Open Access Thesis
Botany--Iowa--Black Hawk County;
Black Hawk County, located in the east-central part of the state of Iowa, is a political subdivision of 570 square miles. The topography of the county is the result of glaciation, erosion and deposition, causing gently rolling plains. The Cedar and the Wapsipinicon rivers transect the county from the northeast to the southwest. With their tributaries, these rivers comprise a natural drainage network which has enhanced agricultural practices throughout the county.
The vascular flora of the county was surveyed in the field during the growing seasons of 1982 and 1983. Over 1500 voucher specimens were collected. Data were also compiled from over 2500 herbarium specimens of collections made in Black Hawk County. The documented flora of native or naturalized plant species known to grow or to have grown independent of cultivation consists of 826 species representing 399 genera and 98 families. Eighteen species are included on the Iowa list of threatened and endangered species, including two species unique to the state: Carex leptalea Wahl. (Cyperaceae) and Dalea villosa (Nutt.) Sprengel (Fabaceae). Another rare species, Rubus hispidus L. (Rosaceae) is also found only in Black Hawk County in the state. An annotated catalog of the species has been compiled and includes nomenclature, common names, frequency of occurrence, habitat, and specimens examined.
Pre-settlement vegetation was examined in relation to the soils, and percentage of vegetation in the county was calculated in a general segregation of forest, prairie, and marsh. Calculations of 13.5%, 91.0%, and less than 0.1%, respectively, were derived from distributions of soil types. Forested areas were found mainly along water courses. Upland forests arose adjacent to the floodplains and prairie areas were generally associated with the uplands. Wet prairies and marshes were found in poorly drained lowland areas. Agriculture has played a major role in diminishing the natural areas in the county. Native vegetation has been confined largely to sandy areas, riparian areas, wetlands, marshes, and railroad right-of-ways.
The vegetation of Black Hawk County has been categorized within six major divisions: forest, savannah, prairie, wetland, pond, and cultural. Subdivisions of floodplain forest, upland forest, sand forest, prairie, sand prairie, limestone prairie, sedge meadow, and marsh have been recognized within the major divisions. Research sites representing each of these areas were visited, and species lists were compiled for each.
A checklist of rare species not collected since 1970 was compiled. Additional field reconnaissance may relocate these species and provide information on their frequency in the county. Sandy areas, formed by eolian (windblown) or alluvial deposition, in the county have provided some interesting habitats for some species not commonly found in the state. These sandy areas could be studied extensively and a sand flora compiled for the county.
Date of Award
Master of Arts
Department of Biology
Tallgrass Prairie Center
Lawrence J. Eilers, Chairman
1 PDF file (viii, 217 pages)
© 1987 Karen E. Van Norman
Van Norman, Karen E., "A survey of the vascular flora of Black Hawk County, Iowa" (1987). Electronic Theses and Dissertations. 194.