The Characteristics and Phytogeographic Affinities of the Flora of Nine-Mile Prairie, a Western Tall-Grass Prairie in Nebraska

Three hundred ninety-two species, subspecies, and varieties have been recorded at Nine-Mile Prairie, a relict tall-grass prairie that has been reduced from 323 to 97 ha in the past 50 years. There are 218 native and 17 introduced herbaceous perennial species, and 73 native and 24 introduced annuals. Analogous numbers for biennials are 15 and 11, for shrubs are 14 and one, for trees are ten and three, and for woody vines are six and none. One hundred twenty-one native species are of central and eastern North American phytogeographic affinity, and 109 are of transcontinental affinity. Seventy-nine of the Prairie's native species occur only in the central part of the continent, but only 27 are characteristic of the western and central parts. Five habitats are utilized to categorize the vegetation: wooded ravine, upland prairie, disturbed upland prairie, wet prairie, and aquatic. Data are presented on the distribution of growth habits and phytogeographic affinities for the habitats. The upland prairies have more native and introduced species than either the wet prairies or ravines. However, the relative proportions of growth habits, flowering phenologies, and phytogeographic affinities are not the same in the various habitats. The flora of the wooded ravines is mostly of eastern affinity, while that of the upland prairies has strong western and central phytogeographic elements.