inventories.