Assessment of Oklahoma Phlox (Phlox oklahomensis: Polemoniaceae) in the Gypsum Hills of Northwestern Oklahoma and Southern Kansas

Phlox oklahomensis Wherry, Oklahoma phlox, occurs within the tall grass prairie of the southern Flint Hills of Kansas, and other populations occur within the southern mixed grass prairie of the Gypsum Hills of northwestern Oklahoma and southern Kansas. The first census of Oklahoma phlox in northwestern Oklahoma and southern Kansas was conducted over a three-year period (1980-1982). The second and third censuses occurred approximately 20 years after the first census, in 2002 and 2003. Since the 1980s two major wildfires and several droughts have occurred throughout its distribution range. The goals of this research were to compare the 1980-1982 census and the 2002 and 2003 censuses of Oklahoma phlox to censuses conducted in 2020 and 2021 and assess the current status of the species. In addition, we used a geographic information system (GIS) to identify factors that influence the likelihood of finding Oklahoma phlox in the region. The final census found that the occurrence of Oklahoma phlox has not changed significantly over the last 40 years. Populations thrive in areas where the fire interval is >5 years, and it commonly occurs on the upper elevations of the landscape on hilltops and/or ridges where the slope is > 7%. Although plants were observed on all landscape exposures, populations occur more frequently on west and northwest facing slopes. The authors recommend an S3 ranking for Oklahoma phlox.