Early changes in forest structure and deer use in a 140-site northern hardwoods alternative silviculture systems study.
Inadequate stocking of desirable stems in sapling classes of northern hardwood forest in some regions of Michigan inspired a 140-site evaluation of silvicultural alternatives to current management by selection silviculture. The study’s goal is to identify combinations of silvicultural treatments that increase the diversity and density of sapling recruits over forested landscapes where deer-browsing pressure and other limiting factors are at play. Here we summarize pre-harvest and early post-harvest (1-2 years) vegetation and deer use data. Pre-harvest data bolstered justification for the research; over most of the Michigan northern hardwood resource stands remain even-aged despite 3-4 partial harvests since the 1960s, with sapling classes often old (>70 yrs, understocked with desirable species, and dominated by American beech and ironwood. Deer use, high basal area, and lack of local seed sources were related to low regeneration density and diversity. Although insufficient to predict long-term outcomes, early post-harvest regeneration (50-137 cm tall (smaller) and >137 cm tall-< 11.4 cm DBH (larger)) densities differed among species and harvest treatments relative to pre-harvest; e.g., American beech declined in smaller and larger classes, especially in the most open treatment (i.e., seed tree harvest); sugar maple and ironwood declined in the larger class but increased in the smaller class, especially when protected from deer by tree tops; pin cherry and paper birch were near absent in pre-harvest forests, with post-harvest density highest in the seed tree harvest. Deer use varied spatially and increased following harvesting, especially in more intense harvest treatments. Browsing preferences varied regionally and among species; e.g., low: American beech, balsam fir, high: yellow birch, pin cherry, elm. We anticipate the combination of early regeneration responses to treatments, and interspecific and environmental differences in growth rates and filtering by deer browsing pressure will drive future canopy composition.