10 May 2012

Brown County Flora Diversity Revealed

A recently issued scientific paper indicates a great diversity of vascular flora occur in Brown County, Nebraska.

There are 726 plant species, subspecies and varieties known to occur, according to research by Megan K. Killion and Steven J. Rothenberger, associated with the University of Nebraska at Kearney. There are 105 plant families represented.

The diversity is due to the variety of native vegetation types occurring in the 1,221 square miles of the county, from the Niobrara River valley south to the Sand Hills. Specific types identified include sand hills mixed grass prairie, gravelly mixed-grass prairie, ponderosa pine forests/savannas, sand hills borders/mixed-grass prairie, upland deciduous prairie and wetlands.

Another explanation for the floral diversity indicated by the authors, is that "post-glacial forests in the valley serve as a transition zone that supports species with both western and eastern affinities."

"Parts of the Niobrara valley represent a unique transition zone where species with northern, southern eastern and western affinities meet," said Rothenberger. "There are plant species that are more representative of the Black Hills or of montane forest environments than the Great Plains."

The significance of the river valley and its flora "runs far beyond the state's border," he noted in an article prepared for the National Park Service. "Management of the scenic river valley is essential to its biological integrity," he said

Some of the rare or unusual species within the Niobrara Valley include paper birch, hybrid aspen (known as "ancestors of the Pleistocene Epoch" of thousands of years ago), harebell, large-flowered tick-clover, wild columbine, prairie alumroot and different types of sedges.

"It is noteworthy that Megan completed this study as a part of her senior undergraduate research project at UNK," Rothenberger said. "All of our undergraduates are required to complete a research project under the guidance of a mentor (a full-time faculty member of the biology department). She was originally from Brown County and was pleased to discover some new county records that were added to the state's known flora."

There were 14 "new county records" collected, according to the article. The "blue scorpion grass" specimen was only the second for the state, being previously known only from Cass County.

The list of species is based upon specimens collected at 21 sites visited during the 2008 growing season, including Long Pine State Park, the Niobrara Valley Preserve, privately owned pastures and hay meadows and Keller State Park. Their work also involved a review of pertinent publications or material in museum collections to determine additional records.

A comparison was included which indicates the difference in the number of species known for four other Nebraska counties:
Banner - 435
Dixon - 439
Keith - 645
Seward - 613

The recently issued article was in the Transactions of Nebraska Academy of Sciences, 2011 edition. It includes a complete list of those plants recorded thus far in the county. Voucher specimens are now in the herbarium at UNK. Records from this effort have also been added to the Flora of Nebraska (second edition, issued in 2011), by Robert Kaul, David Sutherland, and Steven Rolfsmeier.