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Testing Tradescantia ohiensis as an indicator of deer browsing intensity in northeastern Illinois prairies.
Rickey, Marcia 1, Anderson, Roger1, Nelson, Debra2, 1 2
ABSTRACT- We used prairie forb stem counts from deer exclosures and unprotected plots sampled in 1992, 1993, 1994, 1997, 1999, and 2000 to select indicator species to determine deer browsing intensity. Plots were analyzed using Detrended Correspondence Analysis (DCA). Axis one expressed a protection from deer browsing gradient and plots having the longest period of protection had the lowest axis one scores. Stem counts for species were correlated with plot axis one scores to determine the significance and direction of species' responses to the gradient. Of 92 species examined, four (Silphium integrifolium, Monarda fistulosa, Huechera richardsonii, and Solidago canadensis) had significant positive correlations. Ten forb species (Helianthus mollis, Aster ericoides, Rudbeckia subtomentosa, Euphorbia corollata, Veronicastrum virginicum, Rosa carolina, Aster azureus, Tradescantia ohiensis, Commandra umbellata, and Stachys palustris) had negative correlations indicating an increase in stem counts with increasing time of protection from deer browsing. One of these species, (Tradescantia ohiensis), was tested as indicator of deer browsing in six mesic to wet-mesic prairies in northeastern Illinois. Tradescantia was sampled by recording stem heights of flowering plants and the percentage of stems browsed. Sites differed in stem height (p<0.01) and percentage of stems browsed (p<0.0001). Stem height declined as percentage of stems browsed increased (R2=0.1804, p<0.01). Percentage of stems of Tradescantia browsed appeared to increase as deer browsing intensity on sites increased.
KEY WORDS: indicator species, deer browsing, Tradescantia ohiensis, detrended correspondence analysis