| The recent popularity of uneven-aged management as an alternative to clearcutting has prompted a renewed interest in the comparative utility of uneven-aged silvicultural techniques, especially in forest types where both techniques are applicable and where even-aged systems are undesirable because of biodiversity or aesthetic concerns. We examined the influence of single-tree and group selection on productivity and species composition in hemlock-hardwood forests in northeastern Wisconsin. A combination of field and analytical methods was used to assess the influence of canopy openings created by these methods on stand-level production. An empirical forest model was also developed, which integrates understory and overstory productivity.; The standing crop of whole-tree aboveground biomass per hectare was greater in multiple-tree gaps (80–800 m2) than single-tree gaps (<80 m2) of similar age. However, biomass production approached an asymptote at fairly small opening sizes, and 400–800 m2 group-selection openings did not have significantly more biomass per unit area than small-multiple tree gaps (80–100 m2). Similarly, mean tree dimensions, recent height increments, and basal area increments for most species of gap trees approached an asymptote at an opening size of approximately 100 m2. As opening size increased, yellow birch (Betula alleghaniensis) superseded hemlock (Tsuga canadensis) as the species with greatest relative biomass. However, based on estimates of initial opening area, it appears that midtolerant species, such as yellow birch, require an opening >200 m2 to successfully reach the canopy. Consequently, relatively small group-selection openings (200–400 m2) may regenerate a range of species in these forests.; Growing space efficiency (production per unit area) in these structurally diverse hemlock-hardwood stands increased with increasing canopy position, but within a given stratum declined with increasing crown size. No clear trends were observed with shade tolerance class between the species examined. However, once in the canopy, hemlock was the most efficient and productive species.; Based on our field data and permanent plot records maintained by Menominee Tribal Enterprises, we developed an empirical forest model (CANOPY). Preliminary model runs and statistical validation tests suggest that CANOPY may be useful for examining the long-term response of hemlock-hardwood forests to various silvicultural prescriptions. |
