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1 January 2008 Differential effects of understory and overstory gaps on tree regeneration
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Gaps in the forest canopy can increase the diversity of tree regeneration. Understory shrubs also compete with tree seedlings for limited resources and may depress tree recruitment. We compared effects of shrub removal and canopy windthrow gaps on seedling recruitment and understory resource levels. Shrub removal, with the canopy left intact, was associated with increased levels of understory light and soil moisture and coincided with increased species richness and diversity of tree regeneration compared to both control plots and canopy gaps. Canopy windthrow gaps, however, resulted in a more than 500 fold increase in soil nitrate concentrations, and seedling growth rates that were twice as high as that observed with shrub removal. Our results suggest that gaps in the understory shrub layer and the overstory canopy may have complementary effects on resource availability with corresponding benefits to seedling establishment and growth.

Brian Beckage, Brian D. Kloeppel, J. Alan Yeakley, Sharon F. Taylor, and David C. Coleman "Differential effects of understory and overstory gaps on tree regeneration," The Journal of the Torrey Botanical Society 135(1), 1-11, (1 January 2008).
Received: 17 May 2007; Published: 1 January 2008

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