Forest Ecology and Management 256 (2008) 863–871
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Forest Ecology and Management
journal homepage: www.elsevier.com/locate/foreco
Response of vegetation and birds to severe wind disturbance and salvage
logging in a southern boreal forest
Emily J. Lain a, Alan Haney a, John M. Burris b,*, Julia Burton a,1
a
b
College of Natural Resources, University of Wisconsin-Stevens Point, Stevens Point, WI 54481, United States
U.S. Department of Agriculture, 350 1st Avenue South, Wisconsin Rapids, WI 54495, United States
A R T I C L E I N F O
A B S T R A C T
Article history:
Received 5 December 2007
Received in revised form 9 May 2008
Accepted 14 May 2008
Vegetation and birds were inventoried on the same plot before and after a severe windstorm in 1999
disturbed a mature black spruce (Picea mariana)–jack pine (Pinus banksiana) forest in northern
Minnesota. Following the storm, another plot was established in an adjacent portion of the forest that
was salvage-logged. Birds were inventoried on both plots through 2002. The original unsalvaged plot
was prescribed-burned in 2004, but vegetation was surveyed through 2003, and through 2005 on the
salvaged plot. We examined the effects of wind disturbance by comparing the pre-storm bird and
vegetation communities with those developing afterwards through 2002 and 2003, respectively, and
the effects of salvage logging by comparing vegetation and the bird community on the unsalvaged plot
with those in the salvaged area. Wind reduced the canopy of the forest by over 90% with a temporary
increase in the shrub layer, mostly resulting from tip-ups. Several plant species, including jack pine and
beaked hazel (Corylus americana), appeared temporarily in the ground layer (<1 m height), but did not
persist through 2003. Quaking aspen (Populus tremuloides) root sprouts were abundant in 2001, but
decreased dramatically by 2003. Delayed mortality of tipped trees resulted in reduction of the shrub
layer to pre-storm levels, and release of advanced regeneration black spruce and balsam fir (Abies
balsamea). Bird species using the forest changed from dominance by canopy-foraging species to groundbrush foraging species, with an overall increase in bird diversity. Salvage logging resulted in significant
reduction in coarse woody debris, and successful recruitment of jack pine seedlings. Quaking aspen
sprouts were nearly 30 times more abundant in the salvage-logged area compared to the unsalvaged
control. Ruderal species, especially red raspberry (Rubus ideaus), fringed bindweed (Polygonum
cilinode), and several sedges (Carex spp.), were significantly more abundant after salvage logging. The
bird community, on the other hand, was greatly diminished by salvage logging, with a reduction in
diversity, density, and overall richness of species.
Published by Elsevier B.V.
Keywords:
Wind disturbance
Windthrow
Salvage logging
Community structure
Bird diversity
1. Introduction
Recent controversy over the ecological effects of salvage logging
(Donato et al., 2006; Stokstad, 2006), primarily concerning the
effects on species composition of post-disturbance vegetation,
suggests an incomplete understanding of how disturbances alter
forest communities (Greene et al., 2006). There is, however, little
disagreement that composition and structure in the southern
boreal forest, where our study was conducted, reflect disturbance
largely by fire, insect outbreaks, logging, and wind (Van Wagner
* Corresponding author. Tel.: +1 715 343 2243.
E-mail address: John.M.Burris@gmail.com (J.M. Burris).
1
Current address: Department of Forest Ecology and Management, University of
Wisconsin-Madison, Madison, WI 53706, United States.
0378-1127/$ – see front matter . Published by Elsevier B.V.
doi:10.1016/j.foreco.2008.05.018
and Methven, 1978; Bonan and Shugart, 1989; Bergeron, 1991;
Heinselman, 1996; Drapeau et al., 2000; Burris and Haney, 2005).
Although fire and spruce budworm (Choristoneura fumiferana
Clemens) are the most prevalent natural disturbances in this
region (Heinselman, 1996), large-scale wind events alter forest
structure and composition at average return intervals of 1000
years or more (Frelich and Reich, 1996; Larson and Waldron, 2000;
Schulte and Mladenoff, 2005). The risk of severe fire increases
following wind disturbance, with a cumulative impact on the
vegetation that may be greater than the independent effects of
either fire or wind (Canham and Loucks, 1984). Timber salvage is
often used to mitigate economic loss, and was widely assumed to
reduce the risk of fire (Holtam, 1971), a generalization that was
recently challenged (Donato et al., 2006).
During the past 100 years, disturbance from timber harvesting in northeastern Minnesota has equaled or exceeded natural
864
E.J. Lain et al. / Forest Ecology and Management 256 (2008) 863–871
disturbances (Heinselman, 1996). There have been several studies
comparing effects of fire and logging disturbance on plant and
avian communities (Reich et al., 2001; Schulte and Niemi, 1998),
but we know of no studies that examined effects of salvage logging
after severe wind disturbance in the region.
Infrequent, large-scale wind disturbance is an important factor
in forests of the Upper Midwest (Canham and Loucks, 1984;
Peterson, 2000; Lorimer, 2001) although little has been reported on
the early stages of vegetation reorganization after such storms
(Dyer and Baird, 1997; Cooper-Ellis et al., 1999; Frelich, 2002).
Most studies of wind disturbance effects on vegetation are in
tropical and temperate hardwood forests (Everham and Brokaw,
1996). Spurr (1956) and Merrens and Peart (1992) suggested that
severe windthrow and clear-cutting had similar effects on
vegetation in temperate hardwood forest communities. Although
salvage logging after severe wind disturbance is arguably similar to
clear-cutting, the effects of either in a conifer-dominated forest is
likely different than in a hardwood forest. The only known
comparison of the same forest before and after severe wind
disturbance was Whitmore’s (1989) study in the rain forest of the
Solomon Islands and our studies in northeastern Minnesota (Burris
and Haney, 2005, 2006). Our studies were unique in examining
bird communities before and after wind disturbance in a southern
boreal forest where we found that destruction of over 90% of the
canopy resulted in little overall change in avian diversity, density,
or energy consumption three years before the storm compared to
three years afterwards, but there was a nearly complete change in
species composition.
Disturbances can affect availability of many specific resources
(Bazzaz, 1983), but also the balance or congruence of resources, all
of which can favor different sets of species (Carlten, 1998; Bazzaz,
1996). Natural disturbances generally increase patchiness, which
should favor diversity at a landscape scale even as small as a few
hectares (gamma diversity) (Denslow, 1985; Drapeau et al., 2000),
but not necessarily at a scale more comparable to passerine bird
territories (alpha diversity) (Haney et al., unpublished data,
Herrando et al., 2003). However, large changes in habitat structure
result in nearly complete change in avian species composition
(Burris and Haney, 2005, 2006). Recruitment of plant species
following blowdown likely reflects microplot characteristics
(Webb, 1988; Bazzaz, 1996; Carlten, 1998; Elliott et al., 2002),
whereas responses of birds reflect both habitat structure and
patchiness (Herrando et al., 2003; Burris and Haney, 2005, 2006).
Severe wind disturbance alters both.
Cooper-Ellis et al. (1999) concluded that salvage logging of New
England hardwoods following wind could have long-term effects
on tree species composition. Greenburg et al. (1995) found that
most native species in fire-maintained Florida scrub forests
responded similarly to fire followed by salvage logging as they
did to clear-cutting, and cautiously concluded that effects of clearcutting in ecosystems adapted to frequent high intensity
disturbance would be similar to natural disturbances. Greene
et al. (2006) and Donato et al. (2006), however, reported poorer
recruitment of conifer trees on post-fire salvaged plots.
Because vegetation structure as well as patchiness and
microplot characteristics likely will be differently affected by
different disturbances, including salvage logging (Elliott et al.,
2002; Johnson et al., 2005), and vary according to pre-disturbance
characteristics (Baker, 2002), it is not surprising that there have
been contrasting conclusions. Moreover, response to disturbance is
species specific (Greene et al., 2006; McIver and Starr, 2001; Dunn
et al., 1983) and, therefore, would be expected to vary from one
region or cover type to another.
In this paper, we document changes in the structure and
composition of vegetation associated with wind disturbance and
salvage logging in a northeastern Minnesota forest, and examine
the response of the bird communities.
2. Methods
On 4 July 1999 a microburst swept across northeastern
Minnesota, producing heavy rains and straight-line winds in
excess of 90 miles (145 km) per hour, impacting approximately
200,000 ha (USDA Forest Service, 2002). Fortuitously, we had
thoroughly inventoried vegetation and birds in spring 1997 in a
permanent plot in a mature black spruce (Picea mariana) – jack
pine (Pinus banksiana) forest near the middle of the storm track,
and re-surveyed the birds on the same plot in 1998 and 1999,
thereby providing an uncommon baseline from which to evaluate
changes in structure and composition of the vegetation and
associated birds (Burris and Haney, 2006). In 2001, when the plot
was re-surveyed, we extended our study to include a permanent
plot in an adjacent area that was salvaged-logged in 2000. We
compared the structure and floristic composition and birds in 2001
in the unsalvaged plot to the pre-disturbance vegetation in 1997,
and the average of birds using the forest plot in 1997, 1998 and
1999. We also compared the 2001 bird data to inventories the
following year, and 2001 vegetation data to data from 2003 in both
the unsalvaged and salvaged plots. The control area was
prescribed-burned in 2004, thereby truncating our study, although
we re-surveyed the vegetation on the salvaged plot again in 2005.
The study area was located in the Superior National Forest,
Minnesota, USA, in a relatively homogeneous, mature, upland
black spruce–jack pine forest that originated following a 1903
wildfire (Heinselman, 1977). We established the initial 6.25 ha
permanent bird plot within the forest on a 10–20% west facing
slope, with 25 m buffers between the spruce–pine forest and
surrounding wetlands. Location was chosen to represent the cover
type within the most homogeneous area we could find. Postdisturbance data from the unsalvaged plot were collected from the
same plot as the pre-storm data. The salvage-logged plot was
immediately adjacent, separated by a 100 m buffer. It had the same
slope, aspect, and disturbance history, and qualitative examination
of broken and tipped trees indicated that the cover type was the
same as the unsalvaged plot prior to the storm.
For purposes of bird surveys, we divided the 6.25 ha plot into a
5 5 grid with 50 m 50 m cells (Fig. 1). Flagging was hung at the
corners of each cell so that we could easily determine our location
within the plot. Birds were surveyed from dawn to mid-morning
during the last week of May and first two weeks of June using the
same methods previously reported (Apfelbaum and Haney, 1981;
Burris and Haney, 2005, 2006; Haney et al., 2008). All birds seen or
heard inside as well as within 25 m of the outside of the grid were
plotted, providing a survey area of 9 ha. Each census averaged a
minimum of 5–6 person hours. Inventory of birds involved
censusing the area five times, usually spread over two or more
weeks. Censuses were conducted only on days without significant
wind or rain.
Vegetation sampling was done within the bird grid in order to
relate bird and vegetation data. Samples consisted of 10, randomly
located, 50 m transects within each treatment year. Permanent
transects were not used, and random samples were taken each
year. Tree and shrub cover for each species was estimated using the
line intercept method. Trees were defined as stems standing >458
relative to the ground and diameter breast height (dbh) >5 cm.
Shrubs/small trees were identified as stems >1 m in height and
<5 cm dbh, or those trees that were still alive but tipped to <458
relative to the ground. Cover of each ground-layer (vegetation
<1 m tall) species was estimated by five 1 m2 quadrats centered at
5, 15, 25, 35, and 45 m along the transect line. Within the ground-
E.J. Lain et al. / Forest Ecology and Management 256 (2008) 863–871
Fig. 1. The bird survey grid was 250 m 250 m with each grid cell measuring
50 m 50 m. The area inside the grids was 6.25 ha. The area in which birds were
plotted included a 25 m buffer, making a 9 ha total survey area. Vegetation
transects were placed through the middle of 10 of the 25 grid cells, randomly
selected before each vegetation survey (shown as arrows within the grid cells).
layer quadrats, we also estimated percent exposed rock and soil,
bryophyte cover, and cover of course litter (diameter >5 cm), and
fine litter (diameter <5 cm) in contact with the ground (Fig. 2).
The number of alive shrub stems rooted within 1 m to the right
side of the transect were tallied by species. Coarse woody debris
(CWD) volumes were estimated after the blowdown using our line
intercepts. The diameter of each dead stem >5 cm crossed by the
line along each 50 m transect was measured. Diameters of CWD
stems were assumed to be the average for a 1 m stem segment such
that a volume estimate could be calculated for those stem
segments intersected in a 1 m wide quadrat 50 m long. Only
recently downed dead stems not in direct contact with the ground
at the point of intersection were counted. Older stems in direct
contact with the ground were considered coarse litter and percent
cover was visually estimated.
3. Analysis
To better understand effects of the wind disturbance on
vegetation, we compared pre-disturbance data collected in 1997
with data collected on the same plot (unsalvaged) in 2001 and
2003. These data were first examined using SPSS (SPSS Inc., 2007)
for normality (Q–Q plot and Shapiro–Wilk tests) and homogeneity
of variance (Levene’s test) with transformations according to Box–
Cox plots (Box and Cox, 1964) being used when residuals did not
meet assumptions. A one-way analysis of variance (ANOVA) was
then used to examine the effect of time which when significant
(P < 0.05) was followed by pairwise comparisons performed
using a Bonferroni correction procedure (Winer et al., 1991) with
865
alpha set at 0.017 (0.05/3) to identify specific time periods of
significant change.
In examining the effects of salvage logging on vegetation, we
compared 2001 and 2003 data from both the unsalvaged and
salvaged plots. In the same manner as described above, data were
first tested for normality and homogeneity of variance with
transformations being conducted as necessary. A two-way ANOVA
was then conducted to examine differences based both on treatment
(unsalvaged or salvaged) and time with a significant interaction
between the two indicating that the plots were changing differently
with time. Although we were unable to compare the 2005 salvaged
data to unsalvaged due to the unsalvaged plot having been burned in
2004, we did examine the changes over time on the salvaged plot
further by comparing the 2001, 2003, and 2005 data using the same
one-way ANOVA procedure used for the unsalvaged plot.
Bird communities of both the salvaged and unsalvaged plots
were compared using data collected in 2001 and 2002. Locations
and movement for each bird during the five censuses were
compiled by species onto summary sheets and territories were
delineated from clusters of registrations, and other evidence of
established territories, such as active nests, or adults carrying food
or fecal sacs. Particular attention was given to locations of pairs or
observed conflicts between males. Delineated territories were the
basis for estimates of breeding bird density. Birds were considered
non-territorial unless a species was recorded at least three of the
five surveys in the same location. Non-territorial birds were tallied
as visitors, if in the plot, or peripheral if outside the plot. Using
delineated territories, we estimated the number of birds and the
percent area in the plot occupied by each territorial species.
Territorial bird numbers were used to calculate a Shannon–Wiener
diversity index (H0 ) for the breeding community. Using Kendeigh’s
(1970) energetic estimates, we also calculated the existence
energy consumption of each territorial species in the communities.
We then calculated and compared relative importance values for
each species using the sum of relative cover, relative density, and
relative energy consumption.
4. Results
Prior to the disturbance, the forest community had approximately 64% total tree cover (Table 1). Black spruce, jack pine, and
paper birch (Betula papyrifera) were the dominant species
(Table 2). The shrub layer was relatively open (Table 1), with
paper birch being the most abundant species (Table 2). A total of 12
woody species was found in the tree and shrub layer. Twenty-two
species were found in the ground layer. The combined total cover
of ground-layer species was 155%; there was 78% bryophyte cover
(Table 1). Less than 4% of the ground had an exposed mineral
surface (Table 1).
4.1. Vegetation responses to blowdown
As a result of the storm, tree cover was reduced significantly
(P < 0.05) to a total of 5%, leaving a tangle of broken trees and tip-
Fig. 2. Vegetation was sampled using a 50 m transect. Tree and shrub density was estimated by recording the number and diameter of live and dead trees rooted within 1 m to
either side of the transect and the number of live and dead shrub stems within 1 m to the right side of the transect. Herb cover was determined using a 1 m2 circular plot
centered at 5, 15, 25, 35, and 45 m along the transect.
E.J. Lain et al. / Forest Ecology and Management 256 (2008) 863–871
866
Table 1
Mean vegetation characteristics (with standard error included in parentheses) per transect and total herb layer taxa with outcomes of two-way analysis of variance (ANOVA)
on 40 (20 unsalvaged, 20 salvaged) 50 m transects from 2001 and 2003
Abbreviation
ANOVA
X̄
Treatment
Time
F
Treatment time
P
1997
2001
2003
2005
F
P
F
P
CTREE1
4.27
0.046
0.02
0.885
2.53
0.121
S
U
NA
64.2a (3.89)
4.1 (2.89)
5.0b (2.75)
0
8.2b (2.82)
2.1 (2.10)
NA
CTREED2
3.15
0.084
0.02
0.900
0.08
0.782
S
U
NA
21.7 (6.03)
1.0 (0.68)
3.1 (2.33)
0
4.0 (2.52)
0
NA
CTREEE 1
2.46
0.126
0.01
0.950
2.72
0.108
S
U
NA
52.9a (4.04)
3.4 (2.85)
2.8b (1.24)
0
5.9b (2.54)
2.1 (2.1)
NA
CSHRB3
3.19
0.082
2.59
0.116
6.13
0.018
S
U
NA
11.3a (3.38)
11.8 (4.61)
29.5b (3.33)
15.7 (5.75)
12.0a (2.80)
15.1 (3.70)
NA
CSHRBD 4
0.05
0.818
0.24
0.625
1.75
0.194
S
U
NA
4.8 (1.48)
7.5 (3.11)
12.4 (2.71)
14.3 (5.22)
9.6 (2.41)
10.3 (3.11)
NA
CSHRBE 4
7.91
0.008
16.22
<0.001
5.59
0.024
S
U
NA
6.7 (2.41)
5.7 (2.63)
17.9 (4.10)
1.9 (0.90)
2.8 (0.89)
CVR 3
2.34
0.135
4.40
0.043
4.04
0.052
S
U
NA
69.2a (3.40)
15.1 (5.26)
32.6b (3.79)
15.7 (5.18)
18.4c (3.96)
LIVSHR 3
0.19
0.666
0.65
0.426
0.88
0.355
S
U
NA
1,080a (258)
CGRLA 3
6.38
0.016
0.60
0.443
0.01
0.920
S
U
NA
155.2 (24.91)
CFILIT
1.47
0.233
0.47
0.496
0.13
0.724
S
U
CCOLIT
2.71
0.109
2.91
0.097
2.91
0.097
DEBRIS
7.42
0.010
4.90
0.033
4.30
CBRYO
9.04
0.005
2.47
0.125
CMINRL
1.27
0.267
0.10
HEBTAX
5.48
0.025
0.16
3,400 (1,114)
3,740b (740)
5,700 (2,132)
2,220ab (742)
4.9 (1.26)
NA
16.4 (4.47)
NA
6,440 (1,516)
NA
421.0 (57.61)
294.2 (66.21)
367.8 (27.28)
252.6 (38.31)
406.3 (45.49)
NA
NA
49.2 (4.81)
37.9 (5.90)
47.6 (7.24)
44.3 (6.47)
49.6 (4.74)
44.5 (6.71)
NA
S
U
NA
18.4ab (3.07)
31.4 (5.55)
15.9a (2.45)
31.4 (4.33)
31.7b (5.47)
19.4 (2.11)
NA
0.045
S
U
NA
NA
127.0a (13.87)
135.5 (12.76)
70.6b (9.94)
133.7 (15.40)
56.8b (9.90)
NA
0.00
0.962
S
U
NA
78.3a (3.85)
25.0 (6.24)
41.0b (5.01)
16.9 (5.27)
32.5b (4.34)
21.0 (4.95)
NA
0.754
2.47
0.125
S
U
NA
3.9 (1.88)
11.5 (2.80)
12.8 (3.52)
15.0 (2.85)
7.5 (1.65)
14.8 (6.61)
NA
0.689
0.94
0.339
S
U
NA
22a
45
29b
39
31 ab
32
NA
Using ten 50 m transects from each treatment year, both unsalvaged data from 1997, 2001 and 2003 and salvaged data from 2001, 2003, and 2005 were further compared
using a one-way ANOVA with uncommon superscripts above indicating significant (Bonferroni; a = 0.017; P < 0.05) differences between years in the given treatment. Data
from the future salvaged plot was not available (NA) in 1997 while unsalvaged data was not available (NA) in 2005. CTREE, % tree cover; CTREED, % deciduous tree cover;
CTREEE, % evergreen tree cover; CSHRB, % shrub cover; CSHRBD, % deciduous shrub cover; CSHRBE, % evergreen shrub cover; CVR, % shrub or tree cover; LIVSHR, live shrub
stems/ha; CGRLA, sum % ground-layer cover; CFILIT, % fine litter cover (diameter <2.5 cm); CCOLIT, % coarse litter cover; DEBRIS, coarse woody debris (m3/ha); CBRYO, %
bryophyte cover; CMINRL, % mineral cover; HEBTAX, total herb layer taxa; S, salvaged; U, unsalvaged.
1
Data were transformed using reciprocal.
2
Data were transformed using inverse square.
3
Data were transformed using natural log.
4
Data were transformed using inverse square root.
ups >10 m deep in places (Table 1). Balsam fir (Abies balsamea),
paper birch and quaking aspen (Populus tremuloides) survived
differentially better than black spruce and jack pine, and increased
in relative importance following the storm (Table 2). Before the
disturbance, birch and aspen each represented 15% of total canopy
cover, and fir another 9%. Although the cover of each of these
species was reduced by >80%, together aspen, paper birch, and
balsam fir comprised over 84% of the remaining canopy.
As a result of tip-ups which placed live tree canopies in the
shrub layer, shrub cover increased significantly (P < 0.05) in 2001
(Table 1). The windstorm had little long-term effect on shrub-layer
species, however; by 2003 most species had similar cover as before
the disturbance. For example, black spruce cover in the shrub-layer
increased four-fold in 2001, but tipped trees soon died and by
2003, spruce cover was less than before the storm (Table 2).
Although balsam fir and paper birch shrub-layer stem densities
were over twice as high in 2003 as before the storm, no species had
a significant change in stem density. Thirteen woody species were
found in the tree and shrub layer in 2003.
As up-rooted trees died, shrub-layer cover decreased to near
pre-disturbance levels, and coarse litter increased significantly
(P < 0.05) from 2001 to 2003 (Table 1). CWD volume, not
estimated before the storm, exceeded 135 m3/ha afterwards.
Although not significant, exposed mineral surface increased
four-fold in 2001, as a result of tip-ups (Table 1).
The total cover in the ground layer nearly doubled in 2001, and
remained nearly as high in 2003 (Table 1). The total number of taxa
found in the 50 random 1 m2 quadrats increased over 40%.
Bryophyte cover, however, decreased to about half (P < 0.001) in
2003 (Table 1).
E.J. Lain et al. / Forest Ecology and Management 256 (2008) 863–871
867
Table 2
Species responses, comparing mean percent tree cover, percent shrub cover, live shrub stem density, and percent ground layer (standard error included in parentheses) and
outcomes of two-way analysis of variance (ANOVA) on 40 (20 unsalvaged, 20 salvaged) 50 m transects from 2001 and 2003
Category and binomial
ANOVA
X̄
Treatment
F
Time
P
F
Treatment time
P
1997
2001
2003
2005
F
P
0.864
0.92
0.345
S
U
NA
10.5a (2.40)
1.0 (0.68)
1.6b (1.21)
0
2.8ab (2.14)
0
NA
11.75
0.002
1.17
0.287
S
U
NA
33.5a (4.79)
1.4 (1.42)
1.0b (0.69)
0
2.6b (0.82)
2.1 (2.33)
NA
0.927
2.03
0.162
0.25
0.620
S
U
NA
13.2a (5.53)
0.8 (0.59)
0.7b (0.50)
0
0.3b (0.32)
0
NA
0.32
0.578
7.70
0.009
0.31
0.582
S
U
NA
< 0.1a (0.04)
2.8 (1.27)
2.2b (0.79)
0.4 (0.22)
0.3a (0.23)
0.7 (0.62)
NA
Betula papyrifera
6.33
0.016
0.14
0.713
1.15
0.291
S
U
NA
3.5 (1.09)
0.8 (0.50)
6.2 (2.45)
2.0 (0.77)
4.1 (1.28)
1.7 (0.46)
NA
Picea mariana2
7.58
0.009
13.35
0.001
4.21
0.047
S
U
NA
2.0a (0.72)
2.6 (1.72)
9.9b (2.41)
0.2 (0.18)
1.2a (0.55)
1.3 (1.47)
NA
Pinus banksiana
1.30
0.263
1.30
0.263
1.30
0.263
S
U
NA
0
0a
1.9 (1.67)
0a
0
2.0b (0.79)
NA
Live shrub stem density
Pinus banksiana
0.00
1.000
0.00
1.000
2.00
0.166
S
U
NA
0
Populus tremuloides
3.45
0.072
0.19
0.669
5.17
0.029
S
U
NA
0a
Prunus pensylvanica 1
9.53
0.004
4.24
0.047
4.24
0.047
S
U
NA
0
Ground-layer cover
Acer spicatum1
0.06
0.809
8.93
0.005
0.09
0.764
S
U
NA
0.1a (0.06)
2.0a (0.87)
2.3b (1.01)
0.2b (0.13)
0a
0b
NA
Aralia hispida1
7.06
0.012
6.37
0.016
6.37
0.016
S
U
NA
0
0.2 (0.16)
0
2.4 (0.87)
0
4.2 (4.42)
NA
Carex foenea1
1.79
0.190
1.79
0.190
1.79
0.190
S
U
NA
0
0a
0
1.2a (0.77)
0
8.5b (1.97)
NA
10.24
0.003
0.03
0.865
0.03
0.865
S
U
NA
0
1.4 (0.80)
0
1.6 (0.49)
0
<0.1 (0.03)
NA
Carex spp.
5.37
0.026
2.21
0.145
2.21
0.145
S
U
NA
<0.1 (1.84)
0.4 (0.34)
0
2.0 (1.01)
0
0
NA
Clintonia borealis
0.54
0.468
1.53
0.224
1.77
0.192
S
U
NA
0.3 (0.20)
1.0a (0.48)
1.3 (0.58)
1.1a (0.44)
0.2 (0.10)
0b
NA
Cornus canadensis3
3.86
0.057
6.59
0.015
0.00
0.989
S
U
NA
1.7 (0.87)
6.5a (1.35)
5.2 (2.18)
3.2ab (0.99)
1.3 (0.57)
1.0b (0.48)
NA
Linnaea borealis2
0.01
0.979
5.52
0.024
0.01
0.973
S
U
NA
1.3 (0.59)
4.9a (2.47)
2.2 (0.77)
0.7ab (0.36)
0.5 (0.24)
0.1b (0.09)
NA
Polygonum cilinode
8.26
0.007
0.34
0.855
0.03
0.873
S
U
NA
0
2.7 (1.20)
0.3 (0.22)
Rubus idaeus4
2.63
0.113
20.42
<0.001
0.73
0.400
S
U
NA
0a
2.2a (1.04)
1.1b (0.48)
Tree cover
Betula papyrifera
2.04
0.162
0.03
Picea mariana
10.77
0.002
0.01
Pinus banksiana 1
Shrub cover
Acer spicatum1
Carex houghtoniana
0a
20 (20)
1060 (328)
1340b (480)
20 (20)
0
20a (20)
0
2,060b (904)
NA
2880 (1210)
100a (68)
1940 (1094)
NA
140 (60)
0
2.7 (1.24)
<0.1 (0.03)
8.6b (1.64)
5.4c (1.93)
100 (36)
NA
1.3 (0.68)
NA
10.5c (2.30)
NA
Using ten 50 m transects from each treatment year, both unsalvaged data from 1997, 2001 and 2003 and salvaged data from 2001, 2003, and 2005 were independently further
compared using a one-way ANOVA with uncommon superscripts above indicating significant (Bonferroni; a = 0.017; P < 0.05) differences between means in the respective
time period. Data from the future salvaged plot was not available (NA) in 1997 while unsalvaged data was not available (NA) in 2005. Only species which changed significantly
(P < 0.05) are reported. S, salvaged; U, unsalvaged.
1
Data were transformed using inverse square.
2
Data were transformed using reciprocal.
3
Data were transformed using natural log.
4
Data were transformed using inverse square root.
868
E.J. Lain et al. / Forest Ecology and Management 256 (2008) 863–871
Many species in the ground layer significantly increased the
second year following the windstorm, although all but red
raspberry (Rubus idaeus) declined by 2003 (Table 2). Red raspberry
significantly (P < 0.05) increased five-fold from 2001 to 2003.
Paper birch, bush honeysuckle, and red raspberry were not
recorded in the ground layer before the storm, but persisted
through 2003.
4.2. Vegetation responses to salvage logging
Differences in tree cover were not significant between the
unsalvaged and salvaged plots (Table 1). Whereas total shrub-layer
cover on the unsalvaged plot decreased significantly (P < 0.018) in
2003, to near the pre-storm level, it increased slightly in the
salvaged plot (Table 1), primarily because of a three-fold increase
in quaking aspen (Table 2). Live quaking aspen stems decreased
significantly on the unsalvaged plot from 2001 to 2003, but more
than doubled on the salvaged plot (P < 0.029) (Table 2). Quaking
aspen shrub-layer cover was over four times greater in the
salvaged plot in 2003 compared to the unsalvaged plot, although
differences were not significant. Jack pine, on the other hand,
disappeared from the shrub layer on the unsalvaged plot in 2003
but increased significantly (P < 0.023), from 20 stems ha1 in 2003
to 2060 stems ha1 in 2005 as seedlings grew into the shrub layer
(Table 2).
Significantly (P < 0.025) more plant taxa were recorded on the
salvaged than on the unsalvaged plot (Table 1). Bryophytes had
significantly (P < 0.005) less cover on the salvaged plot in both
2001 and 2003 (Table 1).
Jack pine and paper birch, not present in the ground layer before
the storm, were present in both plots in 2001, but remained
common only in the salvaged plot, reaching 2% and 1% cover,
respectively, by 2005. Quaking aspen in the ground layer changed
in similar ways, increasing in both the salvaged and unsalvaged
plots from pre-blowdown cover, but remaining only in the
salvaged plot in 2003 and 2005 (Table 2). Red raspberry,
undetected prior to the storm, increased (P < 0.05) through
2003 in both plots, but was 60% more abundant on the salvaged
plot where cover exceeded 10% in 2005 (Table 2). Common
lowbush blueberry (Vaccinium angustifolium), in contrast,
increased three-fold from 2001 through 2003 on the unsalvaged
plot but remained unchanged on the salvaged plot through 2005,
although differences were not significant. Bristly sarsaparilla
(Aralia hispida), not present before the storm, appeared only on the
salvaged plot, and increased through 2005. Fringed bindweed
(Polygonum cilinode) appeared only after the blowdown, but was
significantly (P < 0.007) higher on the salvaged plot. It was
essentially absent in the unsalvaged plot within two years, but
remained prominent on the salvaged plot. Sedges (Carex spp.) rare
before the storm, were significantly (P < 0.05) more abundant on
the salvaged plot. Houghton’s sedge (Carex houghtoniana),
appeared in 2001 and increased to nearly 2% by 2003, but had
nearly disappeared by 2005. A variety of other sedges, especially
dryspike sedge (Carex foenea), were unique to the salvaged plot.
Dryspike sedge increased significantly (P < 0.05) through 2005 to
become the most abundant ground cover.
4.3. Avian responses
Bird species richness in the pre-disturbance forested plot
remained consistent at 13 territorial species during the three years
before the blowdown. H0 diversity indices varied from 2.17 to 2.28
as a result of small variation in evenness. Visiting species, those for
which we could determine no territory, varied from a high of 15 to
a low of 9, giving an overall bird species richness for the plot of 22–
28 species (Table 3). Breeding bird density, based on the number of
territories delineated on the plot, varied more, from a high of 45 in
1999 to a low of 24 the previous year. This difference was primarily
attributable to an unusually high population of Cape May Warblers
in 1999. The second year after the blowdown (2001), we recorded
25% fewer territorial species with a small decrease in H0 diversity,
but an overall 40% increase in total richness because of more than a
two-fold increase in visiting species (Table 3). Density of bird
territories was higher than the average recorded during the three
years before the storm.
In comparing the salvaged plot with the unsalvaged plot, we
found 20% fewer territorial bird species, 50% fewer visiting species
and 38% fewer total species. The greatest difference, however, was
70% fewer territories. The differences between the salvaged and
unsalvaged plots, although still great, diminished in 2002 (Table 3).
The blowdown resulted in a dramatic shift in bird species
composition (Table 3). Whereas dominant species before the
disturbance were Golden-crowned Kinglet (Regulus satrapa),
Blackburnian Warbler (Dendroica fusca), Bay-breasted Warbler
(Dendroica castanea), and Nashville Warbler (Vermivora ruficapilla),
all canopy-foraging species, the dominant species two years after
the storm were White-throated Sparrow (Zonotrichia albicollis),
Magnolia Warbler (Dendroica magnolia), Winter Wren (Troglodytes
troglodytes), and Chipping Sparrow (Spizella passerina), all species
that usually forage on or near the ground. Although less abundant,
we found similar species in the salvaged plot.
Overall, White-throated Sparrow, Magnolia Warbler, Chipping
Sparrow, Winter Wren, Yellow-bellied Flycatcher (Empidonax
flaviventris), and Swainson’s Thrush (Catharus ustulatus) responded
positively to the blowdown. None of these species were as
common in the salvaged plot. Only Chestnut-sided (Dendroica
pensylvanica) and Mourning Warbler (Oporornis philadelphia), over
the two years we monitored both plots, preferred the salvaged
habitat. Dark-eyed Junco (Junco hyemalis) was common in 2002 on
the salvaged plot, but not in 2001. We did not record them prior to
the blowdown or in the unsalvaged plot.
Woodpeckers were among many visiting species more common
after disturbance. We recorded a portion of only one territory,
however, Black-backed Woodpeckers (Piciodes articus) that used a
snag in the salvaged grid for their nesting cavity.
5. Discussion
The most visible changes associated with the 1999 storm were
the reduction in tree cover, a corresponding increase in CWD, a
temporary increase in shrub-layer cover, and increase in groundlayer cover and diversity. Although quite high, the CWD volumes
that we estimated were comparable to volumes reported for
balsam fir-dominated subalpine forests (Lambert et al., 1980).
Increased sunlight at the ground associated with canopy loss
apparently was largely offset by shading from CWD and shrubs in
the unsalvaged plot. Disruption of the forest floor by tip-ups and
increased fine litter, probably accounted for the decline in
bryophyte cover. Many of the ground-layer species that increased
following the blowdown declined in 2003 in the unsalvaged plot,
presumably because of dense shading at the ground. Red raspberry
and paper birch seedlings, not present before the storm, became
established, largely on tip-up mounds where there was mineral
soil and more light.
The immediate shrub layer increase after the storm was largely
a result of up-rooted trees. As tipped trees died, the augmented
shrub cover declined so that by 2003 shrub cover in the unsalvaged
area was about the same as before the storm. In the salvaged area,
however, most tipped trees were removed, so no shrub augmentation was found. Shrub cover there, however, increased through
E.J. Lain et al. / Forest Ecology and Management 256 (2008) 863–871
869
Table 3
Relative importance values, and number of territories/6.25 ha (in parentheses) of birds with territories in a mature black spruce–jack pine forest before (averaged over 1997,
1998, and 1999) and after (2001 and 2002) a severe windstorm with and without subsequent salvage logging
Guild and species
Pre-storm
Unsalvaged
2001
2002
2001
2002
Flycatchers
Yellow-bellied Flycatcher (Empidonax flaviventris)
Least Flycatcher (Empidonax minimus)
5.5 (1.67)
4.7 (1.75)
4.7 (1.75)
6.0 (1.0)
6.0 (1.0)
V
0 (0)
2.5 (0.5)
V
2.5 (0.5)
Ground-brush foragers
Winter Wren (Troglodytes troglodytes)
Swainson’s Thrush (Catharus ustulatus)
Nashville Warbler (Vermivora ruficapilla)
Chestnut-sided Warbler (Dendroica pensylvanica)
Magnolia Warbler (Dendroica magnolia)
Mourning Warbler (Oporornis philadelphia)
Chipping Sparrow (Spizella passerina)
Swamp Sparrow (Melospiza georgiana)
White-throated Sparrow (Zonotrichia albicollis)
Dark-eyed Junco (Junco hyemalis)
25.1 (7.29)
0.7 (0.3)
1.6 (0.3)
12.7 (4.42)
V
1.2 (0.3)
82.8 (29.0)
10.2 (3.0)
6.6 (1.5)
9.6 (3.5)
V
20.2 (8.5)
V
9.3 (4.0)
81.6 (19.25)
12.7 (2.5)
2.5 (0.5)
5.7 (1.5)
V
16.1 (4.5)
V
7.6 (2.0)
76.8 (7.5)
14.0 (2.0)
97.0 (16.25)
4.3 (0.5)
8.1 (1.0)
26.9 (8.5)
V
37 (8.25)
V
31.5 (2.0)
2.4 (0.5)
5.0 (1.0)
4.1 (0.75)
17.6 (2.75)
10.4 (2.0)
V
45.9 (7.5)
11.6 (1.75)
Timber-drillers
Black-backed Woodpecker (Picoides arcticus)
0 (0)
0 (0)
V
0 (0)
V
14.1 (0.5)
14.1 (0.5)
0 (0)
V
Timber-gleaners
Red-breasted Nuthatch (Sitta canadensis)
4.3 (1.0)
4.3 (1.0)
0 (0)
V
0 (0)
0 (0)
V
0 (0)
Tree-foliage searchers
Black-capped Chickadee (Poecile atricapilla)
Boreal Chickadee (Poecile hudsonica)
Golden-crowned Kinglet (Regulus satrapa)
Ruby-crowned Kinglet (Regulus calendula)
Tennessee Warbler (Vermivora peregrina)
Cape May Warbler (Dendroica tigrina)
Yellow-rumped Warbler (Dendroica coronata)
Blackburnian Warbler (Dendroica fusca)
Bay-breasted Warbler (Dendroica castanea)
Common Yellowthroat (Geothlypis trichas)
Pine Siskin (Carduelis pinus)
64.9 (22.44)
0.7 (0.17)
0.4 (0.08)
17.1 (7.0)
5.9 (2.0)
1.2 (0.25)
5.4 (1.92)
6.5 (1.67)
13.1 (4.75)
12.8 (4.3)
V
1.8 (0.3)
12.5 (3.25)
3.1 (0.75)
V
V
2.0 (0.5)
12.4 (3.0)
9.1 (1.0)
V
0 (0)
V
Total (all guilds)
99.8 (32.4)
100 (34.0)
5.5 (1.67)
4.6 (1.17)
1.8 (0.3)
2.5 (0.5)
V
Salvaged
9.1 (1.0)
9.8 (1.0)
8.5 (2.5)
V
V
V
7.4 (2.0)
V
V
V
9.1 (1.0)
V
V
V
100 (9.0)
99.5 (16.75)
3.9 (0.5)
V
100 (23.25)
Pre-storm and post-storm unsalvaged bird data are based on the same 6.25 ha plot. The salvaged data were collected from an adjacent 6.25 ha plot. Importance value is based
on the sum of relative numbers of breeding birds, relative cover, and relative existence energy. Visitor (V) indicates the species was recorded but no territory could be
determined.
2003, largely as a result of root sprouts from quaking aspen that
grew into the shrub layer. The only tree species that were recruited
by the storm were jack pine and quaking aspen, both completely
absent in the ground layer before the storm. Jack pine and aspen,
greatly decreased in the unsalvaged forest by 2003, but remained
well established in the salvaged forest.
Salvage logging resulted in several shifts that will have longterm effects. Based on recruitment into the shrub layer, we project
that quaking aspen will be at least twice as abundant in the forest
that develops following salvage logging. This extends the
observation of Greene et al. (2006) who noted that salvage
logging after fire in jack pine-black spruce forest in Quebec shifted
the subsequent forest from conifer domination to mixed conifers
and quaking aspen. Jack pine will become a dominant species,
along with quaking aspen, on the salvaged plot, but will largely
disappear from the unsalvaged plot. Although it is less obvious, we
believe paper birch will remain a common species on both plots,
but will be more common on the unsalvaged plot along with
spruce and balsam fir.
Effects of salvage logging on species richness and diversity are
mixed. Our results are consistent with the conclusions of Elliott
et al. (2002) who found significantly more herbaceous species after
blowdown and salvage logging in the southern Appalachians.
Peltzer et al. (2000) also reported increased plant diversity
following fire and clear-cut harvests in the boreal forest, although
Brakenhielm and Liu (1998) reported a reduction in diversity (H0 )
of vegetation during the first five to eight years after clear-cut
harvest. McIver and Starr (2001) found that salvage logging after
fire in the West often was associated with reduced herbaceous
richness, although Macdonald (2007) found no effect on vascular
plant richness or diversity in Alberta. We found 35% more plant
species after the blowdown, and 50% more in the salvaged plot
than in the unsalvaged. This suggests that disturbance from clearcut timber harvest or salvage logging after fire may have different
effects than salvage logging after blowdown.
Based on our study, salvage logging also increased ground
vegetation cover, in contrast to the reduction reported by Purdon
et al. (2004) after fire. The added soil disturbance plus the removal
of some of the CWD on the salvaged plot clearly favored some plant
species, especially jack pine, quaking aspen, red raspberry, fringed
bindweed, sedges, and bristly sarsaparilla. Cover of these species
continued to increase through the first four years after the storm.
Salvage logging resulted in more soil disturbance, seen in the
higher percentage of exposed mineral soil on the salvaged plot. The
combination of more light and more exposed mineral soil probably
explains the appearance of ruderal species such as bristly
sarsaparilla, sedges, and fringed bindweed, as well as jack pine,
on the salvaged plot. McIver and Starr (2001) predicted more
ruderal species with salvage logging, and this was confirmed by
Elliott et al. (2002). Notably rare, even on the salvaged plot, was
fireweed (Epilobium angustifolium), common after fire. Few
bryophytes survived on exposed areas, resulting in significantly
less bryophyte cover after salvage logging. Fringed bindweed was
common on the salvaged plot, but less than after fire (Apfelbaum
870
E.J. Lain et al. / Forest Ecology and Management 256 (2008) 863–871
and Haney, 1986) whereas sedges, some of which we had not
previously seen in the area, were much more abundant. Fringed
bindweed apparently maintains itself in the seedbank as a result of
periodic fire. It seems unlikely, on the other hand, that the sedges,
recruited after windthrow, could be maintained by such infrequent
disturbance events. We, therefore, speculate that ruderal sedges
were either introduced on logging equipment or by birds.
Relatively small differences in species responses in the first few
years after disturbance can have great influences on the future
development of communities (Brakenhielm and Liu, 1998). It
appears likely that the salvaged plot will develop into a mixed
stand of aspen and conifers, primarily jack pine, whereas the
unsalvaged forest will have less aspen and few jack pine. Aspen and
jack pine recruitment largely failed in the heavy shade of CWD in
the unsalvaged plot. Whereas Greene et al. (2006), concluded that
salvage logging after fire reduced recruitment of jack pine, we
found that salvage logging after extensive blowdown resulted in
better jack pine recruitment. Increased recruitment of aspen
following salvage logging after wind is consistent with regeneration after post-fire salvage that was reported by Greene et al.
(2006) and Macdonald (2007).
Consistent with our other studies (Burris and Haney, 2005,
2006), we observed fewer passerine birds with territories the first
three years after severe wind disturbance, relative to the number
on the same plot during the three years before the storm. Overall, it
appeared that salvage logging reduced habitat structure and this
resulted in lower richness of bird species using the area, compared
to the unsalvaged plot, although differences were not great. In
contrast to species richness, we found little change in the density of
territorial birds following severe wind disturbance, but a notable
reduction when the forest was salvage-logged. More dramatic
differences were found in the bird species using the areas. Both
were greatly different from the bird community using the predisturbance forest. The considerable differences in the avifauna
between the salvaged and unsalvaged forests will likely diminish
as the CWD in the unsalvaged forest decays and structure recovers
in the salvaged forest, but long-term differences in tree composition likely will be reflected in the bird communities (Apfelbaum
and Haney, 1986).
Consistent with the observations of others, we found that the
dominant guild using the mature forest was tree-foliage searchers
(e.g., Hutto, 1995; Hannon and Drapeau, 2005) and, as with fire
disturbances (Apfelbaum and Haney, 1986; Haney et al., 2008), the
dominant guild after the severe wind disturbance was groundbrush foragers (Burris and Haney, 2006). Bird species using the
salvaged and unsalvaged plots were similar except for presence of
Chestnut-sided Warbler and Mourning Warbler and great reduction in Magnolia Warbler and Nashville Warbler after salvage
logging. The former species are often found in dense re-growth
following clear-cutting, whereas the latter species are seldom seen
where there is little tree cover (personal observations).
Salvage logging after blowdown altered both the successional
patterns of vegetation and associated birds. Whereas the predisturbance forest was dominated by black spruce–jack pine-paper
birch with a significant aspen component, the regenerating forest
will have a much larger component of balsam fir and black spruce.
Blowdown without salvage appeared to accelerate succession, a
conclusion that is consistent with those of Cooper-Ellis et al., 1999;
Dyer and Baird, 1997; Veblen et al., 1989. Aspen will decrease
greatly and jack pine will essentially disappear. In contrast, the
salvaged forest will become a jack pine-aspen forest with a
significant birch and balsam fir component. Unlike Greene et al.
(2006) and Donato et al. (2006), who found that salvage logging
after fire resulted in poorer conifer recruitment, we found that
salvage logging after blowdown increased jack pine recruitment,
although it was not favorable to recruitment of black spruce.
Both forests, however, will retain a good mixture of conifer and
broadleaf trees.
Acknowledgments
We gratefully acknowledge assistance from dozens who
assisted with collection of field data. Notable among them were
Rick Anderson, Steven Apfelbaum, Tim Bischof, Erin Ernst, Anne
Graham, John Graham, Emil Haney, and Nancy Stevenson. We
appreciate the encouragement and support of Edward Lindquist,
and other personnel of Superior National Forest. Two anonymous
reviewers provided constructive criticism that improved this
manuscript.
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