Lost and Found: Remnants of the Big Savannah and Their
Relationship to Wet Savannas in North Carolina
Author(s) :W. A. Wall, T. R. Wentworth, S. Shelingoski, J. M. Stucky, R. J.
LeBlond, and W. A. Hoffmann
Source: Castanea, 76(4):348-363. 2011.
Published By: Southern Appalachian Botanical Society
DOI:
URL: http://www.bioone.org/doi/full/10.2179/10-046.1
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CASTANEA 76(4): 348–363. DECEMBER 2011
Lost and Found: Remnants of the Big Savannah
and Their Relationship to Wet Savannas
in North Carolina
W.A. Wall,1* T.R. Wentworth,1 S. Shelingoski,2 J.M. Stucky,1 R.J. LeBlond,3 and
W.A. Hoffmann1
1
Department of Plant Biology, Box 7612, North Carolina State University, Raleigh,
North Carolina 27695-7612
2
803 Tarpon Dr., Wilmington, North Carolina 28409
3
PO Box 787, Richlands, North Carolina 28574
ABSTRACT Conversion to agriculture and plantations, development, and fire suppression
have reduced the extent of savannas in the southeastern United States, and there is a need to
catalog and classify the remaining savannas for both restoration and resource management
purposes. The Big Savannah was a wet savanna in North Carolina that was destroyed in the
1950s, and subsequent vegetation classifications have generally not accommodated well the
unique natural plant community of the Big Savannah. Vegetation reminiscent of that
described for the Big Savannah was discovered north of the original site and designated as
Wells Savannah. To evaluate the uniqueness of the savanna vegetation at Wells Savannah, we
compiled a data set from permanent quadrats with information on vegetation and
environmental variables from other Outer Coastal Plain savannas to compare with similar
data from the natural community at Wells Savannah. We also inventoried an additional 26
quadrats on a tract adjacent to Wells Savannah that had experienced fire suppression. Results
from multivariate analyses demonstrated clear differences between the Wells Savannah
quadrats and other regional wet savanna quadrats based on both vegetation and soils. A
number of species and several soil characteristics (higher clay percentage, and higher available
iron and boron) distinguish Wells Savannah from other wet savannas. Although the fire
suppressed quadrats near Wells Savannah had lower species richness, typical savanna species
such as Ctenium aromaticum and Calamovilfa brevipilis were still present. Further exploration of
fire-suppressed tracts in the area may yield more wet savanna inclusions similar to the former
Big Savannah.
INTRODUCTION
Savannas formerly covered large expanses of the southeastern
United States, with pre-European settlement
estimates of longleaf pine coverage at 37
million hectares (Frost 1993); most of this
area was occupied by savannas, which can be
defined as having a relatively open canopy
and a continuous grass understory (McPherson 1997). Savannas in the southeastern
United States in general had high species
diversity at small scales with a high percentage of clonal species. Longleaf pine savannas
*email address: [email protected]
Received November 8, 2010; Accepted June 23, 2011.
were found from east Texas to central Florida
and north into Virginia, and similar communities existed as far north as New Jersey
(Taggart 1990). Savannas were not only
geographically widespread, but occurred under a range of hydrologic regimes, from
subxeric to hydric, the latter typically saturated through the winter and early spring.
Although savannas were once dominant
across the southeastern landscape, anthropogenic activities such as fire suppression, agriculture, residential and commercial development, and timber operations have removed
roughly 97% of their area in the southeastern
United States in the last 200 years (Frost et al.
348
2011
WALL ET AL.: UNIQUE WET SAVANNAS IN NORTH CAROLINA
1986). There is a need for better classification
and understanding of the savannas which
persist in order to inform and direct management and restoration efforts.
The Big Savannah was a 607 hectare site
3 km north of Burgaw, North Carolina. The
site was studied by B.W. Wells, a prominent
early ecologist who pioneered efforts to understand southeastern savannas (or savannahs, in early 20th century spelling). Wells
spent several field seasons during the 1920s
collecting soil and vegetation data in order to
characterize the site, which culminated in a
classic 1928 work, written with his collaborator I. V. Shunk, ‘‘A Southern Upland GrassSedge Bog: An Ecological Study’’ (1928). The
site occurred on a silty soil that remained wet
through much of the year. Local residents
burned the Big Savannah every winter and
grazed cattle on the site during the spring.
Although the Big Savannah was mostly
treeless, Wells found woody sprouts of Nyssa
biflora Walter that were over 50 years old, as
wells as sprouts of Pinus palustris P. L. Mill.
and Pinus taeda L. It contained a remarkable
number of Rhynchospora species, as well as
most of the carnivorous species present in
North Carolina. Employing Clementsian concepts and terminology in wide use at the time,
Wells characterized the open grass-sedge bog
of the Big Savannah as belonging to two
consocies: the Campulosus and Panicum. The
Campulosus consocies was the more widespread of the two and tended to be wetter; it
was named after the dominant species Campulosus (now Ctenium) aromaticum (Walter)
Alph. Wood, or toothache grass. Wells classified all encountered species into groups
within each consocies. The dominants in the
Campulsosus, or ‘‘bog proper,’’ consocies
were Arundinaria tecta (Walter) Muhl., Ctenium
aromaticum, Dichanthelium ensifolium (Baldw.
ex Ell.) Gould, D. longiligulatum (Nash) Feckmann, D. wrightianum (Nash) Feckmann,
Rhynchospora chapmanii, and Scleria ciliata.
The Panicum consocies dominants included
Schizachyrium scoparium (Michaux) Nash ,
Dichanthelium consanguineum (Kunth) Gould
& Clark, D. scabriusculum (Elliott) Gould &
Clark, D. dichotomum (Linnaeus) Gould var.
roanokense (Ashe) LeBlond, Panicum virgatum
L., and Scleria triglomerata Michx. These
species were not represented in the Campulo-
349
sus consocies. A third consocies – Andropogon
– was recognized on the margin of what Wells
termed the ‘‘bog proper.’’ This consocies was
on better-drained soils and included a number of species that presumably could not
persist in the saturated soil conditions of the
bog proper.
The site was privately owned, and despite
efforts by Wells and others to preserve it for
future generations, it was sold in the 1950s.
Many erroneously believed the site was too
wet for agriculture and that preservation was
unnecessary; however, tile drainage allowed
the owner to drain the Big Savannah and
convert it into agricultural fields (Wells 1967).
Wells and others believed that this unique
community type had been extirpated from
the North Carolina landscape.
Landscape-scale classification of savanna
types has only been undertaken in the last
20 yr and the Big Savannah has either been
ignored or included with other extant community types in recent classifications. Taggart
(1990) presented the first classification of
savanna community types in the Carolinas
based on vegetation and soil characteristics
from inventory plots. The area covered included all of North Carolina and South
Carolina north of the Congaree River. Taggart
recognized five savanna categories, naming
them based on the hydrologic regime and the
associated soil order: dry, mesic and wet
Ultisols, and dry and wet Spodosols. He
classified the Big Savannah as a wet Ultisol
variant. Recently, Robert Peet (2006) presented a classification that covers the entire range
of southeastern United States savannas, dividing the southeastern United States into five
geographic regions, with further classification
of savannas within each of the regions based
on soil texture and hydroperiod. The Big
Savannah as a community is not mentioned
in Peet’s longleaf pine classification system.
In the late 1990s, an unexpected opportunity arose to study the unique vegetation
previously documented from the Big Savannah. The North Carolina Natural Heritage
Program Inventory of Pender County (LeBlond 2000) briefly described the savanna
vegetation of two powerline rights-of-way in
the northern part of the county, noting their
occurrence on the same unusual soil type
found at the former Big Savannah. Shelin-
350
CASTANEA
VOL. 76
goski et al. (2005) described this savanna in
greater detail using vegetation and soil data,
comparing the site to the Big Savannah (as
described by B.W. Wells) and other savanna
sites at nearby Holly Shelter Game Land. The
B. W. Wells Savannah—or Wells Savannah—
as the site has become known, was purchased
by the North Carolina Coastal Land Trust in
2002 and is now preserved and managed with
prescribed fire.
We have three objectives in this study: to
investigate (1) vegetation similarities between
the Big Savannah and the existing remnants
at Watha Savannah, which includes Wells
Savannah and Briary Bay Farm; (2) vegetation and soil differences of Wells Savannah
relative to other wet savannas in the Outer
Coastal Plain of North Carolina; and (3)
extent to which fire suppression may have
altered the expression of savanna vegetation
in Watha savanna. We compare recently
compiled species lists from Wells Savannah
and Briary Bay Farm with the historic list
compiled by Wells and Shunk (1928) for Big
Savannah to explore the possibility that two
remnant sites (Wells Savannah and Briary
Bay Farm) may once have had species
composition similar to that of Big Savannah.
To explore the possibility that Wells Savannah supports a community different from
previously characterized Outer Coastal Plain
wet savanna communities, we compare species composition and soil data from both
sources, using a variety of multivariate procedures. We compare vegetation data from
that site with the data from Wells Savannah
to document the effects of fire suppression
upon species composition on Briary Bay
Farm.
savannas in the Outer Coastal Plain of North
Carolina that occur on either Ultisols or
Spodosols, Wells Savannah and the surrounding area (hereafter referred to collectively as
Watha Savannah) occur mainly on the
Liddell soil series. The Liddell soil series is an
Inceptisol with poorly defined horizons and
relatively high silt content. Inceptisols are
generally young soils in humid and semihumid areas that have limited evidence of
illuviation. The Liddell soil series is geographically limited; it mainly occurs on large flats
in northern Pender County, with isolated
patches found in Wayne and Duplin Counties.
Aerial photos from the late 1930s show a
relatively open savanna landscape at Watha
Savannah, the site that includes both Wells
Savannah and Briary Bay Farm (Figure 1).
Subsequent fire suppression of the area that
now includes both Wells Savannah and
Briary Bay Farm allowed for the growth of a
progressively denser canopy for most of the
area. However part of Wells Savannah remained relatively open because of frequent
mowing of two powerline rights-of-way. Briary Bay Farm, a 243 ha privately-owned
parcel adjacent to Wells Savannah and part
of what we refer to as Watha Savannah, has
vegetation and soil characteristics similar to
Wells Savannah, but has been subject to a
different disturbance history. For most of the
20th century there was no noticeable removal
of biomass due to mowing or fire, with an
increasingly closed canopy. The site was clear
cut in the late 1990s and at present Briary Bay
Farm has a mosaic of herbaceous and woody
cover with numerous savanna species represented.
METHODS
Study Area
Objective 1: vegetation similarities between the
Big Savannah (historic reference condition) and
the existing remnants at Watha Savannah
Wells Savannah is located in the Atlantic
Coastal Plain physiographic region in northern Pender County, North Carolina (34.6595,
277.9908).The site is extremely flat with little
topographic relief. Annual rainfall averages
1,318 mm per year and average temperatures
range from a January mean minimum/
maximum temperature of 1.1uC/14.0uC and
a July mean minimum/maximum temperature of 20.6uC/32.1uC (Southeast Regional
Climate Center). In contrast to other wet
We first compiled a list of all the species that
Wells and Shunk documented in their seminal work on the Big Savannah (1928) and
updated the nomenclature. We added to the
list specimens held at the North Carolina
State University herbarium (NCSC) that were
vouchered by B.W. Wells from the Big Savannah (Krings et al. 2005). We compiled a
second list of all species identified either in
vegetation quadrats or collections made dur-
2011
WALL ET AL.: UNIQUE WET SAVANNAS IN NORTH CAROLINA
351
Figure 1. a) Map of the savannas included in this study. b) 1938 aerial photograph of Wells Savannah and
Briary Bay Farm. Photograph reveals continuous herbaceous layer with a sparse, open canopy characteristic of
southeastern savanna physiognomy.
352
CASTANEA
VOL. 76
Table 1. Wet savanna community classification. Names used in the present paper are synonymous with
the Peet classification codes. NatureServe Association codes are synonymous with the Peet classification
codes, except for 6.1.1, which includes both CEGL004501 and CEGL004086 in its concept
Peet Classification
Code (Peet in Jose
et al. 2006)
6.1.1
6.1.2
6.1.5
Not classified
Description of Community and
Dominant Species
NatureServe
Association
Pinus palustris/Sporobolus pinetorumSchizachrium-Eryngium integrifolium
woodland
Pinus palustris-Pinus serotina/Ctenium
aromaticum-Muhlenbergia expansaRhynchospora latifolia woodland
Pinus palustris-Pinus serotina/Sporobolus
pinetorum-Ctenium aromaticum-Eriocaulon
decangulare woodland
Wells Savannah plots
.CEGL004501
.CEGL004086
Dropseed-wiregrass
savanna
CEGL003660
Toothache grassmuhly savanna
CEGL004502
Muhly-dropseed
savanna
Not classified
Switch cane-inkberry
savanna
ing site visits to Watha Savannah. We
compared the species lists from the Big
Savannah and Watha Savannah and calculated the percentage overlap between the two
lists.
Objective 2: establish uniqueness of Wells
Savannah relative to other wet savannas in the
North Carolina Outer Coastal Plain
During summer 2002, ten 100 m2 quadrats
were inventoried at Wells Savannah (Shelingoski et al. 2005) using the single quadrat
protocol developed by the Carolina Vegetation Survey (CVS) (Peet et al. 1998). In this
paper, ‘‘quadrat’’ will refer to sampled areas
of 100 m2 and ‘‘plot’’ will refer to sampled
areas of 0.1 ha. These quadrats were located
in the treeless vegetation found in the regularly-mowed powerline rights-of-way (ROWs).
We then selected 25 plots from the CVS
database that were identified as representing
Outer Coastal Plain savannas at other sites
with vegetation and hydrology similar to
those of Wells Savannah. Criteria for the
selection of the CVS plots were (1) inclusion
in the Pinus palustris community type, (2)
location in the Outer Coastal Plain of North
Carolina, and (3) similar vegetation based on
preliminary multivariate analyses. The selected CVS plots were inventoried from sites that
have traditionally been described as ‘‘wet
savannas’’ that experience long hydroperiods
and host a number of obligate and facultative
wetland species. The 25 CVS plots were
previously classified by Robert Peet (unpubl.
data) into three different community-types
Names Used in the
Present Paper
using his recent classification system (Peet
2006). We denote here the Peet (2006) classes
by the common names of the two most
abundant species in the sampled plots representing each community-type (Table 1). To
use vegetation data from a consistent scale
(100 m2) and to avoid issues of spatial
autocorrelation, we randomly selected one of
the intensively-sampled 100 m2 quadrats
from each of the 25 CVS plots when more
than one intensive quadrat had been inventoried. Taxonomic nomenclature follows
Weakley (2010).
Soil sampling protocol for all quadrats,
including the quadrats selected from the CVS
savanna plots, followed the methods outlined
in the CVS protocol (Peet et al. 1998). Briefly,
soil samples for all quadrats were sampled
from the top 10 cm of the A horizon.
Subsurface soil samples were collected for all
quadrats but were not included in the analyses. Brookside Laboratories (308 South Main
St., New Knoxville, Ohio 45871) performed
nutrient and texture analysis for all CVS
quadrats and nutrient analysis for the Wells
Savannah quadrats. Texture analysis of the
Wells Savannah quadrats was performed at
the North Carolina State University soil
laboratory using the methods of Gee and
Bauder (1986). The following soil properties
were measured for all quadrats: Cation exchange capacity (CEC), pH, organic abundance (percentage loss on ignition), sulfur
(ppm), phosphorus (ppm), calcium (ppm),
magnesium (ppm), potassium (ppm), sodium
(ppm), boron (ppm), iron (ppm), manganese
2011
WALL ET AL.: UNIQUE WET SAVANNAS IN NORTH CAROLINA
(ppm), copper (ppm), zinc (ppm), aluminum
(ppm), calcium (as percentage of base saturation), magnesium (as percentage of base
saturation), potassium (as percentage of base
saturation), sodium (as percentage of base
saturation), and percentage base saturation
We performed two multi-response permutation procedures (MRPP) to test the hypotheses that the 10 Wells Savannah quadrats
from the powerline ROWs differ from other
wet savanna quadrats from the region (as a
single group of 25 quadrats) in terms of (1)
vegetation and (2) soil characteristics. For all
subsequent analyses, we constructed vegetation and soil data matrices. The matrix
elements for the vegetation consisted of cover
values for species in specific quadrats, while
the soil data matrix elements were based on
the results from Brookside Laboratories. No
transformations or standardizations were performed, and we did not remove infrequent
species. For the vegetation data we used the
Sorenson distance measure and for the soil
data we used a Euclidean distance measure.
MRPP was performed using the R package
vegan (Oksanen et al. 2009). To further
evaluate the relationship of the vegetation
in the powerline ROWs at Wells Savannah to
vegetation in other regional wet savannas
(again, combined as a single group), we
performed an indicator species analysis (ISA)
(Dufrêne and Legendre 1997) to identify
diagnostic species. ISA is a multivariate
technique that allows one to identify species
that are good ‘‘indicators’’ of a priori groups of
sampling units–in our case, quadrats belonging to either Wells Savannah or to the other
wet savannas. All analyses were performed
using the R statistical platform (R Development Core Team 2010); ISA was performed
using the R package labdsv (Roberts 2010).
We then used cluster analysis and nonmetric multidimensional scaling ordination
(NMDS) to analyze how a priori classification
(see above) of the Wells Savannah and other
wet savanna quadrats into the four community types (Table 1) reflected observed vegetation patterns in the data set. For the cluster
analysis we selected the flexible beta linkage
method (b 5 20.25), using the agnes()
function in the R package cluster (Maechler
et al. 2005). For both the cluster analysis and
the NMDS ordination, the response variable
353
was abundance values for each species within
quadrats. We used the Sorenson distance
measure, which is less susceptible to loss of
sensitivity with increasing environmental or
species distances relative to many other
distance measures (McCune and Grace
2002). For the ordination, we used the nmds()
function in the R package labdsv (Roberts
2010) with k 5 2, a starting configuration
based upon principal coordinates analysis,
and the maximum number of iterations set to
100. Environmental vectors were displayed
using the envfit function in vegan (Oksanen
et al. 2000).
To identify important soil characteristics
correlated with a priori savanna community
types (again, the four types shown in Table 1)
we used the Random ForestTM (RF) method of
classification (Breiman 2001) in the R package randomForest (Liaw and Wiener 2002).
RF is a classification method similar to
classification and regression trees (CART),
but instead of relying on a single tree, the
method generates multiple trees and averages
the results. For most data sets the method has
lower misclassification rates relative to other
methods (Cutler et al. 2007). The soil variables that were included were CEC, pH,
organic abundance, S, Ca (ppm), Mg (ppm),
K (ppm), B (ppm), Fe (ppm), Mn (ppm), Cu
(ppm), Zn (ppm), Al (ppm), percentage base
saturation, Ca/Mg ratio, percent clay and
percent silt. We generated 1,000 trees and, for
each node in the tree, we specified that the
algorithm randomly select three candidate
variables and sample with replacement. We
calculated importance values (mean decrease
in accuracy) for each included variable.
Higher importance values indicate that a
variable is a better predictor of group membership (Breiman 2001). We used NMDS with
the same parameter settings as above to
graphically represent the distance between
quadrats based on soil characteristics.
Objective 3: determine extent to which fire
suppression may have altered savanna
expression in Watha Savannah
During the summer 2005, we sampled an
additional 26 100 m2 quadrats from Briary
Bay Farm. We started by dividing Briary Bay
Farm into 30 compartments for a projected
fire study. The centroid of each compartment
354
CASTANEA
was located and a 0.1 ha plot was centered on
it, and each of the 10 quadrats in the plot was
designated as either ‘‘woody’’ or herbaceous’’
based on the amount of woody encroachment. We selected one of the quadrats
designated ‘‘herbaceous’’ for intensive sampling. Sampling and soil analyses followed
the same protocol as for the Wells Savannah
quadrats. To analyze the effects of different
disturbance histories on Watha Savannah, we
compared the mean species richness per
quadrat and total number of species for the
Wells Savannah and Briary Bay Farm datasets using a t-test. To compare the total
species richness based on equal-area samples,
we bootstrapped the fire-suppressed quadrats
from Briary Bay Farm 1,000 times by randomly sampling 10 quadrats without replacement and calculating the total number of
species in the sample. In addition, we used
NMDS ordination to compare the vegetation
of the Wells Savannah and Briary Bay Farm
quadrats following the same procedures described previously for the analysis of the wet
savanna quadrats. For this final ordination,
we also included data from two additional
quadrats sampled during the summer of 2002
in the fire-suppressed woodland between the
two powerline ROWs at Wells Savannah
(Shelingoski et al. 2005).
RESULTS
Objective 1
Of the species either documented by Wells
and Shunk (1928) as present at the Big
Savannah or vouchered at NCSC by Wells
(but not included in the 1928 publication),
45% were documented from the quadrats
inventoried from either Wells Savannah or
Briary Bay Farm. In addition, 66% of the
species documented by Wells have also been
found at either Wells Savannah or Briary Bay
Farm, either in inventoried quadrats or as
collections. Of the 13 species that Wells and
Shunk (1928) described as dominants in one
of the three described vegetation consocies, 12
have been documented at Wells Savannah
and/or Briary Bay Farms, and 18 of the 23
species described as sub-dominants have been
found at Wells Savannah and/or Briary Bay
Farm. The Campulosus (Ctenium) consocies –
the community described by B. W. Wells that
most closely resembles Wells Savannah –
VOL. 76
included a number of dominants that also
had high cover values in the Wells Savannah
quadrats. These include Arundinaria tecta,
Ctenium aromaticum, Rhynchospora chapmanii
(data available from the authors).
Objective 2
Multi-response
permutation
procedure
(MRPP) results demonstrated significant differences in species composition (A 5 0.08,
P-value , 0.001) and soil characteristics (A 5
0.07, p-value 5 0.002) between the 10 Wells
Savannah quadrats and the 25 quadrats from
Outer Coastal Plain wet savannas (as a single
group). MRPP results include a measure of
within-group homogeneity (A), the chancecorrelated within-group agreement, along
with a significance estimate (p-value). Larger
A values indicate more homogeneous groups.
For community data, A values are typically
less than 0.1, and a value of 0.3 is considered
high (McCune and Grace 2002).
Indicator species analysis (ISA) comparing
the 10 Wells Savannah quadrats to the 25
quadrats from Outer Coastal Plain savannas
identified 43 species – 26 for Wells Savannah
and 17 for other wet savannas—with indicator values (IV) greater than 0.25 and P-values
, 0.05 (Table 2); examples include Arundinaria tecta, Dichanthelium scabriusculum, and
Lycopodiella alopecuroides (L.) Cranfill as indicators of Wells Savannah and Bigelowia
nudata (Mich.) DC. and Aristida stricta Mich.
as indicators of the other Outer Coastal Plain
savannas.
Cluster analysis of vegetation compositional data separated the 10 Wells Savannah
quadrats from the 25 other wet savanna
quadrats at the first division of the dendrogram (Figure 2). Non-metric multidimensional scaling (NMDS) ordination also separated
the Wells Savannah quadrats from those
representing other wet savanna communitytypes (Figure 3). In addition, soil variables
(with R2 in parentheses) associated with axis
1 included Fe (ppm) (0.33), percentage clay
(0.43), and B (ppm) (0.31) – all increasing
along axis 1. Mg (ppm) (0.24) and Na (ppm)
(0.28) decreased along axis 2, with Ca (ppm)
(0.44), pH (0.33), and percentage base saturation (0.36) increasing. Despite the clear
separation of the Wells Savannah quadrats
(labeled as switch cane-inkberry) from the 25
quadrats representing other wet savanna
2011
WALL ET AL.: UNIQUE WET SAVANNAS IN NORTH CAROLINA
355
Table 2. Indicator species analysis comparing Wells Savannah quadrats to those from other wet savannas
in the Outer Coastal Plain of North Carolina. Species included have significance values less than 0.05 and
indicator values (IV) greater than 0.25 (scale 0 to 1). Group values: 1 = other wet savanna quadrats, 2 =
Wells Savannah quadrats
Scientific Name
Group
IV
P
Aristida stricta Michx.
Bigelowia nudata (Michx.) DC var. nudata
Calopogon pallidus Chapman
Coreopsis linifolia Nutt.
Dionaea muscipula Ellis
Lachnocaulon anceps (Walt.) Morong
Morella cerifera (L.) Small
Pinus palustris P. Mill.
Pityopsis graminifolia (Michx.) Nutt.
Rhynchospora baldwinii Gray
Rhynchospora plumosa Ell.
Sisyrinchium capillare E.P. Bicknell
Sporobolus pinetorum Weakley & P. M. Pet.
Symphyotrichum dumosum (L.) Nesom
Viola primulifolia L.
Xyris caroliniana Walt.
Acer rubrum L.
Amelanchier spicata (Lamarck) K. Koch.
Andropogon glomeratus (Walt.) B.S.P.
Andropogon mohrii (Hack.) Hack. ex Vasey
Andropogon perangustatus Nash
Andropogon virginicus L.
Aronia arbutifolia (L.) Persoon
Arundinaria tecta (Walt.) Muhl.
Clethra alnifolia L.
Coreopsis falcata Boynt.
Dichanthelium scabriusculum (Ell.) Gould & C.A. Clark
Eupatorium rotundifolium L.
Euthamia caroliniana (L.) Greene ex Porter & Britt.
Hypericum densiflorum Pursh
Lachnanthes caroliana (Lam.) Dandy
Lycopodiella alopecuroides (L.) Cranfill
Lyonia ligustrina (L.) DC.
Mitreola sessilifolia (J.F. Gmel.) G. Don
Rhexia lutea Walt.
Rhynchospora chapmanii M.A. Curtis
Rhynchospora filifolia Gray
Rhynchospora inexpansa (Michx.) Vahl
Scleria minor W. Stone
Smilax laurifolia L.
Zigadenus glaberrimus Michx.
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
0.667
0.778
0.444
0.586
0.407
0.519
0.491
0.593
0.444
0.444
0.578
0.593
0.556
0.545
0.556
0.656
0.594
0.3
0.591
0.36
0.4
0.432
0.684
0.788
0.521
0.628
0.8
0.542
0.356
0.4
0.444
0.711
0.429
0.283
0.581
0.497
0.3
0.3
0.53
0.684
0.621
0.005
0.001
0.036
0.031
0.042
0.006
0.034
0.009
0.042
0.022
0.003
0.005
0.005
0.028
0.006
0.001
0.027
0.018
0.005
0.016
0.004
0.048
0.001
0.001
0.005
0.002
0.001
0.019
0.018
0.005
0.025
0.001
0.017
0.022
0.029
0.033
0.013
0.016
0.009
0.003
0.001
community-types (dropseed-wiregrass, toothache grass-muhly, and muhly-dropseed), we
found poor separation among the three
community-types represented by these other
25 quadrats. In addition, the other wet
savanna community quadrats did not exhibit
separation from each other in the NMDS
ordination.
Soil variables identified by randomForest as
better predictors of community classification
included percentage clay, Fe (ppm), and B
(ppm); all three had greater mean decrease in
accuracy scores for the Wells Savannah
quadrats relative to other savannas (Table 3;
Figure 4), and NMDS ordination of the quadrats based on soil characteristics demonstrated that Wells Savanna also differed from
other wet savannas (Figure 5). The overall
classification error rate of the wet savanna
quadrats based on soil variables was 32.4%;
although the error rate was high, it is not
evenly distributed between community types.
None of the Wells Savannah quadrats were
misclassified as belonging to other savanna
community types, and none of the other
savanna quadrats were misclassified as Wells
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CASTANEA
VOL. 76
Figure 2. Cluster analysis of the 35 wet savanna quadrats classified according to community type (see legend).
Results demonstrate separation of the Wells Savannah quadrats from the CVS quadrats representing wet savanna
in the North Carolina Outer Coastal Plain.
Savannah quadrats. However, all of the other
wet savanna quadrats were classified as the
dropseed—wiregrass community type. In other words, randomForest analysis was able to
differentiate the Wells Savannah quadrats
from the other savanna quadrats, but was
unable to differentiate other wet savanna
types from each other.
Objective 3
The fire-suppressed quadrats from Briary Bay
Farm had lower species richness compared to
the Wells Savannah quadrats (40.3 species vs.
52.9 species per quadrat; P , 0.001). Species
richness across an equal number of quadrats
was also different (156 species in the 10 Wells
Savannah quadrats vs. an average of 115
species in 10 randomly selected Briary Bay
Farm quadrats, bootstrapped 1,000 times).
NMDS separated the Briary Bay Farm
quadrats from the Wells Savannah quadrats
(Figure 6). In terms of vegetation, the two
Wells Savannah quadrats in the fire-suppressed woodland between the powerline
rights-of-way (WellsSa18 and WellsSa19)
were closer to the Briary Bay Farm quadrats
(Figure 6). As expected, woody species such as
Acer rubrum L., Clethra alnifolia L., and Ilex
coriacea (Pursh) Chapm. increased in cover
value in the fire-suppressed quadrats and
herbaceous species such as Aletris farinosa L.
and Ctenium aromaticum decreased. However,
of the 220 species found in the Wells Savannah and/or the Briary Bay Farm quadrats, 93
were found at both sites and included a
number of savanna species.
DISCUSSION Based on our comparisons of
species lists and analyses conducted by Shelingoski et al. (2005), Watha Savannah
appears to be a remnant of a unique savanna
association that was previously only known
from the Big Savannah, described by Wells
and Shunk and believed to have been extir-
2011
WALL ET AL.: UNIQUE WET SAVANNAS IN NORTH CAROLINA
357
Figure 3. Non-metric multidimensional scaling ordination of the 35 wet savanna quadrats. Wells Savannah
quadrats (solid squares) separate from other quadrats based on species abundance values. Environmental vector
indicate important soil variables correlated with axes 1 and 2. Savannah labels are as follows: GreenS 5 Green
Swamp, HollSh 5 Holly Shelter, LanQua 5 Lanier Quarry, Lejeun 5 Camp Lejeun, McLean 5 McLean Savanna,
MyrHed 5 Myrtle Head Savanna, Parker 5 Parker Savanna, ShakCr 5 Shaken Creek, SPFun 5 Sunny Point, and
WellS 5 Wells Savannah. Number at the end of labels refers to quadrat number. Final stress 5 16.9.
pated from the North Carolina landscape
(Wells 1967). MRPP results showed significant
separation between the Wells Savannah
quadrats and quadrats inventoried from other
area savannas, and a number of species were
responsible for this separation, according to
indicator species analysis. In addition, cluster
analysis (Figure 2) and NMDS ordination
(Figure 3) support the hypothesis that Wells
Savannah contains vegetation different from
previously classified savanna communities.
The vegetation differences between Wells
Savannah and surrounding wet savannas in
the North Carolina Outer Coastal Plain are
reinforced by the soil differences (MRPP
results, Table 3 and Figures 3 and 4). Soil
variables that differentiate Wells Savannah
quadrats include higher percentage clay, Fe
(ppm), and B (ppm) (Table 3). Other soil
variables that tended to be higher at Wells
Savannah included pH and Ca (ppm), though
other individual savannas, such as Shaken
Creek and Myrtle Head, also had higher pH
and Ca (ppm).
It is not surprising that the Wells Savannah
quadrats are distinct in terms of soil characteristics. This savanna occurs on a geographically limited Inceptisol – the Liddell soil series
– and both the community type and the soil
series may be endemic to the coastal plain of
North Carolina. Previously described savanna
types (that did not include the Big Savannah)
occur mainly on Ultisols and Spodosols, and
these soil relationships have formed the basis
for current savanna classification systems
(Taggart 1990, Peet 2006). Soils from the
Wells Savannah quadrats, relative to other
area savanna soils, may have a higher clay
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Table 3. Means and standard deviations (in parentheses) of 27 soil characteristics for the 35 wet savanna
quadrats grouped according to community type. Community type names (columns) follow those in Table 1.
Soil characteristics that were identified as important discriminators by randomForests algorithm are in bold
6.1.1
Mean (SD)
CEC (meq/100 g)
pH
% Org
N (ENR)
S (ppm)
P (ppm)
Ca (ppm)
Mg (ppm)
K (ppm)
Na (ppm)
% Ca
% Mg
%K
% Na
% Othr
%H
B (ppm)
Fe (ppm)
Mn (ppm)
Cu (ppm)
Zn (ppm)
Al (ppm)
% Base Sat.
Ca/Mg ratio
% clay
% silt
% sand
3.9
4
6.8
56.2
31.7
9
109.3
31.4
23.8
22
14.7
6.6
1.8
2.9
9.5
64.6
0.3
195.8
0.7
0.3
111.3
711.3
26
3.8
3.6
53.4
42.9
(2.1)
(0.3)
(4)
(6.1)
(11.9)
(2.9)
(53.2)
(21.4)
(10)
(12.2)
(4.2)
(1.3)
(0.9)
(1.9)
(0.6)
(4.2)
(0.1)
(55.8)
(0.5)
(0.2)
(309)
(399.3)
(4.8)
(1.2)
(1.5)
(29.6)
(30)
6.1.2
Mean (SD)
8.3
4
3.2
58.7
27.6
11.2
364.6
32.6
26
21.2
19.4
4.3
1.2
1.5
9.4
64.2
0.3
199.6
0.8
0.3
0.9
706.2
26.4
10.5
3.7
78.4
18
percentage because Ultisols are generally
more highly weathered with subsequent
translocation of clay downward (Brady and
Weil 1999). The fact that the Wells Savannah
quadrats are on a relatively young Inceptisol
may indicate that geologic time has been too
short for the translocation of clays downward
in the profile. A possible reason for the higher
iron (ppm) is that long hydroperiods can lead
to the reduction of iron in wetland soils (Buol
et al. 2003). Although percentage organic
matter and pH did not turn out to be useful
variables for predicting community type
(Figure 4), both were higher on average at
the Wells Savannah relative to other community types.
It appears that Wells Savannah represents
the hydric end of the hydrological gradient of
North Carolina wet savannas. A number of
obligate and facultative wetland species are
present at Wells Savannah, and a number of
species with hydrological niches that range
into drier sites, such as Aristida stricta and Xyris
caroliniana Walter (Table 2), are either not
(5.9)
(0.3)
(3.8)
(3.8)
(6.9)
(2.6)
(365.4)
(8.3)
(8.3)
(8.3)
(5.4)
(2.4)
(1)
(0.8)
(0.6)
(4.1)
(0.1)
(42.6)
(0.4)
(0)
(0.4)
(200)
(4.7)
(8.5)
(1.4)
(7.7)
(8.2)
6.1.5
Mean (SD)
3.2
3.9
5
55.3
42.3
11.3
84.5
25.8
22.3
19.5
13.4
6.8
1.8
2.7
9.6
65.8
0.4
198
1
0.2
0.7
831
24.7
3.3
3.7
61.2
35.1
(0.2)
(0)
(5.5)
(6.2)
(11.7)
(4.7)
(4.4)
(1.3)
(3.3)
(4.5)
(0.9)
(0.4)
(0.3)
(0.5)
(0.1)
(0.5)
(0.1)
(104)
(0)
(0.1)
(0.2)
(218.3)
(0.6)
(0.3)
(0.6)
(8.2)
(8.4)
Wells
Mean (SD)
5.1
4.3
6.6
53.8
22.3
9.5
242.9
29.4
29.4
18.7
22.9
6
1.8
2
8.8
58.6
0.5
440.2
0.5
0.5
1.4
838.5
32.6
8.2
9.8
48.1
42.2
(3)
(0.2)
(1.8)
(4.2)
(7.5)
(2.3)
(169.9)
(4.7)
(8.3)
(2.2)
(4.2)
(2.2)
(0.7)
(0.8)
(0.3)
(3.1)
(0.1)
(124)
(0)
(0.1)
(1)
(94.8)
(3.4)
(5.8)
(2.7)
(2.4)
(2.3)
found there or are relatively uncommon.
Aristida stricta was not recorded from the Big
Savannah (Wells and Shunk 1928) and is also
relatively uncommon at Wells Savannah.
Ctenium aromaticum, one of the dominant
grasses over the majority ‘‘bog proper’’ of the
extirpated Big Savannah is known to prefer
hydric soils and was one of the dominants at
Wells Savannah. Other dominant grasses at
Wells Savannah include Arundinaria tecta,
Dichanthelium scabriusculum, and Muhlenbergia expansa, which are all wetland species. B.
W. Wells remarked that the Big Savannah
was saturated for up to 10 months of the year
(Wells and Shunk 1928), and during the
summer of 2005 portions of Briary Bay Farms
remained saturated to the surface until August (Wade Wall, pers. obs.). These hydric
conditions make this community extremely
vulnerable to woody encroachment. Under
fire suppression, this community type in some
ways resembles a pond pine woodland rather
than a remnant wet savanna, with the only
indicators of its former savanna character
2011
WALL ET AL.: UNIQUE WET SAVANNAS IN NORTH CAROLINA
359
Figure 4. Variable importance plot for soil variables from Random Forests (RF) classification used for comparing
Wells Savannah to other wet savannas in the North Carolina Outer Coastal Plain. Soil variables that have higher
‘‘mean decrease in accuracy’’ values are better predictors of classification.
being remnant pockets of wet savanna vegetation.
Does the lack of historic fire at Wells
Savannah explain the species composition
differences between Wells Savannah and
other Outer Coastal Plain wet savannas? It
is well known that fire suppression can lead to
increased woody abundance (Waldrop et al.
1992) and a decrease in species richness
(Walker and Peet 1983); fire suppression
may also result in reduced species richness
and abundance values of Asteraceae, Fabaceae, and bunchgrass species of Poaceae
(Walker and Silletti 2006). The two powerline
corridors at Wells Savannah have been
mowed at 3-year intervals for over 30 years
but had not been burned until being purchased by the North Carolina Coastal Land
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Figure 5. Non-Metric Multidimensional Scaling ordination of proximity scores from Random Forest
classification methods. Quadrats that are close together are more similar in terms of soil characteristics. Wells
Savannah quadrats (solid squares) separate from the other quadrats based on soil characteristics. Label
explanations the same as in Figure 3 caption. Final stress 5 18.9.
Trust (Shelingoski et al. 2005). Although
several members of Asteraceae are indicator
species of other wet savanna sites that have
fire regimes more representative of historical
conditions (Table 2), there are still a number
of representatives of Asteraceae present at
Wells Savannah, where Asteraceae was the
third most-represented family. Although legumes are mostly absent from Wells Savannah, B.W. Wells commented on the absence
of Fabaceae species at the Big Savannah
(1928), so this is not surprising. Although we
cannot rule out the possibility that fire
suppression alone has led to the differences
in vegetation between Wells Savannah and
other wet savannas in the area, additional
analyses performed with the removal of all
woody species from the dataset yielded results
similar to those presented which supported
the unique character of the natural community of Wells Savanna.
Fire suppression of the area surrounding
Wells Savannah has clearly affected the
vegetation, with the fire-suppressed quadrats
(from the pond pine woodland at Wells
Savannah and from Briary Bay Farm) appearing different from those in the mowed
powerline rights-of-way (Figure 6). As expected, the fire-suppressed areas had reduced
species richness and an increased abundance
of woody species; however, a number of
savanna species persist there, including
Ctenium aromaticum, Sabatia difformis (L.)
Druce, Sarracenia flava L., and S. purpurea L.
In addition, several savanna species that
have not been found at Wells Savannah were
located, the most noticeable being Dionaea
muscipula Ellis. This was surprising because it
was assumed that Dionaea muscipula required
frequent fire to maintain open habitat. As
expected, members of Asteraceae were largely
absent from the fire-suppressed quadrats.
2011
WALL ET AL.: UNIQUE WET SAVANNAS IN NORTH CAROLINA
361
Figure 6. NMDS ordination of Watha Savannah quadrats. Results show separation of Wells Savannah quadrats
from both 26 Briary Bay Farm quadrats and 2 quadrats from Wells Savannah in the fire-suppressed woodland
between the two maintained powerline rights-of way. Final stress 5 13.5.
While minor variations in soil characteristics
or hydrology may account for vegetation
differences between the two sites, this does
not appear to be the case. Both Wells Savannah and Briary Bay Farm are mapped as the
Liddell soil series, and there are no differences
in topgography between the two sites.
Although Wells Savannah is a small remnant of the longleaf pine savanna community formerly known only from the Big Savannah, enough differences exist in vegetation
and soil characteristics relative to currently
recognized wet savanna communities to validate the uniqueness of Wells Savannah.
Although additional sites would need to be
located to warrant establishing a new community type based on unique vegetation and
underlying soils, the two sites included in
Watha Savannah—Wells Savannah and Briary Bay Farm – clearly represent a remnant
wet savanna at the extreme end of the
hydrological gradient. Fire suppression has
undoubtedly led to a decrease in species
richness at the Briary Bay Farm site, but as
our results show, pockets of savanna vegetation still persist at the site and it is possible
that other savanna vegetation remnants may
be extant in the general vicinity that resemble
Wells Savannah and the former Big Savannah. Finally, although this community is
most likely limited to the Liddell soil series
that occurs mainly in northern Pender County
and southern Duplin County, North Carolina,
other areas in the Atlantic coastal plain
include Inceptisols under long hydroperiods,
and we recommend that researchers seek
other representatives of this rare community
in the Atlantic Coastal Plain.
ACKNOWLEDGMENTS The authors thank
Joseph Taylor for access to Briary Bay Farm
and excellent accommodations during summer 2005. We also wish to thank Zac Hill for
his assistance in data collection at Briary Bay
362
CASTANEA
Farm and Andrew Walker and Kristen Kostelnik for general guidance. Mike Vepraskas
offered excellent advice regarding interpretation of soil properties and the Department of
Soil Science at North Carolina State University
were gracious enough to allow us to use their
facilities. We thank Robert K. Peet and Forbes
Boyle for providing classification of North
Carolina wet savannas and assistance with
data extraction from the CVS database. Coastal Land Trust has been an excellent partner
and we thank them for both preserving Wells
Savannah for future generations and granting
us access. The Department of Plant Biology at
North Carolina State University and the North
Carolina Agricultural Research Service contributed greatly to the financial support of the
project.
LITERATURE CITED
Brady, N.C. and R.R. Weil. 1999. The nature
and properties of soils, 12th ed. Prentice
Hall, Upper Saddle River, New Jersey.
Breiman, L. 2001. Random forests. Machine
Learning 45:5–32.
Buol, S.W., R.J. Southard, R.C. Graham, and
P.A. McDaniel. 2003. Soil genesis and
classification. Iowa State Press, Ames, Iowa.
Cutler, D.R., T.C. Edwards Jr., K.H. Beard, A.
Cutler, K.T. Hess, J. Gibson, and J.J. Lawler.
2007. Random forests for classification in
ecology. Ecology 88:2783–2792.
Dufrêne, M. and P. Legendre. 1997. Species
assemblages and indicator species: the need
for a flexible asymmetrical approach. Ecol.
Monogr. 67:345–366.
Frost, C.C. 1993. Four centuries of changing
landscape patterns in the longleaf pine
ecosystem. p. 17–37. In: Hermann, S.M.
(ed.). The longleaf pine ecosystem: ecology,
restoration, and management. Proceedings
of the Tall Timbers Fire Ecology Conference.
Volume 18. Tallahassee, Florida.
Frost, C.C., J. Walker, and R.K. Peet. 1986.
Fire-dependent savannas and prairies of the
Southeast: original extent, preservation
and status. p. 348–357. In: Kulhavy, D.L.
and R.N. Connor (eds.). Wilderness and
natural areas in the eastern United
States: a management challenge. Center
for Applied Studies, School of Forestry,
VOL. 76
Stephen F. Austin St. University, Nacogdoches, Texas.
Gee, G.W. and J.W. Bauder. 1986. Particle size
analysis. p. 383–411. In: Klute, A. (ed.).
Methods of soil analysis. Part 1. Physical and
mineralogical methods, 2nd ed. American
Society of Agronomy, Madison, Wisconsin.
Krings, A., A.J. Harris, F.M. Inman, E. Lee, and
A.R. Richardson. 2005. An annotated catalog of the Bertram Whittier Wells Big
Savannah (Pender Co. North Carolina)
collections in the North Carolina State
University herbarium. Vulpia 4:52–67.
LeBlond, R.J. 2000. Natural Area Inventory of
Pender County, North Carolina. North
Carolina Natural Heritage Program, Raleigh, North Carolina.
Liaw, A. and M. Wiener. 2002. Classification
and regression by random Forest. R News
2:18–22.
Maechler, M., P. Rousseeuw, A. Struyf, and M.
Hubert. 2005. Cluster analysis basics and
extensions.
McCune, B. and J.B. Grace. 2002. Analysis of
ecological communities. Mjm Software Design, Gleneden Beach, Oregon.
McPherson, G.R. 1997. Ecology and management of North American savannas. University of Arizona Press, Tucson, Arizona.
Oksanen, J., R. Kindt, P. Legendre, B. O’Hara,
G.L. Simpson, P. Solymos, M. Henry, H.
Stevens, and H. Wagner. 2009. vegan:
Community ecology package. R package
version 1.17-0.
Peet, R.K. 2006. Ecological classification of longleaf pine woodlands. p. 51–93. In: Jose, S., E.J.
Jokela, and D.L. Miller (eds.). The longleaf pine
ecosystem: ecology, silviculture, and restoration. Springer, New York, New York.
Peet, R.K., T.R. Wentworth, and P.S. White.
1998. A flexible, multipurpose method for
recording vegetation composition and
structure. Castanea 63:262–274.
R Development Core Team. 2010. R: a language and environment for statistical computing. Vienna, Austria, Version 2.10.1.
Roberts, D.W. 2010. labdsv: ordination and
multivariate analysis for ecology. R package version 1.4-1.
2011
WALL ET AL.: UNIQUE WET SAVANNAS IN NORTH CAROLINA
Shelingoski, S. 2005. Wells Savannah, an
example of a unique fire-dependent ecosystem in the North Carolina Coastal Plain.
M.S. thesis, North Carolina State University,
Raleigh, North Carolina.
Shelingoski, S., R.J. LeBlond, J.M. Stucky, and
T.R. Wentworth. 2005. Flora and soils of Wells
Savannah, an example of a unique savanna
type. Castanea 70:101–114.
Taggart, J.B. 1990. Inventory, classification,
and preservation of coastal plain savannas
in the Carolinas. Ph.D. dissertation, University of North Carolina, Chapel Hill,
North Carolina.
Waldrop, T.A., D.L. White, and S.M. Jones.
1992. Fire regimes for pine-grassland communities in the southeastern United States.
For. Ecol. Manage. 47:195–210.
Walker, J. and R.K. Peet. 1983. Composition
and species diversity in pine-wiregrass
363
savannas of the Green Swamp, North
Carolina. Vegetatio 55:166–179.
Walker, J. and A.W. Silletti. 2006. Restoring
the ground layer of longleaf pine ecosystems. p. 297–325. In: Jose, S., E.J. Jokela,
and D.L. Miller (eds.). The longleaf pine
ecosystem: ecology, silviculture, and restoration. Springer, New York, New York.
Weakley, A.S. 2010. Flora of the Southern and
Mid-Atlantic States (Working Draft of 8
March 2010). Univerisity of North Carolina
Herbarium, Chapel Hill, North Carolina.
Wells, B.W. 1967. The natural gardens of
North Carolina. University of North Carolina Press, Chapel Hill, North Carolina.
Wells, B.W. and I.V. Shunk. 1928. A southern
upland grass-sedge bog: an ecological
study. North Carolina Agricultural Experiment Station Technical Bulletin no. 32,
Raleigh, North Carolina.