On the relationship between saplings and ingrowth in northern hardwood stands

Abstract

We used long-term data collected from 22 study sites in northern hardwood stands comprised of sugar maple (Acer saccharum Marsh.), yellow birch (Betula alleghaniensis Britt.), and American beech (Fagus grandifolia Ehrh.) to establish relationships between sapling abundance and tree ingrowth. After 10years, postharvest sapling density in the 6cm diameter class (5.1–7.0cm) showed linear relationships with ingrowth. Proportion of variation explained (r2) varied from 36% to 83% depending upon tree species and silvicultural treatment (partial cutting vs. uncut control). After 20years, linear relationships were also established (r2=24–65%) between ingrowth and sapling density in the 2cm diameter class (1.1–3.0cm). From a wide pool of variables related to stand species composition, climate, physiography, and soil nutrients, postharvest sapling density was most strongly correlated to merchantable tree density (r=0.43–0.75). Sugar maple sapling density was also positively correlated with base saturation and calcium saturation of the B horizon (r=0.56 and 0.58). Over a 30-year period, the increase in American beech sapling basal area was substantial compared to mitigated increases found in sugar maple and yellow birch depending upon treatment. Our results provide useful information on integration of sapling data into forest management.