Floristic and Vegetational Analysis of the Hecla Sandhills of Northeastern South Dakota

A floristic survey and vegetational analysis of 71 tracts of land in the Hecla Sandhills of northeastern South Dakota was conducted in the summers of 1996 and 1997. The survey resulted in the compilation of a species checklist of 414 vascular plant species, 3 new to the state and 3 with considerable range extensions. Percentage of exotic species was higher for sites in the western portion of the study area (14.7%) than sites in the central core portion of the study area (11.7%). Kentucky bluegrass (Poa pratensis), big bluestem (Andropogon gerardii), and western ragweed (Ambrosia psilostachya) were dominant species in the central core sites. Kentucky bluegrass, smooth bromegrass (Bromus inermis), and western ragweed were dominant species in the western study sites. Subsamples (releves) were analyzed on each tract of land in order to attain a quantitative assessment of typical plant communities present in the area. Analysis of releve data by Correspondence Analysis (PROC CORRESP in SAS, 1989) ordered the releves and their component species according to an apparent moisture gradient. A floristic quality assessment of sample tracts was done using the Chicago Method (Swink and Wilhelm 1994). The Chicago Method required the assigning of a coefficient of conservatism or C value to each native vascular plant species found in the area. C values ranged from 0 to IO with IO representing the highest degree of conservatism. Based on species composition, a floristic quality index (FQI) value was calculated for each tract. Tracts of land were ranked from high to low quality based on FQI. Native pastures in the central core sites had the highest FQI values, averaging 51. Native hay meadows in the central core site had an average FQI value of 49. Native pastures in the western study sites had an average FQI value of 47. Formerly tilled pastures in the western study sites had an average FQI value of 42. On average, the formerly tilled sites and highly disturbed sites had lower FQI values than native sites