Landform-mediated differences in successional pathways among upland forest ecosystems in northwestern Lower Michigan.

Seedling and sapling densities were compared with current overstory composition in 30 upland forest stands. Patterns of compositional change were strongly related to topographic and edaphic differences among glacial landforms. Glaciofluvial landforms, currently dominated by oak (Quercus spp.) have relatively high densities of oak seedlings (4913 stems/ha) that seldom move into the sapling layer (10 stems/ha). Oak-dominanted ecosystems on hilly ice-contact stratified drift exhibited relatively high densities of red maple Acer rubrum saplings (48 stems/ha). Oak-dominated ecosystems on extremely well drained outwash plains exhibited sparse sapling regeneration of any species; red maple was typically absent, and oak saplings were usually in an apparent state of decline. Difference in the potential for recruitment of saplings into the overstory among these ecosystems may be attributable to differences in fire history or site-dependent effects on the competitive abilities of species. Morainal landforms, currently supporting relatively diverse northern hardwood overstories, showed little potential recruitment of any species other than sugar maple A. saccharinum. -from Authors