Effects of Different Silvicultural Treatments on the Distribution of Light in Upland Hardwood Forest Stands of the Cumberland Plateau.

Although manipulation of the light regime is a common goal of silvicultural treatments, the specific light conditions created are poorly documented for many forest types and geographic locations. To help quantify effects of silivicultural treatments on light conditions, basal area, canopy structure, and photosynthetically active radiation (PAR), collected both instantaneously and across time, were measured in central hardwood forests following silvicultural treatments. These measurements were used to: 1.) investigate the magnitudes of differences in understory percent ambient PAR following implementation of shelterwood and thinning treatments; 2.) document the specific amount and variability of understory percent ambient PAR in shelterwood treatments (mean residual basal area=21 ft2/ac [4.8 m2/ha]), thinning (78 ft2/ac [17.9 m2/ha]), and untreated controls (18 ft2/ac[4.1 m2/ha); and 3.) Examine relationships between: basal area and canopy cover; basal area and measured percent ambient PAR; and canopy cover and measured percent ambient PAR. It was found that greater light levels resulted from greater canopy removals. Indexes of variability in light across time and among locations within a stand were higher in the shelterwood and thinning treatments than in the uncut control. Simple linear regression relationships were observed between basal area and PAR (r2= 0.8784 for instantaneous measurements, r2= 0.9697 for continuous measurements), and basal area and canopy cover (r2=0.8479). Such relationships provide a means for including light management in forest planning and application of silivicultural treatments.