An examination of species-specific growing space utilization

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.