Illinois Natural History Survey Reports

              1
were designed to keep out all
mammals, three contained small
holes at ground level to allow
entry by mice but no larger
mammals, three had gaps at
ground level to allow entry by
squirrels and mice but not deer,
and we left three plots open to all
mammals. In the falls of 2001
and 2002, we buried 25 indi-vidual
northern red oak (Quercus
borealis) acorns in each plot to
simulate squirrel caches, and we
mixed 25 acorns with the leaf
litter on the surface. We counted
surviving acorns the following
ILLINOIS
NATURAL
HISTORY
SURVE Y R e p o r t s
Winter 2004
No. 378
I N S I D E
Evaluation of Dam
Removal on
the Fox River, Illinois
2
Biological Control and
Genetically Modified
Crops
4
Measuring the
Precision of Volunteer
Stream
Monitoring Methods
5
Species Spotlight:
Mantispid
6
Naturalist's Apprentice:
Insect Adaptations
7
Continued on back page
INHS mammalogist Ed Heske digs for acorns in
oak study enclosures. Photo by John Taft, INHS Center for
Biodiversity
Oaks (Quercus sp.) are declining
in their dominance as canopy
species in many midwestern
hardwood forests. Even where
oaks are still prominent in the
forest canopy and acorn produc-tion
appears normal, the propor-tion
of oak seedlings and saplings
in the understory does not seem
adequate to maintain oaks as a
dominant canopy species. Oak
regeneration seems to be least
successful on mesic sites where
faster-growing, shade-tolerant
species such as maples (Acer sp.)
dominate the understory. Some
researchers have predicted that
slow-growing, mast-producing
trees such as oaks and hickories
(Carya sp.) will, in large part, be
replaced in the canopy by meso-phytes,
particularly maples,
within the next 50 years. A de-crease
in the abundance of oaks
could have cascading negative
ecological effects because acorns
are one of the most important fall
and winter foods to wildlife in
many decidu-ous
forests.
Studies of
oak regenera-tion
have
focused
mainly on
factors af-fecting
the
recruitment
of saplings
into the
canopy.
Considerable
evidence has demonstrated how
fire suppression and increased
herbivory by white-tailed deer
(Odocoileus virginianus) may
play major roles in lowering the
From Tiny Acorns...
abundance of oak
seedlings and sap-lings.
Earlier
stages of oak re-cruitment,
such as
acorn survival and
germination, have
received little at-tention
from re-searchers.
Some
acorn consumers,
particularly white-tailed
deer, have
become increas-ingly
abundant in
recent decades,
and others, such as
white-footed mice
(Peromyscus
leucopus) and
many tree squir-rels
(Sciurus sp.),
may reach higher
densities in small
forest fragments
than in extensive
forests. Estimates
of the amount of
the acorn crop
consumed annu-ally
by these species are few and
varied, but sustained increases in
populations of these mast con-sumers
could contribute to low
rates of oak seedling recruitment.
We conducted an experimen-tal
study of acorn survival, ger-mination,
and oak seedling re-cruitment
at four study sites in
east-central Illinois: Allerton
Park, Hart Woods, Brownfield
Woods, and the Vermilion River
Observatory (VRO). At each
site, we constructed 12 experi-mental
exclosures made of steel
and wood frames covered by
hardware cloth. Three exclosures
View of enclosures at
one study site. Photo by
John Taft, INHS Center for
Biodiversity