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Effects of Biennial Fire and Clipping on Woody and Herbaceous Ground Layer Vegetation: Implications for Restoration and Management of Oak Barren Ecosystems

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Abstract

Savannas and oak barrens are threatened in North America, due, in part, to removal of natural disturbance regimes. However, the periodic prescribed fires used in savanna and oak barren management sometimes accelerate the formation of a shrub layer, which can displace herbaceous species. This may be because periodic low severity fires act much like clipping, topkilling shrubs, yet allowing them to accumulate reserves in intervals without fire for more vigorous sprouting. To test this, we compared biennial dormant season burn prescriptions to a fire surrogate (clipping) using three oak barrens sites in the Bluegrass Region of southern Ohio. Fire and clipping treatments did little to suppress the resprouting ability of shrubs (woody stems <2 cm dbh), which regrew rapidly and in equivalent densities following treatment. However, both treatments reduced shrub cover, resulting in a 35% decrease in shrub cover over the course of the study. In contrast, non-manipulated plots experienced a 44% increase in shrub cover over the same time period. Despite this reduction in shrub cover, treatments had no effect on herbaceous plant cover, richness, diversity, or evenness. These results suggest that the use of biennial prescribed dormant season fire, as employed in this study, is equivalent to clipping, and although effective at temporarily reducing shrub cover, is not effective in reducing shrub densities or resprouting potential. Thus, burning during marginal conditions should be avoided for achieving a short-term restoration goal of shrub removal, but can be effective for maintaining the current shrub layer.

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