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Spotted Owls and forest fire: a systematic review and meta-analysis of the evidence

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Citation: Lee, D. E. 2018. Spotted Owls and forest fire: a systematic review and meta-analysis of the evidence. Ecosphere 9(7): Abstract. Forest and Spotted Owl management documents often state that severe wildfire is a cause of recent declines in populations of Spotted Owls and that mixed-severity fires (5-70% of burned area in high-severity patches with >75% mortality of dominant vegetation) pose a primary threat to Spotted Owl population viability. This systematic review and meta-analysis summarize all available scientific literature on the effects of wildfire on Spotted Owl demography and ecology from studies using empirical data to answer the question: How does fire, especially recent mixed-severity fires with representative patches of high-severity burn within their home ranges, affect Spotted Owl foraging habitat selection, demography, and site occupancy parameters? Fifteen papers reported 50 effects from fire that could be differentiated from post-fire logging. Meta-analysis of mean standardized effects (Hedge's d) found only one parameter was significantly different from zero, a significant positive foraging habitat selection for low-severity burned forest. Multi-level mixed-effects meta-regressions (hierarchical models) of Hedge's d against percent of study area burned at high severity and time since fire found the following: a negative correlation of occupancy with time since fire; a positive effect on recruitment immediately after the fire, with the effect diminishing with time since fire; reproduction was positively correlated with the percent of high-severity fire in owl territories; and positive selection for foraging in low-and moderate-severity burned forest, with high-severity burned forest used in proportion to its availability, but not avoided. Meta-analysis of variation found significantly greater variation in parameters from burned sites relative to unburned, with specifically higher variation in estimates of occupancy, demography , and survival, and lower variation in estimates of selection probability for foraging habitat in low-severity burned forest. Spotted Owls were usually not significantly affected by mixed-severity fire, as 83% of all studies and 60% of all effects found no significant impact of fire on mean owl parameters. Contrary to current perceptions and recovery efforts for the Spotted Owl, mixed-severity fire does not appear to be a serious threat to owl populations; rather, wildfire has arguably more benefits than costs for Spotted Owls.
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SYNTHESIS & INTEGRATION
Spotted Owls and forest re: a systematic review and meta-analysis
of the evidence
DEREK E. LEE
1,2,
1
Wild Nature Institute, 15 North Main Street #208, Concord, New Hampshire 03302 USA
Citation: Lee, D. E. 2018. Spotted Owls and forest re: a systematic review and meta-analysis of the evidence. Ecosphere
9(7):e02354. 10.1002/ecs2.2354
Abstract. Forest and Spotted Owl management documents often state that severe wildre is a cause of
recent declines in populations of Spotted Owls and that mixed-severity res (570% of burned area in high-
severity patches with >75% mortality of dominant vegetation) pose a primary threat to Spotted Owl popula-
tion viability. This systematic review and meta-analysis summarize all available scientic literature on the
effects of wildre on Spotted Owl demography and ecology from studies using empirical data to answer the
question: How does re, especially recent mixed-severity res with representative patches of high-severity
burn within their home ranges, affect Spotted Owl foraging habitat selection, demography, and site occupancy
parameters? Fifteen papers reported 50 effects from re that could be differentiated from post-re logging.
Meta-analysis of mean standardized effects (Hedgesd) found only one parameter was signicantly different
from zero, a signicant positive foraging habitat selection for low-severity burned forest. Multi-level mixed-
effects meta-regressions (hierarchical models) of Hedgesdagainst percent of study area burned at high sever-
ity and time since re found the following: a negative correlation of occupancy with time since re; a positive
effect on recruitment immediately after the re, with the effect diminishing with time since re; reproduction
was positively correlated with the percent of high-severity re in owl territories; and positive selection for for-
aging in low- and moderate-severity burned forest, with high-severity burned forest used in proportion to its
availability, but not avoided. Meta-analysis of variation found signicantly greater variation in parameters
from burned sites relative to unburned, with specically higher variation in estimates of occupancy, demogra-
phy, and survival, and lower variation in estimates of selection probability for foraging habitat in low-severity
burned forest. Spotted Owls were usually not signicantly affected by mixed-severity re, as 83% of all stud-
ies and 60% of all effects found no signicant impact of re on mean owl parameters. Contrary to current per-
ceptions and recovery efforts for the Spotted Owl, mixed-severity re does not appear to be a serious threat to
owl populations; rather, wildre has arguably more benets than costs for Spotted Owls.
Key words: adaptive management; evidence-based decision making; meta-analysis; mixed-severity re; Spotted Owls;
Strix occidentalis; systematic review; wildre.
Received 22 April 2018; revised 1 June 2018; accepted 11 June 2018. Corresponding Editor: Joseph A. LaManna.
Copyright: ©2018 The Author. This is an open access article under the terms of the Creative Commons Attribution
License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
2
Present address: Pennsylvania State University, State College, Pennsylvania 16801 USA.
E-mail: derek@wildnatureinstitute.org
INTRODUCTION
Wildres are major natural disturbances in for-
ests of the western United States, and native
plants and animals in this region have been
coexisting with re for thousands of years of
their evolutionary history (Pierce et al. 2004,
Power et al. 2008, Marlon et al. 2012). Western
forest res typically burn as mixed-severity res
with each re resulting in a mosaic of different
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vegetation burn severities, including substantial
patches (range, 570% of burned area; mean,
22%) of high-severity re (Beaty and Taylor 2001,
Hessburg et al. 2007, Whitlock et al. 2008, Wil-
liams and Baker 2012, Odion et al. 2014a, Baker
2015a). High-severity re (high vegetation burn
severity) kills most or all of the dominant vegeta-
tion in a stand (>75% mortality; Hanson et al.
2009, Baker 2015a,b) and creates complex early
seral forests, where standing dead trees, fallen
logs, shrubs, tree seedlings, and herbaceous
plants comprise the structure (Swanson et al.
2011, DellaSala et al. 2014). Post-re vegetation
processes (i.e., succession) then commence
according to the pre-re vegetation, local wild-
re processes, propagules from outside the dis-
turbance, and the dynamic biotic and abiotic
conditions at the site (Gutsell and Johnson 2006,
Johnson and Miyanishi 2006, Mori 2011).
Spotted Owls (Strix occidentalis) occur in west-
ern U.S. forests and have been intensively stud-
ied since the 1970s (Fig. 1). The species is
strongly associated with mature and old-growth
(i.e., late-successional) conifer and mixed
coniferhardwood forests with thick overhead
canopy and many large live and dead trees and
fallen logs (Guti
errez et al. 1995). Its association
with older forests has made the Spotted Owl an
important umbrella indicator species for public
lands management (Noon and Franklin 2002).
The scientic literature has established that the
optimal habitat for Spotted Owl nesting, roost-
ing, and foraging is provided by conifer and
mixed coniferhardwood forests dominated by
medium (3060 cm) and large (>61 cm) trees
with medium (5070%) to high (>70%) canopy
cover (Guti
errez et al. 1995). The populations of
all three subspecies have declined due to wide-
spread historical and ongoing habitat loss, pri-
marily from logging mature and old-growth
forests favored by the owls for nesting and roost-
ing (Seamans et al. 2002, Forsman et al. 2011,
USFWS 2011, 2012, Conner et al. 2013, Tempel
and Guti
errez 2013, Dugger et al. 2016).
Research on Spotted Owl in re-affected land-
scapes did not begin until the early 2000s, and
much of what scientists previously understood
about habitat associations of Spotted Owl was
derived from studies in forests that had generally
not experienced recent re, and where the non-
suitable owl habitat was a result of logging
(Guti
errez et al. 1992, Franklin et al. 2000, Sea-
mans et al. 2002, Blakesley et al. 2005, Seamans
and Guti
errez 2007, Forsman et al. 2011, Tempel
et al. 2014). Because Spotted Owls are associated
with dense, late-successional forests, it has often
been assumed that res that burn at high severity
are analogous to clear-cut logging and have a
negative effect on population viability. It has
become widely believed among wildlife manage-
ment professionals that severe wildre is a con-
tributing cause of recent Spotted Owl population
declines (USFWS 2011, 2012, 2017), and many
land managers believe that forest res currently
pose the greatest risk to owl habitat and are a pri-
mary threat to population viability (Davis et al.
2016, Guti
errez et al. 2017). These beliefs result in
fuel-reduction logging projects in Spotted Owl
habitat (USDA 2012, 2018) which the USDA
Forest Service and US Fish and Wildlife Service
state are actions consistent with Spotted Owl
recovery (USDA 2012, 2018, Guti
errez et al. 2017,
USFWS 2017). Narrative literature reviews
have attempted to summarize the effects of re
on Spotted Owl (Bond 2016, Guti
errez et al.
2017), but evidence-based conservation decisions
should be based upon systematic, transparent
reviews of primary literature with quantitative
meta-analysis of effects (Sutherland et al. 2004,
Pullin and Stewart 2006, Pullin and Knight 2009,
Koricheva et al. 2013).
The following systematic review and meta-ana-
lysis summarize all available published scientic
literature on the effects of wildre on aspects of
Spotted Owl demography (survival, recruitment,
and reproduction), site occupancy, and habitat
selection, from studies using empirical data to
answer the question: How does re, especially
mixed-severity re with substantial patches of
high-severity re within their home ranges, affect
Spotted Owl demography, site occupancy, and
habitat selection in the rst few post-re years?
METHODS
Literature search
I conducted a systematic review of the primary
scientic literature and used meta-analyses and
meta-regression to examine the evidence for the
direct effects of wildre on Spotted Owl demo-
graphy, site occupancy, and habitat selection. My
subject was Spotted Owls; the intervention was
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SYNTHESIS & INTEGRATION LEE
wildre; the outcomes were change or difference
in estimates of demography, site occupancy, and
habitat selection probabilities; and the compara-
tor was pre-re estimates or control estimates
from unburned areas (Pullin and Stewart 2006). I
searched the following electronic databases on 1
April 2018: Agricola, BIOSIS Previews, ISI Web
of Science, and Google Scholar. Search terms
Fig. 1. Range map for the three subspecies of the Spotted Owl (Strix occidentalis).
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SYNTHESIS & INTEGRATION LEE
were as follows: spotted AND owl AND re,
Strix AND occidentalis AND re. My search
included papers published in any year.
I used a threefold ltering process for accepting
studies into the nal systematic review. Initially, I
ltered all articles by title and removed any obvi-
ously irrelevant material from the list of articles
found in the search. Subsequently, I examined the
abstracts of the remaining studies with regard to
possible relevance to the systematic review ques-
tion, using inclusion criteria based on the subject
matter and the presentation of empirical data. I
accepted articles for viewing at full text if I deter-
mined that they may contain information perti-
nent to the review question or if the abstract was
ambiguous and did not allow inferences to be
drawn about the content of the article. Finally, I
read all remaining studies at full text and either
rejected or accepted into the nal review based
upon subject matter (Pullin and Stewart 2006,
Koricheva et al. 2013). Studies that only modeled
effects of simulated res on Spotted Owl habitat
and demography were not considered here.
Because post-re logging often occurred, I also
recorded effects of this disturbance where they
were reported. I believe all studies in the nal
review were generally comparable because time
since re and percent of high-severity burn were
similar among studies (Tables 1, 2), and the high
number of non-signicant results reported indi-
cates little to no publication bias exists in this
topic (Tables 1, 2; Appendix S1: Fig. S1). I consid-
ered the basic sampling unit of all studies to be
the central core of the owl breeding-season terri-
tory (~400 ha, or a circle with radius 1.1 km cen-
tered on the nest or roost stand) because this is
the spatial and temporal scale for sampling used
in almost all Spotted Owl studies. In contrast,
Spotted Owl year-round home ranges vary
according to latitude and dominant vegetation,
but range from 300 to 11,000 ha, or circles with
radius 1.05.9 km (Zabel et al. 1992). I consid-
ered forest res to affect the landscape scale
(~10,000 ha/decade), but that res would affect
numerous individual owl breeding-season terri-
tories (1200 ha) and year-round home ranges
(30019,000 ha) in various ways.
Meta-analyses and meta-regression
I evaluated all nal review papers and
included all papers where effects of re were
reported and could be differentiated from other
disturbances such as post-re logging. I extracted
evidence by reading every paper and tabulating
all quantied results from text, tables, and g-
ures (Table 1). I noted the mean (
x) and variation
(SD) of burned and unburned groups for all sig-
nicant and non-signicant parameters, the
parameters being estimated, sample sizes
(n=number of owl breeding sites in burned and
unburned groups), amount of high-severity re
in the total re perimeter and/or within the owl
territory core areas examined, time since re
(years), amount of post-re logging that
occurred, subspecies (California =Strix occiden-
talis occidentalis, Mexican =Strix occidentalis
lucida, or northern =Strix occidentalis caurina),
and whether the result was statistically signi-
cant (as dened in each paper).
I conducted all analyses in R 3.3.1 (www.r-pro
ject.org). For meta-analysis, I noted or calculated
the mean, variance (SD), and sample size for
burned (treatment) and unburned (control)
groups. I calculated raw effect sizes as mean
differences (
xburned
xcontrol) and signs (positive
or negative) for all reported effects, regardless
of their statistical signicance. Most papers
reported effect sizes as probabilities (occupancy,
survival, and foraging habitat selection) so raw
effect sizes were scaled between negative and
positive one with a mean of zero, making com-
parison among studies easy. When papers
reported multiple effects (e.g., occupancy and
reproduction, or survival and recruitment), I
recorded each effect individually. Where papers
did not report any effect size for a parameter
determined to have no signicant effects from
re, I included a zero to represent the presence of
no signicant effect and to avoid a signicance
bias in the meta-analysis. I stratied data by sub-
species (California, Mexican, or northern) and
parameter type according to whether the study
estimated site occupancy, foraging habitat selec-
tion (substratied into selection for low-, moder-
ate-, and high-severity burned forest), and
demographic rates (substratied into survival,
reproduction, and recruitment). I performed
meta-analyses on parameters for which 4 esti-
mates existed from 4 different res.
I used three quantitative methods for evaluat-
ing the evidence (Koricheva et al. 2013): a ran-
dom-effects meta-analysis of mean effect sizes as
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SYNTHESIS & INTEGRATION LEE
Table 1. Summary of systematic review of studies examining effects of re on Spotted Owls.
No. Ref. Sample size HOD Time since re Context
Fire effects
(=statistically
signicant,
NS =non-
signicant) Fire
Any
effect
Signif.
effect
Post-re
logging
1 Bond et al.
(2002)
21 owls in 11
burned sites
OD 1 yr post-re No effect on
survival, site
delity, mate
delity, or
reproduction. 50%
of territories
burned 3688%
high severity, 50%
burned mostly low
moderate severity,
unknown amount
of post-re logging
No signicant
effects. (3% higher
survival NS, 1%
lower site delity
[occupancy] NS,
26% higher repro
NS)
0/+/+0.032
0.013
+0.259
na na
2 Jenness
et al.
(2004)
33 burned and
31 unburned
breeding
sites
OD 1-yr study,
14yr
post-re
No effect on
occupancy from
re or amount of
high-severity re.
No effect on
reproduction. 55%
of burned
territories area
burned, 18% at
high severity,
unknown amount
of post-re logging
No signicant
effects from re.
(14% lower
occupancy NS,
7% lower repro in
burn NS)
0/0.14
0.07
na na
3 Bond et al.
(2009)
Seven radioed
owls from
four burned
sites
H 1-yr study, 4 yr
post-re
Owls preferred
burned forest for
foraging, especially
high-severity
burned forest.
Owls preferred
roost sites burned
at low severity and
avoided unburned
sites and sites
burned at
moderate and high
severity. 69% of
foraging area
burned, 13% at
high severity, <3%
post-re logging
Positive effect from
re on foraging
habitat selection
(+42%, +42%
+33%), negative
and positive effect
of re on roosting
nesting habitat
selection (+29%,
13%, 28%)
+/+0.33
+0.42
+0.42
+0.29
0.13
0.28
+0.33
+0.42
+0.42
+0.29
0.13
0.28
na
4 Bond et al.
(2010)
Five radioed
owls in
occupied
burned sites
H 1-yr study, 4 yr
post-re
Three of ve owls
occupied burned
forest over winter
No signicant
effects, perhaps
some positive
effect
0/+na na na
5 Clark et al.
(2011)
11 radioed
owls in
burned and
post-re
logged sites,
12 in
unburned
sites
D 2-yr study,
34yr
post logging
No effects on
survival. Reduced
survival in salvage-
logged areas
relative to owls in
unburned forest.
14% high severity,
21% post-re
logged
Negative survival
effect from
combined effects
of re and
post-re logging
(0.07 NS)
?nana0.07
6 Roberts
et al.
(2011)
16 burned and
16 unburned
survey areas
O 1-yr study,
214 yr
post-re
No effect of re on
survey area
occupancy. 14% of
survey area burned
at high severity,
little to no post-re
logging
No signicant
effect from re.
Possible negative
effect from basal
area and canopy
cover model
(26% lower
occupancy in
burned survey
area NS)
0/0.260 na na
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SYNTHESIS & INTEGRATION LEE
(Table 1. Continued)
No. Ref. Sample size HOD Time since re Context
Fire effects
(=statistically
signicant,
NS =non-
signicant) Fire
Any
effect
Signif.
effect
Post-re
logging
7 Lee et al.
(2012)
41 burned and
145
unburned
breeding
sites
O 11-yr study,
17yr
post-re from
six large res
No effect on
occupancy
probability. 32%
high severity.
Unknown amount
of post-re logging
No signicant
effect from re,
perhaps a slightly
positive effect (4%
higher occupancy
in burned sites
NS)
0/++0.041 na na
8 Bond et al.
(2013)
Seven radioed
owls
H 1-yr study, 4 yr
post-re
Owls in burned
forest have same
size or smaller
home ranges than
owls in unburned
forest. 69% of
foraging area
burned, 13% at
high severity, 3%
post-re logging
No signicant
effect from re,
possible positive
effect (HR size
12% smaller in
burned area NS)
0/++0.12 na na
9 Clark et al.
(2013)
40 burned and
salvage-
logged sites
and 103
unburned
sites
O 13-yr study,
14yr
post-re
Lower site
occupancy on
salvage-logged
sites relative to
unburned sites.
11% high severity,
13% post-re
logged
Negative effect on
occupancy from
combined re and
post-re logging
(0.39)
?nana0.39
10 Lee et al.
(2013)
71 burned and
97 unburned
breeding
sites, post-
re logging
on 21 of the
burned sites
O 8-yr study,
18yr
post-re
No effects from re
or logging. Burned
site occupancy 17%
(10% for pairs)
lower than
unburned sites.
Post-re logged
sites occupancy 5%
lower than
unlogged burned
sites. 23% high
severity in burned
sites, 59% logged
in post-re logged
sites
No signicant
effect from re,
negative effect
(17% lower any
occupancy, 10%
lower pair
occupancy in
burn NS)
Same data as ref.
no. 14
0/0.171
0.107
na 0.05
11 Ganey
et al.
(2014)
Four radioed
owls
H 1-yr study,
46yr
post-re
Owls moved to
burned forest over
winter. Burned
wintering sites had
26 times more
prey biomass
relative to
unburned core
areas. 21% high
severity, unknown
amount of post-re
logged
Positive effect from
re
+na na na
12 Tempel
et al.
(2014)
12 burned, 62
unburned
sites
DO 20-yr study of
survival and
reproduction,
6-yr study of
occupancy.
No effect on
survival,
reproduction, or
site extinction.
Reported a
negative effect of
re on colonization
rate, but
colonization
parameter was
faulty due to low
sample size and
zero colonization
events. Unknown
amount of high-
severity re,
unknown amount
of post-re logging
No signicant
effect from re.
Possible negative
effect from re
(6% lower
occupancy when
re frequency
doubled in
simulations that
assumed zero
post-re
colonizations)
0/0
0
0.060
0.060 na
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SYNTHESIS & INTEGRATION LEE
(Table 1. Continued)
No. Ref. Sample size HOD Time since re Context
Fire effects
(=statistically
signicant,
NS =non-
signicant) Fire
Any
effect
Signif.
effect
Post-re
logging
13 Lee and
Bond
(2015a)
45 burned
breeding
sites
O Rim Fire, 1-yr
study, 1 yr
post-re
Higher burned-site
occupancy rates
than any published
unburned area.
100% high-severity
re in territory
surrounding nest
and roost sites
reduced single owl
occupancy
probability 5%
relative to sites
with 0% high
severity. Amount
of high-severity
re did not affect
occupancy by pairs
of owls. In re
perimeter: 37%
high severity, no
post-re logging
Positive (17%
higher occupancy
rates). Small
negative effect on
site occupancy
(3% lower
occupancy in
burn). No
signicant effect
on pair
occupancy
+/0 +0.175
0.04
0
+0.175 na
14 Lee and
Bond
(2015b)
71 burned and
97 unburned
breeding
sites, post-
re logging
on 21 of the
burned sites
OD 8-yr study,
18yr
post-re
Occupancy of high-
quality sites
(previously
reproductive) that
burned was 2%
lower than
unburned sites.
Occupancy of
high-quality sites
that were post-re
logged was 3%
lower. Occupancy
of low-quality sites
(previously non-
reproductive) was
19% lower in
burned vs.
unburned sites and
26% lower after
post-re logging.
Fire did not affect
reproduction. 23%
high severity in
burned sites, 59%
logged in post-re
logged sites
Negative effect on
site occupancy
(2% and 19%
lower), No
signicant effect
on reproduction
/0 0.02
0.19
0
0.02
0.19
0.03
0.26
15 Bond et al.
(2016)
Eight radioed
owls in ve
sites
H 2-yr study,
34yr
post-re
Owls used forests
burned at all
severities in
proportion to their
availability, with
the exception of
signicant
selection for
moderately burned
forest farther from
core areas. 23%
high severity, <5%
post-re logging
No signicant
effect from re
(3% lower
probability of use
in high-severity
burn NS), some
positive effect
(15% higher
probability of use
of low-severity
burn NS, 10%
higher probability
of use in
moderate-severity
burned forest NS,
3% higher
probability of use
of moderate
severity away
from the core)
0/+0.03
+0.15
+0.10
+0.033 na
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SYNTHESIS & INTEGRATION LEE
(Table 1. Continued)
No. Ref. Sample size HOD Time since re Context
Fire effects
(=statistically
signicant,
NS =non-
signicant) Fire
Any
effect
Signif.
effect
Post-re
logging
16 Comfort
et al.
(2016)
23 radioed
owls in
post-re
logged area
H 2-yr study,
34yr
post logging
Scale-dependent
effects of logging
(+/). Owls
selected a
moderate amount
of hard edges
around logged
stands. 14% high
severity, 21%
post-re logged
Positive and
negative effect
from post-re
logging created
edges
?nana+/
17 Jones et al.
(2016)
30 burned
sites, 15
unburned
sites, nine
radioed owls
in seven sites
OH 23-yr study,
1 yr post-re
Negative effects
from high-severity
re. Positive effect
of low- to
moderate-severity
re. 64% high-
severity burn, 2%
post-re logging
>50% high-severity
burned sites had
lower occupancy
(0.49), <50%
high-severity
burned sites had
higher occupancy
(+0.07 NS). High-
severity burned
habitat was
avoided
(0.307), low-
tomoderate-
severity burn was
preferred (+0.04
NS)
+/+0.070
0.490
0.307
+0.04
0.490
0.307
+0.04
na
18 Tempel
et al.
(2016)
43 burned
sites and 232
unburned
sites in four
study areas
O 19-yr study,
examined 3-yr
post-re
effects
No effects of re.
One study area
had positive effect
of re. Lower site
extinction
probability
correlated with
proportion of site
where wildre
reduced canopy
>10%. 1% of all
territories burned,
unknown amount
of post-re logging
No signicant
effect from re,
some positive
effect (1% lower
extinction rate in
burned sites NS)
0/++0.003
0
0
0
na na
19 Eyes et al.
(2017)
13 radioed
owls in eight
sites (14 owl-
year data
sets)
H 3-yr study,
114 yr
post-re
No effect of re on
foraging habitat
selection, owls
foraged in all burn
severities in
proportion to their
availability. 6%
high severity, little
to no post-re
logging
No signicant
effect from re.
Possibly negative
effect (6% lower
probability of use
for highest burn
severity NS; 3%
lower use of
moderate severity
NS)
0/0.06
0.03
na na
20 Rockweit
et al.
(2017)
193 burned
and 386
unburned
encounter
histories
from 28
burned (8, 2,
4, 14) and 70
unburned
sites
D 26-yr study,
426 yr
post-re
Four res had
different effects.
Generally, res
reduced survival
and increased
recruitment. 10%,
12%, 16%, and 48%
high severity, no
post-re logging
reported
Two res had no
signicant effects
on survival or
recruitment. Two
res had reduced
survival (0.17
and 0.30), one
had increased
recruitment
(+0.22)
0/+/0.03
0.10
0.17
0.30
+0.01
+0.02
+0.04
+0.22
0.17
0.30
+0.22
na
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SYNTHESIS & INTEGRATION LEE
the standardized difference in means (Hedgesd;
Hedges and Olkin 1985); multi-level linear mixed-
effects models (hierarchical models) meta-regres-
sion of time since re and percent of high-severity
re in the study area as covariates to explain
heterogeneity in mean effect sizes (Hedges and
Vevea 1998, Nakagawa and Santos 2012); and a
random-effects meta-analysis of variation to
examine differences in parameter variances due to
re with effect sizes as the natural logarithm of
the ratio between the coefcients of variation
(lnCVR; Nakagawa et al. 2015). For analyses, I
used the metafor package of R (Viechtbauer 2010)
and used function metacont for random-effects
meta-analyses, function rma.mv for multi-level
linear mixed-effects model meta-regression, and
function rma for random-effects meta-analysis
of variation (Viechtbauer 2010). Study within
geographic area was included as multi-level
random effects to properly estimate study site-
and region-specic variation and to account
for repeated measurements (pseudo-replication)
within a study or region. Regions were dened as
Sierra Nevada, southern California, national
parks, not California, and the Eldorado density
study area (because several studies used data
from there).
I used all three methods at three levels: on all
parameters, on three main groups of parameters
(occupancy, foraging habitat selection, and
demography), and on subgroups of habitat selec-
tion (for low-, moderate-, and high-severity
burned forest) and demography (survival, repro-
duction, and recruitment). In meta-analyses, I
used ztests to determine if effects were signi-
cantly different from zero (95% condence inter-
val excluded zero). In meta-regression, ztests
determined whether intercepts or slope coef-
cients were signicantly different from zero. I
quantied heterogeneity among effects as
CochransQ(Hedges and Olkin 1985) and I
2
(Higgins and Thompson 2002). I used a funnel
plot and the rank correlation test (Kendallss)to
assess publication bias (Begg and Mazumdar
1994).
RESULTS
Literature search
I found 21 papers reporting empirical evidence
relevant to direct re effects on owls (Table 1).
Three papers presented data from a study area
which was extensively logged post-re and
results did not discriminate between effects of
re and post-re logging (Clark et al. 2011, 2013,
Comfort et al. 2016), so these three papers were
not included in meta-analyses with the meta-
analysis set of papers that were not confounded
(Table 1. Continued)
No. Ref. Sample size HOD Time since re Context
Fire effects
(=statistically
signicant,
NS =non-
signicant) Fire
Any
effect
Signif.
effect
Post-re
logging
21 Hanson
et al.
(2018)
54 burned
sites in eight
res that
were
occupied
immediately
before re,
beforeafter
comparison
O 14-yr study,
1 yr post-re
Eight large res (4
included in Tempel
et al. 2016). Four
groups: 2049%
and 5080% high-
severity re; and
<5% and 5%
post-re logging
within 1500 m of
site center. Mean
63% high severity
in core areas, mean
17% logged if 5%
of core was
post-re logged
Compared burned
site occupancy
with unburned
occupancy from
Tempel et al.
(2016)
No signicant
effect from re,
signicant
negative effect of
post-re logging
(3% reduction in
occupancy if 50
80% of core
burned high-
severity re NS,
52% reduction in
occupancy from
5% post-re
logging)
0/- 0.017
0.013
na 0.52
Notes: HOD indicates habitat selection (H), occupancy (O), or demographic (D) parameters were estimated. A question
mark (?) indicates confounded re and post-re logging effects, so re effects could not be estimated.
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SYNTHESIS & INTEGRATION LEE
Table 2. Summary statistics for published effects of mixed-severity re on Spotted Owls (Strix occidentalis) 1987
2018 used in meta-analysis.
Ref
no. Study Subspecies Region Parameter
n
burned
n
unburned
Raw effect
size (mean
difference)
Signicant
(in study)
Time
since
re
(yr)
Percentage of
high-severity re in
burned territories
1 Bond
(2002)
CNM NotCal Occupancy 18 100 0.013 na 1 30
1 Bond
(2002)
CNM NotCal Reproduction 7 100 0.259 na 1 30
1 Bond
(2002)
CNM NotCal Survival 21 100 0.032 na 1 30
2 Jenness
(2004)
M NotCal Occupancy 33 31 0.14 na 2.5 16
2 Jenness
(2004)
M NotCal Reproduction 33 31 0.07 na 2.5 16
3 Bond
(2009)
C SN Foraging High 7 70.42 0.42 4 13
3 Bond
(2009)
C SN Foraging Low 7 70.33 0.33 4 13
3 Bond
(2009)
C SN Foraging Mod 7 70.42 0.42 4 13
6 Roberts
(2011)
C NP Occupancy 16 16 0.26 na 8 12
7 Lee
(2012)
C SN Occupancy 41 145 0.041 na 4 32
10 Lee
(2013)
C SoCal Occupancy 71 97 0.171 na 4.5 23
10 Lee
(2013)
C SoCal Occupancy 71 97 0.107 na 4.5 23
12 Tempel
(2014)
C Eldorado Occupancy 12 62 0.06 0.06 3 23
12 Tempel
(2014)
C Eldorado Reproduction 12 62 0 na 3 23
12 Tempel
(2014)
C Eldorado Survival 12 62 0 na 3 23
13 Lee
(2015a)
C SN Occupancy 45 45 0.04 na 1 37
13 Lee
(2015a)
C SN Occupancy 45 45 0 na 1 37
13 Lee
(2015a)
C SN Occupancy 45 145 0.175 0.175 1 37
14 Lee
(2015b)
C SoCal Occupancy 71 97 0.19 0.19 4.5 23
14 Lee
(2015b)
C SoCal Occupancy 71 97 0.02 0.02 4.5 23
14 Lee
(2015b)
C SoCal Reproduction 71 97 0 na 4.5 23
15 Bond
(2016)
C SoCal Foraging High 8 80.093 na 3.5 15
15 Bond
(2016)
C SoCal Foraging High 8 80.035 na 3.5 16
15 Bond
(2016)
C SoCal Foraging High 8 80.092 na 3.5 9
15 Bond
(2016)
C SoCal Foraging Low 8 80.115 na 3.5 15
15 Bond
(2016)
C SoCal Foraging Low 8 80.167 na 3.5 9
15 Bond
(2016)
C SoCal Foraging Low 8 80.169 na 3.5 16
15 Bond
(2016)
C SoCal Foraging Mod 8 80.042 na 3.5 15
15 Bond
(2016)
C SoCal Foraging Mod 8 80.033 0.033 3.5 16
15 Bond
(2016)
C SoCal Foraging Mod 8 80.102 na 3.5 9
17 Jones
(2016)
C Eldorado Foraging High 9 90.307 0.307 1 19
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SYNTHESIS & INTEGRATION LEE
by extensive post-re logging (Table 2). All 21
papers are summarized in Appendix S1.
Fifteen of the 18 papers in the meta-analysis
set reported evidence explicitly pertaining to
mixed-severity wildres that burned during the
past few decades and which included propor-
tions of high-severity burn characteristic of this
re regime, while three reported evidence from
an undifferentiated mix of wildre and
prescribed res. The studies reported varying
amounts of high-severity re, a dening feature
of mixed-severity res, and the burn severity
type that is most responsible for vegetation
changes in wildres, with an overall mean per-
cent of high-severity re of 26% (standard error
[SE] =3.6, range 664) within the study area.
Because almost all the studies in this review
reported on effects from recent wildres (all
(Table 2. Continued)
Ref
no. Study Subspecies Region Parameter
n
burned
n
unburned
Raw effect
size (mean
difference)
Signicant
(in study)
Time
since
re
(yr)
Percentage of
high-severity re in
burned territories
17 Jones
(2016)
C Eldorado Foraging Mod 9 90.04 +0.04 1 19
17 Jones
(2016)
C Eldorado Occupancy 14 15 0.490 0.490 1 64
17 Jones
(2016)
C Eldorado Occupancy 16 15 0.07 na 1 19
18 Tempel
(2016)
C SN Occupancy 12 78 0 na 4 23
18 Tempel
(2016)
C Eldorado Occupancy 14 60 0 na 4 23
18 Tempel
(2016)
C SN Occupancy 3 63 0 na 4 23
18 Tempel
(2016)
C NP Occupancy 14 31 0.003 0.003 4 23
19 Eyes
(2017)
C SN Foraging High 13 130.06 0.06 7 6
19 Eyes
(2017)
C SN Foraging Mod 13 130.03 0.03 7 6
20 Rockweit
(2017)
N NotCal Recruitment 8 8 0.01 na 12.5 10
20 Rockweit
(2017)
N NotCal Recruitment 2 2 0.02 na 6.5 16
20 Rockweit
(2017)
N NotCal Recruitment 4 4 0.04 na 4 48
20 Rockweit
(2017)
N NotCal Recruitment 14 14 0.22 0.22 2 12
20 Rockweit
(2017)
N NotCal Survival 4 4 0.30 0.3 4 48
20 Rockweit
(2017)
N NotCal Survival 14 14 0.17 0.17 2 12
20 Rockweit
(2017)
N NotCal Survival 2 2 0.10 na 6.5 16
20 Rockweit
(2017)
N NotCal Survival 8 8 0.03 na 12.5 10
21 Hanson
(2018)
C SN Occupancy 13 201 0.017 0.017 1 63
21 Hanson
(2018)
C SN Occupancy 15 201 0.013 0.013 1 35
Notes: Study indicates rst author and year. Subspecies are C, California (Strix occidentalis occidentalis); N, northern (Strix
occidentalis caurina); M, Mexican (Strix occidentalis lucida); CNM, study included all subspecies. Regions are SN, Sierra Nevada,
California (except El Dorado study area and national parks); SoCal, southern California; Eldorado, El Dorado study area in
Sierra Nevada, California; NotCal, not California Spotted Owl subspecies; NP, national parks. Parameters: habitat selection (for-
aging or roosting) in low-, moderate-, (mod) or high-severity burned forest; occupancy, recruitment, reproduction, and survival.
Sample sizes (n) are number of breeding site territories burned and unburned. Raw mean effect size is
xburned
xcontrol, signi-
cant repeats effects that the individual study determined was statistically signicant. Time since re is the median number of
years between the re and the parameter estimate(s). Percent high-severity re in burned study territories is the mean relevant
to the estimate, or the grand mean if percentage of high severity was not reported (see ).
Habitat selection occurred within territories that contained a mosaic of burn severities and unburned forest.
Percent high-severity re was not reported for burned territories only for all territories burned and unburned, so the grand
mean of reported percentages was used.
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SYNTHESIS & INTEGRATION LEE
res burned in the past 30 yr, mean time since
re =4yr, SE=1.1, range 126), the reported
effects are representative of natural mixed-
severity res as they burned through currently
existing forest structure, re regime, and climate
conditions. Papers reported effects of re on site
occupancy (11), foraging habitat selection (4),
reproduction (4), apparent survival (3), overwin-
ter roosting habitat selection (2), site delity (1),
mate delity (1), breeding-season nesting and
roosting habitat selection (1), home-range size
(1), and recruitment (1). Sample sizes mea-
sured as number of burned sites were variable
among studies (demography CV =122%, site
occupancy CV =56%, and habitat selection
CV =24%).
Meta-analyses
Meta-analysis of 50 reported effects on occu-
pancy, foraging habitat selection, and demo-
graphic rates found effect sizes and signs were
variable (Table 2 and Fig. 2), with high hetero-
geneity among effects (Q=1091, df =51,
P<0.0001; I
2
=95.3%). Funnel plot (Appen-
dix S1: Fig. S1) and rank correlation test (Ken-
dallss=0.108, P=0.27) showed no publication
bias or unusual heterogeneity. Sample sizes
(n=number of reported effects) were variable
among parameter types (Fig. 3). The number of
reported effects were occupancy =20; demogra-
phy =14; and foraging habitat selection =16.
The number of reported effects by demography
subtype were survival =6; reproduction =4;
and recruitment =4. The number of reported
effects by habitat selection subtype were low-
severity burned forest =4; moderate-severity
burned forest =6; and high-severity burned
forest =6.
The mixed-effects model meta-analysis of re
effects on Spotted Owl parameters grouped by
type (occupancy, demography, and foraging
habitat selection), and subtypes of demography
(survival, reproduction, and recruitment) or for-
aging habitat selection (selection for low-, moder-
ate-, and high-severity burned forest), found
mixed-severity re has generally no signicant
effect on Spotted Owls (Fig. 3a). Mean overall
raw effect size was positive (+0.001), but
weighted mean Hedgesdfrom the random-
effects model was not signicantly different from
zero (Fig. 3a, 95% condence interval included
zero). Mean raw effect sizes were negative for
occupancy (0.060), demography (0.006), and
survival (0.095), but no Hedgesdvalue for
these three negative effects was signicantly dif-
ferent from zero (Fig. 3a). Mean raw effect sizes
were positive for reproduction (+0.047), recruit-
ment (+0.073), foraging habitat selection (+0.083),
selection of high-severity (+0.004), moderate-
severity (+0.087), and low-severity burned forest
(+0.195), but Hedgesdvalues were not signi-
cantly different from zero for any of these posi-
tive effects, except for signicant selection of
low-severity burned forest (Fig. 3a).
Variation was generally higher among
parameter estimates from burned areas com-
pared to estimates from unburned areas (mean
CV
burned
CV
unburned
=23%; range 457%).
The mixed-effects meta-analysis of variation in
re effects on Spotted Owl parameters (lnCVR)
found mixed-severity re resulted in signi-
cantly higher variation in parameter estimates
in all parameters and in occupancy, demogra-
phy, and survival (Fig. 3b). There was signi-
cantly lower variation in estimates of foraging
habitat selection probability for low-severity
burned forest (Fig. 3b).
Meta-regression
Meta-regression of all standardized mean
effects found signicant effect of time since re
(Table 3), and a nearly signicant effect of per-
cent high-severity burn in territory cores
(Table 3), so those effects were included in
parameter-specic meta-regressions. Subspecies
was not a signicant factor (Table 3), so effects
from different subspecies were pooled in subse-
quent parameter-specic analyses.
Meta-regression of occupancy probability
found no signicant immediate effect of re on
occupancy (intercept not signicantly different
from zero; Table 4). There was a signicant nega-
tive effect of time since re (Fig. 4, Table 4), but
no effect of percent high-severity re in study ter-
ritories (Table 4). The negative effect of time
since re was sensitive to one study (Roberts
et al. 2011), and when that study was omitted,
the effect disappeared.
Meta-regression of demographic parameters
found a signicant positive effect on recruitment
immediately after the re (intercept signicantly
different from zero), but the effect diminished
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SYNTHESIS & INTEGRATION LEE
Fig. 2. Forest plot of effect sizes for 50 Spotted Owl (Strix occidentalis) parameters (grouped into occupancy,
demography, and foraging habitat selection) affected by mixed-severity wildre as standardized mean difference
(Hedgesd) between burned and unburned samples. Studies and parameters are listed in Table 2.
www.esajournals.org 13 July 2018 Volume 9(7) Article e02354
SYNTHESIS & INTEGRATION LEE
with time since re (Fig. 5, Table 4). Reproduc-
tion intercept was not signicantly different from
recruitment (Table 4), and not signicantly dif-
ferent from zero (z=0.218, P=0.86), but
reproduction was signicantly positively corre-
lated with the percent of high-severity re in owl
territories (Fig. 5, Table 4). Survival was signi-
cantly lower than recruitment (Table 4), but sur-
vival intercept was not signicantly different
from zero (z=0.052, P=0.97). There were no
signicant survival effects of time since re or
percent of high-severity re (Table 4).
Meta-regression of foraging habitat selection
parameters found a signicant positive selection
for low- and moderate-severity burned forest,
with high-severity burned forest used in propor-
tion to its availability, but not avoided (Fig. 5,
Table 4). Time since re did not affect foraging
habitat selection during the period covered by
the studies I examined (up to 7 yr), and the
Fig. 3. Results of mixed-effects meta-analyses of mixed-severity re effects (n=50 effects from 21 studies) on
Spotted Owl (Strix occidentalis) parameters grouped by type (occupancy, demography, and foraging habitat selec-
tion) and subtype of demography (survival, reproduction, and recruitment), or habitat selection (selection for
low-, moderate-, and high-severity burned forest). (a) Hedgesdis standardized mean effect size, and error bars
are 95% condence intervals. The only signicant effect (95% condence intervals excluded zero) was a positive
effect of habitat selection for low-severity burned forest. (b) lnCVR is the natural logarithm of the ratio between
the coefcients of variation, a measure of differences in variation of parameter estimates between burned and
unburned areas. Mixed-severity re resulted in signicantly higher variation in parameter estimates in all param-
eters, occupancy, demography, and survival, and signicantly lower variation in habitat selection for low-sever-
ity burned forest.
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SYNTHESIS & INTEGRATION LEE
amount of high-severity re did not affect habitat
selection overall (Table 4).
Post-re logging had negative effects on Spot-
ted Owls in 100% of the papers that examined
this disturbance and where effects from re and
post-re logging could be differentiated, with
large effect sizes (0.18 occupancy, 0.07
survival).
DISCUSSION
This systematic review and summary of effects
from the primary literature indicated Spotted
Owls are usually not signicantly affected by
mixed-severity re as 83% of all studies and 60%
of all effects found no signicant impact of re
on owl parameters. Meta-analysis of mean effects
found no signicant effects of re on owls, except
a positive effect on foraging habitat selection
for low-severity burned forest. Meta-regression
indicated signicant positive effects in recruit-
ment, reproduction, and foraging habitat selec-
tion for low- and moderate-severity burned
forest. Meta-regression found a signicant
negative effect of time since re on occupancy
probability. Meta-analysis of variation found
mixed-severity re resulted in greater parameter
variation overall, and specically in occupancy,
demography, and survival, and signicantly less
variation in foraging habitat selection for low-
severity burned forest.
These results represent Spotted Owl responses
to mixed-severity wildres that burned within the
past 30 yr with representative proportions of
high-severity re in a landscape mosaic. Addi-
tionally, because most of the studies in this review
reported on effects from wildre, rather than pre-
scribed re, the res and their effects are represen-
tative of wildres as they burned through
currently existing forest structure, re regime, and
climate conditions. Several studies have reported
that res during the past few decades have been
larger and more severe than the historical mean
(Miller and Safford 2012, 2017, Mallek et al. 2013,
Steel et al. 2015), but others have disputed this
Table 3. Results from multivariate mixed-effects meta-
regression model of mixed-severity re effects
(n=50 effects from 21 studies) on Spotted Owl
(Strix occidentalis) parameters related to occupancy,
demography, and foraging habitat selection.
Covariates bSE zP
Intercept (California
subspecies)
1.601 1.070 1.497 0.134
Time since re 0.199 0.099 2.017 0.044
Percentage of area
high-severity re in
study territories
0.044 0.023 1.866 0.062
Mix of California,
northern, Mexican
subspecies
0.467 1.592 0.294 0.769
Mexican subspecies 1.947 1.608 1.211 0.226
Northern subspecies 0.360 1.571 0.229 0.819
Notes: SE, standard error. Time since re was signicant, and
percent high-severity burn in territory cores was nearly signi-
cant, so those effects were included in parameter-specicmeta-
regressions. Subspecies was not a signicant factor, so effects
from different subspecies were pooled in subsequent parameter-
specic analyses. Bold values are signicant at alpha =0.05.
Table 4. Table of model coefcients from multi-level
linear mixed-effects model meta-regression for effects
of mixed-severity re on Spotted Owls 19872018.
Coefcient bSE zP
Occupancy
Intercept 1.854 1.115 1.662 0.096
Time since re 0.512 0.216 2.375 0.018
Percentage of area
high-severity re in
study territories
0.036 0.022 1.645 0.100
Demography
Intercept
(Recruitment)
2.328 1.152 2.021 0.043
Time since re
(Recruitment)
0.153 0.065 2.347 0.019
Percentage of area
high-severity re in
study territories
0.032 0.022 1.466 0.143
Reproduction 6.479 3.337 1.942 0.052
Survival 2.558 1.206 2.121 0.034
Time since re
(reproduction)
0.034 0.422 0.081 0.936
Time since re (survival) 0.101 0.112 0.900 0.368
Percentage of area
high-severity re
(reproduction)
0.234 0.109 2.142 0.032
Percentage of area
high-severity re
(survival)
0.031 0.033 0.924 0.356
Foraging habitat selection
Intercept (High severity) 1.167 2.926 0.399 0.690
Time since re 0.061 0.529 0.115 0.908
Percentage of area
high-severity re in
study territories
0.084 0.068 1.236 0.216
Low severity 1.936 0.732 2.644 0.008
Moderate severity 0.777 0.321 2.416 0.016
Note: SE, standard error. Bold values are signicant at
alpha =0.05.
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SYNTHESIS & INTEGRATION LEE
point (Odion and Hanson 2006, Hanson et al.
2009, Odion et al. 2014a, Baker 2015a). Regardless
of what is correct about trends in re severity,
Spotted Owls appear fairly resistant and/or resili-
ent to effects from recent hot, large res, wherever
these res fall in the long-term range of variability
for size and amount of high-severity burn. This is
corroborated by the meta-regressions that explic-
itly quantied the relationship between amount
of high-severity re and Spotted Owl parameters
and found only a positive signicant correlation
(reproduction). My nding of no signicant
negative relationships between amount of high-
severity re and Spotted Owl parameters demon-
strates that large high-severity re patches,
including territories that burn 100% at high sever-
ity as was seen in sites within several of the stud-
ies in this review, do not have unequivocally
negative outcomes for Spotted Owls.
Contrary to current perceptions, recovery efforts,
and forest management projects for the Spotted
Owl (USFWS 2011, 2012, 2017, USDA 2012, 2018,
Guti
errez et al. 2017) mixed-severity re as it
has been burning in recent decades does not
appear to be an immediate, dire threat to owl pop-
ulations that require landscape-level fuel-reduction
Fig. 4. Results of multi-level linear mixed-effects models (hierarchical models) meta-regression of time since
re and percent of high-severity re in the study area as covariates to explain heterogeneity in effect sizes from
mixed-severity re on Spotted Owl (Strix occidentalis) parameters of breeding site occupancy and survival. The
only signicant effect was a reduction in occupancy with increasing time since re, but the effect was sensitive to
one study. Symbols indicate subspecies: lled black circles, California; white circles with black outline, Mexican;
light gray circles with black outline, northern; and dark gray circles, all three subspecies.
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SYNTHESIS & INTEGRATION LEE
Fig. 5. Results of multi-level linear mixed-effects models (hierarchical models) meta-regression of time since
re and percent of high-severity re in the study area as covariates to explain heterogeneity in effect sizes from
mixed-severity re on Spotted Owl (Strix occidentalis) parameters of foraging habitat selection, recruitment, and
reproduction. Signicant effects included positive selection for low- and moderate-severity burned forest for for-
aging, increased recruitment immediately post-re that diminished with increasing time since re, and increased
reproduction with a positive correlation with amount of high-severity re. In top two panels, all studies were
California subspecies, and colors indicate forest in different burn severity categories: green, low severity; orange,
moderate severity; red, high severity. In bottom four panels, symbols indicate subspecies: lled black circles, Cal-
ifornia; white circles with black outline, Mexican; light gray circles with black outline, northern; and dark gray
circles, all three subspecies.
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SYNTHESIS & INTEGRATION LEE
treatments to mitigate re severity. Empirical stud-
ies reviewed here demonstrated that wildres can
generally have no signicant effect, but effects can
include improved foraging habitat, reduced site
occupancy, and improved demographic rates. Most
territories occupied by reproductive Spotted Owl
pairs that burn remain occupied and reproductive
at the same rates as sites that did not experience
recent re, regardless of the amount of high-sever-
ity re in core nesting and roosting areas.
To place my results into perspective, mixed-
severity re typically affects (50% vegetation
basal area mortality) a very small portion (0.02
0.50%) of Spotted Owl nesting and roosting
habitat per year (Odion et al. 2014b, Baker 2015b,
Stephens et al. 2016). Breeding sites that experi-
enced a typical mixed-severity burn mosaic can
be expected to have occupancy probability
reduced by 0.06 on average. A 0.06 decline in
occupancy is less than typical annual declines in
occupancy rates observed in the Sierra Nevada in
the absence of large res (Jones et al. 2016:
Fig. 3f). In comparison, post-re logging caused a
mean occupancy probability reduction of 0.18.
Post-re logging is likely to be partially
responsible for some of the negative effects
attributed to high-severity re in the studies
reviewed here (Tempel et al. 2014, Jones et al.
2016, Rockweit et al. 2017, Hanson et al. 2018).
Because Spotted Owl studies typically character-
ize territory vegetation only in the breeding core
area within 1.1 km of the nest, these studies
ignore habitat changes and alterations in the
year-round home-range area that can extend up
to 5.9 km from the nest (Zabel et al. 1992). Spot-
ted Owl habitat protections have generally not
included areas beyond 1 km from the nest, a
management policy that has not contributed to
population recovery.
Complex early seral forests created by re differ
from post-re salvage-logged forests in that dead
trees remain on-site, providing perching sites for
hunting owls as well as food sources and shelter
for numerous wildlife species (Hutto 2006, Swan-
son et al. 2011, DellaSala et al. 2014). Longitudi-
nal studies also indicated that burned breeding
sites where owls were not detected immediately
after re were often recolonized later (Lee et al.
2012, 2013, Tempel et al. 2016), and this review
shows burned forest habitat is used for foraging,
demonstrating the mistake of concluding severely
burned sites or habitats are lost to Spotted Owls
or require restoration (Davis et al. 2016). A recent
global meta-analysis found post-re logging is
generally not consistent with ecological manage-
ment objectives (Thorn et al. 2018).
This review on re and Spotted Owls forms
one portion of the evidence base for data-driven
forest management. A recent systematic review
of thinning and re found 56 studies addressing
fuel treatment effectiveness in real (not simu-
lated) wildres from eight states in the western
United States (Kalies and Kent 2016). There was
general agreement that thin +burn treatments
(thinning immediately followed by burning) had
some positive effects in terms of reducing re
severity, while treatments by burning or thinning
alone were less effective or ineffective (Kalies
and Kent 2016). There is also evidence that doing
nothing can achieve many forest restoration
goals related to age structure and fuelsdensity
(Zachmann et al. 2018). Additional systematic
reviews are needed to examine (1) the quanti-
able risk of re to Spotted Owl habitat, as there
are disparate lines of evidence regarding
whether re is impeding the recovery of late-
seral-stage forests; and (2) the impacts of fuel
treatments on Spotted Owl demography and site
occupancy. Thinning immediately followed by
burning to reduce wildre risk may or may not
have adverse effects on Spotted Owls (Franklin
et al. 2000, Dugger et al. 2005, Tempel et al.
2014, 2016, Odion et al. 2014b), but the evidence
presented here indicates re itself has arguably
more benets than costs to the species and thus
suggests thinning is not necessary.
The results presented here should serve to
guide management decisions, but also should be
understood as limited by the available data. The
sample sizes of number of estimated effects
from mixed-severity re on survival and
recruitment were small and limited mainly to the
northern subspecies. There were also very few
studies from the Mexican subspecies. A few
studies presented effect sizes that were inuen-
tial on results, especially meta-regression results
(Roberts et al. 2011), so studies examining longer
times since re are needed. We encourage future
studies to increase sample sizes of each parame-
ter and to provide a more balanced sample of
studies from all subspecies, and over longer time
frames.
www.esajournals.org 18 July 2018 Volume 9(7) Article e02354
SYNTHESIS & INTEGRATION LEE
MANAGEMENT IMPLICATIONS
The preponderance of evidence presented here
shows mixed-severity forest res, as they have
burned through Spotted Owl habitat in recent
decades under current forest structural, re
regime, and climate conditions, have no signi-
cant negative effects on Spotted Owl foraging
habitat selection, or demography, and have signif-
icant positive effects on foraging habitat selection,
recruitment, and reproduction. Forest re does
not appear to be a serious threat to owl popula-
tions and likely imparts more benets than costs
for Spotted Owls; therefore, fuel-reduction treat-
ments intended to mitigate re severity in Spotted
Owl habitat are unnecessary. These ndings
should inform revisions to planning documents to
consider burned forest, including large patches of
high-severity burned forest, as useful habitat that
imparts signicant benets to Spotted Owls. For-
est and wildlife planning documents promote a
diverse mosaic of heterogeneous tree densities
and ages (USFWS 2017, USDA 2018), the very
conditions created by mixed-severity wildre,
and it follows that heterogeneous post-re struc-
ture would lead to greater variation in some
Spotted Owl parameters, as was observed in the
meta-analysis of variation. Planning documents
(USFWS 2011, 2012, 2017, Guti
errez et al. 2017,
USDA 2018) claiming that forest res currently
pose the greatest risk to owl habitat and are a
primary threat to population viability appear
outdated in light of this review.
ACKNOWLEDGMENTS
I thank the many Spotted Owl researchers and eld
technicians who are responsible for the collection and
analyses of the data reviewed here. I also thank Mon-
ica Bond and Justin Augustine for thoughtful com-
ments on the manuscript. I have no conict of interest.
LITERATURE CITED
Baker, W. L. 2015a. Are high-severity res burning at
much higher rates recently than historically in dry-
forest landscapes of the Western USA? PLoS ONE
10:e0136147.
Baker, W. L. 2015b. Historical northern spotted owl habi-
tat and old-growth dry forests maintained by
mixed-severity res. Landscape Ecology 30:655666.
Beaty, R. M., and A. H. Taylor. 2001. Spatial and tem-
poral variation of re regimes in a mixed conifer
forest landscape, Southern Cascades, California,
USA. Journal of Biogeography 28:955966.
Begg, C. B., and M. Mazumdar. 1994. Operating char-
acteristics of a rank correlation test for publication
bias. Biometrics 50:10881101.
Blakesley, J. A., B. R. Noon, and D. R. Anderson. 2005.
Site occupancy, apparent survival, and reproduc-
tion of California spotted owls in relation to forest
stand characteristics. Journal of Wildlife Manage-
ment 69:15541564.
Bond, M. L. 2016. The heat is on: spotted owls and
wildre. Online reference module in earth systems
and environmental sciences. Elsevier Press, Ams-
terdam, The Netherlands.
Bond, M. L., C. Bradley, and D. E. Lee. 2016. Foraging
habitat selection by California spotted owls after
forest re in southern California. Journal of Wildlife
Management. https://doi.org/10.1002/jwmg.21112
Bond, M. L., R. J. Guti
errez, A. B. Franklin, W. S.
LaHaye, C. A. May, and M. E. Seamans. 2002.
Shortterm effects of wildres on spotted owl
survival, site delity, mate delity, and reproduc-
tive success. Wildlife Society Bulletin 30:10221028.
Bond, M. L., D. E. Lee, and R. B. Siegel. 2010. Winter
movements by California spotted owls in a burned
landscape. Western Birds 41:174180.
Bond, M. L., D. E. Lee, R. B. Siegel, and M. W. Tingley.
2013. Diet and homerangesizeofCaliforniaspotted
owls in a burned forest. Western Birds 44:114126.
Bond, M. L., D. E. Lee, R. B. Siegel, and J. P. Ward.
2009. Habitat use and selection by California spot-
ted owls in a postre landscape. Journal of Wildlife
Management 73:11161124.
Clark, D. A., R. G. Anthony, and L. S. Andrews. 2011.
Survival rates of northern spotted owls in postre
landscapes of southwest Oregon. Journal of Raptor
Research 45:3847.
Clark, D. A., R. G. Anthony, and L. S. Andrews. 2013.
Relationship between wildre, salvage logging, and
occupancy of nesting territories by northern spotted
owls. Journal of Wildlife Management 77:672688.
Comfort, E. J., D. A. Clark, R. G. Anthony, J. Bailey, and
M. G. Betts. 2016. Quantifying edges as gradients at
multiple scales improves habitat selection models
for northern spotted owl. Landscape Ecology.
https://doi.org/10.1007/s10980-015-0330-1
Conner, M. M., J. J. Keane, C. V. Gallagher, G. Jehle, T.
E. Munton, P. A. Shaklee, and R. A. Gerrard. 2013.
Realized population change for longterm moni-
toring: California spotted owl case study. Journal
of Wildlife Management 77:14491458.
Davis, R. J., B. Hollwn, J. Hobson, J. E. Gower, and D.
Keenum. 2016. Northwest forest planthe rst
www.esajournals.org 19 July 2018 Volume 9(7) Article e02354
SYNTHESIS & INTEGRATION LEE
20 years (19942013): status and trends of northern
spotted owl habitats. General Technical Report
PNWGTR929. Page 54. USDA Forest Service,
Pacic Northwest Research Station, Portland, Ore-
gon, USA.
DellaSala, D. A., M. L. Bond, C. T. Hanson, R. L. Hutto,
and D. C. Odion. 2014. Complex early seral forests
of the Sierra Nevada: What are they and how can
they be managed for ecological integrity? Natural
Areas Journal 34:310324.
Dugger, K. M., et al. 2016. The effects of habitat, cli-
mate, and Barred Owls on long-term demography
of Northern Spotted Owls. Condor 118:57116.
Dugger, K. M., F. Wagner, R. G. Anthony, and G. S.
Olson. 2005. The relationship between habitat char-
acteristics and demographic performance of north-
ern spotted owls in southern Oregon. The Condor
107:863878.
Eyes, S. A., S. L. Roberts, and M. D. Johnson. 2017. Cal-
ifornia spotted owl (Strix occidentalis occidentalis)
habitat use patterns in a burned landscape. Condor
119:375388.
Forsman, E. D., et al. 2011. Population demography of
northern spotted owls. Studies in Avian Biology
No. 40, Cooper Ornithological Society, University
of California Press, Berkeley, California, USA.
Franklin, A. B., D. R. Anderson, R. J. Guti
errez, and K.
P. Burnham. 2000. Climate, habitat quality, and
tness in northern spotted owl populations in
northwestern California. Ecological Monographs
70:539590.
Ganey, J. L., S. C. Kyle, T. A. Rawlinson, D. L. Apprill,
and J. P. Ward Jr. 2014. Relative abundance of small
mammals in nest core areas and burned wintering
areas of Mexican spotted owls in the Sacramento
Mountains, New Mexico. Wilson Journal of
Ornithology 126:4752.
Guti
errez, R. J., A. M. Franklin, and W. S. LaHaye.
1995. Spotted owl (Strix occidentalis). In A. Poole
and F. Gill, editors. The Birds of North America,
No. 179. The Academy of Natural Sciences,
Philadelphia, and The American Ornithologists
Union, Washington, D.C., USA.
Guti
errez, R. J., P. N. Manley, and P. A. Stine. 2017. The
California spotted owl: current state of knowledge.
U. S. Forest Service General Technical Report
PSWGTR. U.S. Department of Agriculture, Forest
Service, Pacic Southwest Research Station,
Albany, California, USA.
Guti
errez, R. J., J. Verner, K. S. McKelvey, B. R. Noon,
G. N. Steger, D. R. Call, W. S. LaHaye, B. B. Bing-
ham, and J. S. Senser. 1992. Habitat relations of the
California spotted owl. Pages 7998 in J. Verner, K.
S. McKelvey, B. R. Noon, R. J. Guti
errez, G. I.
Gould Jr., and T. W. Beck, editors. The California
spotted owl: a technical assessment of its current
status. General Technical Report PSWGTR133,
U. S. Forest Service, Albany, California, USA.
Gutsell, S. L., and E. A. Johnson. 2006. Wildre and
tree population processes. Pages 441485 in E. A.
Johnson and K. Miyanishi, editors. Plant disturbance
ecology: the process and response. Elsevier Science
& Technology, Amsterdam, The Netherlands.
Hanson, C. T., M. L. Bond, and D. E. Lee. 2018. Effects
of post-re logging on California spotted owl occu-
pancy. Nature Conservation 24:93105.
Hanson, C. T., D. C. Odion, D. A. DellaSala, and W. L.
Baker. 2009. Overestimation of re risk in the
Northern spotted owl recovery plan. Conservation
Biology 23:13141319.
Hedges, L., and I. Olkin. 1985. Statistical methods for
meta-analysis. Academic Press, New York, New
York, USA.
Hedges, L. V., and J. L. Vevea. 1998. Fixed- and ran-
dom-effects models in meta-analysis. Psychological
Methods 3:486504.
Hessburg, P. F., R. B. Salter, and K. M. James. 2007. Re
examining re severity relations in premanage-
ment era mixed conifer forests: inferences from
landscape patterns of forest structure. Landscape
Ecology 22:524.
Higgins, J. P. T., and S. G. Thompson. 2002. Quantify-
ing heterogeneity in a meta-analysis. Statistics in
Medicine 21:15391558.
Hutto, R. L. 2006. Toward meaningful snagmanage-
ment guidelines for postre salvage logging in
North American conifer forests. Conservation Biol-
ogy 20:984993.
Jenness, J. J., P. Beier, and J. L. Ganey. 2004. Associa-
tions between forest re and Mexican spotted owls.
Forestry Sciences 50:765772.
Johnson, E. A., and K. Miyanishi. 2006. Disturbance
and succession. Pages 114 in E. A. Johnson and K.
Miyanishi, editors. Plant disturbance ecology: the
process and response. Elsevier Science & Technol-
ogy, Amsterdam, The Netherlands.
Jones,G.M.,R.J.Guti
errez,D.J.Tempel,S.A.Whitmore,
W. L. Berigan, and M. Z. Peery. 2016. Megares: an
emerging threat to oldforest species. Frontiers in
Ecology and the Environment 14:300306.
Kalies, E. L., and L. L. Y. Kent. 2016. Tamm review:
Are fuel treatments effective at achieving ecological
and social objectives? A systematic review. Forest
Ecology and Management 375:8495.
Koricheva, J., et al. 2013. Handbook of metaanalysis
in ecology and evolution. Princeton University
Press, Princeton, New Jersey, USA.
Lee, D. E., and M. L. Bond. 2015a. Occupancy of Cali-
fornia spotted owl sites following a large re in the
Sierra Nevada. Condor 117:228236.
www.esajournals.org 20 July 2018 Volume 9(7) Article e02354
SYNTHESIS & INTEGRATION LEE
Lee, D. E., and M. L. Bond. 2015b. Previous yearsrepro-
ductive state affects spotted owl site occupancy and
reproduction responses to natural and anthro-
pogenic disturbances. Condor 117:307319.
Lee, D. E., M. L. Bond, M. I. Borchert, and R. Tanner.
2013. Inuence of re and salvage logging on site
occupancy of spotted owls in the San Bernardino
and San Jacinto mountains of southern California.
Journal of Wildlife Management 77:13271341.
Lee, D. E., M. L. Bond, and R. B. Siegel. 2012. Dynamics
of breedingseason site occupancy of the California
spotted owl in burned forests. Condor 114:792802.
Mallek, C., H. Safford, J. Viers, and J. Miller. 2013.
Modern departures in re severity and area vary
by forest type, Sierra Nevada and southern Cas-
cades, California, USA. Ecosphere 4:128.
Marlon, J. R., et al. 2012. Longterm perspective on
wildres in the western USA. Proceedings of the
National Academy of Sciences USA 109:E535E543.
Miller, J. D., and H. D. Safford. 2012. Trends in wildre
severity: 1984 to 2010 in the Sierra Nevada, Modoc
Plateau, and southern Cascades, California, USA.
Fire Ecology 8:4157.
Miller, J. D., and H. D. Safford. 2017. Corroborating
evidence of a preEuroAmerican lowtomoder-
ateseverity re regime in yellow pinemixed coni-
fer forests of the Sierra Nevada, California, USA.
Fire Ecology 13:5890.
Mori, A. S. 2011. Ecosystem management based on
natural disturbances: hierarchical context and non-
equilibrium paradigm. Journal of Applied Ecology
48:280292.
Nakagawa, S., R. Poulin, K. Mengersen, K. Reinhold,
L. Engqvist, M. Lagisz, and A. M. Senior. 2015.
Meta-analysis of variation: ecological and evolu-
tionary applications and beyond. Methods in Ecol-
ogy and Evolution 6:143152.
Nakagawa, S., and E. S. Santos. 2012. Methodological
issues and advances in biological meta-analysis.
Evolutionary Ecology 26:12531274.
Noon, B. R., and A. B. Franklin. 2002. Scientic
research and the spotted owl (Strix occidentalis):
opportunities for major contributions to avian pop-
ulation ecology. Auk 119:311320.
Odion, D. C., and C. T. Hanson. 2006. Fire severity in
conifer forests of the Sierra Nevada, California.
Ecosystems 9:11771189.
Odion, D. C., C. T. Hanson, D. A. DellaSala, W. L.
Baker, and M. L. Bond. 2014b. Effects of re and
commercial thinning on future habitat of the north-
ern spotted owl. Open Ecology Journal 7. https://
doi.org/10.2174/1874213001407010037
Odion, D. C., et al. 2014a. Examining historical and
current mixed-severity re regimes in ponderosa
pine and mixed-conifer forests of western North
America. PLoS ONE 9:e87852.
Pierce, J. L., G. A. Meyer, and A. T. Jull. 2004. Firein-
duced erosion and millennialscale climate change
in northern ponderosa pine forests. Nature 432:87.
Power, M. J., et al. 2008. Changes in re regimes since
the Last Glacial Maximum: an assessment based
on a global synthesis and analysis of charcoal data.
Climate Dynamics 30:887907.
Pullin, A. S., and T. M. Knight. 2009. Doing more good
than harmBuilding an evidencebase for conser-
vation and environmental management. Biological
Conservation 142:931934.
Pullin, A. S., and G. B. Stewart. 2006. Guidelines for
systematic review in conservation and environmen-
tal management. Conservation Biology 20:16471656.
Roberts, S. L., J. W. Van Wagtendonk, A. K. Miles, and
D. A. Kelt. 2011. Effects of re on spotted owl site
occupancy in a latesuccessional forest. Biological
Conservation 144:610619.
Rockweit, J. T., A. B. Franklin, and P. C. Carlson. 2017.
Differential impacts of wildre on the population
dynamics of an oldforest species. Ecology
98:15741582.
Seamans, M. E., and R. J. Guti
errez. 2007. Habitat
selection in a changing environment: the relation-
ship between habitat alteration and spotted owl
territory occupancy and breeding dispersal. Con-
dor 109:566576.
Seamans, M. E., R. J. Guti
errez, and C. A. May. 2002.
Mexican spotted owl (Strix occidentalis) population
dynamics: inuence of climactic variation on sur-
vival and reproduction. Auk 119:321334.
Steel, Z. L., H. D. Safford, and J. H. Viers. 2015. The re
frequencyseverity relationship and the legacy of
re suppression in California forests. Ecosphere 6:8.
Stephens, S. L., J. D. Miller, B. M. Collins, M. P. North,
J. J. Keane, and S. L. Roberts. 2016. Wildre
impacts on California spotted owl nesting habitat
in the Sierra Nevada. Ecosphere 7:e01478.
Sutherland, W. J., A. S. Pullin, P. M. Dolman, and T. M.
Knight. 2004. The need for evidencebased conser-
vation. Trends in Ecology and Evolution 19:305
308.
Swanson, M. E., J. F. Franklin, R. L. Beschta, C. M.
Crisafulli, D. A. DellaSala, R. L. Hutto, D. B. Lin-
denmayer, and F. J. Swanson. 2011. The forgotten
stage of forest succession: earlysuccessional
ecosystems on forested sites. Frontiers in Ecology
and the Environment 9:117125.
Tempel, D. J., and R. J. Guti
errez. 2013. Relation
between occupancy and abundance for a territorial
species, the California spotted owl. Conservation
Biology 27:10871095.
www.esajournals.org 21 July 2018 Volume 9(7) Article e02354
SYNTHESIS & INTEGRATION LEE
Tempel, D. J., R. J. Guti
errez, S. A. Whitmore, M. J.
Reetz, R. E. Stoelting, W. J. Berigan, M. A. Seamans,
and M. Z. Peery. 2014. Effects of forest manage-
ment on California spotted owls: implications for
reducing wildre risk in reprone forests. Ecolog-
ical Applications 24:20892106.
Tempel, D. J., et al. 2016. Metaanalysis of California
spotted owl (Strix occidentalis occidentalis) territory
occupancy in the Sierra Nevada: habitat associa-
tions and their implications for forest management.
Condor 118:747765.
Thorn, S., et al. 2018. Impacts of salvage logging on
biodiversity: a meta-analysis. Journal of Applied
Ecology 55:279289.
U.S. Fish and Wildlife Service [USFWS]. 2011. Revised
Recovery Plan for the Northern spotted owls (Strix
occidentalis caurina). Page 258. U.S. Fish and Wild-
life Service, Portland, Oregon, USA.
U.S. Fish and Wildlife Service [USFWS]. 2012. Final
Recovery Plan for the Mexican spotted owls (Strix
occidentalis lucida). First Revision. Page 413. U.S.
Fish and Wildlife Service, Albuquerque, New Mex-
ico, USA.
U.S. Fish and Wildlife Service [USFWS]. 2017.
California spotted owl (Strix occidentalis occiden-
talis) Conservation Objectives Report. Page 48.
Fish and Wildlife Service, Sacramento, California,
USA.
U.S.D.A. Forest Service [USDA]. 2012. Environmen-
tal Assessment (Revised) Smokey Project. Page
38. U.S.D.A. Forest Service, Willows, California,
USA.
U.S.D.A. Forest Service [USDA]. 2018. Draft conserva-
tion strategy for the California spotted owl. Version
1.0. Page 89. Pacic Southwest Region, U.S.D.A.
Forest Service. https://www.fs.usda.gov/Internet/
FSE_DOCUMENTS/fseprd571788.pdf
Viechtbauer, W. 2010. Conducting meta-analyses in R
with the metafor package. Journal of Statistical
Software 36:148. http://www.jstatsoft.org/v36/i03/
Whitlock, C., J. Marlon, C. Briles, A. Brunelle, C. Long,
and P. Bartlein. 2008. Longterm relations among
re, fuel, and climate in the northwestern US
based on lakesediment studies. International Jour-
nal of Wildland Fire 17:7283.
Williams, M. A., and W. L. Baker. 2012. Spatially exten-
sive reconstructions show variable-severity re
and heterogeneous structure in historical western
United States dry forests. Global Ecology and Bio-
geography 21:10421052.
Zabel,C.J.,G.N.Steger,K.S.McKelvey,G.P.Eberlein,
B. R. Noon, and J. Verner. 1992. Home-range size
and habitat-use patterns of California spotted owls
in the Sierra Nevada. Pages 149164 in J.Verner,K.S.
McKelvey,B.R.Noon,R.J.Guti
errez, G. I. Gould Jr.,
andT.W.Beck,editors.TheCaliforniaspottedowl:a
technical assessment of its current status. General
Technical Report. U.S. Forest Service, PacicSouth-
west Research Station, Albany, California, USA.
Zachmann, L. J., D. W. Shaw, and B. G. Dickson. 2018.
Prescribed re and natural recovery produce simi-
lar long-term patterns of change in forest structure
in the Lake Tahoe basin, California. Forest Ecology
and Management 409:276287.
SUPPORTING INFORMATION
Additional Supporting Information may be found online at: http://onlinelibrary.wiley.com/doi/10.1002/ecs2.
2354/full
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Lee Supporting Information: Spotted Owls and forest fire pg. 1
Spotted Owls and forest fire: A systematic review and meta-analysis of the evidence
DEREK E. LEE,
1
Wild Nature Institute, 15 North Main Street, Concord, NH 03302, USA
Appendix S1
Figure S1. Funnel plot of all reported effects of mixed-severity fire on Spotted Owl (Strix occidentalis)
parameters illustrating no publication bias or unusual heterogeneity exists.
Descriptions of papers
1. Bond et al. (2002) was an examination of survival, reproduction, and site and mate fidelity of northern
(S. o. caurina), California (S. o. occidentalis), and Mexican Spotted Owls (S. o. lucida) 1 year after fire.
Short-term (1-year) postfire survival of 21 color-banded Spotted Owls was reported from four separate
study areas encompassing all subspecies: in northwestern California, southern California, New Mexico,
and Arizona. All nest and roost areas were burned, and no post-fire logging had occurred before owls
were surveyed the year after fire. Vegetation burn severity maps were available for 8 of the 11 breeding
sites, with each breeding site defined as a circle approximately 150400 ha, depending on study area.
Half of the breeding sites where fire severities were mapped burned at low to moderate severity, and
the other half burned 3688% at high severity. The authors found that 18 of 21 (86%) individual owls
were resighted after fire. These survival rates are higher (+0.03) than the mean from unburned sites.
Sixteen of 18 (89%) surviving owls (of all subspecies) were in the same breeding sites after fire (-0.01),
1
Email: derek@wildnatureinstitute.org
Ecosphere
Lee Supporting Information: Spotted Owls and forest fire pg. 2
and all pairs were faithful to their pre-fire breeding site and mate. Productivity of burned Spotted Owl
sites was higher (+0.26) than mean annual rates of reproduction for long-unburned sites.
2. Jenness et al. (2004) reported pre- and post-fire occupancy of 64 Mexican Spotted Owl sites in four
national forests in New Mexico and Arizona. The authors selected owl breeding sites in fires that burned
from 1993 to 1996 and compared levels of occupancy (single, pair, failed reproduction, and successful
reproduction) in 1997 in 33 burned and 31 unburned sites, including 29 paired burned and long-
unburned sites within 12 km of each other. Post-fire logging was minor in most of the fires. Post-fire
occupancy rates were not significantly different between burned and unburned sites and did not
statistically differ with time since fire. The percent of high-severity fire in a burned site had no significant
influence on whether the site was occupied. The number of successfully reproducing Mexican Spotted
Owl sites did not differ between burned and unburned forests. Non-significant effects included lower
occupancy (-0.14) and lower reproduction (-0.07) in burned sites.
3. Bond et al. (2009) quantified roosting and foraging habitat selection by Spotted Owls in a burned
landscape. The authors banded and radiomarked 7 California Spotted Owls occupying the McNally Fire
in the southern Sierra Nevada, California 4 years after fire. Effects of high-severity fire were not
confounded with post-fire logging because <3% of the foraging ranges of these owls had been post-fire
logged. The probability of an owl using a site for foraging was significantly greater in low- (+0.33),
moderate- (+0.42), and high-severity (+0.42) burned forests than unburned forest. In this study,
California Spotted Owls roosted in all fire intensity classes. Owls selected roost sites burned at low
severity (+0.29) and avoided unburned sites and sites burned at moderate (-0.13) and high severity (-
0.28).
4. Bond et al. (2010) documented 3 of 5 radiomarked California Spotted Owls that occupied the McNally
Fire in the southern Sierra Nevada during the breeding season 4 years post-fire, roosted within the
burned landscape during the following winter.
5. Clark et al. (2011) examined the survival rates of northern Spotted Owls 34 years after fire and
postfire logging in two fire areas in southwestern Oregon. Twelve (12) owls were radiomarked in
unburned forest and 11 owls were radiomarked inside the burn perimeter where much of the forest
(2023%) had been post-fire logged. The authors found no significant effect of fire severity or quantity
of forested habitat on Spotted Owl survival. Six of the owls monitored in unburned forest were known
to have moved outside the fire perimeter after fire and salvage logging, but before survival monitoring
took place. In the original paper, the authors considered the owls that moved similar to the owls inside
the fire perimeter. I combined all outside-the-burn owls to compare with inside-the-burn owls. Non-
significant effects: owls that resided within the post-fire logged landscape had lower survival rates (-
0.07) than those residing in unburned unlogged forest.
6. Roberts et al. (2011) compared effects of wildfire and prescribed burns on occupancy of California
Spotted Owls residing in burned (1 to 15 years since fire) and long-unburned forests in Yosemite
National Park, central Sierra Nevada, California. This study compared occupancy in 16 randomly selected
burned and 16 unburned ‘owl survey areas,’ each 3.75 km2. A total of 19 owl pairs were monitored for a
single year, and vegetation at owl sites was compared with sites that yielded no owl response to build
detectability and occupancy models. The mean ‘owl survey area’ that burned at high severity was 14%,
with the greatest amount of high-severity burn in a survey area being 52%. Because this study was
conducted in a national park, no post-fire or recent pre-fire logging had occurred to confound results.
Lee Supporting Information: Spotted Owls and forest fire pg. 3
The authors found no support for a model of occupancy rates that distinguished between burned and
unburned sites. Non-significant effects: occupancy from model based on canopy cover and basal area
was lower at burned versus unburned sites (-0.26).
7. Lee et al. (2012) published an 11-year longitudinal study of California Spotted Owl occupancy on
national forest lands in the Sierra Nevada, California. The authors used data collected by the U.S. Forest
Service to compile occupancy survey histories at 41 breeding sites within six large mixed-severity fires
that occurred from 2000 to 2007 throughout the Sierra Nevada and at 145 long-unburned control sites.
Fires had no significant effect on occupancy probability. Non-significant effects: occupancy probability
was higher in burned sites (+0.041) relative to unburned. Post-fire logging occurred in an unknown
number of territories.
8. Bond et al. (2013) found Spotted Owls in the McNally Fire area, southern Sierra Nevada, California fed
primarily on pocket gophers (Thomomys spp., 40.3% by biomass) and northern flying squirrels
(Glaucomys sabrinus, 25.9% by biomass), whereas owls fed primarily on flying squirrel and woodrats
(Neotoma spp.) in long-unburned study areas. The mean home-range sizes of the McNally Fire owls
were 12% smaller than those recorded in unburned forests using similar time periods and methodology.
9. Clark et al. (2013) investigated the occupancy dynamics of northern Spotted Owls in burned and
salvage-logged landscapes in three fire areas and an adjacent long-unburned demographic study area in
the southern Oregon Cascade Mountains. The three fires all burned within 1 year of each other.
Modeled occupancy rates of 103 Spotted Owl sites in the long-unburned area were compared with 40
burned sites before and after fire and post-fire logging occurred. Post-fire logging was prevalent, thus it
was not possible to quantify the influence of fire alone on occupancy dynamics and survival. Occupancy
probability declined more steeply after post-fire logging than in the unburned area (-0.39).
10. Lee et al. (2013) used Spotted Owl survey data from 97 long-unburned and 71 burned breeding sites
over 8 years to examine the influence of fire and post-fire logging on local rates of extinction,
colonization, and occupancy probability. Post-fire logging occurred on 21 of the burned sites. None of
the fire and logging coefficients were statistically significant. Non-significant effects: model-averaged
effect sizes suggested that high-severity fire that burned >50% of forest in the 203-ha core area was
correlated with lower occupancy relative to unburned sites. Post-fire logging further increased
extinction probability. The majority (75%) of sites burned below the 50% threshold. Non-significant
effects: burned site occupancy -0.062 lower than unburned sites. Post-fire-logged sites occupancy -0.05
lower than unlogged burned sites.
11. Ganey et al. (2014) reported a sample of 4 radiomarked Mexican Spotted Owls in the Sacramento
Mountains, New Mexico, moved to wintering areas that had burned 46 years earlier and that had 26
times greater abundance and biomass of small mammal prey than nest core areas associated with those
owls.
12. Tempel et al. (2014) used data from a long-term (>20 years) demographic study of California Spotted
Owls in the Eldorado and Tahoe national forests of the central Sierra Nevada, California to examine the
influence of timber harvest and wildfire on reproduction, survival, and occupancy over a 6-year
timescale using data from 74 breeding sites. Twelve (12) breeding sites experienced fire during the
course of the study. Fire did not significantly affect survival, reproduction, or site extinction. The
coefficient for the effect of fire on site colonization was negative, but the standard error of the
Lee Supporting Information: Spotted Owls and forest fire pg. 4
coefficient could not be estimated making this parameter estimate of low quality. The authors reported
lower occupancy (-0.06) when fire frequency was doubled in simulations that assumed zero post-fire
colonization. Post-fire logging occurred on public and private lands in the study territories, but was not
reported.
13. Lee and Bond (2015a) examined California Spotted Owl site occupancy in the 2013 Rim Fire near
Yosemite National Park, which was the largest fire in recent recorded Sierra Nevada history, burning
more than 100,000 ha. The fires burned through 45 known Spotted Owl breeding sites in the Stanislaus
National Forest and all sites were surveyed by U.S. Forest Service personnel the following year. For all
detections, 100% severe fire surrounding nest and roost sites decreased occupancy probability (-0.04),
but did not affect occupancy by pairs of owls. Single-season modeled occupancy rates 1 year after the
Rim Fire were significantly higher (+0.175) than other previously published occupancy rates in long-
unburned forests.
14. Lee and Bond (2015b) examined how the quality of a site influenced California Spotted Owl
occupancy and reproduction after fire in southern California (using the same dataset as Lee et al. 2013).
Site quality was measured by whether the site supported a single owl, pair of owls, or pair of owls with
offspring the previous year. Amount of severe fire in a core use area was not a significant variable
influencing reproduction. The influence of severe fire on occupancy was minor in sites that had been
occupied and reproductive the previous year (high quality), and if a site remained occupied, severe fire
did not affect the probability of reproduction compared with unburned sites. Occupancy of high-quality
sites (previously reproductive) that burned was -0.02 lower than unburned sites. Occupancy of high-
quality sites that were post-fire logged was -0.03 lower. Occupancy of low-quality sites (previously non-
reproductive) was -0.19 lower in burned versus unburned sites, and -0.26 lower after post-fire logging.
15. Bond et al. (2016) analyzed foraging habitat selection by 8 radiomarked California Spotted Owls in
the Slide Fire in the San Bernardino National Forest of southern California 3 and 4 years after fire.
Habitat selection with sensitivity analysis at three spatial extents of available habitat showed owls used
forests burned at all severities in proportion to their availability (no significant effects), with the
exception of significant selection for moderately burned forest (+0.03) farther from core areas.
16. Comfort et al. (2016) examined foraging habitat selection by 23 radiomarked Northern Spotted Owls
in the Timbered Rock Fire in southwest Oregon in relation to edges created by fire and post-fire logging.
Because post-fire logging occurred immediately following fire on extensive private lands in the study
area, and their remote-sensing methodology could not distinguish between fire and post-fire logged
areas, the authors created a combined burned–logged variable called the ‘disturbance severity.’ The
edges between forested habitats and burned–logged areas were defined as ‘hard’ edges. At smaller
spatial scales (3.2 and 51.8 ha surrounding telemetry locations), increases in disturbance severity
decreased the probability of use, but at larger spatial scales (829 ha), the opposite was true. The use of a
location for foraging was maximized when about 20% of a 3.2-ha area surrounding the location was
composed of hard edge. Owls avoided areas with larger amounts of hard edge, but selected smaller
amounts of edge. Larger, more contiguous hard edges were described as intensively managed edges
created by post-fire logging.
17. Jones et al. (2016) reported on breeding site occupancy dynamics from 15 unburned and 30 burned
sites (14 of which burned >50% high severity), and foraging habitat selection for 9 owls, in the Eldorado
National Forest, central Sierra Nevada, California after the King Fire of 2014. Occupancy declined in
Lee Supporting Information: Spotted Owls and forest fire pg. 5
burned sites relative to unburned, and >50% high-severity burn further reduced occupancy. Foraging
habitat selection showed owls significantly avoided high-severity burn and a non-significant preference
for low-severity burn.
I included the results from this paper in my review, however methodological difficulties in this study
make their results unreliable. First, the Eldorado owl population that provided the data for Jones et al.
(2016) has documented long-term trends of decreasing site colonization and increasing site extinction
probabilities, as reported before the King Fire (Tempel and Gutiérrez 2013). However, Jones et al. did
not account for these pre-fire trends in their site occupancy analyses. This omission of temporal trends
means their results for 2015 could be due to the fact that this single year of post-fire data was the last
year in the dataset, and should not be attributed unequivocally to the King Fire. Fig. 3f shows that the
2015 post-fire year of decrease in occupancy was not significantly different from the 10 previous
instances of documented declines that occurred in the absence of fire. Second, Jones et al. (2016) used
compositional analysis of foraging habitat selection, a method that is inappropriate for central place
foragers like Spotted Owls (Rosenberg and McKelvey 1999). Compositional analysis relies upon an
assumption of no spatial correlation among foraging locations (Rosenberg and McKelvey 1999, Manly et
al. 2002). Central place foraging behaviour results in a clustered distribution of foraging points near the
center of a territory which violates the assumption of no spatial correlation among foraging locations, a
pattern that was apparent for most of the Spotted Owls in Web Figure 3 of Jones et al. (2016). The
appropriate habitat selection analysis is a ‘resource selection function’, a mathematical function that
accounts for the fact that Spotted Owls, as central place foragers, will return to their nest or roost trees
many times during the night, so their probability of using habitats near the nest or roost core is much
higher than the probability of using habitats farther away (Bond et al. 2009, Bond et al. 2016, Eyes et al.
2017). Third, Jones et al. (2016) reported extinction for a territory in WebFigure 4 when the owls shifted
their location by a distance that was less than the diameter of a territory as defined by the authors, and
less than mean foraging distance reported by the authors. This decision inflated their ‘burned site’
extinction probability by classifying a normal within-territory movement as site extinction. These
methodological difficulties in their data analyses limit the utility of Jones et al. (2016) for guiding forest
management, particularly when weighing the risks from management actions relative to risks from fire.
18. Tempel et al. (2016) examined occupancy dynamics in 43 burned breeding sites and 232 unburned
sites in four study areas across the Sierra Nevada using 19 years of data. The authors found no
significant effects of fire on occupancy, but their top ranked model for one study area (Sequoia Kings
Canyon) included a covariate for proportion of the core area where canopy cover was reduced by >10%
by wildfire. This covariate was negatively correlated with territory extinction probability, meaning more
area burned reduced the site extinction probability, thereby increasing occupancy probability (+0.01).
19. Eyes et al. (2017) radiotracked 13 California Spotted Owls over 3 years and collected data on
foraging habitat selection in Yosemite National Park, Sierra Nevada, California. The authors analyzed
foraging by a sample of owls nesting in and near forest burned 114 years previously from a mix of
wildfires and prescribed burns. Eyes et al. (2017) found no significant effect of burn severity on foraging
habitat selection, but non-significant effects were reported that showed a decrease in probability of use
for the most severely burned locations (-0.06), and moderately burned locations (-0.03), relative to
unburned locations.
Lee Supporting Information: Spotted Owls and forest fire pg. 6
20. Rockweit et al. (2017) examined survival and recruitment rates of northern Spotted Owls in 70
unburned sites and 28 sites burned in four fires. The authors reported wildfires with different mixtures
of burn severity resulted in different effects on survival and recruitment. Ten owl territory cores that
were burned at mostly low severity (1987 and 1999 fires) were associated with no significant effects on
survival or recruitment. When 14 territory cores burned with moderate amounts of high- and low-
severity fire (2008 fire), the result was a significant reduction in survival (-0.17) and a significant increase
in recruitment (+0.22). When 4 territory cores burned at predominantly high severity (2004 fire), there
was a significant reduction in survival (-0.30). The burned territories were partially post-fire logged,
although that was not reported by the authors (C. Hanson, pers. comm.).
21. Hanson et al. (2018) examined naïve site occupancy of California Spotted Owls in 54 sites that
burned in one of 8 large fires between 2002 and 2015. All sites were occupied in the year immediately
prior to the site burning, and comparisons were before-after fire and logging. Sites were classified into 4
groups based on amount of high-severity burn (20-49% or 50-80%) and amount of post-fire logging (<5%
and ≥5%) in a 1500m-radius circle around the nesting roosting core area. Hanson et al. (2018) found no
significant effect of fire severity on occupancy, but significant effects of post-fire logging. Mean amount
of core areas burned at high severity was 63%. Results were: 80% occupancy in sites with 2049% high-
severity fire and <5% post-fire logging, 33% occupancy in sites with 2049% high-severity fire and ≥5%
post-fire logging; and 77% occupancy in sites with 5080% high-severity fire and <5% post-fire logging,
20% occupancy in sites with 5080% high-severity fire and ≥5% post-fire logging. Amongst the sites with
≥5% post-fire logging, the mean amount of such logging of the area within a 1500 m radius of site
centers was 16.7% (SD = 8.7%).
LITERATURE CITED
Bond, M. L., R. J. Gutierrez, A. B. Franklin, W. S. LaHaye, C. A. May, and M. E. Seamans. 2002. Shortterm
effects of wildfires on Spotted Owl survival, site fidelity, mate fidelity, and reproductive success.
Wildlife Society Bulletin 30:10221028.
Bond, M. L., D. E. Lee, and R. B. Siegel. 2010. Winter movements by California Spotted Owls in a burned
landscape. Western Birds 41:174180.
Bond, M. L., D. E. Lee, R. B. Siegel, and J. P. Ward. 2009. Habitat use and selection by California Spotted
Owls in a postfire landscape. The Journal of Wildlife Management 73:11161124.
Bond, M. L., C. Bradley, and D. E. Lee. 2016. Foraging habitat selection by California Spotted Owls after
forest fire in southern California. Journal of Wildlife Management
http://dx.doi.org/10.1002/jwmg.21112.
Bond, M. L., D. E. Lee, R. B. Siegel, and M. W. Tingley. 2013. Diet and homerange size of California
Spotted Owls in a burned forest. Western Birds 44:114126.
Clark, D. A., R. G. Anthony, and L. S. Andrews. 2011. Survival rates of northern Spotted Owls in postfire
landscapes of southwest Oregon. Journal of Raptor Research 45:3847.
Clark, D. A., R. G. Anthony, and L. S. Andrews. 2013. Relationship between wildfire, salvage logging, and
occupanc of nesting territories by northern Spotted Owls. Journal of Wildlife Management
77:672688.
Lee Supporting Information: Spotted Owls and forest fire pg. 7
Comfort, E. J., D. A. Clark, R. G. Anthony, J. Bailey, and M. G. Betts 2016. Quantifying edges as gradients
at multiple scales improves habitat selection models for northern Spotted Owl. Landscape
Ecology http://dx.doi.org/10.1007/s1098001503301.
Eyes, S. A., S. L. Roberts, and M. D. Johnson. 2017. California Spotted Owl (Strix occidentalis occidentalis)
habitat use patterns in a burned landscape. The Condor 119:375388.
Ganey, J. L., S. C. Kyle, T. A. Rawlinson, D. L. Apprill, and J. P. Ward Jr. 2014. Relative abundance of small
mammals in nest core areas and burned wintering areas of Mexican Spotted Owls in the
Sacramento Mountains, New Mexico. Wilson Journal of Ornithology 126:4752.
Hanson, C. T., M. L. Bond, and D. E. Lee. 2018. Effects of post-fire logging on California Spotted Owl
occupancy. Nature Conservation 24:93105. doi: 10.3897/natureconservation.24.20538.
Jenness, J. J., P. Beier, and J. L. Ganey. 2004. Associations between forest fire and Mexican Spotted Owls.
Forestry Sciences 50:765772.
Jones, G. M., R. J. Gutiérrez, D. J. Tempel, S. A. Whitmore, W. L. Berigan, and M. Z. Peery. 2016.
Megafires: an emerging threat to oldforest species. Frontiers in Ecology and the Environment
14:300306.
Lee, D. E., and M. L. Bond. 2015a. Occupancy of California Spotted Owl sites following a large fire in the
Sierra Nevada. Condor 117:228236.
Lee, D. E., and M. L. Bond. 2015b. Previous year’s reproductive state affects Spotted Owl site occupancy
and reproduction responses to natural and anthropogenic disturbances. Condor 117:307319.
Lee, D. E., M. L. Bond, and R. B. Siegel. 2012. Dynamics of breedingseason site occupancy of the
California Spotted Owl in burned forests. Condor 114:792802.
Lee, D. E., M. L. Bond, M. I. Borchert, and R. Tanner. 2013. Influence of fire and salvage logging on site
occupancy of Spotted Owls in the San Bernardino and San Jacinto mountains of southern
California. The Journal of Wildlife Management 77:13271341.
Manly, B. F. J., L. L. McDonald, D. L. Thomas, T. L. McDonald, and W. P. Erickson. 2002. Resource
selection by animals: statistical design and analysis for field studies. Second edition. Kluwer
Academic, Dordrecht, The Netherlands.
Roberts, S. L., J. W. Van Wagtendonk, A. K. Miles, and D. A. Kelt. 2011. Effects of fire on Spotted Owl
site occupancy in a latesuccessional forest. Biological Conservation 144:610619.
Rosenberg, D. K., and K. S. McKelvey. 1999. Estimation of habitat selection for centralplace foraging
animals. Journal ofWildlife Management 63:10281038.
Rockweit, J. T., A. B. Franklin, and P. C. Carlson. 2017. Differential impacts of wildfire on the population
dynamics of an oldforest species. Ecology doi:10.1002/ecy.1805.
Tempel, D. J., R. J. Gutiérrez, S. A. Whitmore, M. J. Reetz, R. E. Stoelting, W. J. Berigan, M. A. Seamans,
and M. Z. Peery. 2014. Effects of forest management on California Spotted Owls: implications for
reducing wildfire risk in fireprone forests. Ecological Applications 24:20892106.
Lee Supporting Information: Spotted Owls and forest fire pg. 8
Tempel, D. J., J. J. Keane, R. J. Gutiérrez, J. D. Wolfe, G. M. Jones, A. Koltunov, C. M. Ramirez, W. J.
Berijan, C. V. Gallagher, T. E. Munton, P. A. Shaklee, S. A. Whitmore, and M. Z. Peery. 2016.
Metaanalysis of California Spotted Owl (Strix occidentalis occidentalis) territory occupancy in
the Sierra Nevada: Habitat associations and their implications for forest management. The
Condor 118:747765.
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No species has touched off more controversy in the Pacific Northwest than the Northern Spotted Owl. The owl was federally listed under the US Endangered Species Act in 1990 due to widespread destruction of its old-growth forest habitat and inadequate species and habitat protections. A series of legal decisions shut down logging across millions of hectares of forests until the landmark Northwest Forest Plan (NWFP) was adopted by President Bill Clinton in 1994. The NWFP served as a de facto owl recovery plan that also protected habitat for hundreds of other old-growth associated species until 2005 when a lawsuit by Seattle Audubon Society forced the George W. Bush administration to develop a species-specific owl recovery plan. That recovery plan was drafted by a “multistakeholder” group stacked with industry and government representatives. At the time, a series of lawsuits between the timber industry (sue) and the Bush administration (settle) was designed to get the cut out. Consequently, the 2008 Bush administration recovery plan was designed to weaken forest protections in the NWFP. Independent peer review and the investigative branch of government declared the recovery plan scientifically flawed and politically motivated. Citing this information, President Barack Obama overturned the Bush administration’s recovery plan in 2009, initiating a revised plan developed by the US Fish & Wildlife Service. While there were improvements to this plan, it contained controversial assumptions about logging in owl territories to reduce fire intensity. I document an abuse of scientific integrity spanning presidential administrations and agency decisions as the owl remains perilously close to extirpation. This is a case study in why scientists need to be persistent when speaking truth to power.
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In fire-adapted forest ecosystems around the world, there has been growing concern about adverse impacts of post-fire logging on native biodiversity and ecological processes. This is also true in conifer forests of California, U.S.A. which are home to a rare and declining owl subspecies, the California spotted owl (Strix occidentalis occidentalis). While there has been recent concern about the California spotted owl occupancy in large fire areas where some territories have substantial high-severity fire effects, the influence of post-fire logging on the California spotted owl occupancy has been investigated very little, leading to some uncertainty about interpretation of conflicting results in different large fires. Research has found these owls preferentially select high-severity fire areas, characterised by high levels of snags and native shrubs, for foraging in forests that were not logged after fire, suggesting that removal of this foraging habitat might impact occupancy. The authors assessed the effect of post-fire logging and high-severity fire, on occupancy of this subspecies in eight large fire areas, within spotted owl sites with two different levels of high-severity fire effects. They found a significant adverse effect of such logging and no effect of high-severity fire alone. These results indicate it is post-fire logging, not large fires themselves, that poses a conservation threat to this imperilled species.
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Ecological disturbances shape and maintain natural communities, but climate change and human land use can alter disturbance regimes and affect population persistence and vital rates in unpredictable ways. Species inhabiting landscapes shaped by wildfire have evolved mechanisms allowing them to persist under this dynamic disturbance type, which creates habitats of varying quality for these species. We utilized data from a 26-year demographic study of northern spotted owls to analyze the influence of wildfire on apparent survival and recruitment rates. Wildfires occurred across different years and affected different spotted owl territories, which allowed us to implement a retrospective Before-After-Control-Impact (BACI) analysis and model the potential effect of wildfire extent and severity. Our results indicated that mixed-severity fires that burned at predominantly low-severity had little effect on survival and recruitment while fires characterized by more medium to high burn severities negatively affected spotted owl survival, with varying effects on recruitment. Reduced survival and increased recruitment rates on some territories affected by medium to high severity fires suggested that post-fire habitat quality was reduced resulting in territories that were marginally capable of supporting owls. We hypothesize these territories may have represented “sinks” that were supported by nearby “source” territories in a spatially heterogeneous landscape created by the mixed-severity fire regime of the region. This article is protected by copyright. All rights reserved.
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California spotted owls (CSOs) (Strix occidentalis occidentalis) have received significant conservation attention beginning with the U.S. Forest Service interim management guidelines in 1992. The most commonly reported forest habitat feature for successful nesting habitat of CSO is canopy cover > 70%. Loss and degradation of Sierra Nevada CSO habitat, however, has been a growing concern, initially from commercial tree harvesting and, more recently, from wildfire. This study examined trends in wildfire impacts on potential nesting habitat of the CSO and discusses different management approaches that might lead to the conservation of CSO in fire-dependent forests. A total of 85,046 ha of CSO potential nesting habitat was burned by fire that resulted in ≥ 50% tree basal area (BA) mortality, reducing canopy cover on average to < 25%, during 2000–2014; this included 2.7%, 12.3%, and 7.6% of dense red fir (Abies magnifica), eastside pine, and westside forests, respectively. Based on regression predictions, within the next 75 yr, the cumulative amount of nesting habitat burned at ≥ 50% tree basal area mortality will exceed the total existing habitat. Four management strategies are discussed that could enhance the conservation of the CSO: (1) increased fire suppression, (2) strategically reducing fire hazards using mechanical treatments and/or prescribed fire, (3) increasing the amount of managed wildfire in CSO habitat, and (4) developing a landscape strategy that uses historical forest structure information to identify areas where high-canopy cover forests are more sustainable. Our estimates of how moderate- and high-severity fire may affect forests into the future poise a substantial threat to CSO persistence. More comprehensive forest restoration activities may be needed in CSO habitat to avoid significant losses of older forests.
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We assessed the occupancy dynamics of 275 California Spotted Owl (Strix occidentalis occidentalis) territories in 4 study areas in the Sierra Nevada, California, USA, from 1993 to 2011. We used Landsat data to develop maps of canopy cover for each study area, which we then used to quantify annual territory-specific habitat covariates. We modeled the relationships between territory extinction and colonization using predictor variables of habitat, disturbance (logging, fire), climate, and elevation. We found that forests with medium (40–69%) and high (≥70%) canopy cover were the most important predictors of territory occupancy in all study areas, and that both canopy cover categories were positively correlated with occupancy. We used analysis of deviance to estimate the amount of variation explained by the habitat covariates (primarily medium and high canopy cover) and found that these covariates explained from 35% to 67% of the variation in occupancy. Climatic covariates were not correlated with occupancy dynamics and explained little of the variation in occupancy. We also conducted a post hoc analysis in which we partitioned canopy cover into 10% classes, because our original partitioning into 3 classes may have lacked sufficient resolution to identify canopy cover levels where occupancy changed abruptly. In this post hoc analysis, occupancy declined sharply when territories contained more area with ,40% canopy cover, and the amount of 50–59% and 60–69% canopy cover had a more positive association with occupancy than did 40–49% canopy cover. Our results suggest that some fuels treatments intended to reduce fire risk and improve forest resilience could be located within Spotted Owl territories without adversely impacting territory occupancy if such treatments do not consistently reduce canopy cover below 50%. We suggest that future work quantify components of forest structure (e.g., large tree density, vertical complexity) known to be selected by owls and relate these characteristics to occupancy and fitness metrics.
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In the context of concerns about degrading forest health, increasing fire activity, and practical restoration alternatives, we analyzed 20 years of data on the response of mixed conifer forest stands in the Sierra Nevada, California to two distinctly different management approaches. Specifically, we used a Bayesian hierarchical modeling approach to evaluate the direction and magnitude of changes in forest structure and fuel variables in areas treated with prescribed fire as well as untreated forest stands in the Lake Tahoe basin. Counter to many regional studies, our results indicated that treated and long-unaltered, untreated areas may be moving in a similar direction. Treated and untreated areas experienced declines in tree density, increases in the size of the average individual, and losses of surface fuels in most size classes. The number of large trees increased in untreated areas, but decreased in treated areas. Our results suggested that untreated areas may be naturally recovering from the large disturbances associated with resource extraction and development in the late 1800s, and that natural recovery processes, including self thinning, are taking hold. Given the high cost and broad extent of treatment required to restore forest health, management approaches that promote naturally recovering landscapes may complement ongoing and planned fuel reduction treatments. Deliberately managing for natural processes to proceed unimpeded may also be important for maintaining or increasing forest heterogeneity, resilience, and biodiversity.
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Fire is a dynamic ecosystem process of mixed-conifer forests of the Sierra Nevada, but there is limited scientific information addressing wildlife habitat use in burned landscapes. Recent studies have presented contradictory information regarding the effects of stand-replacing wildfires on Spotted Owls (Strix occidentalis) and their habitat. While fire promotes heterogeneous forest landscapes shown to be favored by owls, high severity fire may create large canopy gaps that can fragment the closed-canopy habitat preferred by Spotted Owls. We used radio-telemetry to determine whether foraging California Spotted Owls (S. o. occidentalis) in Yosemite National Park, California, USA, showed selection for particular fire severity patch types within their home ranges. Our results suggested that Spotted Owls exhibited strong habitat selection within their home ranges for locations near the roost and edge habitats, and weak selection for lower fire severity patch types. Although owls selected high contrast edges with greater relative probabilities than low contrast edges, we did not detect a statistical difference between these probabilities. Protecting forests from stand-replacing fires via mechanical thinning or prescribed fire is a priority for management agencies, and our results suggest that fires of low to moderate severity can create habitat conditions within California Spotted Owls' home ranges that are favored for foraging.
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Fire was the dominant ecological process controlling forest structure and succession in western North American conifer forests for thousands of years. Because fires are now suppressed, and because widespread logging has greatly altered vegetation structure, land managers often use estimates of pre-Euro-American settlement forest conditions to help guide restoration actions. It follows that it is important to fully understand the characteristics of pre-Euro-American settlement fire regimes. Percentages of high-severity fire, fire rotation period, and proportions of early, mid, and late developmental forests are intricately and inextricably linked. Early twentieth century vegetation maps that appear to reflect aspects of pre-settlement forest conditions demonstrate that large patches of montane chaparral, which is often an early seral community in yellow pine-mixed conifer forests, were mostly restricted to steep south-facing canyon slopes at higher elevations associated with fir or subalpine forests. When resampled to a 16 ha minimum mapping unit, we found that an early twentieth century vegetation map shows montane chaparral occupied only about five percent of the landscape outside of areas that were highly impacted by gold rush era mining. We found that successional modeling suggests that similar levels (7%) of high severity per fire in pre-settlement yellow pine-mixed conifer forests in the Sierra Nevada would permit about half of the forested area to reach late development state, consistent with other estimated amounts of pre-settlement old-growth forests. In contrast, we found that high levels (30%) of high severity per fire—the current average—would result in only about 13% of forests in a late development state. We do not see evidence that large proportions of high-severity fire were typical during pre-settlement fires in yellow pinemixed conifer forests in our study area.