Title

Vegetative Comparison of Two Gravel Ridge Prairies with Different Grazing Histories in Polk County, Minnesota

Document Type

Thesis

Publication Date

1994

Advisor

Steve Saupe

Abstract

The vegetation of a gravel ridge running the length of two native prairie remnants, the Stipa Wildlife Management Area (WMA) and the Tympanuchus WMA, in northwestern Minnesota was compared during June, July, and August 1993. The Stipa WMA was grazed by confined domestic cattle from 1958 to 1977, while the Tympanuchus WMA has been relatively undisturbed. The vegetative composition of each area was compared qualitatively by compiling a plant species list for each ridge. Quantitative vegetative comparisons were conducted by recording abundance and cover values for individual plant species in twenty-five 0.5 m2 random sample plots on each ridge during the first two weeks of August. The calculated Shannon-Wiener diversity index values showed the Tympanuchus WMA ridge vegetation to be more diverse than the Stipa WMA ridge vegetation. Also, 10 plant species predicted to decrease with grazing were found with significantly greater frequency and in higher abundance on the Tympanuchus WMA ridge, while 4 species categorized as weedy invaders under conditions of grazing were found with greater frequency and in higher abundance on the Stipa WMA ridge. Data collected on species expected to increase under heavy grazing pressure, however, were inconclusive. As predicted, the vegetation on the grazed native prairie gravel ridge was less diverse than that on the undisturbed native prairie ridge and consisted of more weedy, introduced plant species and fewer plant species palatable to large grazers.

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