Responses of Planted Native Warm-season Grasses
and Associated Vegetation to Seasonality of Fire in the
Southeastern US
Elizabeth Holcomb, Patrick Keyser, and Craig Harper
Southeastern Naturalist, Volume 13, Issue 2 (2014): 221–236
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22001144 SOUTHEASTERN NATURALIST 1V3o(2l.) :1232,1 N–2o3. 62
Responses of Planted Native Warm-season Grasses
and Associated Vegetation to Seasonality of Fire in the
Southeastern US
Elizabeth Holcomb1, Patrick Keyser1, and Craig Harper1,*
Abstract - State and federal agencies have promoted native grass/forb plantings to increase
and enhance habitat for Colinus virginianus (Northern Bobwhite). However, many
plantings have resulted in dense stands of grass that do not provide suitable structure for
Northern Bobwhite. Prescribed fire is an important tool for managing succession in southeastern
grasslands, and previous research has suggested that the timing of prescribed burns
can influence plant community composition and structure. We examined the response of
planted, native warm-season grasses (NWSG) at three sites in Tennessee to the timing of
annual burns conducted 2008–2011 during March, April, May, and September. The grasses
included Andropogon gerardii (Big Bluestem), Sorghastrum nutans (Indiangrass), Panicum
virgatum (Switchgrass), Schizachyrium scoparium (Little Bluestem), and Bouteloua curtipendula
(Sideoats Grama). We monitored vegetation response once each summer during
July or August). We used mixed-model ANOVAs to analyze the effect of treatment on bare
ground (no plant cover), forbs desirable for Northern Bobwhite, and each NWSG species
individually for each location. Although NWSG did not show strong responses to season
of burn, Switchgrass cover appeared to be increased by spring burns when compared to the
control plots. Forb cover was sparse (<10%) throughout the study, and four years of burning
did not stimulate forbs. Therefore, in high-rainfall environments, soil disturbance may be
necessary to reduce grass cover and stimulate forb cover in dense stands of planted NWSG.
Introduction
There is a long history of fire in the southeastern United States (Pyne 1982,
Stewart 2009, Wright and Bailey 1982). This history includes natural fires started
by lightning and human-induced fires ignited to manage game and increase forage
production (Stewart 2009). Native warm-season grasses (NWSG) such as Andropogon
gerardii Vitman (Big Bluestem), Sorghastrum nutans (L.) Nash (Indiangrass),
Panicum virgatum L. (Switchgrass), Schizachyrium scoparium (Michx.)
Nash (Little Bluestem), and Bouteloua curtipendula (Michx.) Torr. (Sideoats
Grama) were once common in the Southeast, but coverage of these grasses has
been greatly reduced as a result of fire suppression and moden agricultural practices
(Nagahama and Norrmann 2012, Noss 2012). USDA Farm Bill programs, such as
the Environmental Quality Incentives Program (EQIP) and Conservation Reserve
Program (CRP), have promoted NWSG for soil and wildlife conservation, thereby
increasing acreage of NWSG across the Southeast, particularly in Tennessee and
Kentucky (Burger 2005, USDA 2009).
12431 Joe Johnson Drive, Room 274, University of Tennessee, Knoxville, TN 37996. *Corresponding
author - charper@utk.edu.
Manuscript Editor: Brett Serviss
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Native grass plantings associated with Farm Bill programs must follow USDA
Natural Resources Conservation Service (NRCS) recommendations and requirements.
Although it is now common to include forbs when planting native grasses,
many of the early plantings only included grass species (Burger et al. 1990, Dimmick
et al. 2002). Furthermore, restoration efforts are often focused on former
cropland (USDA 2012) with a long history of agricultural production; consequently
seedbanks have become depleted of native perennial and/or pyrophytic forbs
(Batary et al. 2012, Gulden et al. 2011). With no seedbank and a lack of forbs in the
seed mix, these formerly cropped fields often lacked diversity and were comprised
solely of the species planted. Additionally, USDA-recommended seeding rates
were >8 kg PLS ha-1; rates only recommended for forage establishment (Burger
2005, Harper et al. 2007, Keyser et al. 2011) and over 4 times higher than those
currently recommended (<2 kg PLS ha-1) for grassland restoration (Harper et al.
2007, Schramm 1992, Weber 1999). As a result, many of these established NWSG
fields are dominated by dense stands of tall grass species that typically suppress
other plant species, and consequently, these stands have limited value to grasslandassociated
wildlife (Doxon and Carroll 2010, Rodgers 1999).
The influence of fire on plant communities varies depending on various factors,
such as fire frequency, intensity, and seasonality (Engle and Bidwell 2001).
Often, fire intensity and seasonality are related; growing-season burns are usually
less intense than dormant-season burns (Sapsis and Kauffman 1991, Weir 2009).
However, growing-season burns generally have higher residency times, whereas
dormant-season burns have faster rates of spread. Differences in plant response
have been noted between dormant- and growing-season fires (Engle and Bidwell
2001, Harper and Gruchy 2009, Limb et al. 2011). Burning during the growing
season has been used to decrease woody species and stimulate increased forb cover
(Fuhlendorf and Smeins 1997, Gruchy et al. 2006, Winter et al. 2012). This is an
important consideration when working in low diversity, grass-dominated stands
where the goal is to increase forb cover to enhance habitat for pollinators and other
wildlife species.
Phenology varies among NWSG species. Switchgrass is one of the earliest grasses
to break dormancy, and its leaves usually begin to emerge in late March or early
April; growth peaks in early June (Beatty et al. 1978). Big Bluestem and Indiangrass
initiate growth later than Switchgrass, and peak production in these species occurs in
late June and early July. Little Bluestem is one of the last warm-season grasses to initiate
growth in the spring and its growth peaks in early July (Harper et al. 2007).
Our main objective was to examine the vegetation community response of
planted NWSG stands to seasonality of fire. In Tennessee, active growth of NWSG
typically begins in April, when average daily temperatures reach 16 °C, and continues
until senescence in early fall (Harper et al. 2007, NOAA 2012). Therefore,
we examined the vegetation response to fires conducted during the dormant season
(March), early growing season (April), growing season (May), and late growing
season (September). We hypothesized that forb cover would increase and that
NWSG cover would decrease with growing-season fire (April, May, and SepSoutheastern
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tember). Further, we hypothesized that the response of specific grasses would be
dependent on how closely the active growth period overlapped with each burn. For
example, a burn conducted during the growing season in May would more negatively
impact Switchgrass cover than a similar burn conducted during the dormant
season in March.
Field-site Descriptions
We conducted this research at three sites across Tennessee: Ames Plantation
Research and Education Center (Ames), Grand Junction, TN (35.08°N, 89.08°W),
West Tennessee Research and Education Center (West TN), Jackson, TN
(35.62°N, 88.85°W), and Yuchi Wildlife Management Area (Yuchi), Dayton,
TN (35.58°N, 84.84°W) (Fig. 1). Annual rainfall at these sites averaged more
than 1270 mm (NOAA 2012). At each site, we established research plots on land
with a history of >50 yr of agricultural production (i.e., Zea mays L. [Corn], Glycine
max (L.) Merr. [Soybeans], and Gossypium hirsutum L. [Cotton]). Although
plot sizes varied somewhat among sites based on space available to install the experiment,
minimum plot size was 19.8 × 30.5 m. We disked to maintain 7.7-m
wide firebreaks between plots. Grasses had been planted at the USDA NRCS-recommended
rate of 9–11 kg PLS ha-1 (USDA 2002) at each site. Ames was planted
with a mix of Big Bluestem, Indiangrass, and Switchgrass. West TN was
planted with a mix of Big Bluestem, Indiangrass, Switchgrass, Little Bluestem,
and Sideoats Grama. Yuchi was planted with a mix of Big Bluestem, Indiangrass,
Little Bluestem, and Switchgrass. Establishment year varied among the sites but
in all cases occurred between 2001–2006.
Methods
We installed four blocks of five treatments for a total of 20 plots at each location
in a randomized block design with blocking based on soils and slope position. The
treatments consisted of annual prescribed burns which were conducted at 20–50%
relative humidity, 16–32 °C air temperature, and 3–19 kmh-1 wind speed. Treat-
Figure 1. Location of three study sites used for fire seasonality experiments in Tennessee,
2008–2011.
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ments were applied to examine fire responses to dormant, early growing season,
growing season, and late growing season. These treatments corresponded to the
following dates, respectively: 1 March, 15 April, 15 May, and 1 September or at
the first opportunity thereafter with acceptable burning conditions; each block of
treatments included an unburned control. We did not examine burns applied in June,
July, or August because relative humidity levels and fuel moisture precluded any
burning during this period. We initiated prescribed burns in 2008 and conducted
burns annually until completion of the study in September 2011.
In July and August of each year, we monitored vegetation with two, 10-m line
transects in each plot (Canfield 1941). We identified plants that intercepted the line
to species and measured the horizontal distance covered by the plant.
We selected Big Bluestem, Indiangrass, Switchgrass, Little Bluestem, Sideoats
Grama, bare ground, and forbs desirable for Colinus virginianus L. (Northern Bobwhite)
to evaluate responses to timing of fire. We did not analyze litter because it
was highly correlated with time since burn and date of sampling. We did not include
trees, shrubs, or vines in our analyses because they occurred in <1% of the plots. We
classified forbs as beneficial to Northern Bobwhite following Brennan and Hurst
(1995) and Sudkamp et al. (2008). Beneficial forbs included Ambrosia spp. (ragweed),
Desmodium spp. (ticktrefoil), Chamaecrista fasciculata Michx. (Partridge
Pea), and Solidago spp. (goldenrod), which, collectively, comprised 95% of forbs
documented. We calculated the linear cover (cm) per transect for each taxon and
divided that value by the total transect length to determine percent cover for each
species. We transformed the percentage data using arcsine square-root transformation
(Dowdy et al. 2004) to meet the assumption of normality. Subsequently, we
back-transformed data for graphical display. We analyzed the effect of treatment
after averaging the subsamples (n = 2) to obtain a single annual observation for
each plot. We analyzed cover (dependent variable) using the MIXED procedure
(SAS Institute 2010) with repeated measures. Year was the repeated measure,
and plot was the subject. Compound symmetry was selected as the covariance
structure based on Akaike’s information criteria comparisons. We tested effects of
year, month of burn, and year × month of burn interaction on the seven vegetation
variables. We analyzed year and treatment (month of burn) as fixed effects. We
performed the analysis for each location separately because each one represented a
separate experiment and had been established using different grass species. Where
tests for fixed effects were significant (P < 0.05), we used the least square means
procedure to examine relationships among individual means.
Results
Over all treatments and years, vegetation cover was dominated by one or two
species at each location: Big Bluestem (>76%) at Ames, Switchgrass (41%) and
Big Bluestem (27%) at Yuchi, and Indiangrass (28%) and Little Bluestem (25%)
at West TN (Table 1). At Ames, there was not a year × month of burn interaction
for Big Bluestem, Indiangrass, bare ground, or forbs (P ≥ 0.1; Table 2), therefore,
subsequent analyses were pooled among years for these variables. Big Bluestem
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Table 1. Mean percent cover (± 1 SE) of dominant vegetation on three sites in Tennessee during fire
seasonality experiment, 2008–2011.
Ames West TN Yuchi
Dominant cover Mean SE Mean SE Mean SE
Bare ground 6.2 1.3 17.7 2.9 0.6 0.4
Big Bluestem 75.4 4.2 1.3 0.5 27.2 4.7
ForbA 2.5 1.3 1.8 0.7 1.4 0.6
Indiangrass 3.1 1.1 28.5 4.3 1.0 1.0
Little Bluestem 0.1 0.9 25.7 4.1 0.0 0.5
Sideoats Grama 0.0 0.0 2.4 1.3 0.0 0.0
Switchgrass 0.0 0.1 2.3 0.9 45.1 7.4
WoodyB 0.0 0.02 0.0 0.0 1.6 0.4
Sum of dominant vegetationC 87.3 79.8 77.0
AForbs desirable for wildlife were classified following Brennan and Hurst (1995) and Sudkamp et
al. (2008). This included Ambrosia spp. (ragweed), Desmodium spp. (ticktrefoil), Chamaecrista
fasciculata (Partridge Pea), and Solidago spp. (goldenrod).
BWoody cover consists of shrub and tree cover (e.g., Rubus spp. [blackberry], Rhus spp. [sumac].
COther cover not listed in this table includes other forbs (e.g., Lespedeza cuneata (Dum. Cours.) G.
Don. [= Seicea lespedeza]), cool-season grasses, litter, rushes, and vines.
Table 2. F- statistics and P-values for main effects in mixed ANOVA model examining vegetationcover
response to a fire seasonality experiment in Tennessee, 2008–2011. Treatment df = 4, 60; year
df = 3, 60; treatment x year df = 12, 60.
Location Dependent variable Effect F-value P-value
Ames Bare ground Treatment 2.34 0.06
Year 0.88 0.4
Treatment x year 1.57 0.1
Big Bluestem Treatment 5.1 0.001
Year 2.39 0.07
Treatment x year 0.36 0.9
Forbs Treatment 11.44 <0.0001
Year 1.05 0.3
Treatment x year 0.68 0.7
Indiangrass Treatment 3.51 0.01
Year 6.59 0.0006
Treatment x year 1.41 0.1
Little Bluestem Treatment 1 0.4
Year 1 0.3
Treatment x year 1 0.4
Sideoats Grama Treatment - -
Year - -
Treatment x year - -
Switchgrass Treatment - -
Year - -
Treatment x year - -
cover was least with the May burns (65%) compared to March, April, and September
burns (> 81%) (Fig. 2a). Indiangrass cover was <10% in all treatments and only
differed between April and September burns (Fig. 2b). Bare ground was greater
with May burns (7%) compared to control plots (2.5%) (Fig. 2c). Forb cover was
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greater in May burns (P < 0.0001), averaging 8.5% versus 1% in other treatments
(Fig. 2d). At Ames, we did not detect differences in cover among treatments for
Little Bluestem (P = 0.4). There was not enough cover (<1%) of Switchgrass or
Sideoats Grama for analysis.
At West TN, we did not detect differences in cover among treatments for Big
Table 2, continued.
Location Dependent variable Effect F-value P-value
West TN Bare ground Treatment 12.76 <0.0001
Year 12.86 <0.0001
Treatment x year 3.6 0.0005
Big Bluestem Treatment 0.44 0.7
Year 0.47 0.7
Treatment x year 1.16 0.3
Forbs Treatment 0.83 0.5
Year 3.25 0.02
Treatment x year 0.52 0.8
Indiangrass Treatment 8.3 <0.0001
Year 15.41 <0.0001
Treatment x year 1.57 0.1
Little Bluestem Treatment 5.95 0.0004
Year 14.54 <0.0001
Treatment x year 4.43 <0.0001
Sideoats Grama Treatment 1.4 0.2
Year 6.14 0.001
Treatment x year 1.44 0.1
Switchgrass Treatment 1.64 0.1
Year 1.07 0.3
Treatment x year 0.82 0.6
Yuchi Bare ground Treatment - -
Year - -
Treatment x year - -
Big Bluestem Treatment 8.48 <0.0001
Year 1.25 0.2
Treatment x year 3.01 0.002
Forbs Treatment 2.61 0.04
Year 6.96 0.0004
Treatment x year 1.04 0.4
Indiangrass Treatment 1.44 0.2
Year 3.09 0.03
Treatment x year 1.42 0.1
Little Bluestem Treatment - -
Year - -
Treatment x year - -
Sideoats Grama Treatment - -
Year - -
Treatment x year - -
Switchgrass Treatment 20.32 <0.0001
Year 8.18 0.0001
Treatment x year 1.08 0.3
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Bluestem, Switchgrass, Sideoats Grama, and Forbs (P ≥ 0.1). There was not a
year × month of burn interaction for Indiangrass (P = 0.1; Table 2), therefore,
subsequent analyses were pooled among years for this species. Indiangrass
cover was greatest with September burns (36%) and least in control plots (14%)
(Fig. 3a). There was a year × month-of-burn interaction for Little Bluestem (P <
0.0001; Table 2), therefore, subsequent analyses were by year. Little Bluestem
cover was greatest in 2008 in the control plots (60%), but declined for that treatment
in subsequent years (40, 10, and 10%, respectively; Fig. 3b). In 2009 and
2010, Little Bluestem cover was least with May burns and greatest with March
burns. There was a two-way interaction (P < 0.0001) for bare ground, and subsequent
analyses were by year. Bare ground was least in control plots in 2008, 2009,
and 2010 and remarkably high (44%) for the March 2010 burn plot (Fig. 3c).
Indiangrass cover varied by year (Fig. 4) and cover was reduced in 2010 and 2011
vs. the first two years.
At Yuchi, there was a year × month of burn interaction in the analysis of Big Bluestem;
therefore, subsequent analyses were by year for this species. In 2008,
Big Bluestem cover was greatest in the control plots (23%) and lowest with the April
burn plots (1%). However, in 2009, there was little cover of Big Bluestem in control
Figure 2. Least-square means (± 95% CI) for vegetation characteristics at Ames on seasonality
of burn plots sampled in July–August, 2008–2011: a) Big Bluestem, b) Indiangrass,
c) bare ground, and d) forbs. Means with different letters differ (P < 0.05) but where years
are shown, only within years.
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Figure 3. Least-square
means (± 95% CI) for
vegetation characteristics
at West TN on
seasonality of burn
plots sampled in July–
August, 2008–2011: a)
Indiangrass, b) Little
Bluestem, and c) bare
ground. Means with
different letters differ
(P < 0.05) but where
years are shown, only
within years.
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2014 Vol. 13, No. 2
plots (3%) and April burn plots (1%). In 2010, March burn plots contained the greatest
Big Bluestem cover (26%). In 2011, Big Bluestem cover was greatest (21%) with
May burns, whereas April burn plots had the least (1%) (Fig. 5a). Cover in the April
burn plots was lowest or equal to the lowest levels for any treatment over all four
years of the study. We did not detect a year × month of burn interaction in the analysis
of Switchgrass and forbs (P ≥ 0.3; Table 2); therefore, we pooled years for all subsequent
analyses. Switchgrass cover declined from March (73%) to April (51%) and
reached a low for May burn plots (20%), none of which were different from control
plots (23%) (Fig. 5b). Forb cover was minimal and differed only between March
(2.5%) and April burn plots (0.5%) (Fig. 5c). We did not detect any differences in
cover for Indiangrass by treatment. There was not enough cover of Little Bluestem,
Sideoats Grama, or bare ground cover for analysis at Yuchi (cover <1% for all three
species). With respect to year, we detected a trend in Switchgrass cover at Yuchi,
where cover was lower in 2010 and 2011 than 2008 and 2009 (Fig. 6).
Discussion
Management recommendations for NWSG usually prescribe fire as the preferred
management method (Engle and Bidwell 2001, Hall et al. 2012, Harper et al. 2007).
Our results demonstrate that fire can help to maintain dense, planted fields of native
grasses, but fire alone did not cause enough disturbance to substantially influence
Figure 4. Least-square means (± 95% CI) for Indiangrass by year at West TN on seasonality
of burn plots sampled in July–August, 2008–2011. Means with different letters differ (P <
0.05).
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Figure 5. Leastsquare
means (±
95% CI) for vegetation
characteristics
at Yuchi on seasonality
of burn plots sampled
in July–August,
2008–2011: a) Big
Bluestem, b) Switchgrass,
and c) forbs.
Means with different
letters differ (P
< 0.05) but where
years are shown,
only within years.
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2014 Vol. 13, No. 2
the plant community (as defined by percent cover and species response) in our
study areas. Across three study areas and four years of annual burning, we observed
few differences in amount of bare ground, only limited increases in forb cover at
two sites, and mixed results for the dominant grass species. These trends, though
similar in pattern, were less consistent than those reported in other grassland burning
studies conducted in semi-arid, native grassland communities that have shown
changes in the grass community as a result of burn timing (Engle and Bidwell 2001,
Limb et al. 2011).
Our results may seem somewhat contradictory to the numerous prairie studies
of Great Plains grassland communities and their response to fire. However, there
are several considerations regarding planted native grasslands in more humid environments
that suggest fire alone does not stimulate large changes in the vegetation
community. Our sites, like most stands of NWSG established in the southeastern
US over the past several decades, had a long history of row-crop production prior
to being planted in NWSG. Prescribed fire has generally been absent for decades
from sites with this cropping history. Furthermore, when native grasses are planted
at high density, space for forbs to occupy or colonize is limited (Kindscher and
Fraser 2000, McCoy et al. 2001). These factors have led to reduced plant diversity,
depleted native seedbanks, and reductions or elimination of pyrophytic vegetation
(Gulden et al. 2011). Thus, fewer plant species that respond favorably to prescribed
Figure 6. Least-square means (± 95% CI) for Switchgrass by year at Yuchi on seasonality
of burn plots sampled in July–August, 2008–2011. Means with different letters differ (P <
0.05).
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fire are present, and shifts in plant communities may be muted in the presence of
dense, tall-growing grasses in high-rainfall environments like the ones we studied.
Even after four years of annual burning, unvegetated bare ground averaged
<6% at Ames and Yuchi. Although we did not specifically measure openness at
ground level, average NWSG cover measurements on all sites was >80%, verifying
plant growth in these fields was quite dense. Other research suggests that
additional disturbance, such as disking, may be necessary to increase openness
at ground level and stimulate forb growth (Gruchy and Harper, in press; Harper
and Gruchy 2009).
Unlike other studies that have found an increase in forb cover after summer
burns (e.g., Howe 2011, Towne and Kemp 2008), we did not detect a season-ofburn
response among forb species. Although treatment effect on forb cover was
statistically significant at two of three sites, the effect was probably not biologically
important. Seeding rates for all of our locations were high compared to those typically
used for ecological restoration (Packard and Mutel 2005) and growth of forb
species can be inhibited by high seeding densities of dominant grasses (Dickson
and Busby 2009, Kindscher and Fraser 2000, Weber 1999). Furthermore, dense
stands of grass can outcompete forbs that may be present and prevent the seedbank
from responding to disturbance, including fire (Zimmerman et al. 2008). These
established fields had very little unvegetated bare ground, which limited possible
areas where forbs could have germinated and grown (T eague et al. 2008).
Response of dominant grasses was mixed. Little Bluestem at West TN (the only
site where it was relatively common) showed some indication that March burns resulted
in the greatest cover and May burns the least cover, but these patterns were
only present in two of four years. Likewise, Indiangrass, which was only common
at West TN, did not show a strong response pattern among burning treatments. Indiangrass
cover was greater in September burn plots than in the control plots and
appeared to decrease across all treatments over the course of the study. However,
other than the comparison with the control plots, the magnitude of the effect was not
large relative to other burning treatments (i.e., 37% vs. 21, 24, and 31%). At Ames,
Big Bluestem, the only common grass species, showed a reduction in cover with May
burns, but the magnitude of the response was not large relative to other burn treatments
(i.e., 65% vs. 80, 81, and 84%) and was not different from the control plots.
Interestingly, at Yuchi, Big Bluestem showed a marked decrease in all 4 years with
the April burns. The reason for this apparent discrepancy between Ames and Yuchi
(May vs. April) for this species is not clear, but it may have been that Switchgrass,
which was abundant at Yuchi, and is a species with an earlier phenology than Big
Bluestem, outcompeted this species during April. Switchgrass, which was only
common at Yuchi, showed the strongest response to fire and its cover progressively
increased from May to April to March burns. Furthermore, the magnitude of the response
was impressive (73, 51, and 20%, respectively for March, April, and May).
However, Switchgrass cover in May burn plot 3 was similar to Switchgrass cover in
the control plots. This finding suggested that Switchgrass cover increased with March
and April burns, likely the result of competitive release by removing litter and other
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cover. As was the case with Indiangrass at West TN, there appeared to be a modest
overall decrease in Switchgrass cover at Yuchi over the course of the study.
Contrary to what we hypothesized, we did not document consistent responses
to timing of fire for all of the grass species. Likely, fire timing and plant phenology
interacted to some degree and led to the differential responses we observed.
Of the species examined, Switchgrass was the most strongly influenced by fire.
The nature of this response seems consistent with Switchgrass phenology in that
when fires occurred before initiation of spring growth (March), Switchgrass cover
was greater than what we measured in the control plots or for any other fire
treatment. Later fires that occurred as spring growth progressed, resulted in reduced
cover, presumably by impacting actively growing plants. The response of
later-maturing Big Bluestem at Ames seems to be consistent with its phenology.
However, the magnitude of the effect was not as dramatic because Big Bluestem
dominated the site with >75% cover. Treatment effects on Big Bluestem at Yuchi
were more obvious, presumably as a result of the interaction of fire and the
greater abundance of the earlier-maturing species, Switchgrass. Indiangrass, the
latest-maturing of the dominant species on our sites, appeared to be positively
influenced by the late growing-season burn. This effect may have been a result
of Indiangrass’ later phenology, and it may have been able to grow actively for
several weeks after the burn, before it entered fall dormancy, whereas other species
were already senescing.
We did not observe substantial reductions in the competitive position of these
grasses. However, because burning is effective in limiting woody encroachment
and reducing thick thatch that can accumulate over time, we recommend prescribed
fire when managing planted NWSG. We further recommend managers implement
heavy disking or periodic heavy grazing to reduce grass density where needed and
maintain an early seral stage. Soil disturbance not only may diversify plant species
composition by stimulating the seedbank to germinate, but also creates more
open structure at ground level that is desirable for many wildlife species, including
Northern Bobwhite. Our results suggest that fire can be applied to dense, planted
stands of NWSG at various times of the year, providing increased opportunities for
landowners and managers with respect to burning season.
Acknowledgments
This project would not have been possible without the assistance of A. Houston (Ames),
B. Hayes (West TN), B. Sweeney (Yuchi), and the support of their staff at Yuchi Wildlife
Management Area and Ames Plantation and West Tennessee Research and Education Centers.
We also wish to thank J. Gruchy, S. Barrioz, A. West, C. Smithson, and A. Blackburn-
Haynes for their assistance in collecting data.
Literature Cited
Batary, P., A. Holzschuh, K.M. Orci, F. Samu, and T. Tscharntke. 2012. Responses of plant,
insect, and spider biodiversity to local and landscape-scale management intensity in
cereal crops and grasslands. Agriculture Ecosystems and Environment 146:130–136.
Southeastern Naturalist
E. Holcomb, P. Keyser, and C. Harper
2014 Vol. 13, No. 2
234
Beatty, E.R., J.L. Engel, and J.D. Powell. 1978. Tiller development and growth in switchgrass.
Journal of Range Management 31:361–365.
Brennan, L.A., and G.A. Hurst. 1995. Summer diet of Northern Bobwhite in eastern Mississippi:
Implications for habitat management. Southeastern Association of Fish and
Wildlife Agencies 49:516–524.
Burger, L.W., Jr. 2005. The Conservation Reserve Program in the Southeast: Issues affecting
wildlife habitat value. Pp. 135–141, In A.W. Allen and M.W. Vandever (Eds.).
The Conservation Reserve Program: Planting for the Future. Proceedings of a National
Conference. US Government Printing Office, Biological Science Report, USGS/BRD/
BSR-2006-5145, Washington, DC.
Burger, L.W., Jr., E.W. Kurzejeski, T.V. Dailey, and M.R. Ryan. 1990. Structural characteristics
of vegetation in CRP fields in northern Missouri and their suitability as Bobwhite
habitat. Transactions of the 55th North American Wildlife and Natural Resources Conference:
74–83.
Canfield, R.H. 1941. Application of the line-intercept method in sampling range vegetation.
Journal of Forestry 39:388–394.
Dickson, T.L., and W.H. Busby. 2009. Forb species establishment increases with decreased
grass-seeding density and with increased forb-seeding density in a northeast Kansas,
USA experimental prairie restoration. Restoration Ecology 17:597–6 05.
Dimmick, R.W., M.J. Gudlin, and D.F. McKenzie. 2002. The Northern Bobwhite conservation
initiative. Miscellaneous publication of the Southeastern Association of Fish and
Wildlife Agencies, Columbia, SC.
Dowdy, S., S. Wearden, and D. Chilko. 2004. Statistics For Research. John Wiley and Sons,
Hoboken, NJ.
Doxon, E.D., and J.P. Carroll. 2010. Feeding ecology of Ring-necked Pheasant and Northern
Bobwhite chicks in conservation reserve program fields. Journal of Wildlife Management
74:249–256.
Engle, D.M., and T.G. Bidwell. 2001. Viewpoint: The response of central North American
prairies to seasonal fire. Journal of Range Management 54:2–10.
Fuhlendorf, S.D., and F.E. Smeins. 1997. Long-term vegetation dynamics mediated by
herbivores, weather, and fire in a Juniperus-Quercus savanna. Journal of Vegetation
Science 8:819–82
Gruchy, J.P. and C.A. Harper. In press. Effects of management practices on Northern Bobwhite
habitat. Journal of the Southeastern Association of Fish and Wildlife Agencies.
Gruchy, J.P., C.A. Harper, and M.J. Gray. 2006. Methods for controlling woody invasion
into CRP fields in Tennessee. P. 315–321, In S.B. Cederbaum, B.C. Faircloth, T.M. Terhune,
J.J. Thompson, and J.P. Carroll (Eds.). Gamebird 2006: Quail VI and Perdix XII,
Warnell School of Forestry and Natural Resources, Athens, GA.
Gulden, R.H., D.W. Lewis, J.C. Froese, R.C. Van Acker, G.B. Martens, M.H. Entz, D.A.
Derksen, and L.W. Bell. 2011. The effect of rotation and in-crop weed management on
the germinable weed seedbank after 10 years. Weed Science 59:553–561.
Hall, S.L., R.L. McCulley, and R.J. Barney. 2012. Restoration of native warm-season grassland
species in a Tall Fescue pasture using prescribed fire and herbicides. Restoration
Ecology 20:194–201.
Harper, C.A., and J.P. Gruchy. 2009. Conservation practices to promote quality early-successional
wildlife habitat. Pp. 87–115, In L.W. Burger, Jr., and K.O. Evans (Eds.). Managing
working lands for Northern Bobwhite: The USDA Natural Resource Conservation
Service (NRCS) Bobwhite Restoration Project. Washington, DC. 222 pp.
Southeastern Naturalist
235
E. Holcomb, P. Keyser, and C. Harper
2014 Vol. 13, No. 2
Harper, C.A., G.E. Bates, M.P. Hansbrough, M.J. Gudlin, J.P. Gruchy, and P.D. Keyser.
2007. Native Warm-Season Grasses: Identification, Establishment, and Management for
Wildlife and Forage Production in the Mid-South. University of Tennessee Extension
Publication PB1752, University of Tennessee, Knoxville, TN. 189 pp.
Howe, H.F. 2011. Fire season and prairie-forb richness in a 21-y experiment. Ecoscience
18:317–328.
Keyser, P., C. Harper, G. Bates, J. Waller, and E. Doxon. 2011. Establishing native warmseason
grasses for livestock forage in the mid-South, University of Tennessee Extension
Bulletin SP731-B. Knoxville, TN.
Kindscher, K., and A. Fraser. 2000. Planting forbs first provides greater species diversity in
tallgrass-prairie restorations (Kansas). Ecological Restoration 18:115–116.
Limb, R.F., S.D. Fuhlendorf, D.M. Engle, and J.D. Kerby. 2011. Growing-season disturbance
in tallgrass prairie: Evaluating fire and grazing on Schizachyrium scoparium.
Rangeland Ecology and Management 64:28–36.
McCoy, T.D., E.W. Kurzejeski, L.W. Burger, Jr., and M.R. Ryan. 2001. Effects of conservation
practice, mowing, and temporal changes on vegetation structure on CRP fields in
northern Missouri. Wildlife Society Bulletin 29:979–987.
Nagahama, N., and G.A. Normann. 2012. Review of the genus Andropogon (Poaceae: Andropogoneae)
in America based on cytogenetic studies. Journal of Botany 2012. DOI
10.1155/2012/632547.
National Oceanic and Atmospheric Administration (NOAA). 2012. Climate data online.
Available online at http://www.ncdc.noaa.gov/cdo-web/. Accessed on 31 October 2012.
Noss, R.F. 2012. Forgotten Grasslands of the South: Natural History and Conservation.
Island Press, Washington, DC. 320 pp.
Packard, S., and C.F. Mutel. 2005.Tallgrass Restoration Handbook: For Prairies, Savannas,
and Woodlands. Island Press, Washington, DC. 504 pp.
Pyne, S.J. 1982. Fire in America: A Cultural History of Wildland and Rural Fire. Princeton
University Press, Princeton, NJ. 654 pp.
Rodgers, R.D. 1999. Why haven't pheasant populations in western Kansas increased with
CRP? Wildlife Society Bulletin 27:654–665.
Sapsis, D.B., and J.B. Kauffman. 1991. Fuel consumption and fire behavior associated with
prescribed fires in sagebrush ecosystems. Northwest Science 65:1 73–179.
SAS Institute. 2010. SAS/STAT User’s Guide. Version 9.3. Cary, NC.
Schramm, P. 1992. Prairie restoration: A 25-year perspective on establishment and management.
Pp. 169–177 in Proceedings of the Twelfth North American Prairie Conference.
D.D. Smith and C.A. Jacobs (Eds.). University of Northern Iowa, Cedar Falls, IA.
Stewart, O.C. 2009. Forgotten Fires: Native Americans and the Transient Wilderness. University
of Oklahoma Press, Norman, OK. 374 pp.
Sudkamp, S., R.N. Chapman, and R.A. Pierce II. 2008. Quail-friendly plants of the Midwest:
An aid to identifying plants and managing habitat. University of Missouri Extension
Publication MP903. Columbia, MO.
Teague, W.R., S.E. Duke, J.A. Waggoner, S.L. Dowhower, and S.A. Gerrard. 2008. Rangeland
vegetation and soil response to summer patch-fires under continuous grazing. Arid
Land Research and Management 22:228–241.
Towne, E.G., and K.E. Kemp. 2008. Long-term response patterns of tallgrass prairie to
frequent summer burning. Rangeland Ecology and Management 61:50 9–520.
US Department of Agriculture (USDA). 2002. Natural Resources Conservation Service
conservation practice standard, Tennessee. USDA, Washington, DC. 6 pp.
Southeastern Naturalist
E. Holcomb, P. Keyser, and C. Harper
2014 Vol. 13, No. 2
236
USDA. 2009. Summary Report: 2007 National Resources Inventory, NRCS, Washington,
DC, and Center for Survey Statistics and Methodology, Iowa State University, Ames,
IA. 123 pp. Available online at http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/
stelprdb1041379.pdf . Accessed 23 July 2012.
USDA. 2012. Conservation Reserve Program (CRP). NRCS, Washington, DC. Available
online at http://www.tn.nrcs.usda.gov/programs/CRP/ CRP.html. Accessed 23 July 2012.
Weber, S. 1999. Designing seed mixes for prairie restorations: Revisiting the formula. Ecological
Restoration 17:196–201.
Weir, J.R. 2009. Conducting Prescribed Fires: A Comprehensive Manual. Texas A&M University
Press, College Station, TX. 206 pp.
Winter, S.L., S.D. Fuhlendorf, C.L. Goad, C.A. Davis, K.R. Hickman, and D.M. Leslie, Jr.
2012. Restoration of the fire–grazing interaction in Artemisia filifolia shrubland. Journal
of Applied Ecology 49:242–250.
Wright, H.A., and A.W. Bailey. 1982. Fire Ecology: United States and Southern Canada.
John Wiley and Sons, New York, NY. 528 pp.
Zimmermann, J., S.I. Higgins, V. Grimm, J. Hoffmann, T. Munkemuller, and A. Linstadter.
2008. Recruitment filters in a perennial grassland: The interactive roles of fire, competitors,
moisture, and seed availability. Journal of Ecology 96:1033–1044.