Relationships between gap makers and gap fillers in an Arkansas floodplain forest

Question:

In floodplain forests, does frequent flooding allow for self-replacement of shade-intolerant tree species or do small canopy gap openings lead to replacement by shade-tolerant tree species?

Location:

Cache River, Arkansas, US; 55 m a.s.l.

Methods:

The species, diameter-at-breast height, and elevation of primary gap-maker trees were determined for new gaps from 1995–1998. The size and species of gap-filler trees were identified and placed into three classes: definitive, edge, or interior. Transition probabilities were determined.

Results:

The dominant shade-intolerant species Quercus texana is being replaced primarily by the more shade-tolerant A. rubrum var. drummondii, Fraxinus spp. and Ulmus americana. Only 20 of 2767 gap fillers were Q. texana. Replacement probabilities are not constant across elevations, however, as the least shade-tolerant of the three most common species of definitive gap fillers, Fraxinus spp., occurred at lower elevations than A. rubrum var. drummondii, and U. americana.

Conclusions:

The contention that frequent flooding would allow for self-replacement of shade-intolerant species was only partially supported. The small canopy gaps undoubtedly influenced canopy replacement processes.