PARENT SESSION
Poster Session #67: Conservation Ecology.
Friday, August 9. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Species composition of summer herb communities under Acer saccharum regeneration thickets.

Schulz, Kurt^*,1, Marriage, Tara¹, Albrecht, Stephanie¹, Zasada, John², Nauertz, Elizabeth³, Buckley, David⁴, Crow, Thomas², ¹ Southern Illinois University Edwardsville, Edwardsville, IL² North Central Forest Experiment Station, Grand Rapids, MN³ North Central Forest Experiment Station, Houghton, MI⁴ University of Tennessee, Knoxville, TN

ABSTRACT- Sugar maple (Acer saccharum) is the dominant canopy species on mesic sites throughout the northwestern Great Lakes Region. Maple forest understories are typically carpeted with seedling maples. Both natural and harvest canopy openings stimulate the growth of maple seedlings. A few years after disturbance, canopy openings >100 m ² can develop into dense, maple regeneration thickets. Regeneration thickets appear to persist 30+ years, until trees reach pole size. Previous work has shown substantial reductions in understory herb cover, and parallel reductions in species richness within regeneration thickets. A number of herb species are less common under regeneration thickets. Selective harvest systems potentially imperil the herbaceous understory because entire stands pass through the regeneration thicket phase roughly every 100 years. This study examined summer herb community composition beneath natural regeneration thickets in the Sylvania Wilderness, Ottawa NF, Upper Michigan. Samples were species lists for 2 x 2 m quadrats mated with overstory measurements for trees, saplings, and seedlings. Ordination analysis of P/A data for species present in >10% of plots separated high richness, densely vegetated understories from less diverse, sparse understories along the first axis. Overhead canopy structure was not related to herb community composition on this axis. The second ordination axis corresponded to the abundance of saplings in the 5.0-7.5 and 7.6-10.0 cm diameter classes, and a corresponding reduction in Lycopodium spp. There was no evidence of a coherent understory community typifying a regeneration thicket. Logistic regression had limited ability to predict the appearance of individual species in relation to canopy characteristics.

KEY WORDS: Acer saccharum, canopy gap, understory herb, forest management