SREL
Reprint #2580
Microenvironmental
heterogeneity and Quercus michauxii
regeneration in experimental gaps
B.S.
Collins*, L.L. Battaglia
Savannah River Ecology Laboratory, PO. Drawer E, Aiken,
SC 29802, USA
Abstract
Canopy gaps are
foci for forest regeneration; the gap environment ' t promotes
establishment and tree growth into the canopy. In bottomland
hardwood forests, microtopography and light are modified
simultaneously in natural gaps. Their combined effects may
influence seedling establishment and growth. Desirable red
and white oaks are often regenerated in bottomland hardwood
forests through group selection cutting that mimics the
gap environment. We tested effects of canopy openness and
microtopography on regeneration of a moderately shade-intolerant
oak, Qercus michauxii, in experimental canopy gaps
in a bottomland hardwood forest on the Atlantic Coastal
Plain. Gap sizes were centered on the median opening size
of natural gaps in an old-growth bottomland hardwood forest.
Acorns were planted at 100 random level locations in and
around each of two replicate 7, 10, 14, 20, 29, and 40 m
radius gaps in early spring. Acorns were also planted on
pit and mound microtopography complexes created in the center,
at the edge, and under intact canopy surrounding two 29
m and three 40 m radius gaps. Over all gaps, 21-37% of the
randomly located acorns emerged and survived one summer;
8-26% survived two summers. Survival was influenced more
by seedling size than by gap size or distance from gap center.
Seedlings on level locations that survived two seasons were
taller in the first year, had greater maximum leaf area,
and tended to be farther from the center of large gaps than
seedlings that died after I year. Height of second-year
seedlings was related more to first-year plant size than
to distance from gap center or gap size. Seedling emergence
from acorns planted on microtopography complexes was greater
on mounds than in pits at gap center and beneath intact
canopy; no seedlings emerged in pits in the gap center.
Once established, seedling survival and growth on the microtopography
complexes was higher at the gap center. Management of bottomland
hardwoods for Q. michauxii regeneration from acorns
may be most successful if practices that create conditions
favorable for formation of a seedling bank, i.e. raised
topography beneath a thin canopy, are followed by light
harvests that promote seedling growth and ascent into open
canopy.
Keywords:
Bottomland hardwoods; Canopy gaps; Heterogeneity; Microtopography;
Querus michauxii; Oak regeneration
SREL Reprint
#2580
