Light and regeneration patterns following silvicultural gap establishment in Quercus dominated stands of the northern Cumberland Plateau, USA

We assessed short-term light and regeneration dynamics following silvicultural gap creation in intermediately productive oak (Quercus)-dominated stands of the Northern Cumberland Plateau, USA. We established 12 experimental units comprising a harvest gap (30-m radius) and a matrix zone extending 30 m beyond the circumference of the gap. Midstory removal was performed using manual felling and chemical deadening within the matrix zone of six experimental units, while those of the other six units remained undisturbed as controls. Belt transects extending 60 m from the gap center to the end of the matrix zone were delineated within each unit to quantify spatial light patterns and regeneration dynamics of oaks and woody competitors. Mean light transmittance ranged from 86% full sun at the gap center to<10% at the outer margin of the matrix zone. Light transmittance decreased from approximately 70% full sun within the gap at 10 m from the gap edge to 20% full sun at 10 m within the forest matrix. Two-year height growth and total heights of oaks were greatest within the gap interior and decreased toward the gap edge and subsequently into the adjacent forest matrix. We observed no statistical differences in light or regeneration patterns between control and midstory removal forest matrix zones. After two years, woody competition from non-oak stems, particularly yellow-poplar (Liriodendron tulipifera L.), was high within the gap interior, and >50% of non-oak stems were taller than the average oak seedling (50 cm). At the gap edge and within the adjacent forest matrix, <20% of non-oak stems were taller than 50 cm. Light conditions fostering taller oak reproduction and reduced rates of overtopping competition identify the gap edge environment as a zone of competitive oak reproduction within which future regeneration efforts may prove effective.