Document: NIN-3-65-1

Colonization potentials of tree species in fragmented forests.

HEWITT, N.* ¹ and M.KELLMAN ²

Depaul University, Chicago, IL 60614, U.S.A. ¹
York University, Toronto, ON, Canada ²

Abstract:
Forest fragmentation represents a huge change in the biogeographic "context" of forested systems, to which plant species are only now adjusting. Ecologists are concerned that species diversity will decline in fragmented systems because colonization of fragments will be insufficient to counteract ongoing local extinctions. This study examined the potential for tree species to colonize forest fragments in terms of their abilities to be dispersed to and establish seedlings in fragments lacking conspecifics. Seeds and seedlings of four native hardwoods, Carya cordiformis, Betula alleghaniensis, Fagus grandifolia, and Juglans nigra were experimentally introduced into forest fragments in the Long Point Region, Southern Ontario. Survivorship curves were constructed for each species for the period encompassing the post-dispersal seed stage, germination, through to the end of fourth year seedling establishment. The chance of the species' seed arriving in a fragment from an extraneous seed source was indicated by empirical observations of inter-fragment dispersal in the study area. Results indicated that three of the four species had less than a 2 % chance of producing a fourth year seedling in a fragment due to high rates of rodent seed predation and low rates of germination and first year survival. All species had extremely low chances of seed dispersal to fragments located >150 m from a seed source. Tree species thus face severe barriers to inter-fragment colonization as a result of both dispersal and establishment constraints.

Keywords: tree colonization, fragmented forests, tree migration

This abstract is being presented at: 11:00 AM in session:
Oral Session #58: Landscape Ecology.