A Floristic Analysis and Comparison of Plant Communities in Harlan County, Nebraska

Historically, the Republican River Valley in Harlan County, Nebraska, has been extensively explored, but the county flora has continually been under-represented and has been found to lack records for plants that are considered common. During the 2009 growing season, a taxonomic study and comparison of 3 different sites in Harlan County was made. Site #1 was pastureland and Sites #2 and #3 were both riparian, located on the north side of the Republican River. Collections were pressed, dried, identified, and deposited in the University of Nebraska at Kearney Herbarium (NEBK). Forty-eight new county records were verified, in­cluding cutleaf-cucumber (Cyclanthera dissecta), a Tier 2 species listed by the Nebraska Natural Legacy Program. The species com­position of three sites were compared using both Jaccard’s (ISJ) and Sorensen’s (ISS) indices of similarity which are based on the species in common to two given sites and species that are exclusive to each site. According to Sorensen Index values, the two ri­parian sites (Sites #2 and #3) had the greatest percent similarity (ISS =56.6%), followed by Sites #1 and #3 (ISS = 51.9%) and Sites #1 and #2 (ISS = 47.2%). Using Jaccard’s index of similarity, separation among the sites was not as apparent. The floristic quality indices (FQI) for Sites #1, #2, and #3 (25.08, 12.07, and 22.96 respectively) were somewhat low when compared to FQI values from previous studies in the Loup River Valley of Nebraska. This study helps to document the current plant diversity of the area and updates the known flora of Harlan County, which now totals 395 species