A comparison is made among the size–density relationships of sugar maple ( Acer saccharum Marsh.), European beech ( Fagus sylvatica L.), Norway spruce ( Picea abies (L.) Karst), lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.), eastern white pine ( Pinus strobus L.), Scots pine ( Pinus sylvestris L.), loblolly pine ( Pinus taeda L.), and Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var. menziesii ). Species-specific minimum density of full site occupancy (N_MCA) and average maximum density (N_AMax) equations were developed using forest inventory data and existing models. N_MCA and N_AMax estimates were used to compare species growing space utilization over a range of stand diameters (12–50 cm). Results suggest growing space utilization varies among the evaluated species and that species differences may change over the diameter range evaluated. Analysis also highlights that a growing space usage gradient is present across species. One end of the gradient is occupied by species that maintain higher densities at small sizes and exhibit greater rates of density decline as mean diameter increases. In contrast, other species maintain lower densities at small diameter, but have lesser rates of density reduction as diameter increases. Finally, results highlight the importance of using species-specific models when quantifying size–density relationships and developing stand-density management regimes.

This study investigated whether soil scarification during the presence of abundant white oak (Quercus alba L.) acorns and other mast could be used to increase the density of oak reproduction and reduce competitive midstory species in a mid-successional mixed-oak upland forest. The study was conducted in a 7.3 ha forest with a mature oak overstory and a well-developed midstory of sugar maple (Acer saccharum Marsh.) and pawpaw (Asmina triloba Dunal.) in southern Illinois. The soil scarification was conducted in the autumn after acorn dissemination using a crawler tractor with a six-tooth brush rake. One growing season after treatment, significantly higher numbers of oak seedlings, primarily white oak, were present in the scarified plots (5,164 ha^-1) compared to the control plots (1,273 ha^-1). Seedling density of all other species classes did not differ between treatments. Scarification affected 61% of midstory trees and thus reduced their density and competitive position. Of these trees, 21% of stems were completely removed by the scarification treatment. Results suggest that, in the presence of abundant acorns, scarification may increase the number of new oak germinants in stands lacking advanced oak reproduction. Finally, because scarification increased the density of oak seedlings and reduced competing midstory trees, it can play a role in promoting the establishment of advanced oak reproduction. North. J. Appl. For. 20(2):85–91.