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P.A. Wadl, A.M. Saxton, G. Call, and A.J. Dattilo
22001188 SOUTHEASTERN NATURALIST Vo1l7.( 117):,1 N9–o3. 11
Restoration of the Endangered Ruth’s Golden Aster
(Pityopsis ruthii)
Phillip A. Wadl1,*, Arnold M. Saxton2, Geoff Call3, and Adam J. Dattilo4
Abstract - Pityopsis ruthii, Ruth’s Golden Aster, is an endangered herbaceous perennial
that is endemic to small sections of the Hiwassee and Ocoee Rivers in the southeastern US.
Our objective was to test the effect of bonded fiber matrix (BFM) on establishment and
fecundity of Ruth’s Golden Aster in order to develop a robust restoration protocol. We augmented
existing populations with plants grown from achenes collected at each restoration
location. We monitored plantings through 3 growing seasons by measuring stem number,
stem height, leaf number, flowering incidence, and number of flower heads per plant in
the spring and fall of each season. We assessed survival at 1 month post-planting. We randomly
assigned plants at each location to a treatment (BFM vs. no BFM) for analysis as a
randomized complete-block design. Germination rate of filled seeds, number of acclimated
seedlings, and percent of seedlings planted after 14 days of acclimatization differed significantly
across sites. Survival was significantly higher at 1 month, fall year 1, spring/fall year
2, and spring year 3 for the plants mulched with BFM compared to the control. However,
there were no significant differences between treatment for stem number, stem height, leaf
number, flowering incidence, or final 3-year survival. The methods developed herein represent
a major step towards meeting the recovery-plan objective of developing the ability
to establish Ruth’s Golden Aster on suitable habitat. Herein, we provide a framework for
augmentation or restoration of critical populations threatened by extirpation.
Introduction
Pityopsis ruthii (Small) Small (Ruth’s Golden Aster) is a diminutive (10–30
cm tall), fall-flowering member of the Asteraceae that occurs only in cracks of
phyllite boulders (Semple 2006). This species can persist in shaded situations, but
flowering, seed set, and establishment of juvenile plants is most successful in open
habitats where plants receive full sun for a significant portion of the day (Moore et
al. 2016, White 1977). Ruth’s Golden Aster is tolerant of prolonged drought (Moore
et al. 2016) and inundating high-flow events (A.J. Dattilo, unpubl. data), but the
species is a very poor competitor when it becomes established in areas of deeper
soils that build up on the boulder complex or outside of the exposed boulder complexes
where healthy populations occur (Cruzan and Beaty 1998, USFWS 2012).
In the southeastern US, where sites with sufficient soil depth generally succeed to
forest in lieu of anthropogenic disturbance, periodic high river-flow and cyclical
1US Department of Agriculture, Agricultural Research Service, US Vegetable Laboratory,
2700 Savannah Highway, Charleston, SC 29414. 2Department of Animal Science, University
of Tennessee, 2506 River Drive, 232 Brehm Animal Science Building, Knoxville, TN
37996. 3US Fish and Wildlife Service, 446 Neal Street, Cookeville, TN 38501-4027. 4Biological
Compliance, Tennessee Valley Authority, West Tower 11B-K, 400 West Summit Hill
Drive, Knoxville, TN 37902. *Corresponding author - Phillip.Wadl@ars.usda.gov.
Manuscript Editor: Richard Baird
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drought maintain the niche occupied by Ruth’s Golden Aster. The confluence of
appropriate geology and disturbance regime is very rare on the landscape, making
the species inherently vulnerable to extinction caused by natural and anthropogenic
forces capable of significantly altering its habitat.
Plants grow in small crevices of massive rock outcrops situated between the open
river channel and the adjacent forest slopes. It is a narrowly distributed, herbaceous
perennial plant that occurs only along small reaches of the Hiwassee (~4 km) and
Ocoee (~2.5 km) Rivers in Polk County, TN. All occurrences of Ruth’s Golden Aster
occur downstream of Tennessee Valley Authority (TVA) dams in sections of river
that are intensively managed for flood control and electricity generation. The species
is listed as endangered under the Endangered Species Act of 1973 and is considered
critically imperiled (G-1; NatureServe 2015). Although modification of natural river
flows has been implicated in population decline of this species (Bowers 1972; Thomson
and Schwartz 2006; USFWS 1992, 2012; White 1977; Wofford and Smith 1980),
there are no quantitative studies that address how river flows interact with Ruth’s
Golden Aster. Regardless of the net effect of river management, the species has a very
narrow range in a habitat that is subjected to extreme conditions. These combined
factors make Ruth’s Golden Aster vulnerable to isolated events that have the potential
to extirpate or severely degrade 1 or more populations.
The ability to successfully establish plants in unoccupied suitable habitat is a
viable option for reducing extinction risk (Pavlik 1996) and is a stated objective
necessary for the recovery of the species (USFWS 1992). Falk et al. (1996) defined
3 types of restorations for endangered plants: reintroductions, enhancement or reinforcement,
and introductions. Reintroductions occur at sites where a species was
extirpated, introductions occur at previously unoccupied sites, and enhancement
or reinforcement (augmentation) occurs at sites with extant populations. Although
Ruth’s Golden Aster is well adapted to the harsh environment, the growing conditions
pose challenges for managers seeking to restore or enhance populations of the
plant. Initial restoration attempts with Ruth’s Golden Aster were not successful;
only 1% of the plants survived past the first season (Cruzan and Beaty 1998). The
reasons for the failure are not entirely clear, but the investigators recognized the
potential for drought stress and soil disturbance to impact plants. In an attempt to
address drought stress, managers augmented some restoration plots containing both
seeds and transplanted rosettes with a moisture-retaining soil amendment. Over
time, the amended medium swelled significantly, became dislodged from the planting
crevices, and was washed way along with the propagules. Alternate treatments
using sphagnum moss to retain moisture and netting to anchor plants and seeds
were equally ineffective (Cruzan and Beaty 1998).
Subsequent efforts by Wadl et al. (2014) to replant Ruth’s Golden Aster in suitable
habitat employed bonded fiber matrix (BFM), a composite of polymers and wood fiber,
used to stabilize soil and vegetation on disturbed sites. When wetted, BFM forms
a thick slurry that adheres to itself and the surface to which it is applied. Resource
managers assumed that the ability to glue Ruth’s Golden Aster plants in place after
installation in narrow cracks would confer some resistance to scouring river flows
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2018 Vol. 17, No. 1
and moisture loss on the drought- and flood-prone sites. Initial, small-scale efforts
utilizing BFM in replanting proved successful; survival of Ruth’s Golden Asters
transplanted into suitable habitat at a single location on the Ocoee River was 73%
after 1 growing season. Despite the high survival rate, the methodology of the pilot
study limited the applicability of the data to larger restoration efforts. All individuals
transplanted to the study site were derived through clonal propagation of a single
individual of unknown origin growing on the University of Tennessee, Knoxville,
TN, campus. Without replication using multiple genotypes and sites, it is not possible
to make meaningful inferences about the efficacy of the methods across the range
of Ruth’s Golden Aster. In addition, larger-scale efforts involving more individual
plants necessitate using plants derived from seed to avoid genetic swamping within
populations. Given the variability in germination rates and seedling vigor exhibited
by the species, it is possible the clones produced from stem cuttings would outperform
plants grown from seed (Farmer 1977, White 1977).
Our long-term objective is to develop methods to restore Ruth’s Golden Aster
into unoccupied suitable habitat, as outlined in the recovery criteria for the species
(USFWS 1992, 2012). Pavlik (1996) described short-term restoration success as
the point at which a new population can carry on its basic life-history processes of
establishment, reproduction, and dispersal, such that the probability of complete
extinction by random or chaotic forces is low. Our objective in this study was to
build on the work of Wadl et al. (2014) by testing the effect of BFM on abundance
(establishment, fecundity, full life cycle can be completed) of seed-grown Ruth’s
Golden Aster augmented along the Hiwassee and Ocoee Rivers.
Materials and Methods
Plant materials and transplanting
We collected achenes (seeds) from open-pollinated Ruth’s Golden Aster plants
at 5 Hiwassee River locations and 1 Ocoee River location in fall 2012 (Fig. 1)
while plants were blooming and dispersing seeds. We pooled and placed seeds
randomly collected from multiple individuals at each location directly into paper
coin envelopes. Immediately following field collection, we transferred the seed into
paper bags and dried them at ambient temperature (~23–24 °C) for 24 h (Farmer
1977). Filled seeds (embryo within fruit) are visibly larger in diameter compared
to thinner, unfilled seeds (lacking an embryo); thus, we discarded the unfilled seeds
and used only germinated, filled seeds according to Wadl et al. (2014). The general
protocol was as follows. We removed the pappus, disinfected by immersing
in 70% ethanol for 1 min, and briefly passed all seeds through a flame. Seeds were
then placed into 50-mL conical tubes containing a 50% commercial bleach solution
and shaken vigorously for 20 min. We decanted the bleach solution, rinsed the
seeds 3 times with sterile water, placed individual seeds into a Bioworld Magenta®
GA-7 plant culture box (Fisher Scientific, Waltham, MA) containing 50 mL of MS
basal medium (Murashige and Skoog 1962), and incubated the boxes in the dark
at 22–25 °C for up to 3 weeks or until germination. After 3 weeks, we calculated
seed-germination percentages (seeds germinated/total number of seeds x 100).
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We maintained the seedlings for 8 weeks in a growth room at 25 °C under a 16-h
photoperiod provided by cool white fluorescent lamps. The lamps provided a photosynthetic
photon flux of 125 μmol m-2 s-1 as measured by a Licor LI-250 light meter
(LI-COR Inc., Lincoln, NE) held at the top of the culture vessels. After 8 weeks, we
transferred plants to 72-cell flats containing ProMix soilless medium covered with a
humidity dome for acclimatization in a greenhouse. We cut holes into the humidity
dome after 24 h, and completely removed the dome after 3 days. The plants were
acclimated to natural environmental conditions for 14 d at the University of Tennessee,
Knoxville, TN, until outplanting.
Planting and plant measurement
We transplanted the ~3-month-old seedlings into suitable habitat at the seedcollection
sites. At planting, we gently removed the ProMix soilless medium
from the roots and backfilled the rock cracks with native soil from each planting
location. After planting, we applied BFM to the treatment group and left the untreated
control as bare soil (Fig. 2.). We used a metal spatula to apply the BFM as
a thin layer of slurry (2–4 mm). All plantings were at least 1 m from the nearest
native Ruth’s Golden Aster to avoid physical impacts to native plants and confusion
about plant origin during the study period. We designed the study to test the
effect of BFM on establishment and growth of Ruth’s Golden Aster. Competing
vegetation at planting sites could have confounded results; thus, without disturbing
Figure 1. Ruth’s Golden Aster restoration plantings at 5 sites on the Hiwassee River and 1
site on the Ocoee River in Polk County, TN. Hatched bars indicate the upstream and downstream
extent of populations and delineate the entire range of the species.
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Figure 2. (A, C, E, G) Successful restoration of Ruth’s Golden Aster planted with soil, and
(B, D, F, H) soil covered with bonded fiber matrix at (A, B) planting, (C, D) fall 2013, (E,
F) spring 2014, and (G, H) fall 2014.
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Ruth’s Golden Aster plants, we physically removed competing plants rooted in the
same crack and within 50 cm of experimental plants. We marked planting sites so
that we could reliably relocate plants and ensure accuracy of the data collected. To
accomplish this, we used a battery-operated hammer drill to make 1 small hole in
the rock at each of the 6 planting sites. The diameter of the hole accommodated
a rebar stake that we used as a plot center. During sampling, we inserted rebar
into the hole and fastened a meter tape to it. Using the meter tape, we recorded
the distance and bearing to each plant (nearest cm) from the plot center. We used
this information and other pertinent features in the landscape to generate a unique
location for each plant. From this information, we recorded crack location for all
plants and assigned plants in close proximity to each other and with similar habitat
characteristics (boulder aspect, slope, crack orientation) into discrete habitat clusters.
We recorded stem number, stem height, leaf number, flowering incidence, and
number of flower heads per plant. In 2013, we made measurements at the time of
planting (March), 1 month post-planting (April), and in October. In 2014 and 2015,
we measured plants in April and October. To test fecundity, we collected mature
seeds from an individual flower head from 2 plants in fall 2015, planted them, and
assessed germination rate.
Experimental design and statistical analyses
For the population augmentation, we randomly assigned plants at each location
to a treatment (BFM or no BFM) and the experimental design was a randomized
complete block. We compared treatment and period differences for each response
variable using a mixed model ANOVA (SAS v9.4, Cary, NC). Site and habitat-cluster
effects were used as blocks, and we modeled repeated measures across periods
with an autoregressive covariance. We employed Fisher’s LSD to separate least
squares means at the 5% significance level. Normality and equal variance requirements
were met for all variables, including survival (normal approximation to the
binomial). We ran secondary analyses of variance with habitat cluster and specific
crack location as fixed effects to assess environmental effects. We estimated Pearson
correlations within and across periods to assist interpretation.
Results
Germination rate of filled seeds, number of acclimated seedlings, and total number
of seedlings planted after 14 d of acclimatization was significant. Germination
rate varied from 48% (O-01) to77% (H-02), number of acclimated seedlings varied
from 51 (H-03) to 67 (H-01), and total number of seedlings planted varied from
18 (H-05) to 62 (H-01). There were no significant treatment differences for mean
plant height (P = 0.2238), mean leaf number (P = 0.0742), mean flower number
(P = 0.3611), stem number (P = 0.1544), final percent 3-year survival (P = 0.1006),
or final percent 3-year survival if plant was alive at 1 month after planting out (P =
0.9505). Treatment was highly significant (P = 0.005) for percent survival at 1
month post-planting and moderately significant (P ≤ 0.02) for all dates monitored
except the fall in year 3 (Fig. 3). Survival at 1 month was 32.2% across treatments,
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40.8% for plants mulched with BFM, and 23.6% for plants without BFM. By the
end of the first season, survival was 24.4% for BFM plantings compared to 10.6%
for the non-mulched plantings. For the remainder of the monitoring periods, survival
remained relatively stable, and was 17.8% for the BFM planting and 10.5%
for plantings without BFM after 3 seasons. Survival was variable across sites;
plants flowered at H-2 and O-1 in the first season. Flowering occurred for all sites
and treatments within the second season, except for non-mulched plants at H-1,
and by the third season all sites and treatments with surviving individuals produced
flowers (Table 1, Fig. 3). Germination in fecundity tests was 87.5% for a plant at
H-1 (Soil + BFM treatment) and 0% for a plant at H-2 (soil treatment). The effect
of crack location within site was not significant for survival at 1 month or final
3-year survival for any site. However, habitat cluster was significant for survival at
1 month at H-2 (P = 0.0225), H-3 (P = 0.0345), O-1 (P = 0.0119), and final survival
at O-1 (P = 0.0081).
Discussion
Restoration of rare plant populations has become an increasingly common tool
used for conservation of rare plant species, but there is uncertainty surrounding
the long-term efficacy of the practice (Albrecht and Maschinski 2012; Dalrymple
et al. 2012; Godefroid et al. 2011; Guerrant 2012, 2013). In a review of 249 restorations
from 172 taxa from published literature and a survey of botanic gardens,
universities, and conservation organizations, Godefroid et al. (2011), characterized
Figure 3. Percent survival of Ruth’s Golden Aster restoration plantings at 5 sites on the Hiwassee
River and 1 site on the Ocoee River in Polk County, TN. Survival was monitored at
6 different periods for each treatment group and periods labelled with an asterisk (*) differed
between treatments at the 5% level.
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Table 1. Total number of Ruth’s Golden Aster planted into suitable habitat on the Hiwassee and Ocoee Rivers (Polk County, TN) and percent survival and
flowering percent of alive plants for 3 seasons.
First year (2013) Second year (2014) Third year (2015)
Number 1-month Fall Flowering Spring Fall Flowering Spring Fall Flowering
Site Treatment of plants survival (%) survival (%) (%) survival (%) survival (%) (%) survival (%) survival (%) (%)
H-1 Soil + BFM 31 2 (6.5) 2 (3.2) 0 (0.0) 2 (3.2) 2 (3.2) 2 (100.0) 2 (3.2) 2 (3.2) 2 (100.0A)
Soil 31 2 (6.5) 2 (3.2) 0 (0.0) 2 (3.2) 2 (3.2) 0 (0.0) 2 (3.2) 2 (3.2) 2 (100.0)
H-2 Soil + BFM 27 18 (66.7) 11 (40.7) 5 (45.4) 11 (40.7) 11 (40.7) 9 (81.8) 11 (40.7) 9 (33.3) 8 (88.9)
Soil 27 11 (40.7) 6 (22.2) 1 (16.7) 5 (18.5) 5 (18.5) 5 (100.0) 5 (18.5) 5 (18.5) 4 (80.0A)
H-3 Soil + BFM 18 10 (55.6) 8 (44.4) 0 (0.0) 8 (44.4) 8 (44.4) 5 (62.5) 8 (44.4) 6 (33.3) 5 (83.3)
Soil 18 4 (22.2) 2 (11.1) 0 (0.0) 2 (11.1) 2 (11.1) 1 (50.0) 2 (11.1) 2 (11.1) 1 (50.0)
H-4 Soil + BFM 18 3 (16.7) 1 (5.6) 0 (0.0) 1 (5.6) 1 (5.6) 1 (100.0) 1 (5.6) 1 (5.6) 1 (100.0)
Soil 18 2 (11.1) 1 (5.6) 0 (0.0) 1 (5.6) 1 (5.6) 1 (100.0) 1 (5.6) 1 (5.6) 1 (100.0)
H-5 Soil + BFM 9 7 (77.8) 4 (44.4) 0 (0.0) 3 (33.3) 3 (33.3) 2 (66.7) 3 (33.3) 2 (22.2) 2 (100.0)
Soil 9 4 (44.4) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0)
O-1 Soil + BFM 18 6 (33.3) 3 (16.7) 0 (0.0) 2 (11.1) 2 (11.1) 2 (100.0) 2 (11.1) 2 (11.1) 1 (50.0)
Soil 18 5 (27.8) 4 (22.2) 2 (50.0) 4 (22.2) 4 (22.2) 4 (100.0) 4 (22.2) 4 (22.2) 4 (100.0)
AMature achenes (seeds) were harvested and germination was 87.5% for an individual from H-1 and 0% for an individual from H-2.
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mean rates of survival (52%), flowering (19%), and fruiting (16%) as quite low.
Though categorizing the reported rates themselves as low maybe somewhat arbitrary,
Godefroid et al. (2011) also observed a continuing decline in these metrics,
indicating a continuing downward trajectory in the success of the restored plants.
The combination of the survival, flowering, and fruiting rates, and the negative
trend led the author to conclude that “most plant restorations will not be successful
over the long-term.” Survival data for Ruth’s Golden Aster over the 3-year study
period declined most significantly in the first month post-planting. After this initial
decline, sites stabilized, and many locations lost few plants thereafter. Although
stronger initial survival would be more encouraging, downward trends of survival
in the early stages of restoration are not unusual and may not be indicative of
long-term failure (Albrecht et al. 2011, Guerrant 2013). This finding does indicate
the need or continuing monitoring past the 3-year study period to elucidate the
ultimate success of the Ruth’s Golden Aster restoration (Godefroid et al. 2011). In
contrast to the negative trend in flowering incidence observed in many restorations,
Ruth’s Golden Aster generally exhibited increased flowering rates throughout the
3-year study; the mean flowering rate was 59.9% for BFM plantings and 47% for
bare soil plantings. High flowering rates, combined with production of viable seed
from restored Ruth’s Golden Aster, suggest the possibility of new recruitment into
the study sites even during the relatively short study period. However, because of
the small sample size, we cannot draw conclusions about recruitment without further
testing. Although recruitment of new individuals derived from restored plants
may be one of the most relevant metrics of success (Pavlik 1996), measuring this at
the study sites is difficult because the nearby available habitat is largely occupied
by naturally occurring Ruth’s Golden Aster of all age classes.
More narrowly, in the context of direct conservation of Ruth’s Golden Aster, we
contend that our study was successful for multiple reasons. First, we developed a
methodology for restoration of Ruth’s Golden Aster in which the survival rate was
higher than the 1% survival rate reported by Cruzan and Beaty (1998). Also, we
found that survival was significantly higher at 1 month, fall year 1, spring/fall year
2, and spring year 3 for the plants mulched with BFM compared to the control.
Survival rate was not significantly different for the treatment at the final fall year
3 measurement; however, the effect of BFM may still be biologically meaningful
when considered in the context of future larger-scale restoration efforts for Ruth’s
Golden Aster. The longevity of individual Ruth’s Golden Aster plants is unknown,
and it is plausible that increased survival into year 2, when restored plants are flowering
and presumably setting seed, may be sufficient justification for utilizing this
low cost and easily implemented treatment. The decreasing positive effect of BFM
is likely attributable to the ephemeral nature of the amendment, which degrades and
disperses over time. BFM remained largely intact through the first year , but breakdown
of BFM began to accelerate in year 2, and the substance was often absent
or severely compromised by the end of the growing season. The positive effect of
BFM on Ruth’s Golden Aster survival seems to persist as long the material remains
affixed to the substrate around individual plants.
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Our study focused on augmenting existing populations of Ruth’s Golden Aster,
but the methodology could be readily applied to areas of formerly suitable habitat
along the Hiwassee River that have been lost to succession since completion of the
Apalachia Dam in 1943. Previous efforts to clear trees and shrubs around areas of
former Ruth’s Golden Aster habitat were successful in producing the open conditions
that the species requires, but the rock outcrops were not recolonized from
adjacent occurrences of the species (USFS 2014). Lack of recruitment onto the
newly cleared sites could be the result of poor seed dispersal or germination, or
because the crevices in bedrock were not sufficiently cleared of sediments, which
allowed the establishment of aggressive early successional annual plants species
that excluded Ruth’s Golden Aster. The outcome of subsequent restorations could
potentially be improved if managers remove accumulated sediments from boulders,
install propagated Ruth’s Golden Aster plants on the sites using the methods
outlined in this paper, and control competing vegetation until Ruth’s Golden Aster
plants become established. In a larger context, these riparian rock-outcrop habitats,
which are subjected to environmental extremes including frequent drought and
prolonged flooding, are similar to other habitats where land managers try to restore
populations of rare plant species (Homoya and Abrell 2005, USFWS 2008, Wells
2012). BFM may prove useful in other locations and species where plantings could
benefit from increased resilience to scouring flood-flows and greater moisture retention
during dry periods.
The survival percentages, flowering incidence, and fecundity of planted Ruth’s
Golden Aster that we observed during this study are encouraging. However, several
factors (some manageable and some governed by chance) may have influenced the
results. First, the crevices restored with Ruth’s Golden Aster should be carefully
selected to better resemble cracks in which the species naturally grows. Cruzan
and Beaty (1998) attempted to quantify the effect of crevice width on growth for
established Ruth’s Golden Aster and found that plants in 10–15-mm-wide crevices
produced the most stems, though many plants inhabited cracks 3–5 mm wide. All
planting locations for our study were located within larger occupied Ruth’s Golden
Aster sites and were never more than a few meters from native plants. The crevices
into which we placed our plantings fell into this width range, but some may have
been too shallow to effectively support plants. Cruzan and Beaty (1998) noted that
it is difficult to discern crevice depth, but with experience, it is relatively easy to
know when a particular crack is too shallow. For instance, cracks that are less than
1 cm deep and unlikely to naturally accumulate soil over time are probably not appropriate
for restoration even if BFM is used to secure plants (and soil) in place.
The year 1 overall survival rate of 73% observed during the initial Ruth’s Golden
Aster pilot study suggests that using larger individuals may increase transplanting
success (Wadl et al. 2014). Although plants used in the Ruth’s Golden Aster pilot
study had nearly identical values for average stem height (13.4 cm vs. 13.5 cm)
and average number of leaves per stem (6.4 vs. 6.3) when compared to the current
study, plants in the pilot study had over twice as many initial stems per plant (4.2
vs. 1.9). This result indicates that plants used in the pilot study were comparable in
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overall height, but had about twice as much above ground biomass and presumably
greater below ground biomasss. The clonal origin and method of propagation (in
vitro multiplication vs. in vitro seedlings) may have influenced survival, and the
greater initial starting size may have also played an important role. Weather can
strongly influence the results of any outplanting in an uncontrolled setting. On the
whole, 2013 was a very wet year in the watershed encompassing the reintroduction
sites; most areas received 110–150% of normal rainfall (NOAA 2017). Several
large rain-events occurred during the growing season, necessitating 4 releases of
water from Apalachia Dam to minimize potential flooding to human-populated
areas, which likely inundated some percentage of plants and may have lowered
survival by physically dislodging individuals from planting sites, particularly H-1
and H-4. The largest of these releases, in both magnitude and duration, lasted for
11 days in July 2013. During this release, peak flows exceeded 4700 cubic feet/sec
(cfs) for 5 days (TVA, Knowville, TN, unpubl. data). Releases approaching 5000
cfs are uncommon along this part of the Hiwassee River, which normally operates
at a base flow of 25 cfs, because management of the system for electricity generation
and flood prevention necessitates that nearly all water is diverted around the
section of river where Ruth’s Golden Aster occurs. Though it is difficult to quantify,
follow-up field surveys indicated that tributary inputs into this cutoff reach during
the event were much higher than normal because the local area received significant
rainfall with resultant unusually elevated river-flows. While we did not quantify
any losses that may have occurred due to the extreme flood events, to overcome effects
of such environmental variation, restoration efforts should maximize numbers
of propagules for initial planting and incorporate multiple plantings. This approach
would increase the likelihood that suitable conditions for establishment would follow
1 or more planting events and that fit genotypes would become established as
a result of the restoration effort (Reichard et al. 2012).
Ex situ conservation and cultivation of plants is possible through both stem
cuttings and tissue culture, providing robust methods for restoration studies. It is
feasible to grow Ruth’s Golden Aster seedlings in vitro and transplant them into the
natural habitat (Wadl et al. 2011, 2014). Tracking demography within populations
and augmented plantings as well as further work on seed-dispersal mechanisms,
breeding success, and determining optimal time for restoration plantings are still
needed and would be useful in understanding and protecting this endangered
species. Planting season has been demonstrated to affect survival of restoration
plantings (Albrecht and McCue 2009, Guerrant and Kaye 2007). Another factor
to consider, and which cold be addressed in future studies, is the importance of
mycorrhizal associations on the successful establishment of this species.
This study provides a reliable protocol for the successful restoration for the
Ruth’s Golden Aster. Based on population-structure analyses, Hatmaker (2016)
recommended that the species should be managed as 2–4 populations along the
Hiwassee River and 2–3 along the Ocoee River. Thus, combination of the results
of Hatmaker (2016) and our current study provide a foundation for an effective
approach to utilize knowldedge of genetic diversity in future restoration or ex situ
conservation efforts.
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Acknowledgments
This work was supported by the US Department of Agriculture (USDA/MOA number 58-
6404-1-637), and the Tennessee Valley Authority (TVA). Mention of trade names or commercial
products in this article is solely for the purpose of providing specific information and does
not imply recommendation or endorsement by the TVA or the USDA. The USDA is an equalopportunity
provider and employer. The findings and conclusions in this article are those of
the authors and do not necessarily represent the views of the US Fish and Wildlife Service. We
thank Mark Pistrang (USDA, Forest Service), David Nestor (TVA), and Dr. Denita Hadziabdic
(University of Tennessee) for assisting with data collection. Seeds were collected under
Tennessee Valley Authority Permit # TE117405-2 and US Fish and Wildlife Service Permit #
TE134817-1. P.A. Wadl and A.J. Dattilo contributed equally to this project.
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