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s The Connecticut Stand Dynamics Agricultural in Connecticut Experiment Forests: The Station, New Series Plots New Haven (1959-2000) BY JEFFREY WARD S. Bulletin 995 June 2005 Stand Dynamics in Connecticut Forests: The New-Series Plots (1959-2000) JEFFREY WARD S. MostofConnecticutappearsasaseaofhillsswathed containfewconifers, andhaveanunevendistribution withtreeswhenviewedfrom ahighoverlook. This amongsoil moistureclasses. seeminglynever-changingcloakoftreesis, in fact,a Therefore, fouradditional tracts,theNew-Seriesplots, constantly changingassemblageofindividualtrees. Most wereestablished in 1959-1960. Thesetractswere ofourforest, includingthetractsdiscussedinthisbulletin, establishedon siteswitheitherdryormoistsoilmoisture havearisen afterharvestingorfarm abandonmentinthe classes. Datafromtheseplotswereusedtodeterminethe 1800's(WardandBarsky 2000). Theyoungsaplingswhich relationshipbetween defoliationlevelsandsubsequent grewonthosecutoverandabandonedlandsarenowthe mortality (Stephens 1971, 1981).Thesefourtractsrepresent large, uppercanopytrees inourforeststoday. awidergeographical distribution,amoreevendistribution Becauseforestgrowthanddevelopmentarelong-term amongsoil moistureclasses, andagreaterdifferencesin processes,patternsofforestdevelopmenthavebeen largely ageoftrees.Twoofthetractscontained abundantconifers: derivedusingindirectmethodssuchasstandreconstruction easternhemlockandeasternwhitepine(scientificnamesof andcomparingstandsofdifferentages. Indirectmethods woody plants are inAppendixI). Asurveyofthe haveoutlinedthegeneral frameworkofforeststand permanenttracts in 2000documented fortyyearsof dynamics. However,theyareoflimitedutility inproviding dynamicchangeinforestcomposition. Thesechangesin aspecificpredictiononthefuturedevelopmentofan forestcompositionwill affectthequality andvarietyof individual standoftreeswithitsuniqueinitial composition forestresourcesthatareavailabletofuturegenerationsand anddisturbancehistory. wildlife. Therefore, itisprudentfrom bothecological and Ultimately,foreststanddevelopmentistheaggregateof economicperspectivestounderstandthesechanges and thegrowth,ordemise,ofmany individualtrees. theirpossibleconsequences. Understandingthecausal factorsthataffectthefuture growthandsurvivalofindividual treeswill leadtobetter TRACTLOCATIONSANDHISTORY comprehensionofhowthesefactorsinfluenceforest Becausethe initial reportofthesetracts(Stephensand succession. Thisrequiresalarge long-term databasewith Hill 1971) isoutofprint, descriptionsoftheforestsare detailed informationon individualtrees. Fortunately, four repeatedhere. The fourtractsall lie intheuplandregionof large,permanenttracts,theOld-Seriesplots,were metamorphicrocksandglaciatedsoils. TheEastern tracts, establishedinyoungforests(~25-years-old) incentral GayCityandNatchaug,arerelativelyyoungerhardwood Connecticutin 1926-27. Thesetractswerereexamined in forests. TheWesterntracts, Catlin WoodsandNorfolk,are 1937, 1957, 1967, 1977, 1987, and 1997. Thesetracts are olderandhaveasignificantconifercomponent. Thetracts invaluablebecauseofthelength(since 1926-27),depth vary insoil,climate,andhistory. (43,357trees,41 species), andbreadthofinformation TheGay Citytract,mostly intheMeshomasic State (species, dbh, crown class,spatial location, etc.). In ForestnearGay City StatePark, isamixedhardwood addition,theircontinuityandreplicationonfoursitesmake woodlandwithfewconifers. Oneportionoccupiesthecrest thesetractsunique. ofanorth-southridgeatanelevationofabout 850 feet.The Earlierreports(Stephens andWaggoner 1980, Wardet abundanceofrocks,thepresenceofoldcharcoalhearths al. 1999)havedescribedchangesoccurringduringseventy andstonewallsandtheabsenceofaplowlayersuggestthat yearsontheOld-Seriesplots. Changesingrowth,mortality the landwascleared,butnevertilled. In 1980, dominant andingrowthwererelatedtosoil moistureanddefoliation. treesonthesomewhatexcessivelydrainedridgetopwere Thesedatahavealso beenusedtoexaminethe long-term foundtohaveoriginatedbetween 1905-1910andthe effectsofwildfire(Wardand Stephens 1989),gypsy moth smallertrees,between 1910-1920. Scattereddominants defoliation(Stephens 1971),and individual tree originatedbefore 1900onthemoistersites andaround development(Ward and Stephens 1994, 1996, 1997). 1880onthepoorly drainedsite. Theremaining smaller However, all fourtractslierelatively closetooneanother. canopytreesonthesesitesoriginated around 1910. This tract liesclosest, about 10milesnortheast,to threeofthe standDynamics inConnecticutForestsNewSeries Old-Seriesplotsreported inanearlierbulletin (Wardetal. 100 1999). West (conifer) TheNatchaugtract is astandofmixedhardwoodinthe Natchaug StateForestin Eastford, about25 milesnortheast 80 'East (hardwood) ofGayCity. Itsgently rollingtopography ranges in elevation from 700to 750 feetand itsnorth-facingslope c 60 o varies fromoneto sevenpercent. Stonewallsindicatethat thelandwasoncecleared, butabundantrocks andabsence S 40 ofaplowlayersuggestitwasnevertilled. In 1980,the largerscattered dominantswerefoundto haveoriginated a between 1890-1900,whilesmallercanopytreesoriginated 20 between 1910-1920. A CatlinWood isastandofhemlock,whitepine,and transition hardwoods on anearly flatplain atabout900 feet elevation intheWhiteMemorial Foundation inLitchfield. I960 1970 1980 1990 Sloperanges fromoneto fourpercent. Catlin Wood isthe Year oldestofthe fourtracts intheNew Series. Thisstandwas establishedaround 1795. Itsorigin isobscure, butsince Figure 1. Estimated canopydefoliation (%) on New- early 19th centurythemaindisturbancehasbeencuttingor Series plots between 1960-1990. There were no windthrow(Smith 1956). Removalordeathofchestnut observed defoliation episodes after 1989. permittedasecondagegroupofmixedhardwoodsand hemlock,originating around 1910-1920,to develop. Woodbridgesoil ontheupperslopegiveswaytothepoorly TheNorfolktractin theprivatelyownedGreat drainedRidgebury soil onthelowerslope. Mountain Forest, liesabout 18 milesnorth ofCatlinWood AtCatlinWoods,theunderlyingbedrock ismostly in aregionofruggedterrain in the lowerBerkshireHills. Brookfield dioritegneiss. Thesoilsdevelopedon glacio- Itseast-facingslopevaries fromoneto fifteenpercentand lacustrinesandswhichthinlymantletheunderlyingglacial liesbetween 1400and 1500 feetelevadon. In 1980the till. Onthe lowerslopes,theglacialtill formsaweakly largerwhiteashandredoakwerefoundtohaveoriginated developed hardpan atdepthsof20to 30 inches. Onthe between 1880-1890. Thepresenceofsproutclumpsand upperslopes,thewell drainedAgawamandthemoderately charcoalhearthssuggesttheareawasheavily cutaround well drained Sudbury soil formed insandandgravel. The 1880. Smallerandyoungerbeech,yellowbirch andblack poorly drained Walpole soil occupies abroad drainage cherry about90yearsoldsuggestaseconddisturbancein swaleatthe baseoftheterrace. 1910. Hemlockwasnotusedforcharcoal, but itmayhave OntheNorfolktract,soilsareformedon compact beenremovedatalaterdate. Persistentstumpsrevealthat glacialtillderivedprincipallyfromCanaanMountain chestnutwasalsopresentearlier. Theabsenceoffirescars schist. Hardpan is presentatdepthsof20to 30 inches, suggeststhatthistractwasnotburned. restrictingdownwarddrainageandcreating seepageareas nearthebaseoftheslope. Well drainedPaxtonsoil occurs ontheupperslopes,moderately well drained Woodbridge SiteCharacteristics OntheGayCity tract, soilshaveformedon friable onthe lowerslopes,andthepoorlydrainedRidgebury soil glacialtill derived chiefly from Bolton schist. The occursatthebaseoftheslope. somewhatexcessivelydrained,shallowHollissoil predominates. Theremainderofthetractliesabout0.6 Insects and Disease mileseastat500to 550 feetelevationon aneast-facing Annual defoliationmapsprepared from aerial slopeof4to 11 percent. Thewell drainedCharltonsoil reconnaissancebythe StateEntomologistwereusedto occupiestheupperslopes,themoderately well drained estimatedefoliafiononthetracts. Theeasternhardwoods Suttonoccupiesthelowerslopes, andthepoorlydrained tractsweredefoliatedmorefrequently,andmoreseverely, Leicesteroccupiesthedrainageswales. thanthewesternconifertracts(Fig. 1). Theeasterntracts OntheNatchaugtract, soilshaveformedoncompact hadpartial defoliation bygypsy moth (Lymantriadispar) andcankerworm {Paleacritavernatd)during 1962and glacial tillderivedfrom Eastfordgraniticgneiss. Hardpan ispresentthroughouttheareasampled. Thewell drained 1967. Severemulti-yeardefoliation episodeswerenoted during 1971-73 (gypsy moth andelm spanworm{Ennomos ConnecticutAgriculturalExperimentStation 1960 1965 1970 1975 1980 1985 1990 1995 2000 Year Figure2.MeangrowingseasontemperatureandlowestPalmerdroughtseverityindexvaluesduringthegrowingseason (April-September) between 1960-2000. Running threeyearaverages areshown. subsignarius), and 1980-1983 (gypsy moth). Incontrast, Weather defoliationwasnoted inthewesterntractsonly in 1972, Climatevariessomewhatamongtractsbecauseoftheir 1981, and 1989. The 1989 defoliation was controlledby distributionoverthestate. Ingeneral, thewesternconifer thegypsy mothfungus{Entomophagamaimaigd). Gypsy tractsin theLitchfieldHillsarecoolerandmoisterthanthe moth populations inConnecticuthavecontinuedtobe eastern hardwoodtracts. Climaticdatausedhereare from controlledbythefungus. BradleyAirportinWindsorLocks,Connecticut. Gay City Introduceddiseaseshavealsoinfluencedthe isapproximately20milessoutheastoftheairport. Catlin compositionoftheseforests. Americanchestnuthavebeen Woods,Norfolk, andNatchaugareslightlymorethan30 recordedonailthetracts. However,chestnutblightfungus milesfrom theairportand lay southwest,west, andeast, {Cryphonectriaparasitica)has largely relegatedthis respectively. Thearea is inthenortherntemperateclimate formerlyregal speciesthestatusofanunderstoryshrub. zone. Meanmonthlytemperaturerangesfrom 25''F in Dutchelmdisease{Ceratocystisulmi)reachedtheGay City January to 73°F in July. Thereareanaverageof176 frost tract(theonly onewith elm)beforethefirstsurvey in 1959. freedaysperyear. Averageannual precipitation is44.4 in Becauseelmswereneverabundantintheseforests,the peryear, evenly distributedoverallmonths. diseasehadlessimpactthanchestnutblight. Soilmoistureisreplenishedduringwintermonths Beechbarkdisease, acomplexofbeechscale becausetreesdonotremovewaterviatranspiration. {Cryptococcusfagisuga) andafungus {Nectriacoccinea Adequaterainfall duringthegrowingseason iscrucial if var.faginaia),was foundon 14%ofAmericanbeech. treesaretomaximizegrowth. AwetAugustorSeptember Beechbark diseaseweakens,andmay kill trees,by both canmaskthepresenceofadroughtduringtheearly feedingonsugarsflowingthroughthebranchesandtrunk, summer. Therefore,wedeterminedthe lowest(most andbykillingtissuesthatfeedandproducethebark. A severe)Palmerdroughtindexvalueduringtheentire nativecanker,Nectriacanker{Nectriagalligena),wasalso growingseason(April-September) foragivenyear. The present. Itwasfoundon nearly 4%ofblackbirch inthese lowestPalmerdroughtseverity indexvalues,alongwiththe tracts, abouthalftherateof8%observed in theOld-Series meantemperatureduringgrowingseason,arepresentedfor tracts(Wardetal. 1999). Although itrarely killstrees, the period between 1960-2000 (Fig. 2). Threeyear Nectriacankercanweakentreesandcauseconsiderable averagesareshowntoemphasizetrendsby smoothingthe lossofcommercialwoodproduction. oftendramaticyear-to-yearfluctuations.Climatevalues Stand Dynamics inConnecticutForestsNewSeries wereobtained from theNationalOceanicandAtmospheric Administration(NOAA2004). Theclimate in northernConnecticuthasoscillated betweenwetanddry duringthepastfortyyears. Thefirst decade(1959-1970)wasthecoldestand driestperiod. The S m^ followingdecade(1970-1980)wasthewettestperiodand "9. i hadaveragetemperatures. Temperaturesbetween 1980- 2000wereslightly elevated fromtheprevioustwentyyears andhadaverageto slightlymoisterthanaverageconditions. Itshouldbenotedthattherewereyearswithin each 10-year periodwhendroughtseverity differedsignificantly fromthe CSCSDSC SC averageforthedecade. 1 FIELD METHODS Figure3.Schematicdrawingofcrownclasses. D-dominant, In eachtractabaselinewasestablishedgenerally C-codominant,I-intermediate,S-suppressed. perpendiculartothecontourandacross aseriesofdrainage Individual treeswererelocatedusingmapsfromthe classes. Alongthebaseline, soilswere identified according previoussurvey forthesurveys in 1970, 1980, 1990, and toprofilemorphology andslopeposition. Drainageclasses 2000. Atotalof2831 stemswereincluded in thesesurveys. were identifiedaccordingtotheSoil SurveyManual (Anon. Mortalityofpreviously countedstemsand ingrowth(stems 1951). Within eachdrainageclass, transectswere thathadgrowntoatleasttheminimum dbh sinceprevious established parallel tothe contouron oneorboth sidesof survey)werealso recorded. Totalheightofall dominant thebaseline. Thetransectswere 16.5 feetwide(5 m) and treesandeverytenth othertreewasmeasuredtothenearest 66 feet(20m)to 394 feet(120m) long. Theendofeach foot in 1980. Treesmeasured forheightwerealso transectsegmentwaspermanentlymarkedwithan iront-bar examined forstem andcrowndefects. Thedefectswereof androckcairnat66-feetintervals. Wherepossible, formandsymmetryandexternal injurytocrown andstem. approximatelyequal areasweresampledineach drainage Internal defectssuch asheartrotwerenot included. class(Table I). Thedrainageclassesweregrouped into Beginningwiththe 1980 survey,theperpendiculardistance threesites: moist,containingthevery poorlydrained, ofeach stem fromthecenterlineofthetransectwas poorly drainedandsomewhatpoorly drainedsoils; medium measuredandrecorded. Stemsweremeasuredusingthe moist,containingthemoderatelywell drainedandwell metricsystem duringthe 1990and2000inventories. drainedsoils;anddry,containingthesomewhatexcessively Diametersweremeasuredtothenearest0.1 cm andthe drainedandexcessivelydrainedsoils. minimum diameterwasslightly decreasedto 1.2cm(0.47 Alongthetransects,eachstemwithadiameterofat inches). least0.5 inchesat4.5 feetaboveground,wasplottedon a Regeneration(stems <0.5 inchesdbh)wasfirst map, identified, anddescribed. The 1959-60tree inventoriedin 1980 using 1/300 acrecircularplots. The descriptions includedspecies, dbh, crown class,and centerofeachregeneration plotwas located halfway,or33 whetherthestemwaspartofasproutclump. Diameters feet, betweenthecairnswithstakes. Aslightly smaller 1/ weremeasuredtothenearest0.1 inch.TheNorfolk, Gay 1000hectare(1/405 acre) circularplotwasused forthe City, andCatlinWoodstractswereestablishedin 1959.The 1990 and2000 inventories. Stemsweretalliedby species NatcChraouwgnsctluadsysaisreaaqwuaalsiteasttiavbelimsehaesduirne1o9f60a.tree'sposition iFnoronteh-isfoBoutllheetiignh,trcelgaesnseersat(i<o1n,w1a-s1.9c,at2e-2g.o9r,i.z.e.d, >as9efitthtaelr1). inthecanopy relativetoitsneighbors(Smith 1962). The seedlings(<4 feettall) orsaplings(>4 fttall and<0.5 uppercanopyofaforestiscomprisedofdominantand inchesdbh). codominanttrees(Fig. 3). Uppercanopytreeshavewell- developedcrownsthatreceivedirectsunlightfrom above Species groups andpartly ontheside. Intermediateandsuppressedtrees Therewere26majortreespeciesrepresented, 7 minor formthelowercanopy. Intermediatetreesonly receive species, and 13 shrubspecieswhich includedsmall directsunlightfrom above. Suppressedtreesarefound understorytrees,chestnutsprouts and largeshrubs. Species undertheothercrownclassesandreceivenodirect arecategorized into similargroupstosimplifythe sunlight,exceptforoccasionalsunflecks. discussion. Asbefore,extensivetableswithsummariesby ConnecticutAgriculturalExperimentStation 500 Total density Oak - - ^>- -• Vlaple 1^400 j Conifer —•<<— Birch Other —->.-— Beech 1959 1970 1980 1990 2000 1959 1970 1980 1990 2000 Eastern tracts Western tracts Figure4. Totalstand density(stems/acre) byspecies group andsurveyyearforNew-Series plots. individual speciesareprovided. Thesearefoundattheend GayCity)werecombined,aswerethesimilarwesterntracts oftheBulletin. Precedingthesetablesis aspecies listwith (CatlinWoodsandNorfolk)thathadasignificantconifer theircommonandscientificnames. component. Total treedensity isthemeandensity (stems/ TheOAKgroup includednorthern red,black,scarlet, acre)ofthecombinedspeciesoverall moistureclasses. white,andchestnutoak. TheBIRCH group includesblack, In 1959thenumberofstemsperacrevariedamong yellow, andpaperbirch. TheMAPLEgroupincludesred tractsand sites. Therelativelyyoungereasterntractshad and sugarmaple. Americanbeech isthesolespecies inthe higherdensitiesthantheolderwesterntracts. This BEECHgroup. TheCONIFERgroup includeseastern differencehas largely disappearedoverthepastfortyyears. whitepineandeastern hemlock. TheOTHERgroup Thesetractsareincreasingly dominated by late-seralor includesthosespeciesthatcan form partoftheupper "climax"species. Between 1959-2000,Maple/Birch/Beech canopy inamatureforest,butwerefoundatlowdensities haveincreased from44%to 59%ofstems intheeastern onthesetracts. To fitthe individual speciestableson a tracts. Inthewesterntractsoverthesametimeperiod,the pagethefollowingspecieswerecombined: green andwhite proportionofMaple/Beech/Coniferincreasedfrom 70%to ash,slippery andAmericanelm,thevariousspeciesof 90%. shadbush. Speciesthatrequiremoresunlighttoreachtheforest MINORspeciesarethosespeciesthatdonotgrowlarge understory fortheirseedlingstogrow,anddependon more atmaturity andgenerally donotappearinthecanopy severedisturbancesto increasethe sunlight,havebeen exceptinveryyoungstands. Thisgroupincludes intolerant declining innumbersoverthepastfortyyears.Thisgroup pioneerspecies(e.g. graybirch)andspeciesthatcan grow includestheoaks, ashes,aspens, andblackcherry. Itis anddevelopintheunderstory (e.g., floweringdogwood, likelythesespecieswill continuetodeclineinnumbersuntil blue-beech,shadbush,andhophombeam). American there inamajordisturbanceeventsuchasahurricaneor MINOR chestnutisalso includedinthe speciescategory intensewildfire. becausechestnutblightkillsstemsbeforetheygrowlarge Thedecline inoakandothermoreshade intolerant(sun enoughtoentertheuppercanopy. Speciesthatdonotgrow loving)speciesisnotuniquetothisstudy,otherunmanaged tall enough to form partoftheuppercanopy (e.g. forests(Christensen 1977,Nigh etal. 1985, Barton and witchhazel andhighbushblueberry,andspicebush)were Schmelz 1987,Ward andParker 1989, Wardand Stephens includedintheSHRUBcategory. 1993)orforeststhatarepartially harvested(Heiligmannet al. 1985, Jokelaand Sawtelle 1985, Smith andMiller 1987, COMBINEDCROWNCLASSES Abramsand Scott 1989,AbramsandNowacki 1992). This Density will leadto largescalechanges inthe landscapefrom even- Forthereader's convenience, all tablesareattheendof agedtouneven-aged forests, andmay acceleratetheshiftin thisBulletin. To simplifytheanalysispresented inthis dominance from midtoleranttotolerantspecies. Stand Bulletin,thesimilareasternhardwoodtracts(Natchaugand growthratesmay slowwhenstandsbecomedominatedby StandDynamics inConnecticutForestsNewSeries 1200 a-S? 000 S Initial 800 Ingrowth 600 i n Persistence 400 B Mortality B 200 SSJ3 a -200 U -400 Initial 1959- 1970- 1980- 1990- Initial 1959- 1970- 1980- 1990- 1970 1980 1990 2000 1970 1980 1990 2000 Eastern tracts Western tracts Figure5. Components oftotalpopulation dynamics bysur\'eyyearforNew-Series plots. moretolerantspecies(Lamson and Smith 1991).These tractswaswitchhazel. Therewasalsoasignificant changeswill affectnotonlythequality andmakeupof componentofspicebushandelderberry intheeasternand forestproductsavailableto futuregenerations,butwill also westerntracts,respectively. affectthequality andvarietyofwildlifehabitats(Scanlon 1992). Components ofchange Totaltreedensity decreasedontheeasterntracts Weexaminedthenetchangesin stemdensity from between 1959-70,rosebetween 1970-80, andhassteadily decadeto decade intheprecedingsection. Decade-to- decreasedbetween 1980-2000 (Table 2, Fig. 4). This decadechangescanbeseparatedintothreecomponents pattern issimilartothatnotedfortheOld-Seriestractsand (persistence, mortality, andingrowth)tobetterunderstand was attributedto alagresponseto theperiodofdroughtand theunderlyingdynamicsaffectingourforests(Fig. 5). defoliation duringtheearly 1960's(Wardetal. 1999)that Persistence isthenumberofstemsthatsurviveduringa killedmanyoftheuppercanopy trees. Deathoftheupper giventimeperiod. Persistence isimportantbecause it canopytreesallowedincreasedsunlighttoreachtheforest conveysasenseofthepopulation stability. Mortality isthe floor-thisresultedin an increasein regeneration. numberofstemsthatdie,andingrowth isthenumberof Increasedpopulationsofblackbirchand spicebush newstemsduringagivenperiod. Mortalitymeasures accountedformostofthe increaseddensity. disappearancefromtheforest. Thenetchangeinthe Densityonthewesterntracts, incontrast, rosesteadily population isdeterminedbythebalancebetweenmortality from 1959-1990. Thesetractsexperiencedonlyminor and ingrowth. Population density canbestableunder defoliationoverthepastfortyyears. Easternhemlock and scenarioswheremortality andingrowth areboth low,or Americanbeechaccountedforallofthe increase. Density wheremortality andingrowtharebothhigh. ofeveryotherspecies, except stripedmapleandelderberry, decreasedduringthis period. Thedecreaseofall species Persistence between 1990-2000wasprobably dueto self-thinningof Thesmall decadalchangesindensitycanberelatedto theverydensestands, andnottoan introduced insect. thehighpersistenceofmostspeciesgroupsbetweenthe Hemlockwoollyadelgid(Adelgestsugae)andelongate surveys(Fig. 6). Persistencepeakedbetween 1970-1990on hemlock scale(Fioriniaexterna)wereobserved inthe theeasterntractsandbetween 1980-1990onthewestern westerntracts in2000,buthadnotcausedany appreciable tracts. Persistencewassimilaron alltracts(~630 stems/ damageormortality. acre) betweenthemostrecentsurveys, 1990-2000. The Minorspecies density peakedin 1980. American numberofstemsthatpersisted exceededthecombinedtotal chestnutwasthepredominantMinorspecies intheeastern ofmortality andingrowth foragivenperiod. tracts, andstripedmapleinthewesterntracts. Themost Thereweredifferences inpersistenceamongspecies numerousShrubspeciesinboththeeasternandwestern groups. Ontheeasterntracts,BirchandMapleexhibited ConnecticutAgriculturalExperimentStation •a 350 a 300 Persistence -K—Oak ^z ci 250 M' Maple us ?00 M- M- M-_:-^^ -C—" Conifer rS- 150 B ff- --B—- Birch 100 Otiier ws 50 - b - Beech R- "IBW- IRM- TVl 4^ LU. Pn 1959- 1970- 1980- 1990- 1959- 1970- 1980- 1990- 1970 1980 1990 2000 1970 1980 1990 2000 Eastern tracts Western tracts Figure6. Persistence(stems/acre/decade) by species group and surveyyears for New-Series plots. Persistence includes stemsthatsurvived from onesurveyto the next. higherpersistencethanOak. Birchpersistence increased increasedovertimeforspeciesgroupswithlargenumbers from 1959-2000,whileMaplepersistenceslightly ofstems inthesubcanopy (e.g., Shrubs,Conifer,Beech). decreasedoverthesameperiod. Differentpatternsof Speciesthatwereprimarily intheuppercanopy,suchas persistencewerenotedforthewesterntracts. Coniferand Oak and Other, demonstratedapatternofdecreasing Beechpersistencedramatically increasedfrom 1959-1990, mortality overtime. Themortality foragivendecadewas whileMapleandBirch persistencedecreasedsteadily. It highly correlated(r^= 82%)withthedensityatthe will takeanother 10-20yearstoknow ifthedrop in Conifer beginningoftheperiod(Fig. 7). Thiswasexpected,given and Beech persistencebetween 1990-2000 ispartofalong- thattrees arecompetingforlimitedresources(light, termtrend. moisture,nutrients). Moretreeson agiven acremeans thereare fewerresourcespertree. Forsometreesthis Mortality meansdeathfromcompetition. Asnoted above, mortality isthelossofstemspresentat Grossmortalitynumbersonlytellhowmany stemshave oneinventory andabsenton asubsequentinventory. The died, nothowfastthestemsaredying. Forexample, letus causesofmortality arevaried. Largecanopytreesusually dieasaresultofstorm damage,disease,ordecliningvigor. 500 Astreesbecome largerand larger,moreandmoreofthe ^ sugarsproducedbythetreeareutilizedtokeepalivethe t 400 w massivesupportstructure(trunkandbranches)thatliftthe leavesabovecompetingtrees. Therefore, lessenergy can I 300 % in beallocatedtodefenseagainstinsectanddiseaseattacks. .•§ 200 \Wv Thus, asan agingtreebecomes larger, itbecomesmore w likelytosuccumbtoan infestation. Competition forlight, s 100 waterandnutrientseliminatesstemsfromthelowercanopy andunderstory. Attackby insectsanddiseaseeliminates stems fromall canopy strata. Sometreesarebrokenby 400 800 1200 snoworice, severestormsorotherfallingtrees. Mortality Initial density(stem.s/acre) can alsooccuronareas floodedbybeaverimpoundment. Figure7.Relationshipbetweeninitialdensityandmortality Foranygiventen-yearperiod,mortalityvariedfrom duringthe followingdecadeforNew Series plots. 238-385 stems/acre intheeasterntractsand 110-296 stems/ E-eastern tracts,W-western tracts. acre inthewesterntracts(Table3). Mortalitygenerally — StandDynamicsinConnecticutForestsNewSeries 50 —K— Total mortality Oak « 40 u o --M'• Maple —C— 3 30 Conifer - B- Birch ^20 - •-^-«^1 ^x^ - b - Beech 10 1959- 1970- 1980- 1990- 959- 1970- 1980- 1990- 1970 1980 1990 2000 1970 1980 1990 2000 Eastern tracts Western tracts Figure8. Mortalityrate(%/decade)byspeciesgroupandsurveyyears forNew-Seriesplots. Mortalityrateispercentof stems thatdied between surveys. imaginethatthemortality oftwospeciesgroups,AandB, Distinctpatternswerenotedforthedifferentspecies wasboth 50stems/acre/decade. Ifatthebeginningofthe groups. Themortality rateforOakdecreasedovertimeon periodspeciesgroupAhad 100 stemsandspeciesgroup B alltractsfrom ahigh of48%between 1959-1970toalow had 1000 stems,then speciesgroupAwouldhaveahigher of11%between 1990-2000. In contrasttothedeclining mortality rate(50%)thanspeciesgroupB (5%). These mortality rateexhibited byOakoverthe pastfoityyears. mortality rates(%/decade)arepresented inFigure 8. Maplemortality increased from 16%to23%, and Conifer Themortalityratevariedfrom decade-to-decadeinboth mortality increased from 2%to 31%. Itissurprisingthat theeastern andwesterntracts. In all periods except 1990- Beechmortalityhas increasedonly slightlyoverpastforty 2000,themortalityratewashigherintheeasternhardwood yearsbecause 18%oftreeswere infectedwith beech bark tracts, 29-36%,than inthewesternconifertracts, 18-32% disease (Sirococcusclavigignenli-JuglandacearumINectria (Table3).As notedabove, muchofthisvariation can be coccineavar.faginataorN. galligend). This disease explainedbythecorrelationwith initial densityand complexhasresulted in severemortality (>50%)ofupper subsequentmortality. canopy trees inotherregions(Houston 1999). 160 1l40 — Ingrowth -K—Oak -nV|- Maple i •-^ -C—Conifer -B - Birch I 100 -• Other -b-- Beech 80 60 ^.,.,..|r-r.:.:^.. o 40 en 20 ^ B- —« M- -»- 1959- 1970- 1980- 1990- 1959- 1970- 1980- 1990- 1970 1980 1990 2000 1970 1980 1990 2000 Eastern tracts Western tracts Figure9.Ingrowth(stems/acre/decade)byspeciesgroupandsurveyyearsforNew-Seriesplots. Ingrowthincludessteins thatgrewtothreshold diameterbetween sui-veys. 10 ConnecticutAgriculturalExperimentStation —K— 400 Subcanopy ——C——OCoankifer ---MB---• MBiarpclhe • Other - b-- Beech -i 300 200 3 100 ^--^^^^ ^^.rrrr^ I 1959 1970 1980 1990 2000 1959 1970 1980 1990 2000 Eastern tracts Western tracts Figure 10. Subcanopydensity (stems/acre) byspecies group andsurveyyearforNew-Series plots. Subcanopyincludes trees inintermediateand suppressed classes. Somespecies, such asgray birch andbigtoothaspen, are observedonthesetractssince 1980. Amongthe species pioneerspeciesthatcolonizerecentlydisturbedareas, grow capableofgrowingintotheuppercanopy inthesemature quickly,anddieatarelativelyyoungage(fortrees).These forests.MapleandBirchaccountedfor83-95%ofingrowth specieshadveryhigh mortalityratesandhavedisappeared ontheeasterntracts(Fig. 9). Onthewesterntracts, Beech fromtheseundisturbedforests. Mortality ratesofMinor andConiferaccountedfor94-99%ofingrowth. and Shrubspeciesweregenerally higher,oftenmuchhigher, Strikingdifferencesbetweentheeasternandwestern thanmortalityratesfortheotherspeciesrates. tractswerealsoobservedinthecomposition anddensity of MinorandShrub ingrowth. Between 1980-2000, there Ingrowth werefewerthansixstems/acreofMinoringrowth inthe Thegrowingspace(andassociatedlimitedresources) westerntracts,comparedwith44stems/acre intheeastern thathad beenutilizedby atreebecomesavailablewhen that tracts. MostofthisingrowthwasAmericanchestnutand treedies. Someofthegrowing space iscapturedbythe thedeerresistantstripedmaple. Shrubingrowthhasbeen expandingrootandcrown systemsofneighboringtrees. minimalonthewesterntracts,especially since 1980. In Someofthegrowingspaceiscolonizedby newseedlings contrast. ShrubandMinorspecieshaveaccounted for49- thatmaythen grow largeenough(0.5 inchesdbh)tobe 65%ofall ingrowthstems intheeasterntracts. American includedinoursurveys. Thesenewtrees(ingrowth)arethe chestnutwasthemostcommonspecies,withsome pool ofindividualsthatwill formthe futureforest. Someof bluebeechandhophombeam in recentyears. Witchhazel theingrowthwillsurviveandgrowintotheuppercanopy andspicebushhavebeenthedominantShrubspecies. withthepassageoftime. Examiningthecompositionofthe ingrowthprovidesuswith clues astothemakeupofour SUBCANOPYTREES futureforests. In an unmanagedforestwithadisturbanceregimeof Ingrowth peakedbetween 1970-1980 inboththeeastern single-treeorsmallgroupmortality, ingrowthtrees andwesterntractswith 383 and297 stems/acre, (discussed above)form partofthesubcanopy. Subcanopy respectively (Table4). Thiswasprobably alagresponseto treesare inthe intermediateandsuppressedcrownclasses theperiodsofdefoliationsofthe 1960's and 1970's. Itcan undertheuppercanopy (Fig. 3). The morenumerous take 10-20yearsforaseedlingtogrowlargeenough to be suppressedtrees livecompletely intheshadeoflowertrees, includedinoursurveys. Ingrowth densitiesdecreased in whileintermediatetreesreceivesunlightonthetopoftheir eachofthefollowingdecadeswiththeabsenceofany crowns. Thesubcanopy formsthepool oftreesfromwhich additiondisturbance. futureuppercanopy treeswill emergeinamatureforest Although awidediversityofspecieswasfoundonthese withoutmajordisturbance, suchastheNew-Seriestract. tracts,almostallofthe ingrowthwaslimitedtoseveral However, mostsubcanopytreesgrowand diebeforea species. Thesespeciesdiffered betweentheeastern and westerntracts. Therehasbeennooakorhickory ingrowth