Replacing Hay-mowing with Prescribed Fire Restores Species Diversity and Conservation Value in a Tallgrass Prairie Sampled Thrice: A 59-Year Study

We examined changes in plant species composition at * avilie Fraine in southeastern Wisconsin, based on surveys in permanently-marked, 2 X 2 m quadrats in 19461948, 1976-1978 and 2005. Permanent quadrats were distributed across a wide soil moisture gradient. During settlement he site was never cultivated but was mowed for hay for several decades prior to 1946, and burned most years during the dormant season after 1946. Total species richness increased 47% between 1946-1948 and 2005, while species density per quadrat doubled. Only nine non-native species were present in 2005 and most were uncommon. Species density of habitat generalists increased nearly fourfold; moderate specialists increased 43%; and remnant specialists increased nearly twofold. Species density of endangered, threatened and special concern species (collectively conservation-dependent species) increased ninefold. Species density of C3 graminoids, C4 grasses, legumes, woody plants and forbs all increased through time. The majority of species density increases were attained by the 1976-1978 sampling period and remained high since. Elsewhere in Wisconsin, prairie habitat specialists have been declining. Our findings run counter to general trends throughout the state. It is likely that the change from annual mowing to annual prescribed burns accounts for the increases in species density.