Observations of Speyeria diana (Diana Fritillary) Utilizing Forested Areas in North Carolina that have been Mechanically Thinned and Burned
Josh W. Campbell, James L. Hanula, and Thomas A. Waldrop
Southeastern Naturalist, Volume 6, Number 1 (2007): 179–182
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2007 SOUTHEASTERN NATURALIST 6(1):179–182
Observations of Speyeria diana (Diana Fritillary) Utilizing
Forested Areas in North Carolina that have been
Mechanically Thinned and Burned
Josh W. Campbell1,*,3, James L. Hanula1, and Thomas A. Waldrop2
Abstract - Speyeria diana (Diana fritillary) is a forest dwelling butterfly that has
been eradicated from portions of its native habitat in North Carolina. This loss has
been attributed to habitat destruction and pesticide use, resulting in its status as a
species of special concern. During the spring and summer of 2003 and 2004, we
conducted butterfly surveys on forested 10-ha plots in the southern Appalachians of
North Carolina in which various forest management practices had been applied.
During one survey (June 2004), we observed male Diana fritillary butterflies feeding
on flowering Oxydendrum arboretum (sourwood) within plots that had been mechanically
thinned and burned. These plots also had the greatest herbaceous plant
cover. Our observations suggest that some forest management related disturbances,
resulting in increased herbaceous plant cover, may help in conserving this species.
Speyeria diana Cramer (Diana fritillary) is considered very rare in much
of its known range. Preferring deciduous and pine woodlands near streams,
its core habitat is the southern Appalachians from West Virginia to north
Georgia and Alabama, and the Ozark and Ouachita Mountains in Arkansas
and Oklahoma. Formerly found in southeastern Virginia (Scott 1986), the
Ohio River valley, and northeastern North Carolina (Glassberg 1999, Opler
and Malikul 1992), it is now considered extinct or a stray within these areas.
Cutting and conversion of old-growth hardwood forests to agricultural land,
is considered one of the main reasons for their decline (Hammond and
McCorkle 1983). However, Hammond and McCorkle (1983) point out that
populations in the Appalachians “appear quite healthy and may actually be
expanding with the regrowth of hardwood forests.” To further this recovery,
it is important to understand one aspect of past forest management had been
the removal of fire from the ecosystems. Here we present an observation that
forest management practices that include fire with other disturbances may
enhance food resources for the Diana fritillary.
Our study was part of the National Fire and Fire Surrogate Study
designed to examine the impacts of fuel reduction treatments on multiple
1USDA Forest Service, Southern Research Station, 320 Green Street, Athens, GA,
30602-2044. 2USDA Forest Service, Southern Research Station, 233 Lehotsky Hall,
Clemson University, Clemson, SC 29634. 3Current address - School of Sciences and
Mathematics, Shorter College, 315 Shorter Avenue, Rome, GA 30165. *Corresponding
author - firstname.lastname@example.org
180 Southeastern Naturalist Vol. 6, No. 1
components of forested ecosystems across the United States (Youngblood
et al. 2005). We sampled pollinating insects on three study blocks on the
Green River Game Management Area in the Blue Ridge Mountain Province
near Hendersonville, NC (Polk and Henderson counties). Twelve
study sites were selected on the basis of size, stand age, cover type, and
management history. Each site comprised a minimum of 14 ha to allow for
a 10-ha measurement area and a buffer of at least one tree length (approximately
20 m) around the measurement area. Treatments applied to 10-ha
plots consisted of: (1) untreated control, (2) dormant-season burn, (3)
mechanical, and (4) mechanical plus dormant-season burn. The mechanical
treatments consisted of chainsaw felling and bucking of the shrub understory,
composed primarily of Rhododendron maximum L. (rhododendron),
Kalmia latifolia L. (mountain laurel), and small diameter trees (< 7.5 cm).
Cut material was left in place for both the mechanical and mechanical-plus
-burn plots. Shrubs were cut during winter, 2001–2002, and plots that were
burned were treated on March 12 or 13, 2002.
Approximately once a month during the spring and summer, colored pan
traps and malaise traps were used to assess diversity and abundance of floral
visiting insects (Campbell 2005). Flowering plant and butterfly surveys
were also conducted each time the traps were operated. The survey consisted
of slowly walking a 200-m transect and identifying and counting each
butterfly seen. Butterfly counts during transect walks have been used effectively
to evaluate abundance and diversity (New et al. 1995, Pollard and
Yates 1993). We also identified plants that were flowering during survey
walks. Surveys were done between 10 AM and 3 PM on days with average
temperatures and weather (i.e., rainfall, wind, etc.) typical for the corresponding
time of year. Butterfly surveys allowed us to note species that were
not being captured in the pan or malaise traps and to better estimate species
richness for this group.
Herbaceous plant cover was estimated on 200 one-m2 subplots within each
10-ha treatment plot and was categorized within a series of ranges: < 1%, 1–
10%, 11–25%, 26–50%, 51–75%, and > 75%. We used the midpoint of each
range to calculate plant cover per m2 for the treatment plots. Herbaceous plant
cover was analyzed using PROC GLM (SAS 1985) to conduct two-way
ANOVAs with treatments and blocks as dependent variables, and the %
herbaceous plant cover as the independent variable. The Ryan-Einot-Gabriel-
Welsch (REGWQ; SAS 1985) multiple-range test was used to determine
differences in percent herbaceous plant cover between treatments.
Results and Discussion
During the June 17, 2004 survey, four male Diana fritillaries were observed
visiting Oxydendrum arboretum (L.) DC. (flowering sourwood) on the
three mechanical plus burn plots. Although not part of the survey, several
male S. diana were again observed visiting sourwood within the mechanicalplus-
burn treated sites when picking up traps on June 23, 2004. Speyeria diana
is considered to be a federal species of concern in North Carolina by the Fish
2007 Campbell, J.W., J.L. Hanula, and T.A. Waldrop 181
and Wildlife Service, Asheville, NC, and is also on the North Carolina Animal
Watch List compiled by the North Carolina Natural Heritage Program
(Legrand et al. 2004). Although it has a widespread distribution in the
southeastern United States, its populations are scattered and have been shown
to fluctuate greatly between years (Vaughan and Shepherd 2005). It has been
eradicated in portions of eastern North Carolina due to habitat alteration and
pesticide use (Vaughan and Shepherd 2005).
Mechanical-plus-burn treatments caused the greatest changes in basal area
of trees because increased fuel loads on the plots resulted in hotter fires and
more tree mortality (Campbell 2005). Tree mortality and the mechanical
removal of dense shrubs (mostly Rhododendron sp. and Kalmia sp.) allowed
more sunlight to reach the forest floor. Likewise, removal of competing
shrubs and some trees probably increased nutrient availability to herbaceous
plants. We observed greater herbaceous plant cover (Fig. 1), and Hutchinson
and Phillips (2006) reported greater species richness of understory plants, on
the mechanical plus burn plots, which should have increased the amount and
diversity of nectar resources available to the Diana fritillaries. Speyeria diana
depends on abundant nectar resources to maintain populations, and prescribed
fire increases nectar resources (Rudolph et al., 2006). Our observations are
consistent with Thill et al. (2004), who reported that thinning and burning on
plots in Arkansas resulted in higher abundances of the Diana fritillary due to
increased abundance of nectar resources. Thus, Hammond and McCorkle’s
(1983) observation that Speyeria spp. are indicators of native, undisturbed
ecological communities may not be complete. Our observations and those of
Thill et al. (2004) suggest that some disturbances that reduce tree and shrub
density, including prescribed burning, favor this species.
This is Contribution Number 100 of the National Fire and Fire Surrogate (FFS)
Research Project. This research was funded by the USDA Forest Service (SRS-4104)
through the National Fire Plan. Although the authors received no direct funding for
Figure 1. Average %
of herbaceous plant
cover (± st. dev.)
found among the various
treated sites on
the Green River
Area near Hendersonville,
NC. B =
burn only, C = control,
M = mechanical,
MB = mechanical
plus burn. Columns with the same letter are not significantly different at p 0.05
(Ryan-Einot-Gabriel-Welsch multiple-range test [REGWQ]; SAS 1985).
182 Southeastern Naturalist Vol. 6, No. 1
this research from the US Joint Fire Science Program (JFSP), it was greatly facilitated
by the JFSP support of existing FFS project sites. We thank D. Simon and the
North Carolina Wildlife Resources Commission for allowing us to work at the Green
River Game Management Area and for assistance in site selection and treatment
installation. R. Phillips, H. Mohr, and G. Chapman provided invaluable assistance in
plot establishment and plant surveys. We also thank D. Dyer, R. Malloy, M. Ulyshen,
and S. Horn for field assistance. We gratefully acknowledge C. Rudolph and two
anonymous reviewers for their helpful suggestions.
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