1 Windstorm disturbances create a wide range of microsites which can have c
omplex effects on forest regeneration patterns. We investigated the combine
d effects of light and microtopography on emergence, mortality and size of
seedlings of two bottomland hardwood canopy tree species, Quercus michauxii
and Liquidambar styraciflua, over a 2-year period. A split-plot design in
experimental tanks represented the range of light levels and the pits and m
ounds found in a disturbed floodplain forest.
2 Emergence was always higher on mounds than in pits, except for L. styraci
flua in full sunlight. For both species, mortality was consistently lower,
and seedlings of both species grew better in both years on mounds. Light le
vels did not affect the two later stages.
3 There were species-specific interactions between the effects of two facto
rs on seedling emergence, Lower emergence of L. styraciflua on mounds in fu
ll sunlight suggested that full sunlight at this stage can eliminate the ad
vantage to later stages of being on a mound. The combined stresses of low l
ight and a high water table significantly reduced emergence of Q. michauxii
in pits at low light.
4 Microsites optimal, for one regeneration component of a species were not
always optimal for others as seen for L. styraciflua. The relative signific
ance of environmental factors also varied with regeneration stages, such th
at neither light nor a light-water interaction influenced regeneration afte
5 Environmental factors may have independent or interacting effects on rege
neration, and the nature or presence of these effects can vary among demogr
aphic stages. Within each environmental combination, effects may be consist
ently positive or negative across stages; alternatively, demographic confli
cts may develop.