Response by Three Plant Indicator Groups of Upland Habitat to Manipulation of a Black Oak (Quercus velutina) Sand Barren

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Natural Areas Journal


In the absence of a disturbance regime, flora at historical oak sand barrens change as leaf litter builds up and increasing canopy cover shades bare soils. Over time, black oak sand barrens become more mesic, and other trees including Acer rubrum, Fraxinus sp., Prunus serotina, and Sassafras albidum often mix with oaks in the canopy. Three different restoration techniques were applied to recreate disturbance across 10 sites within degraded black oak (Quercus velutina) glacial kames, which are mounds of sand and gravel deposited by melting ice sheets: select canopy tree thinning favoring 5-30% tree canopy cover, forest floor leaf litter removal, and prescribed fire. Ground layer richness and abundance 1 and 3 y after treatment were assessed within modified North Carolina Vegetation Survey plots and compared against both temporally and spatially equivalent control sites. Thinning the canopy induced the greatest vegetation response in species diversity, whether as xeric-tolerant indicator species, graminoid species, as a taxonomic group, or pooling all plants. Leaf litter removal produced a modest pulse response from a few select species released from the shade-creating effects of accumulating leaf litter. Prescribed burns did not create a disturbance sufficient for any significant plant response, presumably because low-intensity burning minimally reduced leaf litter cover. Thus, manipulations that opened the canopy and reduced soil moisture more directly induced barren-species recovery than did efforts to recreate historical disturbance processes.