Tree Damage and Annual Mortality in a Montane Forest in , Author(s): Teri J. Matelson, Nalini M. Nadkarni and Rodrigo Solano Source: Biotropica, Vol. 27, No. 4 (Dec., 1995), pp. 441-447 Published by: The Association for Tropical Biology and Conservation Stable URL: http://www.jstor.org/stable/2388956 Accessed: 04-05-2015 04:36 UTC

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This content downloaded from 155.97.178.73 on Mon, 04 May 2015 04:36:20 UTC All use subject to JSTOR Terms and Conditions BIOTROPICA 27(4): 441-447 1995

Tree Damage and AnnualMortality in a MontaneForest in Monteverde,Costa Rica1

Teri J. Matelson P.O. Box 4755, Santa Barbara, California93104, U.S.A. Nalini M. Nadkarni2 The EvergreenState College, Olympia,Washington 98505, U.S.A. and Rodrigo Solano Monteverde,-5655, Costa Rica, CentralAmerica

ABSTRACT In fourhectares of primarymontane wet forestin Monteverde,Costa Rica, 1403 live trees(> 10 cm diameterat breastheight) were censusedfor major damage and mortalityduring a four-yearperiod. Overall treedamage and mortalityafter four years was 15.9 treesha-' yr-', with over 80 percentdue to snappingof trunksand uprooting of wholetrees. Of the 73 stemsthat snapped during the studyinterval, 20 regeneratedlive foliagefrom their broken stems.This resultedin an actual mortalityrate of 12.7 treesha-' yr-', or 2.2 percent,which is in the mid-rangeof annual treemortality reported for other forests. Tree death occurredduring all seasonsof the year,but rateswere highestduring the wet season. Individualsof gap-colonizingspecies died at a higherrate than expectedfrom their representationin the population.This studysuggests that althoughmontane sites are subjectto high winds and unstablesoils, overallrates and typesof mortalityare similarto lowlandforest sites.

Keywords: treemortality; tree crown damage; vegetative regeneration;forest dynamics; montane forest; snags; Monteverde; Costa Rica.

THE LOSS OF TREE CROWNS and the death of whole suinggap thatmay subsequentlydeter or facilitate treesaffects forest nutrient cycling, regeneration, and seed germinationof some species(Putz & Milton speciesrichness. The frequencyand typesof small- 1982, Brandaniet al. 1988, Swaine et al. 1990). scale forestdisturbances such as loss of crownsand Althoughmany damaged treesdie, some con- treefalls(hereafter "tree damage") are determined tinueto live by producingnew shootsfrom above- by local climaticforces, physical characteristics of or below-groundparts. Regeneration from broken the substrate,and biologicalattributes of the trees plant segments(hereafter "resprouting") has been (Brokaw 1982, Putz & Milton 1982, Putz et al. documentedin a numberof cloud foresttrees (Law- 1983, Denslow1987, Putz& Brokaw1989). When ton & Putz 1988) and shrubs(Kinsman 1990). wholetrees, tree parts, and theirassociated epiphytes Documentationof resproutingin tropicalforests is fallto the forestfloor, they: cause pulsesof organic scarce,since most researchhas centeredon regen- materialand nutrientsthat can subsequentlybecome erationfrom seeds, seedlings,or clonal regrowth available to terrestriallyrooted plants (Denslow (Clark & Clark 1989, Eriksson& Ehrlen 1992). 1987); increasethe biomass of theforest floor, thus The species compositionof regenerationof gaps creatingadditional habitats for terrestrial organisms; dependson thetype of disturbancethat created the reduceresources used by arborealanimals and ep- gap (e.g., Connell 1989, Whigham 1991). Re- iphytes,but at the same time creatingsnags for sproutingfrom standing broken stems might replace nestingby key avian seed dispersers(e.g., Wheel- thelost canopy and affectthe form and durationof wrightet al. 1984); crushseedlings, saplings, and gap regenerationfaster than regeneration from seed- understoryplants (Aide 1987, Gartner1989, Kins- lings.The abilityto resproutmight allow a species man 1990); and affectthe microclimateof the en- to maintainits frequency in thepopulation (Knight 1975, Putz& Brokaw1989, Whighamet al. 1991). Most studiesof tree damage and mortalityhave I Received 13 September1993; revisionaccepted 29 No- been carriedout in lowland tropicalforests, with vember1994. relativelyfew studiesin tropicalmontane forests. 2 Authorfor reprints. The ratesand frequencyof treedamage mightbe 441

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TABLE 1. Date of initiationand numberof monthsin bylow windspeeds and convective storms originat- whichtree damage and mortalitywere mea- ingin the Pacific lowlands. Measured annual rainfall suredin thestudy area. The datesgiven are is 2000-2500 mmyr-', but totalwet deposition whentrees were tagged and monitoringbegan. ishigher due to substantial wind-driven mist (Hart- Thefinalcensus for all areas was in September shorn1983, Clark& Nadkarni1990). 1992. The total numberof monthsof moni- toringis in brackets.(N.M. indicatesnot mea- sured.) METHODS Stem diameter A four-hectarestudy area was establishedand di- Location >30 cm DBH 10-30 cm DBH videdinto 100 20 x 20 m subplots.Trees were Hectare 1 12-87 [45) 6-89 [39) measuredand classifiedby size (diameter at breast Hectare 2 2-87 [45) N.M. height,DBH) and tagged.In twoof thehectares, Hectare 3 5-89 [40) 5-89 [40) all trees> 10 cmDBH weremeasured; in two other Hectare4 4-90 [29) N.M. hectares,all trees>30 cm DBH weremeasured (Table 1). Treelocations were ascribed to 20 x 20 m subplots.In April1990, halfof all treesin the expectedto be greaterin higherelevation forests studysite were identified tospecies by W. A. Haber because of steeperslopes, less stable soil, and ex- and E. Bello (Nadkarni et al., in press). Tagged posure to more wind. Plant adaptationsto these treesthat died beforebeing identified (i.e., priorto environmentalcharacteristics might also be expected April1990) weredesignated as unknown.All ex- in montaneforests. In thispaper, we describethe tantstanding broken stems >10 cm DBH were types,rates, and seasonalityof tree damage and taggedand numbered. mortality,and reportthe frequencyof resprouting In ourfrequent visits to thestudy area (ca. two of snappedtrees in a lowermontane forest in Mon- timesper week), we madenote of thetrees that teverde,Costa Rica. sustainedmajor crown damage, snapped, or fell. We censusedthe entire site for damaged, snapped, STUDY SITE or fallentrees annually (September 1990, 1991, and1992). Tree damage and mortality were divided Field workwas conductedfrom April 1987 to Sep- intofive categories: standing broken stems-clas- tember1992 in a lowermontane wet forest (Hold- sifiedby the height of the break relative to the total ridge 1967) in the MonteverdeCloud ForestRe- treeheight (high, middle, low); uproot-fallen trees servein Costa Rica (10?18'N, 84048'W) (1480 m withexposed root-balls; knockdown-a broken or in elevation).The studyarea was in leewardcloud uprootedtree falling as a resultof a neighboring forest(Lawton & Dryer 1980), the floristiccom- treehitting it; standingdead-tree dead, but stem positionand structuralcharacteristics of whichare notbroken or uprooted; or missing-tree that was describedin Nadkarniet al. (in press).The forest notfound again. During the final census, all stand- floorsoils are wetthroughout the year (Bohlman et ing brokenstems were checked for evidence of al. 1995), are derivedfrom volcanic rhyolites, and sproutingof foliageanywhere on thestem. Stems are classifiedas TypicDystrandept (Vance & Nad- withfoliage were recorded alive, and those with no karni1990). The studysite encompassed slopes of evidenceof sproutingof foliagewere recorded as 5 percentto 20 percent. dead. This forestis notedfor its windiness throughout We recordedthe standing broken stems that theyear due to itslocation on thecontinental divide, fellto the ground during the study period. Longevity withair funnelled through the adjacent Penas Blan- ofstanding broken stems was calculated by counting cas Valley.Wind gustsin the area have been esti- thenumber of months between the time of damage mated as high as 100 km hr-I (Lawton & Putz andwhen we notedthe stem fallen to theground. 1988). Althoughvariable from year to year,the We couldnot be certainof the actual time of falling climateof Monteverdecan be divided into three for8 ofthe 16 standingbroken stems that fell. seasons.The misty-windyseason (November-Feb- ruary)is characterizedby substantialmist carried RESULTS by strongnortheast trade winds. The dry season (March-April)has strongwinds and some cloud waterand mistdeposition, but low measurablerain- TREE DAMAGE AND MORTALITY.-Of the 1403 live fall.The wetseason (May-October) is characterized trees(742 10-30 cmDBH, 661 > 30 cmDBH)

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100 TABLE 2. The numberof treessustaining damage by 90 seasonexpressed as an averageper monthto s0 compensatefor the unequal number of months

70 Ns in each season.The timeof damage of 43 of the 147 treescould not be determined,and 60- IIh are notincluded in thecalculations. The misty- 50- MMKD windyseason is November-February,wet sea- 40- SD sonis May-October,and dryseason is March-

30- Li April. Damage types:standing broken stem (SBS), uproot(UP), knock-down(KD). 20- 10= Season SBS UP KD Total

. =. - Wet 3.5 3.2 1.0 11.3 10 30 30-50 50-70 70-90 c90

STM DUMETER (cm) Dry 2.5 2.0 1.5 7.5 Misty-windy 3.0 1.8 0.3 5.3 FIGURE 1. Size classdistribution (percent of total stems) of the 147 treesthat were damaged or died duringthe study divided into five categories(MI, missing; SD, thestudy, 73 (50%) wereidentified to species.They standingdead; KD, knockdown;UP, uproot;SBS, stand- represented19 plant families,20 genera,and 21 ing brokenstem). species.Trees in most of the plant familieswere damaged at similarproportions to that expected fromtheir distribution in thelive population (Table taggedin the four-haresearch area, 147 were se- 3). Treesin sevenplant families, however, sustained verelydamaged duringthe four-yrstudy period. damageat strikinglyhigher rates than expected (their The mean numberof damaged and dead treeswas proportionof individualsin the pool of damaged 15.9 treesha-' (std = 6.2) (9.9 10-30 cm DBH, stemswas morethan twice their proportion in the 6.0 > 30 cm DBH) or 2.8 percentof the tagged totalmarked population). Nearly all of thesewere trees.Of these,61 percentsuffered broken stems, gap-colonizing,rapid-growing, short-lived trees (Ta- 22 percentwere uprooted, 7 percentwere knocked ble 4). down,4 percentwere standing dead, and 10 percent weremissing (Fig. 1). The 91 standingbroken stems REGROWTH OF DAMAGED TREES AND "TRUE" TREE thatwere created during the studyperiod were di- MORTALITY.-Of the91 standingbroken stems that videdinto three height categories: high-break (3 5%), werecreated during the study,30 (34%) had live mid-break(32%), and low-break(33%). The pro- sprouts(resprouted) by the finalcensus. Of these, portionsof standingbroken stems by DBH relative mostwere high-breaks (43%) ormid-breaks (40%), to thetotal tagged population was significantlydif- whereasonly 17 percentof the standingbroken ferentfrom random (X2 = 11.7, P < 0.01), with stemsthat were low-breakshad resprouted.One more damaged and dead stemsin the largersize uprootedtree resprouted. classesthan expected (Fig. 2). The totalnumber of The identifieddamaged treesthat resprouted extantstanding broken stems (stems already broken werein 10 plantfamilies; those that did notresprout when tagged) was 77 (19.3 per ha) (std = 6.9), were in 19 families(Table 3). Two of the most or 5 percentof the totalnumber of taggedtrees. commongenera (Ocotea and Guarea) accountedfor Seasonalityof treedamage was determinedby 50 percentof the damaged treesthat resprouted. poolingthe number of damaged stems by the season Of the 147 treesdamaged, snapped, or fallen in which theywere damaged, regardlessof year. duringthe study, 116 appearedto be dead, as there (The time of damage of 29 percentof the trees was no evidenceof resprouting.This "true mor- could not be determinedand werenot induded in tality"was due to standingbroken stems that did thecalculations.) The largestproportion of damage not resprout(5 3%), followedby uprootsthat did occurredduring the 6-monthwet season (47%), not resprout(28%), knock-downs(7%), extant intermediateamounts in the 2-monthdry season standingdead (3%), and 9 percentdue to missing (31%), and lowest in the 4-monthwindy-misty treesthat were presumed dead. The mean annual season (22%). This trendis consistentwith the mortalitywas 12.7 treesha-' (std = 5.9) (8.2 for calculatedmonthly rates, which compensate for the 10-30 cm DBH, 4.6 for >30 cm DBH). This is unequal numberof monthsin each season (Table equivalentto an annualtrue mortality of 2.2 percent 2). forall sizedasses (2.1% for10-30 cm DBH, 2.8% Of thetrees that were damaged or died during for> 30 cm DBH). The expectationof furtherlife

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60T TABLE 3. The compositionof damaged trees by family. so The percentof the total treesdamaged, not resprouted,resprouted, and proportionof all taggedtrees. The totalnumber of individuals 30 E in each categoryis shownat thebottom. (Cal- L ALLDAESTBMS

culationsdo not includethe 74 unidentified 20- * _ _ damagedtrees in thestudy site.)

Damaged trees 1 0-30 S0-50 50-70 70-90 >-90

STM DEER (n Not re- Re- FIGURE 2. Proportionalsize class distributionsof all sprout-sprout- All trees(black bars) and of the 90 treesthat died during Family Total ed ed trees the three-yearstudy (white bars). Annonaceae 2.7 3.8 1.4 Aquifoliaceae 1.4 1.9 0.7 Araliaceae 1.4 1.9 0.2 (calculatedas the inverseof the averageproportion Asteraceae 4.1 5.7 2.7 Bombacaceae 2.7 3.8 2.7 of treesdying per year,Putz & Milton 1982) was Boraginaceae 2.7 3.8 1.9 43.8 yroverall (48.3 yrfor 10-30 cm DBH, 34.6 Cecropiaceae 12.3 13.2 10.0 6.1 for>30 cm DBH). Turnovertime was calculated Flacourtiaceae 4.1 3.8 5.0 3.2 as the number of years necessaryfor all of the Lauraceae 17.8 13.2 30.0 14.5 inventoriedtrees to die of Malvaceae 6.8 7.5 5.0 2.3 originally [number orig- Melastomataceae 4.1 3.8 5.0 4.2 inallytagged trees/(number of dead and snapped Meliaceae 5.5 - 20.0 6.6 trees/timeobserved)) (Uhl 1982) and was 55.5 yr Moraceae 4.1 3.8 5.0 2.0 for 10-30 cm DBH, and 42.4 yr fortrees >30 Myrsinaceae 2.7 1.9 5.0 5.5 cm DBH. Myrtaceae 4.1 5.7 1.7 Rubiaceae 4.1 5.7 5.7 We consideredthe population of standingbro- Tiliaceae 13.7 1.7 5.0 2.1 kentrees in theoriginal census separately from those Urticaceae 4.1 1.9 10.0 1.6 thatwere created during the studyperiod since the Verbenaceae 1.4 1.9 0.6 originalstanding broken stems were of undeter- Total number minableage. Of the 77 originalstanding broken of trees 73 53 20 1403 stems,69 percentremained standing, 18 percent fell,and 13 percentresprouted during the 4 yrof the study.The mean "longevity"(the amountof time dead standingstems remained standing) was and the TABLE 4. Thepercent mortality regenerationof 16.3 mo. This is an estimatebecause we wereun- fivemost common tree species in thestudy site (and thosewith the highest rate ofdamage). certainof the exact date of fallingfor half of the Percentof stem density within the population; fallenbroken stems. percentof stems damaged relative to thetotal population;number of stems damaged, percent of regenerationof damagedstems, number of DISCUSSION stemsthat regenerated. The rate of true annual mortality in this study To- (2.2%) is in themid-range of annual mortality rates tal Regen- of othertropical forests (1-3%) (Putz & Milton live Dead erated 1982, Uhl 1982, Brownet al. 1983, Lang& Knight pop Tempera- Genus (%) % No. % No. ment 1983, Higuchi 1987, Manokaran& Kochummen 1987, Hartshorn 1990, Lieberman et al. 1990, All damaged Swaine et al. 1990), most of which are fromlowland trees 8.0 100 148 21 (31) All tropicalregions. The lengthof expectation of further Ocotea 13.3 8 13 46 (6) Climax Guarea 7.6 9 8 50 (4) Climax life,tumover rates, and seasonalityof treedamage Conostegia 4.4 4 2 50 (1) Climax and deathwere also withinthe rangeof thosedoc- Cecropia 7.1 12 10 39 (3) Pioneer umentedfor other forests. Hampea 2.8 16 5 20 (1) Pioneer The wet steepslopes of montanesites, coupled Heliocarpus 2.5 24 7 14 (1) Pioneer withstrong seasonal winds and highepiphyte loads

This content downloaded from 155.97.178.73 on Mon, 04 May 2015 04:36:20 UTC All use subject to JSTOR Terms and Conditions Tree Damage and Mortality 445 mightbe expectedto increasethe incidenceof tree on BCI and on theYucatan Peninsula,for example, damage.Mountain sites have higherepiphyte loads frequentdisturbance is thoughtto lead to local (Pocs 1980, Tanner 1980, Nadkarni 1984) and dominanceby species that recoverquickly from larger"rain loads" thatadd weight(Gloyne 1968) injury (Knight 1975, Putz & Brokaw 1989, and possiblypromote tree breakage. The ratesof Whighamet a/. 1991). As predicted,the common treedamage and mortalityduring the study period, main canopyspecies in Monteverdewere those that however,were withinthe same range as lowland sproutreadily (Table 3). sitesthat experience less wind, have flattertopog- Our data generallysupport the trendthat in raphy,and supportlower epiphyte loads (Putz & matureforests, gap-colonizing species suffer higher Milton 1982, Manokaran& Kochummen1987, mortalityrates than other taxa (Manokaran& Ko- Liebermannet a/. 1990). chummen1987) (Tables 3 and 4). The pioneer The mode of damage and deathin our sitewas speciesCecropiapolyphlebia (Cecropiaceae), Hampea also quite similarto some othertropical forests. In appendiculata(Malvaceae) and Heliocarpusappen- our studyarea, 65 percentof theseriously damaged diculatus(Tiliaceae) had highermortality rates and treessnapped and 22 percentwere uprooted. In the lowerresprouting rates than the main canopy("cli- nearbyelfin woodland on thewindward side of the max") species Ocoteatonduzii (Lauraceae) (Table mountain,Lawton and Putz (1988) reportedthat 4). 39 percentof treefallgaps resultedfrom snaps, and Ocoteatonduzii, the most commonspecies in 41 percentfrom uproots. On BarroColorado Island our site (10% of basal area) had the highestinci- (BCI), Panama, a 1980 studyreported 52 percent dence of damage of the climax speciesas well as snapped and 17 percentuprooted (Putz & Milton the highestproportion of damaged treesthat res- 1982). In anotherstudy on BCI, 70 percentof prouted(46% of snappedtrees). Gap regeneration mortalitywas attributedto snaps, and 25 percent could be affectedby the incidenceof treesthat are to uproots(Putz et a/. 1983). In Cocha Cashu, a capable of resproutingafter snapping versus those CentralAmazonian lowland forest,46 percentof that snap and die, thus needingto relyon regen- dead treeswere snapped (Rankin-De-Merona et al. erationfrom seeds and seedlings(Putz & Brokaw 1990). In La Selva, Costa Rica, in contrast,Lie- 1989). The abilityto resproutcould help maintain bermanand Lieberman(1987) reportedthat fallen the dominanceof commonspecies, such as 0. ton- dead trees(uproots and snaps combined)was 31 duzii, in thepopulation. Live standing broken stems percentof totalmortality. of a. tonduziiare importantnesting sites for im- The majordifference between our montanesite portantlocal bird speciessuch as the resplendant and thelowland sites described in theliterature was quetzal. thatfew trees died standing in theMonteverde forest Long-termdata are neededto recordsuch phe- (3% of total mortality),whereas this is far more nomenaas resproutingof broken stems and attrition common in some lowland tropicalsites (Putz & of dead standingstems that appear to occuron a Appanah 1987). For example, La Selva had 26 timescale of severalyears to severaldecades. More percentof mortalityas standingdead (Lieberman studiesare also needed in othertropical montane & Lieberman 1987); Cocha Cashu, 25 percent forestsfor comparison with these results and to help (Rankin-De-Meronaet al. 1990); BarroColorado determinethe processes affecting the species richness Island,Panama, 15 percent(Putz & Milton1982); and forestdynamics. and tierrefirme forest in Venezuela,10 percent(Uhl 1982). We documentedthat one-third of thestanding ACKNOWLEDGMENTS brokenstems formed during our studyperiod re- We thankthe ScienceCenter and theMontever- sprouted(Table 3). Only a fewstudies have mea- Tropical de Cloud ForestReserve for access to and protectionof suredthis phenomenon or incorporatedit intotheir the fieldsite. A sincerethanks to W. A. Haber forhis calculationsof treemortality so that the ratesof untiringassistance with tree identifications.This work annual "mortality"reported in some studiesmay was supportedby NSF (BSR 86-14935 and 90-18006), overestimateactual tree mortality.Resprouting theWhitehall Foundation, and the National Geographic SocietyCommittee for Researchand Exploration.We would be expectedto be morecommon where winrd thankD. Lieberman,M. Lieberman,K. HoffmanMas- and/or forcefulstorms are frequentagents of dis- ters,A. Masters,M. Dickinson, M. Pinard, and F. E. turbance,such as in montaneforests. In the forest Putz forhelpful comments on earlierdrafts of thispaper.

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