sunlight between control and moderate damage plots and light and
moderate damage plots; based on measures of light at breast
height. We did not find significant differences in measures from
our hemispherical photographs. The difference between percent
of full sunlight on control v. light damage plots was not discernible,
which does not necessarily mean canopy gaps had been completely
filled, but rather that well-developed individuals in the midstory
increased sufficiently in height and crown volume to negate the
increases in light from canopy gaps. Although the canopy was still
open at our sampling, midstory stems restricted light to the
seedling and sapling layers. Consequently, even though the mean
percent of full sunlight in the moderate plots fell within the 20–
50% range required for understory Quercus stems (Dey, 2002), light
levels below breast height (i.e. light level in the regeneration layer)
were insufficient for Quercus recruitment.
Percent of full sunlight on control and light damage plots, which
best represented actual understory light levels at breast height,
were comparable to those from the region (Canham et al., 1990;
Schweitzer and Dey, 2011 ). Schweitzer and Dey (2011) quantified
forest response to different levels of regeneration harvests in north
Alabama and the levels of canopy openness and gap fraction they
documented after three growing seasons were comparable to those
found in this study after the same time since disturbance. The stage
of stand development is particularly important when evaluating
the effects of intermediate-scale disturbances on understory light
levels. The majority of stems disturbed by the wind event were
canopy trees, and during the understory reinitiation stage the midstory in these forest systems is well-developed. Thus, rather than
creating new opportunities for the establishment of new stems,
the disturbance served largely as a mechanism to release stems
already present in the midstory. Consequently, the resultant
changes in the light regime at breast height were ephemeral and
lasted only a few growing seasons.