Effects of harvest gap size, soil scarification, and vegetation control on regeneration dynamics in sugar maple-yellow birch stands

Abstract

We investigated short-term regeneration dynamics after group selection cutting with understory vegetation control and soil scarification in a northern hardwood forest. We used three gap sizes based on mean height (H) of neighboring trees in a replicated experiment: small (0.75H), medium (1.25H), and large (1.75H) gaps. After 5 years, all gap sizes led to abundant density of yellow birch (Betula alleghaniensis Britt.) and sugar maple (Acer saccharum Marsh.) regeneration, associated with sufficient light (>38% of canopy transmittance), favorable seedbeds (50% of ground cover in disturbed leaf litter or exposed mineral soil), and reduced competition from noncommercial species due to vegetation control. We found no differences in tree species diversity patterns among gap sizes, but diversity patterns changed over time due to increased density of shade-tolerant conifers. After 5 years, yellow birch regeneration was positively influenced by increasing distance from the gap center and stand species composition, but negatively influenced by percent cover of undisturbed leaf litter, graminoid cover, and raspberry cover. The percent variation explained was relatively low (R2 = 0.26). Overall, group selection with soil scarification and vegetation control was successful in establishing desired tree species, especially yellow birch and sugar maple, but further monitoring is required to determine its long-term efficacy.