Woody vegetation diversity of longleaf pine communities in Calcasieu Parish, Louisiana

10 Pages·1998·3.3 MB·English

by  Ray Neyland

Phytologia(July 1998)85(l):51-60.
WOODY VEGETATION DIVERSITY OF LONGLEAF PINE COMMUNITIES IN
CALCASIEU PARISH, LOUISIANA
RayNeyland,HarryA.Meyer,&HeatherHarrington
DepartmentofBiologicalandEnvironmentalSciences,McNeeseStateUniversity,
LakeCharles,Louisiana 70609-2000 U.S.A.
ABSTRACT
LocatedinsouthwesternLouisiana, Calcasieu Parish oncesupported large
areas of undisturbed longleaf pinelands. These pinelands were clear cut
around 1900and have beenconverted largely toforest, range, and cropland.
AlthoughvirginlongleafpinelandsnolongerexistintheParish, afew remnant
sitesretainmanyoftheirpresettlementplantspeciesand characteristics. Three
distinctlydifferentlongleafpine communitieswere identified and sampled to
determinewoody species diversity and importance. Diversity values of the
threecommunitiesdiffered significantly from each other. The acid longleaf
pineflatwoodscommunitywas lessdiversethaneitherthehillsideseepagebog
community or the sodic longleaf pine flatwoods community. The low
diversity value for the acid longleaf pine flatwoods community was due
primarily to low species richness when compared to the other two
communities. Although the hillsideseepage bogand the sodic longleaf pine
flatwoods each had identical species richness values, the disparity in their
diversity values is explained primarily by the greater evenness of species
abundance at the sodic longleaf pine flatwoods community. The various
mixtures of woody species sampled suggest a high degree of heterogeneity
amongthesiteschosenforstudy. Forexample,oftheelevendifferentspecies
found among the three communities, only Pimis palustris was present at all
three. Piniispaliistriswas themostimportantinallbut thesodic longleafpine
flatwoods community where it was second to P. elliottii. The importance
value forall combinedcommunitieswas clearlydominated by P. palustris at
140.69. Pinus eUiottii had the second highest importance value for all
combinedcommunitiesat62.83 with Myricacerifera third at31.58. Relative
coverageforall communitiescombined was alsodominated by P. palustrisat
55.82% withP. elliottiiandM. ceriferaat31.73% and6.56% respectively.
KEY WORDS: Calcasieu Parish, Louisiana, longleaf pine communities,
woodland remnants
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52 July 1998 volume85(1):51-60
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The longleaf pineland region of the West Gulf Coastal Plain (Bridges Orzell
1989) extends across northern Calcasieu Parish (Figure 1). This region originally
extendedfromsoutheasternTexastonorth-central Louisiana(Wahlenberg 1946; Little
1971). These pinelands were clearcut in the early 1900's (Roy & Midkiff 1988;
Smith 1991) and now existprimarilyas forest, range and cropland (Roy & Midkiff
1988). Remnantlongleafpinecommunitiesofthe WestGulfCoastal Plain identified
byOrzell(1987)andBridges(1988) arecurrentlythreatenedby grazing, silvaculture,
andwildlifemanagement(Bridges&Orzell 1989). Theoncevirginlongleafpinelands
as described by Schwarz(1907) and Wahlenberg (1946) are now rare in Louisiana
(Smith 1991). However, a few comparatively undisturbed sites within Calcasieu
Parish appear to retain many of their presettlement plant species and remain
recognizablelongleafpinecommunities(sensu Bridges & Orzell 1989; Smith 1991,
1996). Theseraresitesaresmallandmaybeconsideredremnantsofaoncedominant
ecosystem.
The purpose of this study is to characterize the adult woody vegetation of three
remnantlongleafpinecommunitiesin CalcasieuParish in termsofdensity, frequency
coverage, and importance. These communities are referred to as hillside seepage
bogs, sodic longleaf pine flatwoods (sodic flatwoods), and acid longleaf pine
flatwoods(acidicflatwoods). ThisterminologyissensuSmith(1996).
STUDYAREA
Located in southwestern Louisiana, Calcasieu Parish is adjacent to Beauregard
Parish to the north, Jefferson DavisParish totheeast, Cameron Parish to the south,
andtheSlateofTexastothewest(Figure 1). Approximately46%oftheParish's land
isdevotedtoeitheragricultureorrangeland;approximately23% is woodland; 11% is
marsh;4%swamp;andtheremainingareaisurban (Roy & Midkiff 1988). Land use
isdevotedprimarilytotimber,cattle,rice,andsoybeans. Peux)leum-relatedindusuies
arepresentintheP^shandareconcentratedaround theareaof Westlake. Calcasieu
Parishisnoteworthyfortheabrupttransition from thelongleafpinelands in the north
totheprairieandcoastalmarshesinthesouth(Figure 1).
The first study site is a hillside seepage bog situated about 8 km northeast of
DeQuincy;(93** 23' 83" x 30** 28' 92");rangeand township (RlOW x T7S Sect. 1)
(Figure 1). This is the only known representative of this community type in the
Parish. The siteextends approximately600 m on a north-south-axis by 36 m on an
east-westaxis and is bounded to the west by a semi-evergreen broadleaf acid seep
forest {sensu Bridges & Orzell 1989), and to the east by a stand of Pinus eUioaii
Engelm. Thisbogappearstobetheheadwatersofasmall unnamed stream. The soil
type is "Glenmora silt loam" (Roy & Midkiff 1988) and is characterized by an
extremelyacidicsilt loam surface layer and a strongly acid silty clay loam subsoil.
Distinctiveherbaceous species include Rhynchospora oligatuha A. Gray, Sarracenia
alata (Wood) Wood, and Utriculariacomuta Michx. Charred bases of P. palustris
Mill, indicatethesitehadburnedwithinthepastseveralyears.
Neylandetal.: WoodyvegetationinCalcasieuParish 53
CoastalMarsh
BottomlandForests
CoastalPrairie
Swampland
LongleafPine
Figure 1. Area of longleaf pineland in relation to other regions within Calcasieu
Parish, Louisiana. Insetshows thelocationofthe Parish within the State. Study site
#1 = hillsideseepagebog;#2= sodicflatwoods;#3 =acidicflatwoods.
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54 July 1998 volume85(1):51-60
Thesecondstudysiteisasodic flatwoods thatis situated nearafew othersimilar
sites in thewestern part of Calcasieu's longleaf pineland region (Figure 1). These
flatwoods are typicallysaturatedduring the winterand spring but may become very
dry during summer droughts. The specific site studied is situated about 22 km
southwest ofDeQuincy;(93' 34' 15" x 30** 18' 74");rangeand township (RllW x
T8SSect.35)(Figure 1). Itisboundedtothesouth by the Houston Riverand to the
westbyCreekRoad. Thecommunityis approximately2.5 km long on itseast-west
axisand2.0 km longon its north-southaxis. Distinctiveherbaceous species include
Spartina spartinae (Trin.) Hitch., Chaetopappa asleroides (Nutt.) DC., Evolvulus
sericeus Sw., and Liatris punctata Hook. The understory woody vegetation is
stunted. Thesoil typeis"Brimstone"andhas avery stronglyacidicsiltloam layer, a
subsurfacethatismediumacidsiltloam,andasubsoilofalkalinesiltyclaythatis high
insodium(Roy&Midkiff1988).
Thethirdstudysiteis an acidicflatwoodsand is situated in thecentral partof the
longleafpinelandregion,about10kmsoutheastofDeQuincy;(93** 20' 85" x 30** 22'
63");rangeand township (R9W x T7S Sect. 11) (Figure 1). This acidicflatwoods
extends about 1.2 km on its north-south axis and about0.4 km on its east-westaxis
and is bounded on the east by Hoibrook Park Rd. and to the west by cleared land.
Thesoil type is "Caddo-Messersiltloam"and has avery strongly acidicsurface and
subsurfacelayer(Roy&Midkiff1988). Thesubsoil isstronglyacidsiltyclayloamor
siltloam. Theterrainisleveltogentlyrollingwithsmallelevatedareastermed"pimple
mounds"byHolland^/a?. (1952). Under natural conditionsand frequentfires, these
flatwoods support a sparse canopy of longleaf pine with few other tree species
(Bridges& Orzell 1989). The plantingofpine plantationsand firesuppression have
neariyeliminatedthesecommunitiesin the Parish. Distinctiveherbaceous species in
this communityincludeStylisma aquatica (Walter) Raf. and Platantfieranivea (Nutt.)
Luer. Toour knowledge, this is the only acidic flatwoods community in Calcasieu
Parishthatsupportsarichherbaceouslayer.
MATERIALSANDMETHODS
Thethreerepresentativecommunitytypeschosenforthisstudysharethefollowing
characteristics: 1) longleaf pine is a major component; 2) community maintenance
requires frequent fires; 3) herbaceous ground cover is species rich. Each site was
selected torepresentone ofthe three longleaf pine communities in Calcasieu Parish
that shares these criteria. Although these sites are not pristine, we consider them
&
recognizable longleafpine communities(sensu Bridges Orzell 1989; Smith 1991,
1996).
Eachsampledareameasured 100malongitslongaxisand36 m on its short axis.
Datawerecollectedon treeandshrubspecies(vineswereexcluded) with adiameterat
breastheight(DBH);(1.3 m)of 1 cmor greater. Randomly selected ten by ten meter
quadrats(plots)wereusedforsamplingwithin thedefined study sites. Plotsize was
basedon thatrecommendedfor forest trees by Cox (1996) and Brower etd. (1998).
:
Neylandetal. WoodyvegetationinCalcasieuParish 55
The numberofplots sampled persite was determinedby constructinga species area
curvetoensureweencounteredthebulkofspecies present (Cox 1996). Specifically,
aplotofcumulativenumberofspeciesencounteredversuscumulativenumberofplots
sampled indicated fifteen plots was adequate to sample neariy all of the species
present. Samplingforhillsideseepage bog, sodic fiatwoods and acid fiatwoods sites
were performedon April8, May3, and May 20, 1998 respectively. Nomenclature
followsKartesz(1994).
Frequency,density,coverage(basalarea)andimportancevalueswerecalculatedto
determinethe dominantwoody species (Cox 1996). Basal area was estimated from
DBHvalues. Theimportancevalue is equal to the sum of relativefrequency, relative
density,andrelativecoverage. Thesevalueswerecalculatedforeachof the threesites
individually and for all sites combined. Species diversity was calculated using
Simpson's DiversityIndex(Cox 1996)andwascalculatedfromdensitydata. Because
we consider the few small "pimple mounds" to be "intrusions" into the acidic
fiatwoods site, woody species were excluded from sampling. However, a complete
inventoryofthewoody speciesinhabitingthese mounds was madeand is included in
thefollowingsection.
RESULTS
Species area curves (Cox 1996) suggest that fifteen samples were sufficient to
encounter the bulk ofspecies presentateach site. That is, the final plot number for
eachsitewas positionedwellintotheasymptoticportionofthecurve.
Woodyvegetationdiversityvaluesamongthecommunitiesdifferedsignificantly(p
< 0.05) (Table 1). The low diversity value for the acidic fiatwoods site was due
primarily to low species richness as compared to the other two communities.
Although the hillside seepage bog and the sodic fiatwoods site each had identical
species richness values (Table 1), the disparity in diversity values is explained
primarilybygreaterevennessofspeciesabundanceatthesodicfiatwoods.
Density, frequency, coverage, and importancevalues forall sites are summarized
inTable2. Thevarious mixturesofwoody species sampled suggest a high degreeof
heterogeneityamongthethreesites. Oftheelevendifferentspecies discovered among
thesites, onlyFinnspaliistriswas presentinallthree. Myricacerifera L. was present
in all three communities but no individuals metour size criterion for sampling in the
acidic fiatwoods due to a recent burn. Additionally, seven species were present in
only one of the three sites: P. elliottii. Ilex vomitoria Aiton, Quercus nmrilandica
Muench, ViburnumdentatianL., /. coriacea(Pursh) Chapm., Uquidambarstyraciflua
L., and Sapium sebiferum (L.) Roxb. (Table 2). Heterogeneity among the
communities is also demonstrated by the importancevalues ofP. palustris. That is,
although P. palustris was the most important species for all communities combined
(Table3), it was onlv the second most importantspecies in the sodic fiatwoods site
(Table2).
PHYTOLOGIA
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Table 1. Simpson's Diversity Index, variance, and species richness of woody
vegetationbystudysite.
Site
Neylande/a/.: WoodyvegetationinCalcasieuParish 57
Tables. Density,frequency,coverage, andimportancevaluesby species summarized
forallsites. Speciesarearrangedinorderofimportance.
Species
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criterion. Ofthesethreespeciesencountered,onlyM. ceriferaappearedtobe common
onthesite. Thewoodyvine,Smilaxlaurifolia, wasalsopresent.
A completeinventoryofthe woody species inhabiting the pimple mounds within
the acidic flatwoods community includes Sapium sebiferum, Acer rubrum, Myrica
cerifera. Sassafrasalbidum (Nutt.) Nees, Quercusfalcata Michx., Q. nigra L., Ilex
opaca, andLiquidambarstyraciflua.
DISCUSSION
Although not pristine, the three remnant sites analyzed in this study resemble
longleafpinecommunities before settlementand clearcutting. However, the current
stateofthesepinelandsisundoubtedlydifferentfrom thetimeprior tosettlement. For
example,themostimportantspecies found in thesodic flatwoods site, Piniiselliotlii,
is native only in Louisiana parishes east of the Mississippi River (Rora of North
AmericaCommittee 1993) and, therefore, would have been absent in preseltlement
times. Althoughthiscommerciallyintroducedspecieshistoricallyhasbeenused forits
naval stores, P. elliottii has become an increasingly important plantation pine for
lumberandplywood(RoraofNorthAmericaCommittee 1993). The establishmentof
P. elliottiihasalmostcertainlydisplacedothernativewoodyspecies.
Stepshaverecentlybeentakentopreserve atleasta partof the sodic flatwoods in
Calcasieu Parish. The Nature Conservancy of LxDuisiana has recently purchased
approximately240 contiguous acres ofsodic flatwoods along Persimmon Gully that
areadjacenttostudysitenumbertwo(RichardMartin,pers. comm., 1998).
Theacidflatwoodsandhillsideseepagebog sites support afew individualsof the
introduced Sapium sebiferum. This native of subtropical China, commonly called
Chinesetallow,hasbeenplantedinseveralareasoftheworidasanornamentalandfor
theproductionofvegetabletallow and stillingiaoil from its fruits (Kahn etd. 1973).
This species was introduced to the Southeast by the U.S.D.A. Bureau of Plant
Industryintheearly 1900's toestablish local soap industries (Jamieson & McKinney
1938). TheabilityofSapium toaggressively invadeand quickly alterhabitatis well
documented(Cameron& Spencer 1989; Bruceetd. 1995; Neyland &. Meyer 1997).
Atpresent, theincidenceofSapiumatthesetwositesis low. However, itremains an
openquestiontowhatextentthis species will altertheecologyofthese communities.
Additionally, species composition in the hillside seepage bog has been altered since
settlementtimes by the introducedPinus elliottii. Specifically,all but the lowermost
36mofthehillsideseepagebognow supportsadensestandofP. elliottii.
The future of these remnant longleaf pine communities in Calcasieu Parish is
uncertain. Most remain threatened by urbanization, wildlife management practices,
and silvaculture. Withoutactiveprotection, these rarecommunities may be destined
forextinctioninCalcasieuParish.
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Neylandetal. WoodyvegetationinCalcasieuParish 59
ACKNOWLEDGMENTS
We thankLatimcweSmith from the National Heritage Program of the Lx>uisiana
&
DepartmentofWildlife Fisheriesforreviewingpreviousdraftsofthis paperand for
providingusthelocationofthehillsideseepagebogstudysite. Wealso thank Lowell
E. Urbatsch (Louisiana State University) and Mark Paulissen (McNeese State
University)forreviewingthispaperpriortosubmission.
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