Horse ranching increases biodiversity in a foothills parkland prairie in northern Kananaskis Country, western Alberta

Abstract

Vascular plant biodiversity was evaluated in two adjacent sections of a continuous prairie glade. One section has been subject to moderate grazing by feral horses (Equus ferus caballus) in late summer and fall for the past 25 years, while the other has been protected. From 28 June to 2 July 2009, we recorded cover for all vascular plants present in ten 1-m2 quadrats along five transects in each section. We calculated biodiversity measures, including species richness, evenness, and Shannon-Wiener and Simpson's diversity indexes. Horse grazing did not affect richness but significantly increased evenness. Grazing increased the Shannon-Wiener index, but did not affect the Simpson's index. Cover and frequency values for most species differed significantly between the two sites. Mountain Rough Fescue (Festuca campestris Rydberg) dominated the nongrazed site but several shorter grasses and different forbs dominated the grazed site. The plant community in the grazed areas can be seen as an earlier serai stage of the fescue community with a different contingent of plant species. Light grazing in part of the prairie glade increased overall plant diversity so that it provided more diverse animal habitat.