Response of Federally Threatened Scutellaria montana (Large-flowered Skullcap) to Pre-transplantation Burning
and Canopy Thinning
H. Mae Kile, Joey Shaw, and Jennifer Nagel Boyd
Southeastern Naturalist, Volume 12, Issue 1 (2013): 99–120
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2013 SOUTHEASTERN NATURALIST 12(1):99–120
Response of Federally Threatened Scutellaria montana
(Large-flowered Skullcap) to Pre-transplantation Burning
and Canopy Thinning
H. Mae Kile1, Joey Shaw1, and Jennifer Nagel Boyd1,*
Abstract - Federally threatened Scutellaria montana (Large-flowered Skullcap) is a perennial
herbaceous species endemic to southeastern Tennessee and northwestern Georgia.
A large population of S. montana is located at the 648-ha Tennessee Army National Guard
Volunteer Training Site (VTS) in Catoosa County, GA. Due to necessary operational
activities that include vegetation clearing along site boundaries to maintain security and
prescribed burning and overstory clearing to reduce fuel loads as a wildfire-prevention
measure, S. montana individuals and groups at the VTS may be disturbed unavoidably
at times. Our objectives were to provide recommendations for land managers at the VTS
and elsewhere regarding the response of S. montana to transplantation when plant rescue
is necessary and to guide site selection for transplantation by elucidating the effects of
pre-transplantation burning and canopy thinning on transplant survival and subsequent
success. We relocated 100 S. montana individuals in spring 2010 from a site scheduled
for clearing to plots that were burned (B), thinned (T), treated with a combination of
burning and thinning (B+T), or not treated (C; control). Survival, growth, reproductive
potential, development, and physiological measurements were used throughout the 2010
and 2011 growing seasons to evaluate the success of transplantation overall and in various
relocation plots. At one year post-transplantation, 91% of the original transplants had survived
relocation, and among all transplants, mean stem height and the numbers of stems,
leaves, and flowers per individual significantly increased. Additionally, the percentage of
total transplants that were juveniles was much lower one year post-transplantation than
immediately following transplantation (5.7% vs. 27%), while the proportion that were
reproductive adults was greater one year post-transplantation (37.5% vs. 22%). However,
reduced survival was found in the canopy-thinned plots (84% in both plot T and plot
B+T) compared to plot B (100%) and plot C (96%) one year post-transplantation. The
main effects of both burning and thinning included significant increases in stem damage
and in the proportion of transplants that were vegetative adults, with an associated
decrease in the proportion of reproductive adults. Combined, these findings may have
resulted from increased trampling and feeding activity of vertebrate herbivores in burned
and thinned plots. Overall, we considered our transplantation efforts to be successful
due to high survivability and continued growth and development of individuals one year
post-transplantation. However, to maximize the success of S. montana relocation, we
suggest that transplants be relocated into unburned, unthinned forests and that vertebrate
herbivory be subsequently controlled though the use of exclosur es.
Transplanting plants from one location to another is a process that can be used
to relocate plants from areas with planned habitat modification or destruction
1The University of Tennessee at Chattanooga, Department of Biological and Environmental
Sciences, Chattanooga, TN 37403. *Corresponding author - jennifer-boyd@
100 Southeastern Naturalist Vol. 12, No. 1
(Fahselt 2007). However, numerous issues that could impede successful transplantation
have been well documented and include proper transplantation site
selection, poorly understood life histories, disturbance and stress to plants, stochastic
loss of genetic diversity leading to inbreeding depression or hybridization
at the transplantation site leading to outbreeding depression, high economic costs,
poor survivability, and few long-term monitoring protocols (Allen 1994, Fahselt
2007, Montalvo and Ellstrand 2000, Walters et al. 1994). Some of these impacts
can be minimized through methodology; however, poor conceptual planning for
success goals and long-term monitoring—all identified as causes of transplantation
failure—have led to some discouragement of this practice (Berg 1996).
Given the potential negative outcomes of transplantation efforts, reservations
concerning transplantation as a form of conservation mitigation have been voiced
(Allen 1994, Fahselt 2007, Falk et al. 1996, Primack 2006, Wendelberger et al.
2008). Transplantation of plant species of special concern is especially troubling
to critics, since the persistence of such species is often dependent on undisturbed,
intact habitat (Fahselt 2007, Falk and Olwell 1992). In general, habitat preservation
is essential to conservation efforts, because habitat destruction due to human
activities is considered the primary threat to biological diversity (Primack 2006).
Since habitat destruction has not yet been abated as a practice, and when the alternative
is plant loss in a condemned area, transplantation is an option for the rescue
of at-risk plants (Fahselt 2007, Falk and Olwell 1992, Wendelberger et al. 2008).
For mitigation to be successful, projects must move beyond the traditional view
of success, in which transplants are expected to survive for only a few years, into
an ecological view of success where transplants become a viable, self-maintaining
population reflecting natural communities (Fahselt 2007, Jusaitis 2005, Pavlik et
al. 1993, Primack 1996). The latter perspective requires long-term monitoring of
survival, reproduction, seedling establishment to recruitment, and population viability
estimations in comparison to natural reference populations (Menges 2008,
Primack 1996). Since transplantation mitigation can be costly and characterized by
low success, small-scale transplantation experiments can guide the feasibility of
such action and help avoid some of its common pitfalls (Jusaitis 2005).
This transplantation study was prompted by unavoidable vegetation clearing
at the Tennessee Army National Guard (TNARNG) Volunteer Training Site
(VTS), in Catoosa County, GA, that would drastically disturb the existing habitat
of Scutellaria montana Chapm. (Large-flowered Skullcap). Scutellaria montana
is an herbaceous perennial species found in scattered populations in the Ridge
and Valley physiographic province and the eastern escarpment of the Cumberland
Plateau, including known populations in nine counties in northwestern Georgia
and four in southeastern Tennessee (USFWS 2012). This rare species was listed
in 1986 as federally endangered under the United States Endangered Species Act,
but it was reclassified as federally threatened in 2002. Currently, S. montana also
is considered endangered at the state level by both Georgia (GDNR 2008) and
Tennessee (TDEC 2008). As suggested by its protection statuses, S. montana is
usually found in low density, rarely exceeding more than a few plants per square
2013 H.M. Kile, J. Shaw, and J. Nagel Boyd 101
meter (Cruzan 2001). Forests in which S. montana occurs typically feature a
relatively open, mid-to-late successional, and predominately oak-hickory or
mixed-oak canopy with possible occurrences of native Pinus spp. (pine) and
Vaccinium spp. (blueberry) (Cruzan 2001, Mulhouse et al. 2008, USFWS 2002).
Associated soils are generally shallow, loose, rocky, well-drained, and slightly
acidic (USFWS 2002; H.M. Kile, J. Shaw, and J. Nagel Boyd, pers. observ.).
At the time of its federal reclassification, 48 populations of S. montana had
been documented with a viable population defined as having over 100 individuals
and separated by a distance of 0.8 km from another occurrence (USFWS 2002).
The VTS has a large population of this species, and although S. montana individuals
at the VTS are protected, at times plants may be disturbed unavoidably
by necessary activities associated with the training and security directives of
military operations. Such activities include complete clearing of vegetation taller
than grasses and herbs along site boundaries in accordance with site security
procedures and prescribed burning to reduce fuel loads to prevent and control
wildfires that could be produced by training at an on-site tank-firing range and
small-arms weaponry practice.
Prescribed burning treatments in forested communities often increase light, soil
moisture, and short-term nutrient availability to perennial herbaceous understory
species (Huang et al. 2007). Consequently, to persist and perform successfully in
burned conditions, these species must be able to respond positively to increased
resource availability resulting from fire. A recent study conducted in a mixed-oak
forest in the central Appalachian Mountains reported that understory perennial
species in that community generally responded positively to prescribed burning
with enhanced photosynthetic performance and productivity (Huang et al. 2007);
however, the magnitude, timing, and frequency of fire regimes can be important
factors to consider in elucidating the impacts of fire on plant species responses.
For example, frequent low-severity fires during a dormant season may only minimally
impact the understory light environment (Hutchinson et al. 2005), while
severe and/or infrequent fire during a growing season could produce more dramatic
changes in resource availability. Canopy thinning, which also increases light
availability to the deciduous forest understory, has been associated with altered
understory vegetation cover (Thomas et al. 1999). However, the magnitude and
degree of such responses can be influenced by thinning intensity, vegetation life
form, and compounding environmental conditions (Thomas et al. 1999).
Reports of the observed responses of S. montana to burning, clearing, and
associated alternations in resource availability have been limited and somewhat
contradictory. Previous observation has suggested that S. montana survives prescribed
burning and logging activities, but it has been speculated that recruitment
after such disturbances is low (USFWS 2002). It also has been suggested that
canopy disturbances resulting in greater light availability are beneficial to this
species (Nix et al. 1993, USFWS 2002), but soil disturbances could negatively
impact S. montana due to competition pressures (Nix et al. 1993). Furthermore,
Fail and Sommers (1993) suggested that fire suppression activities may be a fac102
Southeastern Naturalist Vol. 12, No. 1
tor influencing the rarity of S. montana, yet as late as 2005, the United States
Forest Service classified S. montana as adversely affected by fire (Owen and
Brown 2005). Mulhouse et al. (2008) reasoned that since S. montana habitat often
had a strong understory grass component, its habitat would tend to also have
relatively high light availability. However, an evaluation of canopy openness at
the location of S. montana individuals sampled in the Tennessee River Gorge
with hemispherical photography found no correlation between percent canopy
openness and growth or reproductive variables including leaf number and flower
number in this species (see Hopkins 1999).
To understand how operational disturbances at the VTS could influence
S. montana there, we designed a field investigation to study the effects of burning
and thinning treatments on S. montana transplants removed from site boundaries
prior to their clearing. Our objectives were to provide recommendations for
land managers at the VTS and elsewhere regarding the response of this species
to transplantation and anthropogenic disturbances and to guide site selection for
future transplantation when plant rescue is necessary. The individuals that were
transplanted were largely adult-stage plants, which have been proposed to have
higher initial survivability than seeds or seedlings (Drayton and Primack 2000,
Wendelberger et al. 2008). We assessed the post-transplantation survival, growth,
reproductive potential, and development, which are all early fitness indicators
and are thought to be site dependent and influenced by ecological pressures
(Jusaitis 2005, Menges 2008, van Andel 1998). Additionally, because photosynthetic
activity in response to resource availability has been shown to positively
affect plant productivity (Bazzaz 1990, Ceulemans and Mousseau 1994, Eamus
and Jarvis 1989, Kimball 1983, Lawlor and Keys 1993, Mooney et al. 1991), we
also investigated leaf-level gas exchange and related factors of S. montana individuals
The VTS is a 648-ha military training facility (≈34°93′N, 85°06′W) located
in Catoosa County, GA (Fig. 1). In nearby Chattanooga, TN, July is the warmest
month with an average high temperature of 32.2 ºC and an average low of
20.9 ºC; January is the coolest month with an average daily high temperature
of 10.2 ºC and an average low of -0.6 ºC (NWS 2012). Mean annual precipitation
in Chattanooga is 133.4 cm; February is the wettest month with 12.7 cm
of precipitation, while October is the driest month with 8.3 cm of precipitation
(NWS 2012). Mean elevation of the VTS is 250 m. Approximately 80% of the
site is covered by mixed-oak forest, and several streams and gravel roads cross
Military installations with significant natural resources are required to draft
plans for managing these resources, which should include endangered-species
management guidelines, in conjunction with the USFWS and state wildlife agencies
(Army 2007). The purposes of such plans are to promote sustainable use of
2013 H.M. Kile, J. Shaw, and J. Nagel Boyd 103
military lands while maintaining operational missions. The VTS was first surveyed
for S. montana in 2002 at the recommendation of the USFWS, which resulted in
the documentation of more than 1500 individual plants distributed in 60 clusters
(SAIC 2002). These clusters were subsequently grouped into 26 management
Figure 1. Location of the study site. Portions of Tennessee, Alabama, and Georgia are
shown with counties outlined in light gray. The inset is of Catoosa County with the
Tennessee Army National Guard Volunteer Training Site shown in dark gray. Scutellaria
montana also is known to occur in the dark gray counties surrounding Catoosa
104 Southeastern Naturalist Vol. 12, No. 1
groups based on their proximity (SAIC 2002). To monitor population trends and
to determine the impacts of operational activities on S. montana, forty-six 10-mradius
permanent plots were established within the VTS in 2004 (SAIC 2006).
As of the last formal survey of these monitoring plots in spring 2010, the number
of S. montana individuals in plots (n = 1346 plants) was greater than the average
number of individuals observed in plots during growing seasons since plot establishment
(mean = 1156 plants; Boyd et al. 2010).
A security directive at the VTS requires vegetation clearing of a ≈7.6-m (25-
ft) buffer inside the fenced property line, which would result in a drastic habitat
change from forest to an open area without a canopy. During spring 2009, S. montana
individuals along site boundaries in four locations were determined to be
affected by vegetation clearing scheduled for 2010 because they occurred within
the interior buffer of the training site. To mitigate potentially negative impacts
of this disturbance, the TNARNG was required to replace three times the number
of affected plants with S. montana grown from local seeds (L. Lecher, State
of Tennessee Military Department, pers. comm.). Additionally, we were given
permission to relocate S. montana individuals occurring along areas of the VTS
boundary scheduled for vegetation clearing to a non-plot area of the VTS. We
decided to utilize these individuals toward quantifying the effects of prescribed
burning and canopy clearing prior to transplantation on initial transplantation
success and subsequent performance in this species.
In January 2010, we selected a site for the relocation of S. montana individuals
scheduled to be impacted by 2010 boundary-line vegetation clearing.
The relocation site is located within one of the existing management groups
of known S. montana habitat at the VTS and had no plans for development in
the foreseeable future. Within the relocation site, four 35-m2 plots were established
on a gentle slope of an east-facing aspect approximately 25 m below a
gravel road and several meters upland from an ephemeral stream. A low-grade
prescribed burning treatment was applied to two of the plots by VTS personnel
in March 2010, and only the leaf litter was consumed with this treatment. In
one of the burned and one of the unburned plots, woody stems less than 15-cm
diameter at breast height were manually cleared, and larger woody stems were
girdled. The burned area was spaced approximately 100 m from the unburned
area, and the plots within each area were approximately 5 m apart. The resultant
pre-relocation plot treatments consisted of control (C), burned only (B), canopy-
thinned only (T), and combined burned and canopy-thinned (B+T) plots.
During the 2009 growing season, we located and flagged 100 S. montana
individuals occurring within three clusters on the western boundary and one
2013 H.M. Kile, J. Shaw, and J. Nagel Boyd 105
cluster on the eastern boundary of the VTS and assigned each of these
individuals randomly to a specific location within one of four pre-treated relocation
plots. Therefore, plots had 25 transplants each. Because S. montana can
be cespitose, all stems within 10 cm of each other were considered to be parts
of an individual plant. Approximately one week prior to transplantation in
spring 2010, holes were pre-dug in the relocation plots spaced 1 m apart along
north–south transects. Transplantation occurred during three days in late April
and early May 2010.
Given the shallow soils characteristic of the site and to minimize root disturbance,
an approximately 30-cm-diameter, 15-cm-deep cylinder of intact
soil was carefully dug around each S. montana individual. Each plant (and
its surrounding soil) was transferred quickly into a large nursery container
for transport by vehicle to the relocation site during the same day. All individuals
were placed in their pre-assigned specific location in the relocation
plots and immediately covered with soil and any available leaf litter. Because
transplantation disturbs the soil and root contact, water stress can result in dry
soils before sufficient establishment takes place (Jusaitis 2005, Taiz and Zeiger
2006). To prevent this, all transplants were watered daily through the first
week after transplantation and then on a weekly basis, if there was no rain, up
until the end of July 2010.
Post-transplantation site analyses
To determine the influence of prescribed burning on soil resource availability,
we collected soil samples in July 2010 at a depth of approximately 10 cm from
the plot centers. These samples were homogenized and sent to the Soil, Plant,
and Water Laboratory at the University of Georgia in Athens, GA for soil nutrient
analysis. In August 2010, hemispherical photographs were taken according
to previous methods (see Rich 1990, Zhang et al. 2005) with a digital camera
mounted on a tripod from the center of each plot to determine the percent canopy
openness provided by thinning treatments. Photographs were analyzed with internet-
downloadable software, Gap Light Analyzer 2.0 (Simon Fraser University,
Burnaby, BC, Canada, 1999).
Surveys to monitor transplanted S. montana individuals were conducted
throughout the 2010 and 2011 growing seasons. Reported inventories were
conducted on 7 May 2010, 27 May 2010 for flowering, 20 May 2011, and
both 10 August 2010 and 15 July 2011 for transplant survival. Survival was
expressed as transplants with existing aboveground biomass as a percentage
of the total transplants at the beginning. Baseline metrics for growth included
stem height (of the tallest stem in multiple-stemmed individuals), the number
of stems, and the number of leaves of each individual plant. Reproductive
potential and development were assessed by determining the developmental
stage classes of all individuals and counting the numbers of flowers per
106 Southeastern Naturalist Vol. 12, No. 1
individual. We defined stage classes as juvenile for plants with stem height
<10 cm and not showing any thickened bases (a clear indication that they
had been damaged, e.g., by vertebrate browsing), vegetative adult for plants
with stem height >10 cm, and flowering adult for plant bearing flowers or
fruits. Additionally, we noted damage during all inventories including irregular
patterns of leaf biomass removal as could be caused by herbivores
and stem damage, which was largely assumed to result from vertebrate grazing,
especially when apical biomass was found missing, although stems were
occasionally found bent or broken after heavy rains, or possibly from vertebrate
To elucidate the physiological mechanisms underlying growth, reproductive,
and developmental observations, we measured instantaneous leaf-level gas exchange
with a portable gas-exchange analyzer (LI-6400XT, LI-COR, Lincoln,
NE) on 21 July 2010. All plants were watered in the morning prior to gas-exchange
measurements. A clear-top leaf cuvette was used to provide ambient light
conditions during measurements, and conditions within the cuvette were set to
mimic ambient conditions of 400 μmol CO2 mol-1 and 29 ºC temperature. Gasexchange
measurements included net photosynthetic rate (A; μmol CO2 m-2 s-1),
as well as transpiration rate (E; mol H2O m-2 s-1) and stomatal conductance (gs;
mol H2O m-2 s-1) expressed per unit leaf area. Additionally, small subsamples of
leaf biomass were collected immediately following gas-exchange measurements
and dried to calculate the leaf mass per unit area (LMA), which is generally correlated
with leaf-level photosynthetic activity (Field and Mooney 1986; Reich et
al. 1991, 1992, 1997).
A two-way analysis of variance (ANOVA) was conducted to evaluate the
main effects and interactive effect of burning and canopy-thinning treatments on
measured variables. Main and interactive effects of treatments were considered
significant if P ≤ 0.05. Principal component analysis (PCA) with an orthogonal
rotation was used to test relationships between variables. All statistical analyses
were performed with IBM SPSS Statistics 19 (SPSS, Inc., 2010, S omer, NY).
Burning had a positive influence on the availability of select soil nutrients. In
comparison with control plot C, plot B was characterized by 26% greater ammonium
+) availability and 67% greater potassium (K) availability (Table 1).
In addition, soil K was 75% greater and nitrate (NO3
-) was 33.3% greater in plot
B+T than in plot C (Table 1). With the exception of NO3
-, differences in soil
nutrient availability between plots T and C were more minimal than differences
between plots B and C (Table 1). Overall, canopy thinning increased the openness
of relocation plots. Specifically, percent canopy openness was 10.4% in plot
C, 13.5% in plot B, 20.8% in plot T, and 18.7% in plot B+T.
2013 H.M. Kile, J. Shaw, and J. Nagel Boyd 107
Overall transplant survival, growth, and reproduction
When baseline metrics were assessed less than one week after transplantation
was complete, two transplanted S. montana individuals were missing from their
relocation positions. During the 2010 growing season, four individuals senesced;
two of these plants appeared to have experienced mechanical basal damage,
while the other two individuals exhibited no apparent reasons for sensescence.
Two senesced individuals grew new shoots within a few weeks, while the other
two individuals regenerated during the next year. Including senesced individuals,
98% of transplanted S. montana individuals survived to our August 2010 inventory.
During the May 2011 inventory, 12 plants were not found in their relocation
positions (including the two individuals missing during our May 2010 inventory).
However, three of these individuals produced aboveground biomass by our
July 2011 inventory, resulting in 91% survival of original transplants by late into
the second growing season after being relocated.
During our May 2010 baseline measurements, we found that S. montana
transplants across all relocation plots were mostly single-stemmed, but the number
of stems per individual plant ranged from 1–3. Individual plant stem height
ranged from 2.5–45 cm, and the number of leaves per plant ranged from 2–16
(Table 2). In addition, leaf damage was observed on 58% of the total transplanted
S. montana individuals, while stem damage was observed on 14% of transplants.
Across all relocation plots, 27% of transplants were juveniles, 51% were vegetative
adults, and 22% were reproductive (i.e., flowering or fruiting) adults. A total
of 50 flowers were counted for all transplants.
Table 1. Amount (mg/kg) of soil ammonium (NH4+), nitrate (NO3-), phosphorus (P) and potassium
(K) in control (C), burned only (B), thinned only (T), and burned and thinned (B + T)
Scutellaria montana relocation plots at the Tennessee Army National Guard Volunteer Training
Site in Catoosa County, GA.
Soil nutrients (mg/kg) C B T B+T
+ 8.8 11.1 9.8 9.7
- 0.8 1.7 1.7 3.3
P 10.5 11.8 8.9 9.5
K 68.8 115.0 76.5 120.5
Table 2. Mean (± SE) values of growth variables of Scutellaria montana individuals approximately
two weeks (May 2010) and one year (May 2011) post-transplantation across relocation plots at the
Tennessee Army National Guard Volunteer Training Site in Catoosa County, GA.
Variable May 2010 (n = 98) May 2011 (n = 88)
Number of stems 1.1 ± 0.38 1.7 ± 0.10
Stem height (cm) 12.0 ± 8.1 20.0 ± 1.1
Number of leaves 6.8 ± 2.7 21.2 ± 1.6
Number of flowers 0.5 ± 1.5 3.3 ± 0.6
108 Southeastern Naturalist Vol. 12, No. 1
By approximately one year post-transplantation, the upper ranges of growth
measurements were greater than during baseline measurements. Specifically,
the number of stems per plant ranged from 1–5, stem height ranged from
1–54.5 cm, and the numbers of leaves per plant ranged from 0–78 across all
relocated plots in May 2011 (Table 2). However, damage to both leaves and
stems also increased from 2010 to 2011. Leaf damage was observed on 67%
of the total transplanted S. montana individuals, while 57% of transplants exhibited
stem damage in May 2011. In addition, the transplants included 5.7%
juveniles, 56.8% vegetative adults, and 37.5% flowering adults in May 2011,
and a total of 293 flowers were counted at that time, evidencing that the transplanted
individuals as a group were aging.
Our PCA of measured growth factors (stem height, and stem, leaf, and flower
number per individual plant) revealed that two components explained 87.3% of the
variation in growth exhibited by the transplants (Table 3). Stem number of S. montana
individuals was strongly and positively associated with leaf number, while
stem height was strongly and positively associated with flower number (Fig. 2).
Responses of transplants to burning and thinning
When compared with survival in control plot C, the percent of S. montana
transplants that survived to July 2011 was greater with burning alone, but lower
when the relocation area was subjected to canopy thinning. Transplant survival
was 96% in the plot C, 100% in plot B, and 84% in both plot T and plot B+T.
In May 2010, there were no significant differences in any of the measured
growth, reproductive, and developmental variables or observed biomass damage
of S. montana transplants between relocation plots (all P > 0.10); however,
significant differences in several of these variables was exhibited in May
2011. These differences included both main and interactive effects of burning
and canopy thinning. Specifically, burning negatively influenced both the
proportion of plants with leaf damage (P < 0.001, F3,87 = 14.322; Fig. 3a) and
the proportion of plants that were flowering adults (P = 0.003, F3,87 = 9.036;
Fig. 3b), while the proportion of plants exhibiting stem damage (P = 0.030,
F3,87 = 4.845; Fig. 3c) and the proportion of plants that were vegetative adults
Table 3. Varimax-rotated matrix of a principle component analysis (PCA) showing the variable
loading per component, total eigenvalue, and cumulative variance explained (%) in growth
variables measured for Scutellaria montana in May 2011 at the Tennessee Army National Guard
Volunteer Training Site in Catoosa County, GA.
Variable 1 2
Number of stems 0.973
Stem height (cm) 0.880
Number of leaves 0.468 0.837
Number of flowers 0.903
Total eigenvalue 1.81 1.68
Cumulative variance explained (%) 45.3 42.0
2013 H.M. Kile, J. Shaw, and J. Nagel Boyd 109
(P = 0.009, F3,87 = 7.242; Fig. 3d) were positively influenced by burning. However,
burning did not influence significantly the mean stem height (P = 0.254)
per transplanted S. montana individual, the mean number of stems (P = 0.819),
leaves (P = 0.277), or flowers (P = 0.099) of transplants, or the proportion of
transplants that were juveniles (P = 0.714).
Canopy thinning negatively influenced both mean stem height per individual
(P = 0.009; F3,87 = 7.107; Fig. 4a) and the proportion of plants that were flowering
adults (P = 0.009, F3,87 = 7.075; Fig. 4b), while both the proportion of plants
exhibiting stem damage (P = 0.001, F3,87 = 10.838; Fig. 4c) and the number of
vegetative adults responded positively to canopy thinning (P = 0.025, F3,87 =
5.185; Fig. 4d). In contrast, canopy thinning did not influence significantly the
number of stems (P = 0.074), leaves (P = 0.926) and flowers (P = 0.083) per
individual transplant, the proportion of plants with leaf damage (P = 0.123), or
proportion of plants that were juveniles (P = 0.595).
Interactive effects of burning and canopy thinning on S. montana growth, reproductive
potential, development, and biomass damage were more limited than
the main effects of either treatment. Only mean stem height (P = 0.004, F3,87 =
Figure 2. Principal component analysis (PCA) projection of stem height, and numbers of
stems, leaves, and flowers of transplanted Scutellaria montana individuals in May 2011
at the Tennessee Army National Guard Volunteer Training Site in Catoosa County, GA.
Percentages of the two components represent total variance explained, and projections
in the same direction show positive correlations, while opposite directions would have
represented negative correlations.
110 Southeastern Naturalist Vol. 12, No. 1
8.844) and the number of leaves per S. montana transplant (P = 0.015,
F3,87 = 6.151) were influenced significantly by the interaction of burning and
canopy thinning. Specifically, burning negatively influenced both the mean stem
height and number of leaves per transplanted S. montana individual when combined
with canopy thinning but positively influenced stem height in unthinned
plots relative to the absence of burning (Fig. 5).
Leaf-level gas exchange and related factors of S. montana transplants exhibited
some shared responses to the main effects of burning and canopy thinning.
Specifically, transplants in burned plots were characterized by significantly
greater LMA than those in unburned plots (P < 0.001, F3,76 = 55.223; Fig. 6a),
while transplants in thinned plots were characterized by significantly greater
LMA than those in unthinned plots (P < 0.001, F3,76 = 27.526; Fig. 6b). Similarly,
transplants in burned plots were characterized by significantly greater E
than those in unburned plots (P = 0.007, F3,60 = 7.710; Fig. 6c), while transplants
in thinned plots were characterized by significantly greater E than those in unthinned
plots (P = 0.004, F3,60 = 8.919; Fig. 6d). Burning also was associated with
a significant increase in leaf A (P = 0.045, F3,60 = 4.191; Fig. 6e), while canopy
thinning also was associated with a significant increase in leaf gs (P = 0.011,
Figure 3. The significant main effect (P ≤ 0.05) of burning on the proportion of plants
with leaf damage (a; % of total), the proportion of plants that were flowering adults (b;
% of total), the proportion of plants with stem damage (c; % of total), and the proportion
of plants that were vegetative adults (d; % of total) of transplanted Scutellaria montana
individuals at the Tennessee Army National Guard Volunteer Training Site in Catoosa,
GA. Values shown on means ± 1 SE.
2013 H.M. Kile, J. Shaw, and J. Nagel Boyd 111
Figure 4. The significant main effect (P ≤ 0.05) of thinning on the stem height (a; cm),
the proportion of plants that were flowering adults (b; % of total), the proportion of plants
with stem damage (c; % of total), and the proportion of plants that were vegetative adults
(d; % of total) of transplanted Scutellaria montana individuals at the Tennessee Army
National Guard Volunteer Training Site in Catoosa, GA. Values shown on means ± 1 SE.
F3,60 = 6.824; Fig. 6f). In contrast, leaf gs did not differ significantly between
burned and unburned plots (P = 0.078), while leaf A did not differ significantly
between thinned and unthinned plots ( P = 0.229).
Figure 5. The significant interaction effect (P ≤ 0.05) of burning and canopy thinning
on mean stem height (a; cm) and the number of leaves per individual (b) of transplanted
Scutellaria montana at the Tennessee Army National Guard Volunteer Training Site in
112 Southeastern Naturalist Vol. 12, No. 1
Transplantation as mitigation
Overall, we consider our S. montana transplantation efforts to be successful
because transplants exhibited high survival, maturation in terms of both individual
growth and collective development, and increased reproductive potential as evidenced
by total flower production one year after their relocation (Table 2). However,
seedlings were not observed concurrently, so we cannot yet determine if the transplants
will comprise a self-sustaining group. In general, the transplantation of rare
plant species often has been associated with less-than-ideal long-term results due to
inherent life-history traits, such as low seed set and recruitment (Fahselt 2007).
Figure 6. The significant main effect (P ≤ 0.05) of burning on leaf mass per unit area (a;
LMA in g m-2), instantaneous leaf-level transpiration rate (b; E in mol H2O m-2 s-1), and
instantaneous leaf-level photosynthetic rate (c; A in μmol CO2 m-2 s-1), and the significant
main effect (P ≤ 0.05) of thinning on LMA (d), E (e), and instantaneous stomatal conductance
(f; gs in mol H2O m-2 s-1) of transplanted Scutellaria montana individuals at the
Tennessee Army National Guard Volunteer Training Site in Catoosa, GA. Values shown
on means ± 1 SE.
2013 H.M. Kile, J. Shaw, and J. Nagel Boyd 113
Seedling survival, in particular, has been identified as one of the most significant
barriers to self-sustenance in transplanted populations, especially for
at-risk species (Jusaitis 2005, Lofflin and Kephart 2005), and recruitment is
influenced by both seed availability and favorable environmental conditions
for seedling establishment (Eriksson and Ehrlen 1992). Previous observations
of S. montana have suggested that this species is characterized by limited
flowering, fruit set, and seed set in natural conditions (Cruzan 2001, Hopkins
1999, Kemp 1987, Nix et al. 1993, USFWS 2002). However, because flower
number has been associated positively with fruit set in this species (Hopkins
1999), the increased number of flowers we found one-year post-transplantation
in our study could be indicative of future increased seed availability. Yet,
the establishment of any future seeds could be impacted negatively by abiotic
and biotic factors such as summer droughts (Manzaneda et al. 2005), herbivory,
and competition from neighboring vegetation (Jusaitis 2005). Continued
monitoring of S. montana transplants and surveys of the relocation plots utilized
in this study for recruits will be important for evaluating the longer-term
success of our efforts.
Importance of site selection
Despite previous suggestions that S. montana habitat may be characterized
by relatively high light availability within the forest understory (Mulhouse et al.
2008) and that canopy disturbances resulting in greater light availability are beneficial
to this species (Nix et al. 1993, USFWS 2002), we found that transplant
survival was reduced in thinned relocation plots in comparison to plots with intact
canopy. Furthermore, S. montana in thinned plots were comparatively shorter in
stature, had more stem damage, and exhibited less reproductive potential than in
unthinned plots (Fig. 4). We suggest that the concurrent increases in leaf LMA, E,
and gs that we observed for S. montana in thinned plots compared with unthinned
plots are indicative of leaf acclimation to increased light availability (Chabot
et al. 1979; Fig. 6). The positive association of light availability with LMA, in
particular, is considered an ecological adaptation that increases leaf surface area
for greater light interception in low-light conditions and reflects the greater incorporation
of photosynthetic enzymes and machinery in leaves under high-light
conditions (Poorter et al. 2009). Although such leaf-level factors theoretically
could reflect an increased capacity for energy assimilation, we did not observe
any concurrent positive responses of growth or development of S. montana with
increased light availability provided by canopy thinning. As such, our results
suggest that canopy thinning does not benefit, and could negatively impact, the
success of S. montana transplantation efforts.
In contrast to the effects of canopy thinning, we found that S. montana
transplant survival in this study was minimally enhanced by burning (in the
absence of thinning) in comparison to a lack of burning. Although it has
been suggested previously that S. montana responds poorly to fire (Owen
and Brown 2005, USFWS 2002), these suggestions were based largely on the
114 Southeastern Naturalist Vol. 12, No. 1
survival of existent plants to burning rather than the use of burning as a pretreatment
for future transplants. However, while burning influenced survival
positively in our study, burning also was associated with greater stem damage
and reduced reproductive potential among S. montana transplants than
observed in unburned plots (Fig. 3). Burning also had a negative impact on
both stem height and the number of leaves produced per S. montana individual
when combined with canopy thinning (Fig. 5). As with canopy thinning, we
suggest that the increased leaf LMA, E, and A exhibited by S. montana individuals
in burned plots compared with unburned plots could reflect leaf
acclimation to increased light availability to some extent given the effect of
our low-grade burning treatment on the density of surrounding understory
vegetation (Fig. 6). We also suggest such acclimation could have been influenced
by greater availability of soil N in burned compared with unburned plots
(Table 1) since N is incorporated into photosynthetic enzymes.
While we did not measure foliar nitrogen (N) in this study, this factor typically
is positively correlated with increased photosynthetic capacity (Evans 1989, Frak
et al. 2001, Niinemets 1999, Reich et al. 1997). Additionally, positive correlations
between foliar N content and gas exchange have previously been evidenced
in plant responses to prescribed burning treatments, and E, in particular, was
increased at all times of the day (Reich et al. 1990). However, as with canopy
thinning, we did not observe any concurrent positive responses of growth or development
of S. montana with burning alone, suggesting that leaf-level changes
had limited influence on whole-plant processes within this species and the scope
of our study. Given the negative impacts of burning on S. montana stem damage
and transplant development observed in this study, we conclude that burning
could negatively impact the success of S. montana transplantation efforts. However,
because Native Americans are thought to have greatly influenced the Ridge
and Valley physiographic providence with fire before Europeans settlers arrived
(Delcourt and Delcourt 1998), we suggest that further investigations of the fire
adaptability of S. montana, including investigation of the effects of burning on
seed germination, recruitment, and interspecific competition of surrounding postfire
vegetation, are warranted.
Possible impact of herbivores
The increased stem damage of S. montana that we observed with transplantation
and in response to burning and canopy thinning indicate that herbivores
may have been especially attracted to our relocation plots. Across treatments,
the 3.6-fold increase in stem damage that we observed one year post-transplantation
was unexpected. Naturally occurring S. montana individuals
sampled across the VTS in May 2010 (n = 1346) exhibited 8% stem damage,
while individuals within the two permanent monitoring plots closest in proximity
to the relocation plots exhibited 12% (n = 150) and 19% (n = 26) stem
damage (Boyd et al. 2010). The similarity of stem damage in plot C (27%) to
those monitoring plots suggests that overall stem damage among transplants
2013 H.M. Kile, J. Shaw, and J. Nagel Boyd 115
was influenced greatly by the very positive impact of burning and canopy
thinning on this factor (Figs. 3, 4).
Furthermore, we suggest that increased herbivory in burned and thinning
plots could have skewed our site-selection analysis regarding the influence
of these treatments on the success of S. montana transplantation. Specifically,
stem damage typically was observed as missing apical portions of biomass;
inherently, this would decrease stem height. Because S. montana has a terminal
inflorescence, we also suggest that flowers may have been produced and
subsequently consumed by grazers prior to survey times, which could have
reduced our flower counts and affected our assessments of flowering adults.
Hopkins (1999) reported a positive relationship of the number of leaves with
the number of flowers per individual of S. montana, but our PCA suggested
that stem height was a better indicator of flower number in the transplants than
leaf number, lending further support to our hypothesis that flower counts were
influenced by grazing in this study (Fig. 2).
Comparison with previous transplantation efforts
Previous attempts at transplantation of S. montana have had mixed results
(Snyder and Lecher 2010, McKerrow 1996, USFWS 2002). However, high initial
survivability was found after our transplantation of S. montana at a nearby
site prior to our implementation of this study (Kile et al. 2011). Specifically,
we transplanted 49 S. montana individuals in May 2009 from a small location
in the Enterprise South Nature Park in Chattanooga, TN, that was scheduled
to be impacted by highway construction project to a nearby area with existing
S. montana individuals, as recommended by the USFWS. One month after this
relocation, an ≈1.25-m-tall chain-link fence was constructed around the relocation
site to exclude human traffic given its close proximity to a road and hiking
and biking trails. Overall, survival of these plants was very high (98%) one year
post-transplantation, similar to our VTS transplants. Our Enterprise South transplants
experienced an approximate 190% increase in stem height, 45% increase
in the number of stems per individual, 130% increase in the number of leaves
per individual, and 2000% increase in the number of flowers per individual one
year post-transplantation (Kile et al. 2011). In contrast, the VTS transplants experienced
a 67% increase in stem height, 55% increase in the number of stems
per individual, 212% increase in the number of leaves per individual, and 547%
increase in the number of flowers per individual (Table 2) one year post-transplantation.
The Enterprise South transplants also experienced a 93% reduction
in the proportion of plants with stem damage one year post-transplantation, in
contrast to the increase in stem damage observed for the VTS transplants after
this same duration. Combined, these comparisons suggest that protection of
S. montana transplants from herbivores could maximize their success and allow
for better elucidation of the influence of disturbances like burning and thinning
on transplantation success.
116 Southeastern Naturalist Vol. 12, No. 1
Our overall S. montana transplantation results evidenced initial success with
high survivability, continued maturity, and increased reproductive effort. However,
both burning and canopy thinning were associated with reduced transplant
development and reproductive potential, increased stem damage, and likely
increased associated herbivory compared with a lack of these treatments. As
such, we recommend that future relocation sites include locations with known
S. montana occurrences and avoid areas recently disturbed by burning or canopy
thinning unless plans are made for the subsequent control of vertebrate herbivory.
More broadly, we suggest that herbivore exclosures be utilized for all S. montana
transplants to maximize their post-transplantation success. Additionally,
we suggest that the S. montana transplants described in this study continue to be
monitored, and that future monitoring include a search for new recruits to determine
if transplants will be self-sustaining.
Because human activities have an ongoing environmental impact at many
scales, effective plant species conservation and management should benefit
from increased understanding of the effects of such activities on these species.
Ultimately, the findings of this study should aid efforts to protect and support
S. montana in the VTS and other locations impacted by necessary human disturbance,
as well as provide insight into the potential influence of such disturbances
on other endangered, threatened, and/or rare herbaceous plant species of the
deciduous forest understory.
We acknowledge the Tennessee Army National Guard for providing the primary funding
for this project. We thank Laura Lecher of the State of Tennessee Military Department
and Sgt. Todd Anderson and his staff at the Tennessee Army National Guard Volunteer
Training Site for their assistance and cooperation in accommodating and providing logistical
support for our research. We also thank Emily Blyveis, Heather Chang, Dusty
Rumley, Kira Spears, Jacob Whitt, and Neal Wolfe for assistance with fieldwork related
to this project.
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