PARENT SESSION
Oral Session #59: Conservation Ecology: Terrestrial Biodiversity. Presiding: K. Schulz.
Thursday, August 9, 2001. 8:00 AM to 12:15 PM. Madison Ballroom D.
Effects of partial canopy removal on the richness and cover of understory flora in northern hardwood forests.
Crow, Thomas1, Buckley, David2, Nauertz, Elizabeth 1, Zasada, John1, Szabo, Lidia3, 1 2 3
ABSTRACT- To improve our understanding of how management affects the composition and structure of understory vegetation (woody species < 1 m in height and herbaceous species) in northern hardwood forests, we compared unmanaged sugar maple (Acer saccharum Marsh.) dominated forests to those with a partial removal of overstory trees. Unmanaged forests included both old growth and second growth. Three replicates of each condition were located on the Winegar Moraine in Michigan's Upper Peninsula. As expected, thinning the overstory and disturbing the forest floor through tree harvesting promoted the development of understory vegetation. Total cover of understory vegetation increased significantly under management and the number of understory species in managed stands doubled compared to unmanaged baselines. Increases in number of species occurred in all species groups - summer green herbs, graminoids, ferns and allies, and woody plants - although as a proportion of the total flora, graminoids increased and ferns and allies decreased under management. Four of the 55 species (7%) sampled in old growth were not sampled elsewhere. In comparison, 31 of the 110 species (28%) sampled in managed uneven-aged forests were not sampled elsewhere. However, the added species in managed forests were common in the landscape and so they added little to species richness at larger spatial scales. More attention should be given to those species thought to be sensitive to disturbances related to human activities
KEY WORDS: plant composition, forest understory, biodiversity, management