relationship to wet savannas in north carolina lost...

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Lost and Found: Remnants of the Big Savannah and TheirRelationship to Wet Savannas in North CarolinaAuthor(s) :W. A. Wall, T. R. Wentworth, S. Shelingoski, J. M. Stucky, R. J.LeBlond, and W. A. HoffmannSource: Castanea, 76(4):348-363. 2011.Published By: Southern Appalachian Botanical SocietyDOI:URL: http://www.bioone.org/doi/full/10.2179/10-046.1

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Lost and Found: Remnants of the Big Savannahand Their Relationship to Wet Savannas

in North CarolinaW.A. Wall,1* T.R. Wentworth,1 S. Shelingoski,2 J.M. Stucky,1 R.J. LeBlond,3 and

W.A. Hoffmann1

1Department of Plant Biology, Box 7612, North Carolina State University, Raleigh,North Carolina 27695-7612

2803 Tarpon Dr., Wilmington, North Carolina 284093PO Box 787, Richlands, North Carolina 28574

ABSTRACT Conversion to agriculture and plantations, development, and fire suppressionhave reduced the extent of savannas in the southeastern United States, and there is a need tocatalog and classify the remaining savannas for both restoration and resource managementpurposes. The Big Savannah was a wet savanna in North Carolina that was destroyed in the1950s, and subsequent vegetation classifications have generally not accommodated well theunique natural plant community of the Big Savannah. Vegetation reminiscent of thatdescribed for the Big Savannah was discovered north of the original site and designated asWells Savannah. To evaluate the uniqueness of the savanna vegetation at Wells Savannah, wecompiled a data set from permanent quadrats with information on vegetation andenvironmental variables from other Outer Coastal Plain savannas to compare with similardata from the natural community at Wells Savannah. We also inventoried an additional 26quadrats on a tract adjacent to Wells Savannah that had experienced fire suppression. Resultsfrom multivariate analyses demonstrated clear differences between the Wells Savannahquadrats and other regional wet savanna quadrats based on both vegetation and soils. Anumber of species and several soil characteristics (higher clay percentage, and higher availableiron and boron) distinguish Wells Savannah from other wet savannas. Although the firesuppressed quadrats near Wells Savannah had lower species richness, typical savanna speciessuch as Ctenium aromaticum and Calamovilfa brevipilis were still present. Further exploration offire-suppressed tracts in the area may yield more wet savanna inclusions similar to the formerBig Savannah.

INTRODUCTION Savannas formerly cov-ered large expanses of the southeasternUnited States, with pre-European settlementestimates of longleaf pine coverage at 37million hectares (Frost 1993); most of thisarea was occupied by savannas, which can bedefined as having a relatively open canopyand a continuous grass understory (McPher-son 1997). Savannas in the southeasternUnited States in general had high speciesdiversity at small scales with a high percent-age of clonal species. Longleaf pine savannas

were found from east Texas to central Floridaand north into Virginia, and similar commu-nities existed as far north as New Jersey(Taggart 1990). Savannas were not onlygeographically widespread, but occurred un-der a range of hydrologic regimes, fromsubxeric to hydric, the latter typically saturat-ed through the winter and early spring.Although savannas were once dominantacross the southeastern landscape, anthropo-genic activities such as fire suppression, agri-culture, residential and commercial develop-ment, and timber operations have removedroughly 97% of their area in the southeasternUnited States in the last 200 years (Frost et al.

*email address: [email protected]

Received November 8, 2010; Accepted June 23, 2011.

CASTANEA 76(4): 348–363. DECEMBER 2011

348

1986). There is a need for better classificationand understanding of the savannas whichpersist in order to inform and direct manage-ment and restoration efforts.

The Big Savannah was a 607 hectare site3 km north of Burgaw, North Carolina. Thesite was studied by B.W. Wells, a prominentearly ecologist who pioneered efforts to un-derstand southeastern savannas (or savan-nahs, in early 20th century spelling). Wellsspent several field seasons during the 1920scollecting soil and vegetation data in order tocharacterize the site, which culminated in aclassic 1928 work, written with his collabora-tor I. V. Shunk, ‘‘A Southern Upland Grass-Sedge Bog: An Ecological Study’’ (1928). Thesite occurred on a silty soil that remained wetthrough much of the year. Local residentsburned the Big Savannah every winter andgrazed cattle on the site during the spring.Although the Big Savannah was mostlytreeless, Wells found woody sprouts of Nyssa

biflora Walter that were over 50 years old, aswells as sprouts of Pinus palustris P. L. Mill.and Pinus taeda L. It contained a remarkablenumber of Rhynchospora species, as well asmost of the carnivorous species present inNorth Carolina. Employing Clementsian con-cepts and terminology in wide use at the time,Wells characterized the open grass-sedge bogof the Big Savannah as belonging to twoconsocies: the Campulosus and Panicum. TheCampulosus consocies was the more wide-spread of the two and tended to be wetter; itwas named after the dominant species Cam-

pulosus (now Ctenium) aromaticum (Walter)Alph. Wood, or toothache grass. Wells classi-fied all encountered species into groupswithin each consocies. The dominants in theCampulsosus, or ‘‘bog proper,’’ consocieswere Arundinaria tecta (Walter) Muhl., Ctenium

aromaticum, Dichanthelium ensifolium (Baldw.ex Ell.) Gould, D. longiligulatum (Nash) Feck-mann, D. wrightianum (Nash) Feckmann,Rhynchospora chapmanii, and Scleria ciliata.The Panicum consocies dominants includedSchizachyrium 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. Thesespecies were not represented in the Campulo-

sus consocies. A third consocies – Andropogon– was recognized on the margin of what Wellstermed the ‘‘bog proper.’’ This consocies wason better-drained soils and included a num-ber of species that presumably could notpersist in the saturated soil conditions of thebog proper.

The site was privately owned, and despiteefforts by Wells and others to preserve it forfuture generations, it was sold in the 1950s.Many erroneously believed the site was toowet for agriculture and that preservation wasunnecessary; however, tile drainage allowedthe owner to drain the Big Savannah andconvert it into agricultural fields (Wells 1967).Wells and others believed that this uniquecommunity type had been extirpated fromthe North Carolina landscape.

Landscape-scale classification of savannatypes has only been undertaken in the last20 yr and the Big Savannah has either beenignored or included with other extant com-munity types in recent classifications. Taggart(1990) presented the first classification ofsavanna community types in the Carolinasbased on vegetation and soil characteristicsfrom inventory plots. The area covered in-cluded all of North Carolina and SouthCarolina north of the Congaree River. Taggartrecognized five savanna categories, namingthem based on the hydrologic regime and theassociated soil order: dry, mesic and wetUltisols, and dry and wet Spodosols. Heclassified the Big Savannah as a wet Ultisolvariant. Recently, Robert Peet (2006) present-ed a classification that covers the entire rangeof southeastern United States savannas, di-viding the southeastern United States into fivegeographic regions, with further classificationof savannas within each of the regions basedon soil texture and hydroperiod. The BigSavannah as a community is not mentionedin Peet’s longleaf pine classification system.

In the late 1990s, an unexpected opportu-nity arose to study the unique vegetationpreviously documented from the Big Savan-nah. The North Carolina Natural HeritageProgram Inventory of Pender County (Le-Blond 2000) briefly described the savannavegetation of two powerline rights-of-way inthe northern part of the county, noting theiroccurrence on the same unusual soil typefound at the former Big Savannah. Shelin-

2011 WALL ET AL.: UNIQUE WET SAVANNAS IN NORTH CAROLINA 349

goski et al. (2005) described this savanna ingreater detail using vegetation and soil data,comparing the site to the Big Savannah (asdescribed by B.W. Wells) and other savannasites at nearby Holly Shelter Game Land. TheB. W. Wells Savannah—or Wells Savannah—as the site has become known, was purchasedby the North Carolina Coastal Land Trust in2002 and is now preserved and managed withprescribed fire.

We have three objectives in this study: toinvestigate (1) vegetation similarities betweenthe Big Savannah and the existing remnantsat Watha Savannah, which includes WellsSavannah and Briary Bay Farm; (2) vegeta-tion and soil differences of Wells Savannahrelative to other wet savannas in the OuterCoastal Plain of North Carolina; and (3)extent to which fire suppression may havealtered the expression of savanna vegetationin Watha savanna. We compare recentlycompiled species lists from Wells Savannahand Briary Bay Farm with the historic listcompiled by Wells and Shunk (1928) for BigSavannah to explore the possibility that tworemnant sites (Wells Savannah and BriaryBay Farm) may once have had speciescomposition similar to that of Big Savannah.To explore the possibility that Wells Savan-nah supports a community different frompreviously characterized Outer Coastal Plainwet savanna communities, we compare spe-cies composition and soil data from bothsources, using a variety of multivariate pro-cedures. We compare vegetation data fromthat site with the data from Wells Savannahto document the effects of fire suppressionupon species composition on Briary BayFarm.

METHODSStudy AreaWells Savannah is located in the AtlanticCoastal Plain physiographic region in north-ern Pender County, North Carolina (34.6595,277.9908).The site is extremely flat with littletopographic relief. Annual rainfall averages1,318 mm per year and average temperaturesrange from a January mean minimum/maximum temperature of 1.1uC/14.0uC anda July mean minimum/maximum tempera-ture of 20.6uC/32.1uC (Southeast RegionalClimate Center). In contrast to other wet

savannas in the Outer Coastal Plain of NorthCarolina that occur on either Ultisols orSpodosols, Wells Savannah and the surround-ing area (hereafter referred to collectively asWatha Savannah) occur mainly on theLiddell soil series. The Liddell soil series is anInceptisol with poorly defined horizons andrelatively high silt content. Inceptisols aregenerally young soils in humid and semi-humid areas that have limited evidence ofilluviation. The Liddell soil series is geograph-ically limited; it mainly occurs on large flatsin northern Pender County, with isolatedpatches found in Wayne and Duplin Coun-ties.

Aerial photos from the late 1930s show arelatively open savanna landscape at WathaSavannah, the site that includes both WellsSavannah and Briary Bay Farm (Figure 1).Subsequent fire suppression of the area thatnow includes both Wells Savannah andBriary Bay Farm allowed for the growth of aprogressively denser canopy for most of thearea. However part of Wells Savannah re-mained relatively open because of frequentmowing of two powerline rights-of-way. Bri-ary Bay Farm, a 243 ha privately-ownedparcel adjacent to Wells Savannah and partof what we refer to as Watha Savannah, hasvegetation and soil characteristics similar toWells Savannah, but has been subject to adifferent disturbance history. For most of the20th century there was no noticeable removalof biomass due to mowing or fire, with anincreasingly closed canopy. The site was clearcut in the late 1990s and at present Briary BayFarm has a mosaic of herbaceous and woodycover with numerous savanna species repre-sented.

Objective 1: vegetation similarities between the

Big Savannah (historic reference condition) and

the existing remnants at Watha SavannahWe first compiled a list of all the species thatWells and Shunk documented in their semi-nal work on the Big Savannah (1928) andupdated the nomenclature. We added to thelist specimens held at the North CarolinaState University herbarium (NCSC) that werevouchered by B.W. Wells from the Big Savan-nah (Krings et al. 2005). We compiled asecond list of all species identified either invegetation quadrats or collections made dur-

350 CASTANEA VOL. 76

Figure 1. a) Map of the savannas included in this study. b) 1938 aerial photograph of Wells Savannah andBriary Bay Farm. Photograph reveals continuous herbaceous layer with a sparse, open canopy characteristic ofsoutheastern savanna physiognomy.


ing site visits to Watha Savannah. Wecompared the species lists from the BigSavannah and Watha Savannah and calcu-lated the percentage overlap between the twolists.

Objective 2: establish uniqueness of Wells

Savannah relative to other wet savannas in the

North Carolina Outer Coastal PlainDuring summer 2002, ten 100 m2 quadratswere inventoried at Wells Savannah (Shelin-goski et al. 2005) using the single quadratprotocol developed by the Carolina Vegeta-tion Survey (CVS) (Peet et al. 1998). In thispaper, ‘‘quadrat’’ will refer to sampled areasof 100 m2 and ‘‘plot’’ will refer to sampledareas of 0.1 ha. These quadrats were locatedin the treeless vegetation found in the regu-larly-mowed powerline rights-of-way (ROWs).We then selected 25 plots from the CVSdatabase that were identified as representingOuter Coastal Plain savannas at other siteswith vegetation and hydrology similar tothose of Wells Savannah. Criteria for theselection of the CVS plots were (1) inclusionin the Pinus palustris community type, (2)location in the Outer Coastal Plain of NorthCarolina, and (3) similar vegetation based onpreliminary multivariate analyses. The select-ed CVS plots were inventoried from sites thathave traditionally been described as ‘‘wetsavannas’’ that experience long hydroperiodsand host a number of obligate and facultativewetland species. The 25 CVS plots werepreviously classified by Robert Peet (unpubl.data) into three different community-types

using his recent classification system (Peet2006). We denote here the Peet (2006) classesby the common names of the two mostabundant species in the sampled plots repre-senting each community-type (Table 1). Touse vegetation data from a consistent scale(100 m2) and to avoid issues of spatialautocorrelation, we randomly selected one ofthe intensively-sampled 100 m2 quadratsfrom each of the 25 CVS plots when morethan one intensive quadrat had been inven-toried. Taxonomic nomenclature followsWeakley (2010).

Soil sampling protocol for all quadrats,including the quadrats selected from the CVSsavanna plots, followed the methods outlinedin the CVS protocol (Peet et al. 1998). Briefly,soil samples for all quadrats were sampledfrom the top 10 cm of the A horizon.Subsurface soil samples were collected for allquadrats but were not included in the anal-yses. Brookside Laboratories (308 South MainSt., New Knoxville, Ohio 45871) performednutrient and texture analysis for all CVSquadrats and nutrient analysis for the WellsSavannah quadrats. Texture analysis of theWells Savannah quadrats was performed atthe North Carolina State University soillaboratory using the methods of Gee andBauder (1986). The following soil propertieswere measured for all quadrats: Cation ex-change capacity (CEC), pH, organic abun-dance (percentage loss on ignition), sulfur(ppm), phosphorus (ppm), calcium (ppm),magnesium (ppm), potassium (ppm), sodium(ppm), boron (ppm), iron (ppm), manganese

Table 1. Wet savanna community classification. Names used in the present paper are synonymous withthe Peet classification codes. NatureServe Association codes are synonymous with the Peet classificationcodes, except for 6.1.1, which includes both CEGL004501 and CEGL004086 in its concept

Peet ClassificationCode (Peet in Jose

et al. 2006)Description of Community and

Dominant SpeciesNatureServeAssociation

Names Used in thePresent Paper

6.1.1 Pinus palustris/Sporobolus pinetorum-Schizachrium-Eryngium integrifoliumwoodland

.CEGL004501

.CEGL004086Dropseed-wiregrass

savanna

6.1.2 Pinus palustris-Pinus serotina/Cteniumaromaticum-Muhlenbergia expansa-Rhynchospora latifolia woodland

CEGL003660 Toothache grass-muhly savanna

6.1.5 Pinus palustris-Pinus serotina/Sporoboluspinetorum-Ctenium aromaticum-Eriocaulondecangulare woodland

CEGL004502 Muhly-dropseedsavanna

Not classified Wells Savannah plots Not classified Switch cane-inkberrysavanna


(ppm), copper (ppm), zinc (ppm), aluminum(ppm), calcium (as percentage of base satu-ration), magnesium (as percentage of basesaturation), potassium (as percentage of basesaturation), sodium (as percentage of basesaturation), and percentage base saturation

We performed two multi-response permu-tation procedures (MRPP) to test the hypoth-eses that the 10 Wells Savannah quadratsfrom the powerline ROWs differ from otherwet savanna quadrats from the region (as asingle group of 25 quadrats) in terms of (1)vegetation and (2) soil characteristics. For allsubsequent analyses, we constructed vegeta-tion and soil data matrices. The matrixelements for the vegetation consisted of covervalues for species in specific quadrats, whilethe soil data matrix elements were based onthe results from Brookside Laboratories. Notransformations or standardizations were per-formed, and we did not remove infrequentspecies. For the vegetation data we used theSorenson distance measure and for the soildata we used a Euclidean distance measure.MRPP was performed using the R packagevegan (Oksanen et al. 2009). To furtherevaluate the relationship of the vegetationin the powerline ROWs at Wells Savannah tovegetation in other regional wet savannas(again, combined as a single group), weperformed an indicator species analysis (ISA)(Dufrene and Legendre 1997) to identifydiagnostic species. ISA is a multivariatetechnique that allows one to identify speciesthat are good ‘‘indicators’’ of a priori groups ofsampling units–in our case, quadrats belong-ing to either Wells Savannah or to the otherwet savannas. All analyses were performedusing the R statistical platform (R Develop-ment Core Team 2010); ISA was performedusing the R package labdsv (Roberts 2010).

We then used cluster analysis and non-metric multidimensional scaling ordination(NMDS) to analyze how a priori classification(see above) of the Wells Savannah and otherwet savanna quadrats into the four commu-nity types (Table 1) reflected observed vege-tation patterns in the data set. For the clusteranalysis we selected the flexible beta linkagemethod (b 5 20.25), using the agnes()function in the R package cluster (Maechleret al. 2005). For both the cluster analysis andthe NMDS ordination, the response variable

was abundance values for each species withinquadrats. We used the Sorenson distancemeasure, which is less susceptible to loss ofsensitivity with increasing environmental orspecies distances relative to many otherdistance measures (McCune and Grace2002). For the ordination, we used the nmds()function in the R package labdsv (Roberts2010) with k 5 2, a starting configurationbased upon principal coordinates analysis,and the maximum number of iterations set to100. Environmental vectors were displayedusing the envfit function in vegan (Oksanenet al. 2000).

To identify important soil characteristicscorrelated with a priori savanna communitytypes (again, the four types shown in Table 1)we used the Random ForestTM (RF) method ofclassification (Breiman 2001) in the R pack-age randomForest (Liaw and Wiener 2002).RF is a classification method similar toclassification and regression trees (CART),but instead of relying on a single tree, themethod generates multiple trees and averagesthe results. For most data sets the method haslower misclassification rates relative to othermethods (Cutler et al. 2007). The soil vari-ables 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 basesaturation, Ca/Mg ratio, percent clay andpercent silt. We generated 1,000 trees and, foreach node in the tree, we specified that thealgorithm randomly select three candidatevariables and sample with replacement. Wecalculated importance values (mean decreasein accuracy) for each included variable.Higher importance values indicate that avariable is a better predictor of group mem-bership (Breiman 2001). We used NMDS withthe same parameter settings as above tographically represent the distance betweenquadrats based on soil characteristics.

Objective 3: determine extent to which fire

suppression may have altered savanna

expression in Watha SavannahDuring the summer 2005, we sampled anadditional 26 100 m2 quadrats from BriaryBay Farm. We started by dividing Briary BayFarm into 30 compartments for a projectedfire study. The centroid of each compartment


was located and a 0.1 ha plot was centered onit, and each of the 10 quadrats in the plot wasdesignated as either ‘‘woody’’ or herbaceous’’based on the amount of woody encroach-ment. We selected one of the quadratsdesignated ‘‘herbaceous’’ for intensive sam-pling. Sampling and soil analyses followedthe same protocol as for the Wells Savannahquadrats. To analyze the effects of differentdisturbance histories on Watha Savannah, wecompared the mean species richness perquadrat and total number of species for theWells Savannah and Briary Bay Farm data-sets using a t-test. To compare the totalspecies richness based on equal-area samples,we bootstrapped the fire-suppressed quadratsfrom Briary Bay Farm 1,000 times by ran-domly sampling 10 quadrats without replace-ment and calculating the total number ofspecies in the sample. In addition, we usedNMDS ordination to compare the vegetationof the Wells Savannah and Briary Bay Farmquadrats following the same procedures de-scribed previously for the analysis of the wetsavanna quadrats. For this final ordination,we also included data from two additionalquadrats sampled during the summer of 2002in the fire-suppressed woodland between thetwo powerline ROWs at Wells Savannah(Shelingoski et al. 2005).

RESULTSObjective 1Of the species either documented by Wellsand Shunk (1928) as present at the BigSavannah or vouchered at NCSC by Wells(but not included in the 1928 publication),45% were documented from the quadratsinventoried from either Wells Savannah orBriary Bay Farm. In addition, 66% of thespecies documented by Wells have also beenfound at either Wells Savannah or Briary BayFarm, either in inventoried quadrats or ascollections. Of the 13 species that Wells andShunk (1928) described as dominants in oneof the three described vegetation consocies, 12have been documented at Wells Savannahand/or Briary Bay Farms, and 18 of the 23species described as sub-dominants have beenfound at Wells Savannah and/or Briary BayFarm. The Campulosus (Ctenium) consocies –the community described by B. W. Wells thatmost closely resembles Wells Savannah –

included a number of dominants that alsohad high cover values in the Wells Savannahquadrats. These include Arundinaria tecta,Ctenium aromaticum, Rhynchospora chapmanii(data available from the authors).

Objective 2Multi-response permutation procedure(MRPP) results demonstrated significant dif-ferences 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 WellsSavannah quadrats and the 25 quadrats fromOuter Coastal Plain wet savannas (as a singlegroup). MRPP results include a measure ofwithin-group homogeneity (A), the chance-correlated within-group agreement, alongwith a significance estimate (p-value). LargerA values indicate more homogeneous groups.For community data, A values are typicallyless than 0.1, and a value of 0.3 is consideredhigh (McCune and Grace 2002).

Indicator species analysis (ISA) comparingthe 10 Wells Savannah quadrats to the 25quadrats from Outer Coastal Plain savannasidentified 43 species – 26 for Wells Savannahand 17 for other wet savannas—with indica-tor values (IV) greater than 0.25 and P-values, 0.05 (Table 2); examples include Arundi-naria tecta, Dichanthelium scabriusculum, andLycopodiella alopecuroides (L.) Cranfill as indi-cators of Wells Savannah and Bigelowianudata (Mich.) DC. and Aristida stricta Mich.as indicators of the other Outer Coastal Plainsavannas.

Cluster analysis of vegetation composition-al data separated the 10 Wells Savannahquadrats from the 25 other wet savannaquadrats at the first division of the dendro-gram (Figure 2). Non-metric multidimension-al scaling (NMDS) ordination also separatedthe Wells Savannah quadrats from thoserepresenting other wet savanna community-types (Figure 3). In addition, soil variables(with R2 in parentheses) associated with axis1 included Fe (ppm) (0.33), percentage clay(0.43), and B (ppm) (0.31) – all increasingalong 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 satu-ration (0.36) increasing. Despite the clearseparation of the Wells Savannah quadrats(labeled as switch cane-inkberry) from the 25quadrats representing other wet savanna


community-types (dropseed-wiregrass, tooth-ache grass-muhly, and muhly-dropseed), wefound poor separation among the threecommunity-types represented by these other25 quadrats. In addition, the other wetsavanna community quadrats did not exhibitseparation from each other in the NMDSordination.

Soil variables identified by randomForest asbetter predictors of community classificationincluded percentage clay, Fe (ppm), and B(ppm); all three had greater mean decrease inaccuracy scores for the Wells Savannah

quadrats relative to other savannas (Table 3;Figure 4), and NMDS ordination of the quad-rats based on soil characteristics demonstrat-ed that Wells Savanna also differed fromother wet savannas (Figure 5). The overallclassification error rate of the wet savannaquadrats based on soil variables was 32.4%;although the error rate was high, it is notevenly distributed between community types.None of the Wells Savannah quadrats weremisclassified as belonging to other savannacommunity types, and none of the othersavanna quadrats were misclassified as Wells

Table 2. Indicator species analysis comparing Wells Savannah quadrats to those from other wet savannasin the Outer Coastal Plain of North Carolina. Species included have significance values less than 0.05 andindicator 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. 1 0.667 0.005Bigelowia nudata (Michx.) DC var. nudata 1 0.778 0.001Calopogon pallidus Chapman 1 0.444 0.036Coreopsis linifolia Nutt. 1 0.586 0.031Dionaea muscipula Ellis 1 0.407 0.042Lachnocaulon anceps (Walt.) Morong 1 0.519 0.006Morella cerifera (L.) Small 1 0.491 0.034Pinus palustris P. Mill. 1 0.593 0.009Pityopsis graminifolia (Michx.) Nutt. 1 0.444 0.042Rhynchospora baldwinii Gray 1 0.444 0.022Rhynchospora plumosa Ell. 1 0.578 0.003Sisyrinchium capillare E.P. Bicknell 1 0.593 0.005Sporobolus pinetorum Weakley & P. M. Pet. 1 0.556 0.005Symphyotrichum dumosum (L.) Nesom 1 0.545 0.028Viola primulifolia L. 1 0.556 0.006Xyris caroliniana Walt. 1 0.656 0.001Acer rubrum L. 2 0.594 0.027Amelanchier spicata (Lamarck) K. Koch. 2 0.3 0.018Andropogon glomeratus (Walt.) B.S.P. 2 0.591 0.005Andropogon mohrii (Hack.) Hack. ex Vasey 2 0.36 0.016Andropogon perangustatus Nash 2 0.4 0.004Andropogon virginicus L. 2 0.432 0.048Aronia arbutifolia (L.) Persoon 2 0.684 0.001Arundinaria tecta (Walt.) Muhl. 2 0.788 0.001Clethra alnifolia L. 2 0.521 0.005Coreopsis falcata Boynt. 2 0.628 0.002Dichanthelium scabriusculum (Ell.) Gould & C.A. Clark 2 0.8 0.001Eupatorium rotundifolium L. 2 0.542 0.019Euthamia caroliniana (L.) Greene ex Porter & Britt. 2 0.356 0.018Hypericum densiflorum Pursh 2 0.4 0.005Lachnanthes caroliana (Lam.) Dandy 2 0.444 0.025Lycopodiella alopecuroides (L.) Cranfill 2 0.711 0.001Lyonia ligustrina (L.) DC. 2 0.429 0.017Mitreola sessilifolia (J.F. Gmel.) G. Don 2 0.283 0.022Rhexia lutea Walt. 2 0.581 0.029Rhynchospora chapmanii M.A. Curtis 2 0.497 0.033Rhynchospora filifolia Gray 2 0.3 0.013Rhynchospora inexpansa (Michx.) Vahl 2 0.3 0.016Scleria minor W. Stone 2 0.53 0.009Smilax laurifolia L. 2 0.684 0.003Zigadenus glaberrimus Michx. 2 0.621 0.001


Savannah quadrats. However, all of the otherwet savanna quadrats were classified as thedropseed—wiregrass community type. In oth-er words, randomForest analysis was able todifferentiate the Wells Savannah quadratsfrom the other savanna quadrats, but wasunable to differentiate other wet savannatypes from each other.

Objective 3The fire-suppressed quadrats from Briary BayFarm had lower species richness compared tothe Wells Savannah quadrats (40.3 species vs.52.9 species per quadrat; P , 0.001). Speciesrichness across an equal number of quadratswas also different (156 species in the 10 WellsSavannah quadrats vs. an average of 115species in 10 randomly selected Briary BayFarm quadrats, bootstrapped 1,000 times).

NMDS separated the Briary Bay Farmquadrats from the Wells Savannah quadrats(Figure 6). In terms of vegetation, the two

Wells Savannah quadrats in the fire-sup-pressed woodland between the powerlinerights-of-way (WellsSa18 and WellsSa19)were closer to the Briary Bay Farm quadrats(Figure 6). As expected, woody species such asAcer rubrum L., Clethra alnifolia L., and Ilex

coriacea (Pursh) Chapm. increased in covervalue in the fire-suppressed quadrats andherbaceous species such as Aletris farinosa L.and Ctenium aromaticum decreased. However,of the 220 species found in the Wells Savan-nah and/or the Briary Bay Farm quadrats, 93were found at both sites and included anumber of savanna species.

DISCUSSION Based on our comparisons ofspecies lists and analyses conducted by She-lingoski et al. (2005), Watha Savannahappears to be a remnant of a unique savannaassociation that was previously only knownfrom the Big Savannah, described by Wellsand Shunk and believed to have been extir-

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 savannain the North Carolina Outer Coastal Plain.


pated from the North Carolina landscape(Wells 1967). MRPP results showed significantseparation between the Wells Savannahquadrats and quadrats inventoried from otherarea savannas, and a number of species wereresponsible for this separation, according toindicator species analysis. In addition, clusteranalysis (Figure 2) and NMDS ordination(Figure 3) support the hypothesis that WellsSavannah contains vegetation different frompreviously classified savanna communities.

The vegetation differences between WellsSavannah and surrounding wet savannas inthe North Carolina Outer Coastal Plain arereinforced by the soil differences (MRPPresults, Table 3 and Figures 3 and 4). Soilvariables that differentiate Wells Savannahquadrats include higher percentage clay, Fe(ppm), and B (ppm) (Table 3). Other soil

variables that tended to be higher at WellsSavannah included pH and Ca (ppm), thoughother individual savannas, such as ShakenCreek and Myrtle Head, also had higher pHand Ca (ppm).

It is not surprising that the Wells Savannahquadrats are distinct in terms of soil charac-teristics. This savanna occurs on a geograph-ically limited Inceptisol – the Liddell soil series– and both the community type and the soilseries may be endemic to the coastal plain ofNorth Carolina. Previously described savannatypes (that did not include the Big Savannah)occur mainly on Ultisols and Spodosols, andthese soil relationships have formed the basisfor current savanna classification systems(Taggart 1990, Peet 2006). Soils from theWells Savannah quadrats, relative to otherarea savanna soils, may have a higher clay

Figure 3. Non-metric multidimensional scaling ordination of the 35 wet savanna quadrats. Wells Savannahquadrats (solid squares) separate from other quadrats based on species abundance values. Environmental vectorindicate important soil variables correlated with axes 1 and 2. Savannah labels are as follows: GreenS 5 GreenSwamp, 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, andWellS 5 Wells Savannah. Number at the end of labels refers to quadrat number. Final stress 5 16.9.


percentage because Ultisols are generallymore highly weathered with subsequenttranslocation of clay downward (Brady andWeil 1999). The fact that the Wells Savannahquadrats are on a relatively young Inceptisolmay indicate that geologic time has been tooshort for the translocation of clays downwardin the profile. A possible reason for the higheriron (ppm) is that long hydroperiods can leadto the reduction of iron in wetland soils (Buolet al. 2003). Although percentage organicmatter and pH did not turn out to be usefulvariables for predicting community type(Figure 4), both were higher on average atthe Wells Savannah relative to other commu-nity types.

It appears that Wells Savannah representsthe hydric end of the hydrological gradient ofNorth Carolina wet savannas. A number ofobligate and facultative wetland species arepresent at Wells Savannah, and a number ofspecies with hydrological niches that rangeinto drier sites, such as Aristida stricta and Xyriscaroliniana Walter (Table 2), are either not

found there or are relatively uncommon.Aristida stricta was not recorded from the BigSavannah (Wells and Shunk 1928) and is alsorelatively uncommon at Wells Savannah.Ctenium aromaticum, one of the dominantgrasses over the majority ‘‘bog proper’’ of theextirpated Big Savannah is known to preferhydric soils and was one of the dominants atWells Savannah. Other dominant grasses atWells Savannah include Arundinaria tecta,Dichanthelium scabriusculum, and Muhlenber-gia expansa, which are all wetland species. B.W. Wells remarked that the Big Savannahwas saturated for up to 10 months of the year(Wells and Shunk 1928), and during thesummer of 2005 portions of Briary Bay Farmsremained saturated to the surface until Au-gust (Wade Wall, pers. obs.). These hydricconditions make this community extremelyvulnerable to woody encroachment. Underfire suppression, this community type in someways resembles a pond pine woodland ratherthan a remnant wet savanna, with the onlyindicators of its former savanna character

Table 3. Means and standard deviations (in parentheses) of 27 soil characteristics for the 35 wet savannaquadrats 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 6.1.2 6.1.5 WellsMean (SD) Mean (SD) Mean (SD) Mean (SD)

CEC (meq/100 g) 3.9 (2.1) 8.3 (5.9) 3.2 (0.2) 5.1 (3)pH 4 (0.3) 4 (0.3) 3.9 (0) 4.3 (0.2)% Org 6.8 (4) 3.2 (3.8) 5 (5.5) 6.6 (1.8)N (ENR) 56.2 (6.1) 58.7 (3.8) 55.3 (6.2) 53.8 (4.2)S (ppm) 31.7 (11.9) 27.6 (6.9) 42.3 (11.7) 22.3 (7.5)P (ppm) 9 (2.9) 11.2 (2.6) 11.3 (4.7) 9.5 (2.3)Ca (ppm) 109.3 (53.2) 364.6 (365.4) 84.5 (4.4) 242.9 (169.9)Mg (ppm) 31.4 (21.4) 32.6 (8.3) 25.8 (1.3) 29.4 (4.7)K (ppm) 23.8 (10) 26 (8.3) 22.3 (3.3) 29.4 (8.3)Na (ppm) 22 (12.2) 21.2 (8.3) 19.5 (4.5) 18.7 (2.2)% Ca 14.7 (4.2) 19.4 (5.4) 13.4 (0.9) 22.9 (4.2)% Mg 6.6 (1.3) 4.3 (2.4) 6.8 (0.4) 6 (2.2)% K 1.8 (0.9) 1.2 (1) 1.8 (0.3) 1.8 (0.7)% Na 2.9 (1.9) 1.5 (0.8) 2.7 (0.5) 2 (0.8)% Othr 9.5 (0.6) 9.4 (0.6) 9.6 (0.1) 8.8 (0.3)% H 64.6 (4.2) 64.2 (4.1) 65.8 (0.5) 58.6 (3.1)B (ppm) 0.3 (0.1) 0.3 (0.1) 0.4 (0.1) 0.5 (0.1)Fe (ppm) 195.8 (55.8) 199.6 (42.6) 198 (104) 440.2 (124)Mn (ppm) 0.7 (0.5) 0.8 (0.4) 1 (0) 0.5 (0)Cu (ppm) 0.3 (0.2) 0.3 (0) 0.2 (0.1) 0.5 (0.1)Zn (ppm) 111.3 (309) 0.9 (0.4) 0.7 (0.2) 1.4 (1)Al (ppm) 711.3 (399.3) 706.2 (200) 831 (218.3) 838.5 (94.8)% Base Sat. 26 (4.8) 26.4 (4.7) 24.7 (0.6) 32.6 (3.4)Ca/Mg ratio 3.8 (1.2) 10.5 (8.5) 3.3 (0.3) 8.2 (5.8)% clay 3.6 (1.5) 3.7 (1.4) 3.7 (0.6) 9.8 (2.7)% silt 53.4 (29.6) 78.4 (7.7) 61.2 (8.2) 48.1 (2.4)% sand 42.9 (30) 18 (8.2) 35.1 (8.4) 42.2 (2.3)


being remnant pockets of wet savanna vege-tation.

Does the lack of historic fire at WellsSavannah explain the species compositiondifferences between Wells Savannah andother Outer Coastal Plain wet savannas? Itis well known that fire suppression can lead toincreased woody abundance (Waldrop et al.1992) and a decrease in species richness

(Walker and Peet 1983); fire suppressionmay also result in reduced species richnessand abundance values of Asteraceae, Faba-ceae, and bunchgrass species of Poaceae(Walker and Silletti 2006). The two powerlinecorridors at Wells Savannah have beenmowed at 3-year intervals for over 30 yearsbut had not been burned until being pur-chased by the North Carolina Coastal Land

Figure 4. Variable importance plot for soil variables from Random Forests (RF) classification used for comparingWells 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.


Trust (Shelingoski et al. 2005). Althoughseveral members of Asteraceae are indicatorspecies of other wet savanna sites that havefire regimes more representative of historicalconditions (Table 2), there are still a numberof representatives of Asteraceae present atWells Savannah, where Asteraceae was thethird most-represented family. Although le-gumes are mostly absent from Wells Savan-nah, B.W. Wells commented on the absenceof Fabaceae species at the Big Savannah(1928), so this is not surprising. Although wecannot rule out the possibility that firesuppression alone has led to the differencesin vegetation between Wells Savannah andother wet savannas in the area, additionalanalyses performed with the removal of allwoody species from the dataset yielded resultssimilar to those presented which supportedthe unique character of the natural commu-nity of Wells Savanna.

Fire suppression of the area surroundingWells Savannah has clearly affected thevegetation, with the fire-suppressed quadrats(from the pond pine woodland at WellsSavannah and from Briary Bay Farm) ap-pearing different from those in the mowedpowerline rights-of-way (Figure 6). As expect-ed, the fire-suppressed areas had reducedspecies richness and an increased abundanceof woody species; however, a number ofsavanna species persist there, includingCtenium aromaticum, Sabatia difformis (L.)Druce, Sarracenia flava L., and S. purpurea L.In addition, several savanna species thathave not been found at Wells Savannah werelocated, the most noticeable being Dionaea

muscipula Ellis. This was surprising because itwas assumed that Dionaea muscipula requiredfrequent fire to maintain open habitat. Asexpected, members of Asteraceae were largelyabsent from the fire-suppressed quadrats.

Figure 5. Non-Metric Multidimensional Scaling ordination of proximity scores from Random Forestclassification methods. Quadrats that are close together are more similar in terms of soil characteristics. WellsSavannah quadrats (solid squares) separate from the other quadrats based on soil characteristics. Labelexplanations the same as in Figure 3 caption. Final stress 5 18.9.


While minor variations in soil characteristicsor hydrology may account for vegetationdifferences between the two sites, this doesnot appear to be the case. Both Wells Savan-nah and Briary Bay Farm are mapped as theLiddell soil series, and there are no differencesin topgography between the two sites.

Although Wells Savannah is a small rem-nant of the longleaf pine savanna communi-ty formerly known only from the Big Savan-nah, enough differences exist in vegetationand soil characteristics relative to currentlyrecognized wet savanna communities to val-idate the uniqueness of Wells Savannah.Although additional sites would need to belocated to warrant establishing a new com-munity type based on unique vegetation andunderlying soils, the two sites included inWatha Savannah—Wells Savannah and Bri-ary Bay Farm – clearly represent a remnantwet savanna at the extreme end of thehydrological gradient. Fire suppression has

undoubtedly led to a decrease in speciesrichness at the Briary Bay Farm site, but asour results show, pockets of savanna vegeta-tion still persist at the site and it is possiblethat other savanna vegetation remnants maybe extant in the general vicinity that resembleWells Savannah and the former Big Savan-nah. Finally, although this community ismost likely limited to the Liddell soil seriesthat occurs mainly in northern Pender Countyand southern Duplin County, North Carolina,other areas in the Atlantic coastal plaininclude Inceptisols under long hydroperiods,and we recommend that researchers seekother representatives of this rare communityin the Atlantic Coastal Plain.

ACKNOWLEDGMENTS The authors thankJoseph Taylor for access to Briary Bay Farmand excellent accommodations during sum-mer 2005. We also wish to thank Zac Hill forhis assistance in data collection at Briary Bay

Figure 6. NMDS ordination of Watha Savannah quadrats. Results show separation of Wells Savannah quadratsfrom both 26 Briary Bay Farm quadrats and 2 quadrats from Wells Savannah in the fire-suppressed woodlandbetween the two maintained powerline rights-of way. Final stress 5 13.5.


Farm and Andrew Walker and Kristen Kostel-nik for general guidance. Mike Vepraskasoffered excellent advice regarding interpreta-tion of soil properties and the Department ofSoil Science at North Carolina State Universitywere gracious enough to allow us to use theirfacilities. We thank Robert K. Peet and ForbesBoyle for providing classification of NorthCarolina wet savannas and assistance withdata extraction from the CVS database. Coast-al Land Trust has been an excellent partnerand we thank them for both preserving WellsSavannah for future generations and grantingus access. The Department of Plant Biology atNorth Carolina State University and the NorthCarolina Agricultural Research Service con-tributed greatly to the financial support of theproject.

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