Effect of Fire Intensity on Understory Composition and Diversity in a Kalmia-Dominated Oak
Forest, New England, USA
Author(s): Mark J. Ducey, W. Keith Moser and P. Mark S. Ashton
Reviewed work(s):
Source: Vegetatio, Vol. 123, No. 1 (Mar., 1996), pp. 81-90
Published by: Springer
Stable URL: http://www.jstor.org/stable/20048654 .
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123: 81-90,
1996.
Vegetatio
1996 Kluwer Academic Publishers.
?
Effect
of fire
intensity
81
Printed
in Belgium.
on understory
composition
oak forest, New England, USA
Kalmia-dominated
and diversity
in a
Mark J.Ducey, W. Keith Moser & P.Mark S. Ashton
Yale School of Forestry
Received
21 December
and Environmental
1994; accepted
Key words: Community
in revised
Studies, 360 Prospect
form 5 September
structure, Ordination,
Street, New Haven,
CT 06511, USA
1995
Prescribed burning, Regeneration
Abstract
This
stands following fire of varying intensity.
study investigates the understory dynamics of two mixed-oak
and
and
of
herbaceous
in
the
in two stands
Composition
woody
diversity
species
understory were measured
7-8 years after a prescribed burn. On both sites, unburned areas, low-intensity fire areas, and areas where the
overstory had been severely damaged were measured. Patterns of species presence and absence following fire
were consistent with an initial-floristics model. Most species increased in density and
frequency following fire;
only Aralia nudicaulis and Quercus alba showed statistically significant decreases in density. Overall, 29 species
increased in density following fire, while 8 declined; 29 species increased in frequency, while 6 declined. However,
diversity and equitability measures were depressed on themoderately burned sites, due to rapid regrowth of Kalmia
to both
latifolia. Ordination using binary discriminant analysis suggested species responded individualistically
burning
and
site
variation.
Introduction
Evidence suggests that recurrent fire played a major
role in promoting the pre- and post-settlement
dom
inance of oak (Quercus) forests in the landscape of
eastern North America
some
(Abrams 1992). While
and
historial
studies
disagreement remains, ecological
suggest that many forested areas, including southern
New England, experienced periodic burning with a
return frequency of one to over fifteen years (Buell
et al. 1954; Day 1953; Little 1974; Russell
1983).
The absence of fire or other disturbance has been cited
as
the
a
potential
apparent
cause
conversion
for
oak
regeneration
of many
oak
failures
forests
and
to other
1992; Abrams & Downs
types (Abrams & Nowacki
et
al.
Host
Lorimer
1990;
1987;
1984). However, two
factors suggest that fire may play an increasing role
in northeastern American forest ecosystems. First is
a renewal of interest in prescribed fire as a manage
ment ool (Boerner et al. 1988; Crow 1988; Niering et
al. 1970; Nyland et al. 1982; Wendel & Smith 1986).
Second is the prospect of large-scale climate change
due to increases in atmospheric CO2, which could
alter vegetation distributions and disturbance regimes
(Overpeck et al. 1990,1991). Past warm climates have
been associated with episodes of increased burning
by Native Americans
(Thompson & Smith 1970) and
with increases in regional importance of oak (Davis
1985; Watts
1980). A warmer, drier climate could
increase rates of both prescribed and accidental fires,
helping maintain or increase oak forests (Overpeck et
al 1991).
Despite the importance of fire to oak forest ecosys
tems, a clear picture of the relationship between fire
intensity and the dynamics of oak forests has yet to
emerge. This is particularly true of the herbaceous
and woody understory, which are frequently grouped
together in a single layer. This layer is believed to con
trol short-term nutrient flux in some ecosystems
(e.g.
Gilliam 1988; Peterson & Rolfe 1982; Siccama et al
this layer is important because
1970). Successionally,
it contains
advance
regeneration
for many
tree
species
and both woody and herbaceous competition for any
future recruits. The condition of this layer prior to
major disturbances or during understory reinitiation
82
can influence future forest composition dramatically
(Oliver & Larson 1990).
This study examines the effects of fire on understo
ry diversity and composition at two sites in northeast
ern Connecticut. We hypothesized that severely burned
areas with no overstory would be characterized by a
high diversity of both woody and herbaceous species,
with little or no loss of species characteristic of the
unburned sites. Such a response would closely follow
Egler's (1954) initial floristics model of succession. We
considered it possible, however, that intensely burned
areas where the overstory was killed would show a
shift in species
dramatic
ination
of many
composition
late-successional
the elim
with
herbs,
shrubs,
and
that on burned
tree seedlings. We also hypothesized
areas, where the overstory remained largely intact, the
sprouting ability and shade-tolerance of Kalmia lati
folia would allow it quickly to reoccupy the site and
exclude
other
shade-tolerant
tive
species,
woody
while
species
on more
would
sites,
open
gain
a
less
competi
advantage.
slow (approximately 1m min-1 ), and flame length was
variable but generally less than 30 cm. While Kalmia
foliage is somewhat flammable, flame heights seldom
extended to the laurel canopy (Nute 1985; Yale Forest
file report). The pre-fire canopy of the Red Front site
was dominated by Pinus strobus, Quercus velutina,
Quercus alba, and Betula lenta, with a total density of
550 stems ha-1 and a basal area of 32 m2 ha"1. On the
lightly burned part of the site, approximately 40% of
the density and 30% of the basal area were eliminated
by the fire. On the severely burned portion, 70% of the
density and 60% of the basal area were eliminated.
The Buell Brook site is located on moderately well
drained Woodbridge
extremely stony fine sandy loam,
a mixed mesic Typic Fragiochrept (USDA 1981). The
current stand is approximately 90 years old. The stand
was thinned in the late 1970's and burned in the final
week of April 1984. Burn conditions were similar to
those for the Red Front site. The pre-fire canopy of
the Buell Brook site was dominated by Quercus rubra,
Betula
alba,
Quercus
Acer
and
lenta,
rubrum,
with
a total density of 1,050 stems ha-1 and a basal area
of 39 m2 ha-1. On the lightly burned portion of the
Study area
site,
there
extensive
studied two sites, both on the Yale-Myers Forest
at 41? 55' N 72? 05' W.
in Eastford, Connecticut,
were
Both sides
approximately 4 ha in area. Prior to
burning, each site had a homogenous overstory stand
We
structure, with an understory dominated by Kalmia lat
in the
ifolia, an evergreen ericad which is widespread
formed
Kalmia
both
On
sites,
region (Kurmes 1967).
dense thickets known locally as "laurel hells", includ
ing stems greater than 5 cm DBH and over 2 m tall.
Half of each site was subjected to controlled burning;
the Red Front site in 1985, and the Buell Brook site in
1984. On both sites, the burn was hotter than expect
was
little
stem
mortality,
On
the
apparent
occurred.
scarring
severely
although
burned
portion, 95% of the density and basal area were elimi
nated.
Methods
We measured understory vegetation
and the Red Front burn in August,
4.047
sixteen
sites,
ically located
control,
and
circular
plots
were
in each of three treatments:
moderate
severe
m2
at Buell Brook
1993. At both
burn
burn
with
with
heavy
light
overstory
overstory
damage.
systemat
unburned
damage,
Ferns,
1 ha patch of the burn area,
ed on an approximately
to
extensive
mortality in the overstory.
leading
The Red Front site is located on somewhat exces
fine
sively drained and well drained Charlton-Hollis
fern allies, and sedges were tallied by presence and
absence on each plot. All other species were counted by
stem number. Species identification and nomenclature
followed Fernald (1950). Densities were compared
loams, comprised of Typic and Lithic Dys
trochrepts derived from thin glacial tills (USDA)
1981). The current stand is about 80 years old. The
stand was thinned in the late 1970's, and a prescribed
burn was conducted during the final week of April
1985. At that time of year, herbaceous ephemerals had
leafed out, but bud break was just beginning in peren
nials and in the overstory. Fuel moisture was 28% in
the morning, but decreased to 18% by afternoon, con
was
tributing to hotter burn conditions. Rate of spread
test (PROC
for all species using the Kruskal-Wallis
Institute
SAS
NPAR1WAY,
1988).
statistics were calculated separately for
Diversity
for herbs (not
each site and treatment combination,
and
all
species com
including sedges), woody species,
sandy
bined. Simpson's
(1949) diversity
(D) and equitability
83
(E) were calculated
as (Begon et al
Species stem density by site and treatment is shown in
Table 1.Among the herbaceous species, Aster divari
=
my
D
Results
1986):
Desmodium
catus,
=1
um bor?ale,
ciliare,
Gali
virginiana,
Fragaria
Gaultheriaprocumbens,
Mitchellarepens,
and Rubens pubescens
increased in density on burned
sites, while Aralia nudicaulis declined on the Red
*=?
Front
where S is the number of species observed, N is the
total number of individuals, and n? is the number of
individuals of species i. Shannon-Weaver
diversity
(J) were calculated as (Begon
(H) and equitability
etal 1986;Whittaker
1972):
site,
it was
where
um hirsutum,
Impatiens
Uncommon
sites include Epilobi
Monotropa
capensis,
uniflora,
strobus,
latifolia, Pinus
Kalmia
Betula papyrifera,
rubra,
Quercus
resinosa,
velutina,
Quercus
Kubus idaeus, and Vitis labrusca increased in density
on the burned sites, while Quercus alba declined. Sas
safras albidum also declined, but the populations were
not significantly different. Uncommon
species found
on
Amelanehier
burned
sites
included
sp., Betula
only
H
J=
abundant.
Solidago bicolor, and an unidentified composite, while
Cypripedum reginae and Epigaea rep ens were found
the woody species,
only on unburned plots. Among
Pinus
s
most
found only on burned
species
In S
Betula
allegheniensis,
Cornus
populifolia,
racemosa,
a and the sampling error of S and N were
calculated, and the adequacy of the limiting distribu
tion was tested, following Fisher et al (1943). The
nonlinear equation for a was solved directly using the
method with safeguards
constrained Newton-Raphson
as implemented by Press etal. (1992).
Relationships between species, site, and treatment
found only on unburned sites.
in Table 2.
statistics are summarized
Diversity
Number of species increased significantly with burning
only on the Red Front site. No site and treatment com
were
bination differed
Fisher's
investigated using Q-mode binary discriminant
analysis of the plot frequency data (Strahler 1978). The
method involved three stages: test of significance in
contingency tables, calculation of standardized resid
uals, and principal components analysis. Significance
of the 2x2 site contingency table was evaluated using
Fisher's exact test (PROC FREQ, SAS Institute 1988).
Significance of the 3 x 2 treatment contingency tables
was evaluated using the likelihood ratio chi-square test
(PROC FREQ, SAS Institute 1988). Where the 3 x 2
contigency
between
tables
treatments
were
were
sparse,
made
pairwise
using
comparisons
Fisher's
exact
test, and significance was rejected if no comparison
tested as significant using Bonferroni-adjusted
proba
bilities. Species were retained for further analysis if
either site or treatment were probably significant at
(1973) standardized residu
p < 0.10. Haberman's
als were calculated following Strahler (1978). Prin
cipal components analysis (PROC PRINCOMP, SAS
Institute 1988) was performed using all the treatment
residuals and the Red Front residuals; the Buell Brook
residuals
were
redundant.
sp.,
Crataegus
tremuloides,
Populus
Fraxinus
americana
bution
among
and
species
Front
site.
in diversity
In general,
measures
Carya
cordiformis,
were
baccata
Gaylussacia
from the density distri
significantly
a showed significant
latifolia,
Spirea
while
and Viburnum acerifolium,
assumed
a.
by Fisher's
Fisher's
treatment effects only on the Red
in number
increases
were
greater
and
and more
changes
consistent
on the Red Front site than on the Buell Brook site.
Species frequencies and significance of site and
treatment are shown in Table 3. Results of the prin
cipal components analysis are shown in Table 4. The
first principal component is positively associated with
shaded plots and a preference for themore mesic Buell
Brook site over the Red Front site. The second princi
pal component indicates a strong association with the
Red
Front
site
and,
to a
lesser
degree,
with
interme
diately burned plots. The third principal component,
which accounts for only 18 percent of the variance, is
associated
with
a
preference
for
the
control
plots
over
the moderately burned plots, and weakly with a prefer
ence for the Red Front site. Species scores are plotted
in Figure 1.
84
Table
1. Species
by site and treatment
per hectare,
density
Red Front
Control
Species
Buell Hill
No
Overstory
Intact
Herbaceous
Cypripedum
reginae
Desmodium
ciliare
Epilobium
hirsutum
0
canadense
Maianthemum
Monotropa
uniflora
99,700
0
40,600
5,600
18,400
23,600
152,600
135,100
4,200
48,800
2,600
2,600
4,800
7,400
15,900
1,500
11,300
9,400
770
3,200
4,500
1,900
2,000770
133,000
154
2,000
0
0
0 0 0 150
0 0
composite
000 0
620
310
49,400
0
150
4,800
0
bicolor
borealis
0
0
0
Trientalis
0 1,100
0150
150
Kubus pubescens
Unknown
00 0
310
61,800
repens
0
4604,300
0 0
0
0
capensis
Mitchella
Woody
Sig.
Overstory
02,200
02,300
25,600
0
460
1,400
procumbens
Solidago
No
0
0
0 0
bor?ale
Impatiens
48,800
0 150
0 00
virginiana
Gaultheria
0
62,100
repens
Fragaria
Gallium
Intact
Overstory
0
nudicaulis
Epigaea
Overstory
species
Aster divaricatus
Aralia
Control
620
3,700 0
1,100
4,200
0 0
770
5,600
17,100
14,400
00 0 460
0
0
species
Amelanchier
Betula
0 00927 0
Betula
lenta
populifolia
0 0
Betula
papyrifera
0 0
Carya
cordiformis
Carya
0
620
Betula
8,000
0
glabra
racemosa
150
16,700
0 0
150
620 00 0
0 150
00 0
dentata
0
620
0 0 150
0
0
0 000150
0
Crataegussp.
0 000 150
0
Fraxinus
0 310
0 0 0
0
0 1,080
0 0 0
0
Cornus
americana
Gaylussacia
baccata
Hamamelis
virginiana
Kalmia
resinosa
Pinus
strobus
Populus
Prunus
22,500
ser?tina
Quercus
Quercus
rubra
velutina
460
0
0 0
tremuloides
Quercus
96,400
0 0
0 150620
150
0 772
0309
1,080
latifolia
Pinus
0
150
3,100
1,200
allegheniensis
Castanea
00
150 460
0
sp.
Acerrubrum
35,700
90,200
76,100
00 0
620
310
0
78,100
4,8000 310 1,200
0 0
0
2,000
0
0
alba 0
150
0
460
460
1,400
620
310
2,300
0
42,800
0Kubus idaeus
460
2,500
2,200
150
2,000
0310
21,800
1,500
1,100
4,300
3,400
2,200
22,200
85
Table
1. Continued.
Red Front
Buell Hill
Control
Species
No
Overstory
Intact
albidum
Sassafras
0
canadensis
Tsuga
Viburnum
0
Vaccinium
corymbosum
0
angustifolium
0
Vitis labrusca
p <
**
0.05;
p <
Table 2. Diversity
0.01;
statistics
***
620
620 00
0
0
0
150 1,1000
300
770 00
770
8,500
0.001.
p <
by site and treatment
Control
of individuals
Number
of species
a
Simpson's
D
Simpson's
E
923 a
a
Overstory
405 b
2114c
Overstory
Intact
J
0.999
0.638
0.267
1.032
0.827
ab
1494 e
6 ab
1.520 b
8 be
1.131b
No
Overstory
1.110b
1533 e
9 be
1.268 b
3.466
2.043
2.056
2.690
0.315
0.341
0.257
0.299
1.493
0.462
0.744
227 d
lie
1.603
2.551
Shannon-Weaver
1.041
0.623
1.049
0.581
0.504
1.359
0.618
species
Number
of individuals
Number
of species
a
Simpson's
D
Simpson's
E
714 b
8a
185 a
8a
356 d
996 c
15b
11 ab
824 e
916 ce
13b
12 ab
1.703 ab
1.262 a
2.505
1.587
1.299
2.867
2.219
1.887
2.913
0.202
0.145
0.244
0.198
0.162
0.191
Shannon-Weaver
H
0.921
0.550
1.413
Shannon-Weaver
J
0.443
0.264
All
b
2.150
ab
1.300
0.522
0.542
2.191b
1.085
1.950 ab
1.525
0.423
0.614
2318 d
2449 d
species
Number
Number
Fisher's
of individuals
1108 a
14 a
1.881a
2.255
583 c
3110b
26 b
1119a
12 a
of species
a
a
17ac
21bc
3.889 b
3.278 b
3.186b
21bc
3.155 b
Simpson's
D
3.453
2.530
5.914
4.128
3.717
5.171
Simpson's
E
0.288
0.181
0.227
0.243
0.177
0.246
Shannon-Weaver
H
Shannon-Weaver
J
Row
entries
followed
1.464
0.589
by the same
1.305
0.495
letter are not significant
Discussion
No common herbaceous
following
Control
Intact
6 ab
0.537
H
Fisher's
Overstory
4a
Shannon-Weaver
Woody
Buell Hill
No
species
Number
Fisher's
20,100
4,000
0
Red Front
Herbaceous
Sig.
Overstory
01500150
150
0 2,300 0
00
Intact
00
2,300
460
acerifolium
Vaccinium
0
No
Overstory
Overstory
620
1,400
latifolia
Spiraea
Control
disturbance,
or woody species disappeared
and few showed a clear pattern
2.094
1.868
0.643
0.659
different
at p <
1.712
0.562
2.082
0.684
0.05.
of decline. On the contrary, most species increased in
density following disturbance. This observation sup
ports an initial floristics model of understory composi
86
Table 3. Species
in percent
frequency
by site and treatment
Red front
Species
Control
Buell
Overstory
Intact
Amelanchier
Aralia
0 6
sp.
nudicaulis
94 88
Aster divaricatus
0 0
Betula
allegheniensis
Betula
lenta
0
63
Betula
papyrifera
0 0
Betula
populifolia
0 0
Carex
Carya
cordiformis
Carya
glabra
Castanea
0
0
94
25
0 0
0
0
0 0
0
0
ciliare
0
6
13
0
0
13
0
0
0
0
0
0
6
06
31
19
0
19
0
0
6
0 0
repens
Epigaea
0
0
punctiloba
Desmodium
25
0
reginae
Cypripedum
Dennstaedtia
0
0
6 0
sp.
Crataegus
0
0
racemos a
Cornus
0
81
19
6
0
Fragaria
virginiana
6
0
88
13
Fraxinus
americana
0
0
0
13
Galium
0 0
hirsutum
Epilobium
procumbens
Gaylussacia
baccata
Hamamelis
Kalmia
0
virginiana
Impatiens
Mitchella
uniflora
Pinus
resinosa
0 0
Pinus
strobus
0 19
0
6
0 0
rubra
Quercus
velutina
0
13
0
0
19
38
13 25
0 0
albidum
0
0
19
Kubus pubescens
94
0
0
0 6
Quercus
6
13
69
0
0
aquilinum
alba
94
19
0 0
ser?tina
Quercus
Sassafras
0
13
tremuloides
idaeus
0
13
81
0
cinnamomea
Kubus
0
0 0
Osmunda
Pteridium
6
0 0
canadense
Monotropa
Prunus
0
94
lucidulum
repens
Populus
94
0
94
latifolia
Lycopodium
0
6
0 6
capensis
Maianthemum
50
256
0 0
bor?ale
Gaultheria
50
69
69
0 19
13 25
6
hill
Significance
Overstory
Intact
25
0 0
dentata
Control
Overstory
19
13
sp.
No
0
100
0
31
38
0
0
0
0
0
56
0
38
6
31
6
0
0
6
19
0
6
13
0
0
50
0
6
0
0
0
0
25
0
0
0
13
0
25
94
0
13
0
100
0
56
56
0
0
0
13
0
19
0
44
63
44
0
25
0
No
Site
Burn
Symbol
Overstory
0
31
6
0
44
0
0
44
0
6
6
6
6
0
31
6
0
0
94
0
75
81
0
19
0
100
6
25
56
0
13
0
25
0
44
19
19
100
56
88
13
6
AN
BL
CX
P.S.
DP
DC
FV
GB
GP
P.S.
MC
MR
P.S.
PS
RS
QA
QR
P.S.
QV
RI
P.S.
RP
87
Table 3. Continued.
Red front
Species
No
Overstory
Intact
No
Overstory
Intact
Overstory
Site
bicolor
0 13
0
0
0
latifolia
0 13
0
0
0
0
38
69
75
13
0
0
0
0
0
50
69
39
0 00
6
0
13
0 00
0
13
0
0
0
0
88
borealis
Vaccinium
Viburnum
<
0
composite
0
13
60 6
angustifolium
corymbosum
acerifolium
0 0 19
Vitis labrusca
P.S.p
50
6 1313
Tsuga canadensis
Vaccinium
69
*
0.10;
p <
**
0.05;
p <
:
p <
0.01;
Table 4. Principal
0.001.
front lot
Red
Control
-0.296197
0.865139
0.524589
0.690784
tion for the oak forest community, although a rapid
the herbaceous
relay cannot be precluded. Among
species, exceptions to the rule are Cypripedum reginae
and Epigaea
repens. Cypripedum is characteristic of
wet habitats (Gray 1950), and may not survive well in
xeric
of a severe
environment
burn.
In neither case is there a statistically significant differ
ence in either frequency or density. Carya cordiformis
Fraxinus
appear
only
the
americana,
on
the
control
only woody
are both
plots,
species
to
characteris
tic of pioneer communities
(Burns & Honkala 1992).
Their occurrence only on the unburned sites probably
reflects low frequency and small sample size. Overall,
these results are consistent with those of Swan (1970),
who found few decreasing species after fire in oak
stands in New York. The common pattern of changes
in density
borealis,
among
Maianthemum
and Sassafras
canadense,
not
while
albidum,
Trientalis
related
resource
tables
Fraction
always
sig
which
gradients
or gross
to disturbance
are
not
topography.
necessarily
of
Variance
burn
Severe
burn
explained
0.491694
-0.628737
61.16%
0.446211
-0.178390
22.70%
-0.078814
16.14%
-0.593972
At first glance, the diversity statistics appear to
support our initial hypothesis that moderate burning
would be followed by rapid domination of the site by
Kalmia. Qualitatively,
there was a structural change
from an irregular layer of large Kalmia, characterized
by gaps and a heterogeneous forest floor light environ
ment (Kittredge & Ashton 1990), to a uniform, planar
layer
with
few
the number
However,
gaps.
of
species
present on the different treatments suggests thatKalmia
did not exclude species. Rather, the decline in diver
sity and equitability appears to be related to the large
relative proportion of shoots represented by Kalmia.
there were
In general,
uals
on
of
the
common
woody
less
and
may
are
larger
be
than
preventing
as
present
stages
individ
burns
on
seedlings
these
sites.
of both red and black oak are less frequent,
vigorous,
and
have
lower
dense Kalmia
of the moderate
severe
or
1995).
the moderate
Kalmia
which
sapling
and more
species,
on
However,
species
attaining
Seedlings
more
species,
controls.
some
from
nificant, suggests that these species may be responding
local
of the frequency
residuals
Moderate
-0.143557
0.414725
open,
VA
Variable
Component
the relatively
0
Eigenvectors
Principal
Symbol
refers to figures.
Symbol
of the standardized
components
Burn
Overstory
Solidago
Unidentified
to
Significance
Control
Spiraea
Trientalis
and
hill
Buell
Control
burns
the
unburned
survival
rates
under
the
burns than on either the
controls
(Moser
et al.
2-5-7
i AN
2-h
*
C
0
c
1.51
a
E
o
O
IS
Q.
O
C
1
AR
RP
*
Sb<
05+
MC
o
"Q?"
tf
c
C\J
:%IDP
--GL
-0.51"
MR
.1..
GP
RS
-1.54
1st Principal Component
MC
1.54
RS
c
CD
c
o
1?
?O
CO
Q.
?
c
c
CL
"2
CO
AN
-ftt
-iQVjj.
BL
FV
QA
01
PS
MR
GL
..RR..
-0-5
-^A-GP
AR
CX
-H
QR
-1.54
-1
1
0
1st Principal Component
Fig.
I.
a and b. Species
Binary discriminant
analysis illuminates several
attributes of the herbaceous layer community on these
sites. The first principal component appears to reflect
principal
components
scores.
the species' relative ability to take advantage of a high
light, relatively xeric environment, while the second
and third principal components each explain only a
89
small fraction of the variance. There is little appar
ent clustering in the ordination. These factors suggest
that species distribution on these sites reflects their
individual physiological
traits, with light and moisture
relations playing a key role (Smith & Huston 1989). In
addition, some of the increase in plant abundance could
be due to increases in nutrient availability
(Gilliam
1988), although the time since the burn would indicate
this effect is likely to be small. There does not appear
to be a guild of understory plants which is confined to
unburned habitats.
A moderate burn on these sites does not appear to
initiate succession
in the understory in the classical
sense. This is similar to the pattern of behavior report
ed for communities
in Florida by Abrahamson
(1984a,
the moderate burn does appear to
1984b). However,
have caused changes which persist over the time scale
of the return interval in some presettlement oak forests
(Buell et al 1954; Day 1953; Little 1974; Russell
1983). Thus, a small increase in the frequency of nat
ural or anthropogenic fire in the region could have
significant impacts on the subsequent development of
the forest landscape, even if other disturbances, such
as wind, were ultimately responsible for opening the
overstory (Oliver 1981; Oliver & Larson 1990). Even
a severe burn does not introduce community instability
in the sense reported by Anderson & Brown (1986).
Fire appears to promote a similar community to that
previously on the site, consistent with the argument of
Henderson & Long (1984) and Abrams (1992) that fire
may be an important factor inmaintaining oak forests.
Furthermore, the relationship between fire and commu
nity continuity extends to species and subcommunities
other
than
canopy
oaks.
Two
carried
anonymous
on
out
1992. Fire and the development
Abrams, M.D.
Bioscience
42: 346-353.
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M.D. & Downs,
J.A. 1990. Successional
of
replacement
in south
hardwoods
old-growth white oak by mixed-mesophytic
west Pennsylvania.
Can. J. For. Res. 20: 1864-1870.
Abrams,
Abrams, M.D. & Nowacki, G.J.
recruitment and post-logging
1992. Historical
accelerated
variation
in fire, oak
succession
in central
Bull. Torrey Bot. Club 119: 19-28.
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R.C. & Brown, L.E.
1986. Stability and instability
Anderson,
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following fire. Am. J. Bot. 73: 364-368.
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