Demography of Sugar Maple Seedlings

Dr. Kerry D. Woods, Bennington College, VT

2002-2004

Sugar maple seedlings, living in the deep shade of the forest understory, may be much older than they look; despite low light and heavy deer browse, some surive for several decades. Many older seedlings have extensive 'stem-layering'. Prostrate portions of stems, buried beneath leaf litter, produce adventitious roots. This project attempts to understand the consequenes of this little-studied habit for growth and survival of individuals in this 'seedling bank'.

Bennington College students, Daniel Brese and Peregrine Whitehurst, measuring maple seedlings. Photo, Kerry Woods

Here is the Abstract of a paper reporting results of this study, currrently under review at the Canadian Journal of Forest Research.

"Suppressed seedling banks are important in replacement dynamics in late-successional forests. However, demographic properties of seedling populations are poorly known and there has been little attention to traits that might affect fitness in suppressed seedlings. Acer saccharum, a shade-tolerant dominant in eastern North American forests, frequently develops adventitious roots along prostrate portions of prostrate stems (‘layering’). Measurements of Acer seedlings in old-growth forests in Michigan, USA, indicate that layered seedlings reduce structural allocations to older layered stem tissues, retain allometric properties of younger, unlayered seedlings, and tend to survive longer. In tree seedlings, allometric consequences of normal stem growth lead to declining ratios of photosynthetic to non-photosynthetic biomass; potentially reducing shade-tolerance and limiting age. The layering habit may defer this penalty by changing the allometry of growth. Resulting increases in life expectancy should increase chance of access to increased light and of reaching the canopy. Since flowering is generally restricted to canopy trees, the tendency to layer may thus increase fitness. Properties of individuals in suppressed seedling banks may be selectively and ecologically important, shaping life-histories and population dynamics."