The patterns of understory light environments in central Appalachian oak-hickory forests have not been well studied. The purpose of our study was to evaluate the effect of prescribed burn regimes on light availability in forest understory plots on the Wayne National Forest in southern Ohio. Hemispherical fisheye photography was used to record vegetative cover above 108, 0.125-ha plots evenly divided among three treatments (Control, Infrequently, Frequently burned). Images were digitized and then analyzed with the GLI/C canopy assessment software. Reported measurements include percentages of Open Sky and total seasonal Global Radiation estimates. No significant differences were detected among burned and unburned plots after one year. Frequently burned plots had significantly higher light availability than the Control and Infrequently burned plots after two years (P < 0.05). After two growing seasons, mean measures (± S.E.) of percent Open Sky for Control, Infrequently, and Frequently burned treatments were 3.67 ± 0.30, 3.78 ± 0.43, and 4.61 ± 0.48, respectively. Third year light transmission data were regressed against a previously determined integrated moisture index (IMI) value for each plot. Relationships between IMI and light indices were significant, but of low predictive value (low R2).

Key words: forest understory, gap light index, light availability, prescribed burns