The Effects of Fire on Species Composition in Cypress Dome Ecosystems


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The Effects of Fire on Species Composition in Cypress Dome Ecosystems
Series Title:
Florida Scientist
Physical Description:
Ewel, Katherine C.
Mitsch, William J.


Subjects / Keywords:
fire ecology
cypress swamp
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United States


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Pages: 25-32

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University of Florida
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No.1,1978] Endronmental SciencesEWELANDMITSCH-FIREEFFECTSONCYPRESS25THEEFFECTSOFFIRE ON SPECIES COMPOSITION IN CYPRESSDOMEECOSYSTEMS'KATHERINECARTEREWEL(1)ANDWILLIAMJ.MITSCH(2)'CenterforWetlandsandSchoolofForestResourcesandConservation (1),andCenterforWetlandsandDepartmentofEnvironmentalEngineeringSciences (2), UniversityofFlorida, Gainesville,Florida32611 ABSTRACT:Cypress trees were more successful than pines lIm/hctrdwo/N!s in surddng a fire which destroyed42%ofthe trees in two cypress dome ecosystems. Cypress treeshadcomprised nearlyhnl!the treesinthe domes, which hml heen drained for secemlyear.s.After the fires. lin acerage of 890/0 ofthe trees were cypress, 9%were hardwoods. ant! 2% were pines. Greatest mortalityIVas illthe centerofthe dome. where organic matter was deepest. BALDCYPRESS(Taxodium distichum(L.)Rich.)andpondcypress(Taxodiumdistichumvar.nutans(Ait.) Sweet)arecommonly found in swamps throughout the southeastandas far north as southern Illinoisandsouthern New Jersey.InFlorida, small, circular swamps (usually lessthan5 halarefrequently called domes, because the trees are taller in the middlethanat the edges, giving the swamps a dome-shaped profile. Cypress ecosystems normally have standingwateratleastpartof the year; manyaredry from late fall through late spring.Ithas longbeenrecognized (e.g.Harper,1927; Garren, 1943)thatcypress swampsareoftenburnedduring the dry season, yetthereislittle documentation of the effects of fire on the ecosystems. BeavenandOosting (1939) mentionedthata firethatburnedfor 6 months in the cypress-dominated Pocomoke Swamp in Marylanddestroyed the trees as well as most ofthepeatthathad accumulated.Cypert(1961) described the damage done by fires in the Okefenokee Swamp in 1932andin 1954and1955. Allbutthe largest pondcypress treeswerekilled intwoareas, although more trees survived on the site where peat depoSits were shallower.Inboth areas, most of the regrowth wasbycoppicing. KurzandWagner(1953) postulatedthatthe characteristic shape of cypress domesisduetothegreaterlikelihood of fire around the outside of the swamp, where thegroundmayhedryfor agreaterpartof a year. Researchersatthe University of Florida are currently investigating the feasi bility of utiliZing cypress swamps for the disposal of secondarilytreatedsewage.Partof the field work for the projectisbeing carriedoutata sitenearGainesville,'ThispaperisUniversity of Florida Agricultural Experiment Station Journal Series No.9]l.'WJMat Pritzker Departmentof Environmental Engineering, Illinois Institute of Technology,Chicago,llIinois 60616.'The costs of pnhli{'ati011 of this ar!ide were defrayedillpart hythepayment of {harges from made availablein support of the rcsc

26FLORIDASCIENTIST[Vol. 41Florida, where several small cypress domes are located in a slash pine plantation(Pinus elliottiiEngelm.) Following an unusually dry fall, a forest fire swept thesiteinDecember 1973; the locationofthe domesand-the extentofthe fire areshown in Fig.1.Two oftheseverely burned domes have been studied intensively since then.Whenthe project began in June 1973, pondcypress, black gum(Nyssa bifloraWalL), sweet gum(Liquidambar styracifluaL.),and sweet bay(Magnolia virginianaL.)were the most common treesinthe domes. Since the area had been drainedbya series of ditches for many years, several slash pines grewinthe domesaswell. The understory was very dense, but had not been characterizedprior tothefire.Thefloor of the two burned domes smoldered for several weeks after the fire,butdid notburnextensively enough to expose the mineral soil. After the fire, nostanding water was present in the domes until March 1974, when secondarily treated sewage effluent was pumped into one and groundwater into the other.Pumping rates varied initially from 0 to14cm/wk,but have been constant at 2.5cm/wksince April 1975. Many trees in the two badly burned domes perished in the fire.Thedifferen tial rates of mortality among the three kinds of trees (cypress, pines, and hardwoods) were of interest because of their implications for long-term survival of cypress ecosystemsinareas where invasion by other species follows drainage.METHoos-After the fire, maps were made of the two badly burned domes.Both live and dead trees were recorded forDomeI, but only live trees weremappedin Dome 2. Heights and diameters of all live and dead trees in both domes were recorded. Another survey was conducted the following year to de termine delayed tree mortality. In both surveys, dead hardwoods were grouped together because they could notbepositively identified to species. REsuLTs-The numbers of live and dead trees before and oneyrafter the fire are shown in Table1.In both domes, the majority of pine treesandhardwoodsTABLE1.Effectsoffire on numhers and hiomassofcypress treesin domes.Dome2Kindof%ofTrees %of LivingTree Before Fire%Decrease Trees Cypress51.9 18.0 96.2Pines27.2 95.7 2.6Hardwoods20.9 97.61.1TOTAL(599 trees)55.7(265 trees) Cypress43.6 22.5 81.6Pines14.2 95.81.4Hardwoods42.2 83.3 17.0TOTAL(1334 trees)58.5(553 trees)were killed, while only a small percentage of the cypress were killed. Cypress comprised about half the trees in the dome before the fire,and80 to 90% afterthefire. Cypress in Dome 2 suffered heavier mortality thaninDomeI,but a


No.1,1978JONCypRESSFIREEFFECTSANDMITSCHEWEL27IIo o NII500FEET1000TRAILERPARKANDCLEAREDAREABURNEDoCYPRESSSWAMPtalsiteofthe <:YI atthe expcrunen d es:-; domes '1 LocationofJmrne <.ypr Fl<...'IIFlorida.near Gainesvle,lresswetlandsproJc<.t


28FLORIDA SCIENTIST[Vol. 41 larger proportion of the hardwoods, which had equalled cypress in number be fore the fire, survived. Dome 2isthe larger of the two (0.69haand0.57 hal and had a higher density of trees both before and afterthefire.ithadnot beensoseverely drained originally, andhada considerably lower percentage of pinetrees than didDome1.Table 2 shows the differencesinsize between live and dead trees in the domes. With the exceptionofpine treesinDome2, the surviving trees tended to be larger than the trees killed.TABLE2.Mean heights and diametersofthree classes of trees intwoburned cypress domes. Mortalitywasdeterminedoneyear after the fire ..DomeDome 2Mean HeightMeanDBHMeanHeightMeanDBHClass1m)(em)(m)(em)Cypress:Live17.3 24.0 17.7 21.6 Dead10.5 12.3 11.3 12.0 Pine: Live14.217.9 9.6 10.6 Dead13.9 16.3 12.814.7Hardwood:Live10.117.7 8.6 10.4Dead8.310.7 6.8 7.2....Significant difference at 1%level.Distribution of surviving cypress treesinDome 1 after the fireisoutlinedinTable 3. Density of the trees varied from 0.17/m' in the center to O.09/m' at30-40 m.Thehighest mortality occurred inthe 315-m' central area where there were 55 trees before the fire: 29 cypress, 19 hardwood, and 7 pine. Only10trees survived, all cypress. Average height and DBH of the treesthatdied were close to the averages given for dead trees in Table 2. DISCUssION-Hare (1965) analyzed fire resistance in14southern trees, find ing that, for trees of equal bark thickness, longleaf pine(Pinus palustris, Mill.) and slash pine are the most resistant to cambial damage, followed by loblollyTABLE3.Patternofsurvival of trees inDome1.Areas are given for (.'oncentrk rings in thedomeat specified distances from the center.Distance from center(m)0-10 10-20 20-30 30-40 40-50 50-60 315 942ISil 1363 405 216 Survivors{%)1854 48.'335950


No.1,1978]EWELANDMITSCH-FIREEFFECTSONCYPRESS29 pine(Pinus taedoL.)and baldcypress, then by several hardwoods, of which theleast resistant are sweetgum, black cherry (Prunu8 seratina Ehrh.), and Americanholly(flex 0pocoAit.).Fora given tree, fire resistance generally increases withtree diameter, since thickerbarkand a higher crown prevent damage to either cambiumorcrown. Both cypress and pine might thereforebeexpected tosurvive burning better than hardwoods. However, the cypress trees at the experimental site were larger than either the pines or the hardwoods.Since crown damageisusually more likely to kill a slash pine thanisbole damage (CooperandAltobellis, 1969), slash pine less than 1.5 m tallareeasily killed in a light fire. Control burningistherefore inadvisable beforethetrees are 3.5 m tall (Cooper, 1965).Thepine trees in the plantation surroundingtheexperimental site averaged 4.5 m tall,sothey probably could have withstood a lightfire. Nevertheless, all these trees were destroyed.Hardwoods, on the other hand, are seldom completely destroyed by a fire, particularly in the winter when rootstocks are healthiest (Cooper, 1961). The factthatmany of the hardwoods in the cypress domes were killed attests to theintense heat that must have built upinthe organic matter on the floorofthe cypress dome. Komarek (1972) observed that the bark ofthecypressisfairly thickand fire-resistant, and that the formationofadventitious buds even after severe damage assists recovery. The majority of the cypress trees burned at the experi mental site did put out adventitious branches, and someofthe more severelydamaged trees survived by coppicing. In this case, the firehada "cleansing" effect on the cypress dome, destroy ing most of the pines which were growing inthedome. Many of the hardwoodswere also destroyed, but cypress trees are clearly capableofsurviving a verydamaging fire.Cypert(1961) observedthatgreater mortality of cypress on one burned siteatthe Okefenokee Swamp may have been due to greaterdepthof or ganic matter, since a smaller proportion of the roots would have extended into the mineral soil where they might have been more protected from fire. In a study of15cypress domes in north-central Florida, Monk and Brown (1965) found more organicmatter(25-33 em) in the soil beneath the central pool thanattheedges (5-10 em). Accordingly, Coultas and Calhoun (1975)hadfound that the organic andAlhorizons were 43 em deep in thecenterof Dome 1 and13em deep half way totheedge. The Ap horizon was15em deepatthe edge. No measurementshadbeen made intheother dome. The unusually low proportion of cypress trees that survived in the center of Dome 1 therefore supports Cypert's conclusion, and suggeststhata fire whichishot enough to burn into thepeatmay have moreserious consequences in the center than around theedges.Ina cypress dome with a normal hydroperiod, the existence ofanopen central pool maybeattributed to both the effects ofanoccasional fire during a dry spellasdemonstrated in this study, andtheprevention of germination by thepresenceofstanding water during normallywetyearsasshown by Demaree(1932). Pine trees invade cypress domes which remain dry for several years.Other work at the cypress dome experimental site indicates that decompositionofcypress needles occurs more slowlyindry areas than inwetareas (Deghi,


30FLORIDASCIENTIST[Vol. 41 1976).Moreover,netproductivityappearstobegreaterindraineddomesthanin undisturbed ones (CarteretaI.,1973;Mitsch,1975),solitterwillaccumulatefairly rapidly onthesurfaceofadrydome. Fires whichburnthroughcypress domesafterlongerandlonger drying periods will therefore do progressivelygreaterdamage, sincetheorganic layers onthefloor ofthedomeswillhavebuiltuptoagreaterextent. Cases havebeendocumentedin which cypress havebeeneliminated entirely from aburnedsite. Wells(1928)described shrub-choked bogs which developed afterNorthCarolina swamp forests(characterizedbyNyssa, Taxodium,andChamaeclJParis)hadbeendamagedbyfire.Whenwetconditions prevailed in such bogs, titi(Cyrilla racemifloraL.)predominated.Cypert(1961)showedthatfires in1954and1955causedtheformation of prairies intheOkefenokee Swampbyburningintothepeatbedand killingthetrees.Nootherfires since1844hadhadsuch a severeimpactontheswamp. Periodic fireswillhave little effect onthespecies composition of a cypress domeundernormally wet conditions,andcypresswillcontinue tobedominantin adrainedcypress domethatissweptbyperiodic fires. Lack of fire indrainedordrycypress domes will allow a mixedstandofcypress andpinetodevelop. Afirewhichoccurs after a long drying period in either casewilldo its greatestdamageinthecenterof a dome,andmay eliminate cypressaltogetherifsufficientorganicmatterhasaccumulatedaroundtheedges.ACKNOWLEDGMENTS-Thiswork wassupportedbytheNational ScienceFoundation'sprogramofResearch Applied to National Needs,GrantAEN 73-07823 AOl (formerly GI-38721), andbyTheRockefeller Foundation,GrantRF-73029 (H,T.OdumandK.C.Ewel, principal investigators).LITERATURECITEDBEAVEN,G. F.ANDH. H.OoSTING.1939. Pocomoke Swamp: A study of a (:ypressswampontheeast ern shore of Maryland. Bull. TorreyBot.Club 66:367-389. CARTER,M.R,L.A.BURNS,T. RCAVINDER,K.R DUGGER, P.L.FORE,D.B.HICKS,H.L. Rf-:VELLS, ANDT.W.ScHMIDT.1973. Ecosystem analysis oftheBig Cypressswampandestuaries. U.S. E.P.A. RegionIV.Atlanta.COOPER,R W. 1961. Effects of prescrihed fire on understory stems inpine-hardwoods standsof Texas. J.Forest. ____. 1965. Prescribedburningand control of fire. In Guide to lohlollyandslashpineplanta tionmanagementin southeastern U.S.A. Ga. Forest Res. Coune. Rept. 14:131. ____ ,ANDA.T.ALTOBELLIS.1969.Firekillinyoung loblolly pine. USDA For.ServoFireContr. Note, 30(4),14-15.COULTAS,C.L.ANDF. G.CALHOUN.1975. A toposeqllence of soils inandadjoining a cypress domeinNorthFlorida. SoilCropSci. Soc.Florida35:186-191. CYPERT, E.1961.Theeffects of fires in the OkefenokeeSwampin 1954 and 1955. Amer. MidI. Nat. 66,485-503. DEGHI,G. 1976. Litterfall and litter de(.'ompositioninfom cypress domes. Pp. 197-231. In OduOl, H.T.etal. (eds) CypressWetlandsforWaterManagement,RecyclingandConservation.ThirdAnnual Report to National Science FoundationandTheRockefeller Foundation.DEMAREE,D. 1932. Submerging experiments withTaxodium.Ecology 13:258-262.GARREN,K.H.1943. Effects of fire on vegetation ofthesoutheastern United States. Bot. Rev.9:6]7654. HA.RF., RC.1965.Contrihutionof hark to fire resistanee of southern trees. J.Forest. 63:248-251. IIA.RPER, R t>,1. 1927. Natural resources of south Florida. Florida Ceol. Surv., 18th Ann. Rept.:27-192.


No.1,1978JEWELANDMITSCH-FIREEFFECTSONCYPRESS31KOMAREK,E.V.,SR.1972. Ancient fires.Pp. 219-240.InProc.Ann.TallTimbersFireEeol.Conf.No. 12.TallTimbersRes. Sta. Tallahassee.KURZ, H.,ANDK.A.WAGNER.1953.Factorsincypress dome development. Ecology .34:157-164.MITSCH,W.J.1975. Systems AnalysisofNutrientDisposalinCypressWetlandsandLake Ecosys tems in ,Florida. Ph.D. Dissert. Univ. Florida. Gainesville.MONK,C.D.ANDT. W.BROWN.1965. Ecological considerationsofcypress headsinnorth-centralFlorida. Amer. MidI. Natl. 74:126-140.WELLS,B.W. 1928. Plant communities of the coastal plain of North Carolina and their slKTessional relations. Ecology 9:230-242.Florida Sci. 41(1):25-31. 1978.Earth SciencesTHE TAMIAMI FORMATION-HAWTHORN FORMATION CONTACT IN SOUTHWEST FLORIDATHOMASM.MISSIMERMissimer and Assoc., Inc., 2500 Del Prado Blvd., SuiteB,CapeCoral, Florida 33904 ABSTRACT: Stratigraphic placementofthe Tamiami Fonnation-Huwthorn Formation contact has been arbitrary in subsurface inustigations in southwest Florida. This contactisproperly posi tioned beneath a dark colored carbonatemudunit, which containslargeconcentrationsofdetrital phosphorite, quartz sand,and various clay minerals. Themud unit, known infomudly as theFortMyers claymemberofthe Tamiami Formation, cot.:'ers the Hawthorn Formationinnearly allofsouthwest Florida. The formational contactisdistinctiveinwestern Lee andCharlotte Countie .... whereit is a stratigraphic disconformity.andbecomes less distinctivetothe southandeast, where deposition has been continuous andno breakinthe stratigraphic record is evident. G PROPERDELINEATIONof the contact between the Tamiami Formation and the underlying Hawthorn Formation in stratigraphicandhydro-geologic investiga tions hasbeena recurring problem in soutb Florida. Both units are lithologically complexandcontain numerous differing sediment facies. Although these forma tions are separated in partbyan unconformity,thelower-most Tamiami sedi ments sometimes have a similar composition to the uppermost Hawthorn sedi ments. Different contact placements have been made onthesame stratigraphic sequence with early investigators placing the contact high in the sequence (Cooke, 1945; Klein, Schroeder and Lichtler, 1964; Puri and Vernon, 1964) and later investigators placing the contactata lower stratigraphic position (Sproul, BoggessandWoodard, 1972; Boggess and Missimer, 1975; Missimer, 1975; Peck, MissimerandWise, 1976; Peck, 1976).Theincreased emphasis being placed on groundwater investigations in south west Florida necessitatestheneed for detailed, accurate, stratigraphic control in order to properly delineate regional hydraulically connected aquifers. New paleontologic data andbetterstratigraphic control have nowpermittedthees-Thecosts of publication of this article were defrayedinpart hy the payment of charges from funds made availablein support of the research whichisthe subject of Ihis article. In accordance with18U.S.C. 1734, this article must thereforebehereby marked "advertisement" solely to indicate this fact.