Assessing small-stem density in northern hardwood selection system stands

Data from three uneven-aged northern hardwood stands in New York State were analyzed to assess the effects of understory American beech (Fagus grandifolia Ehrh.) density on changes of small stems within the 2.54 to 5.08 cm diameter class during the first cutting cycle under single-tree selection system. Findings show that the amount of understory American beech on a regeneration plot, quantified using a species index value (SIV), affects the abundance of other species. Results reveal the future plot-level stocking of these small trees for (i) all species (including American beech) as related to time since cutting and residual basal area or (ii) non-beech species as influenced by beech interference (SIV), time since cutting, and residual basal area. Findings indicate that for plots with limited understory beech, small-stem stem density will increase from postcut levels to a peak at 8–12 years after selection system cutting and then decrease. The higher the residual basal area is, the sooner the numbers of small trees reach a peak level and the fewer are present of that threshold size. Findings confirm that no or only minimal numbers of small non-beech trees develop on plots with high levels of understory American beech (SIV ≥ 0.5).