CHARACTERIZATION OF THE HYDROLOGIC VARIABILITY OF HABITATS INHABITED BY THE ENDANGERED BUNCHED ARROWHEAD (SAGITTARIA FASCICULATA) IN THE UPPER PIEDMONT OF SOUTH CAROLINA

The Bunched Arrowhead, Sagittaria fasciculata, is an endangered plant that thrives in very limited and specific hydrologic and geographic settings in the Piedmont region of North and South Carolina. The plant requires a shallow, continuous, and slowly flowing water supply, a well-hydrated organic soil with an underlying sandy substrate, and partial or complete shade. The plant appears to be hydrologically very sensitive, yet prior to this study little was known about the hydrologic variability of its habitat and the plant’s tolerance to hydrologic disturbance. This study used pressure transducers recording at five minute intervals to monitor the hydrologic variability and stage response to storm events at six different Bunched Arrowhead sites in Greenville County, South Carolina from June – December 2012. The health and density of the Bunched Arrowhead populations were also tracked at each site for the duration of the study. The six sites reflect the broadest range of hydrologic regimes in which the plant naturally resides within the Piedmont region of South Carolina. In addition to the stage and health assessments, detailed habitat characterization (e.g., shade extent, flow rates, land cover type) was also assessed. Four of the sites exhibited fairly stable, essentially static water levels that, barring very large rain events (>9 cm), rarely fluctuated more than 10 cm during storm events. These sites also had the most robust, healthy, and largest populations of the six sites, with plants that were taller, with broader leaves, and a vibrant green color. The other two sites have recently been impacted by residential development and exhibited surprisingly flashy responses with stages fluctuating as much as 25 cm with individual storm events. The health and populations at these two sites are now limited and have been significantly impaired, with plants noticeably smaller and yellow-brown in color. The plant’s distinct and sensitive habitat requirements make it particularly vulnerable to changes in the hydrogeology and/or land cover from encroaching development. This study highlights the importance of quantifying the Bunched Arrowhead’s hydrologic tolerances to determine how to best manage and protect this endangered plant.