Document: KUR-3-99-137

Does dense sugar maple regeneration in gaps reduce herbaceous understory species richness in western Great Lakes conifer-hardwood forests?

SCHULZ, K.* ¹, J.ZASADA ², K.KAHL ¹, E.NAUERTZ ³ and D.BUCKLEY ⁴

Southern Illinois University Edwardsville, Edwardsville, IL 62026 USA ¹
USDA Forest Service Grand Rapids, MN 55744 USA ²
USDA Forest Service Rhinelander, WI 54501 USA ³
University of Tennessee, Knoxville, TN 37901 USA ⁴

Abstract:
Sugar maple, Acer saccharum, is the dominant species in the mesic conifer-hardwood forests of states adjacent Lake Superior. Forest management practices, logging history, and heavy browsing pressure by white-tailed deer, Odocoileus virginianus, maintain, and have probably increased the dominance of maple in the region. Maple recruits heavily to the entire forest floor. Formation of large, single tree gaps and bigger openings permits stands of seedlings to develop into crowed populations of larger individuals 2-5 m tall. Light availability beneath these populations is low (typical midday PAR < 20 E m^-2 s^-1). Cover of herbaceous species in these areas is conspicuously low. Widespread propagation of canopy openings during harvest could conceivably convert large parts of the forest understory into this kind of herb habitat. We examined summer herb communities beneath an array of seedling/sapling canopies in the Sylvania Wilderness (Ottawa NF in the MI Upper Peninsula) to determine whether this pattern of forest regeneration eliminated certain species locally, and potentially reduced species richness. Seeding/sapling overstories in the 2-5 m height range were associated with a doubling in the area of non-vegetated surface, but no reduction in species richness. Shorter and taller overstories were not associated with a reduction in cover or richness, suggesting that this phase of canopy replacement forms a temporary constraint on understory species. If microsuccessional patterns of herb diversity are a predictable result of maple canopy dynamics, it is important to limit the extent of canopy opening in forest harvest. Small, isolated herb populations created as part of the microsuccessional sequence are prone to local extinction.

Keywords: Acer saccharum

This abstract is being presented at: 3:30 PM in session:
Oral Session #16: Plant Demography: Trees and Shrubs.