PARENT SESSION
Poster Session #49: Reproductive Ecology.
Friday, August 10, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
114
Sugar Maple and Eastern Hemlock forest dynamics at the seed and seedling stage.
Olander, Deborah1, Reich, Peter1, 1
ABSTRACT- We are trying to understand the mechanisms that allow predominantly sugar maple Acer saccharum and predominantly eastern hemlock Tsuga canadensis stands to exist side-by-side, during steady-state conditions, for centuries without mixing. Plots were placed in adjacent sugar maple and hemlock stands in three sites: Porcupine Mountains State Park, Upper Peninsula (U.P.) of Michigan; Sylvania Wilderness Perimeter area, also in the U.P. of Michigan; and Woodruff, Wisconsin in the U.S.A. Natural regeneration among various microhabitats and litter treatments were monitored. An additional set of plots with planted seeds was also monitored for the same treatments. We proposed that sugar maple litter interfered with the emergence and survival of hemlock seedlings under the sugar maple canopy and that this effect would be ameliorated if seeds dispersed on mounds and logs rather than onto flat ground. We hypothesized that microtopography would have no effect on the establishment of sugar maple seedlings under the hemlock canopy. The results demonstrate a higher rate of emergence and survival of hemlock seedlings on logs and mounds under both canopy types. There are significantly fewer sugar maple seedlings under the hemlock canopy than under a conspecific canopy. Dispersing onto a log is detrimental for sugar maple emergence and survival under both canopies. In addition, litter treatments showed that disturbance or removal of sugar maple litter under the sugar maple canopy did improve germination of hemock seedlings, but not their survival. Litter treatments had no effect upon sugar maple seedlings. The combination of positive seed rain and substrate microsite interactions beneath each canopy appear to contribute to the maintenance of patch boundaries in this old-growth ecosystem.
KEY WORDS: Acer saccharum , Tsuga canadensis , patch maintenance, seedling emergence and survival