North American Prairie Conference


Date of this Version



Published in Dave Egan & John A. Harrington, editors, Proceedings of the 19th North American Prairie Conference: The Conservation Legacy Lives On..., University of Wisconsin-Madison, August 8-12, 2004 (Proceedings of the North American Prairie Conference, 19), Madison, WI: University of Wisconsin-Madison, 2004.


Mound-building Formica ants may be important biotic factors within prairie restorations because mounds found in virgin prairies can exist for decades, with densities up to 1,148 mounds/ha (465 mounds/acre). Research on the effects of Formica ant mounds on a virgin and an adjacent restored prairie (treatments) was established in 2003 near Olathe, Kansas; and it was expected that percent soil moisture, soil bulk density, plant species' distributions, and percent plant cover would be significantly affected. Data were collected from active mounds (28 in virgin prairie, 21 in restored prairie), and from paired off-mound sites 1 m (3 .3 ft) north of each mound. On-mound soils were significantly drier and less dense when both treatments were combined, and within each treatment (P < 0.05, respectively). Goldenrod (Solidago spp.) and sleeping plant (Chamaecrista fasiculata) occurred significantly less often, and with lower cover, on mounds when both treatments were combined (P < 0.01). Within the virgin prairie, goldenrod differences were significant (P < 0.03), and within the restored prairie, sleeping plant differences were significant (P < 0.01). The cover of big bluestem (Andropogon gerardii) was significantly higher on mounds when both treatments were combined (P < 0.03), and when compared within the restored prairie (P < 0.02). This paper demonstrated that mound-building ants significantly affected the virgin and restored prairies' soils and plants, but with variable intensities. These variable effects may have been caused by soil structure and plowing history interactions because mound surfaces were different colors between treatments. These possible interactions should be studied. Also, effects may not be the same at other locations because some prairie restorations have many mound-building ants while others have few. It may be determined, with more study, that mound-building ants should be included in restoration plans.