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Northern Prairie Wildlife Research Center

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Floristic Quality Assessment for Plant Communities of
North Dakota, South Dakota (excluding the Black Hills),
and Adjacent Grasslands


The natural landscape of North and South Dakota has been modified extensively since pre-European settlement. Large tracts of land have been tilled and put into agricultural production; wetlands have been drained, filled, and farmed; rangelands have been grazed by domestic livestock at timings and intensities that do not match those of native herbivores; and natural fires have been suppressed. Consequently, remaining natural areas display varying degrees of quality due to habitat alterations, and many of the region's native plant species have been reduced or eliminated from vast areas where they formerly occurred. As habitats have been altered, plant species adapted to these habitats have been replaced by other (often non-native) species better suited to the new ecological conditions. As pressures to develop remaining natural areas continue, so does interest in preserving, restoring, and managing them. Effective methods are needed to identify areas of high floristic quality for preservation and to evaluate the effectiveness of current restoration and management efforts.

Swink and Wilhelm (1979, 1994) developed and later refined a system (floristic quality assessment) for assessing the quality of natural areas in the Chicago region of Illinois. Their system was based on the concept that plant species display varying degrees of tolerance to disturbance, as well as varying degrees of fidelity to specific habitat integrity. They termed this tolerance and fidelity "species conservatism" and assigned each native plant species in the Chicago region a coefficient of 0 to 10 based on its conservatism relative to other native species in the region's flora. Given the assumption that the floristic quality of an area is directly related to its richness in conservative species (Wilhelm and Ladd 1988), the assigned coefficients of conservatism (C values), together with a list of native plant species present in an area, can be used to index the floristic quality of that area (Swink and Wilhelm 1994). Subsequently, floristic quality assessment has been expanded to include Michigan, Missouri, the remainder of Illinois, and northern Ohio (Ladd 1993, Andreas and Lichvar 1995, Taft et al. 1997, Herman et al. 1997), and interest to expand the effort to other regions is growing. Here we provide C values for plant species of North Dakota and South Dakota, excluding the Black Hills, (hereafter referred to as the Dakotas) to facilitate the use of floristic quality assessment in this region and adjacent grasslands.

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