Tree Damage and Annual Mortality in a Montane Forest in Monteverde, Costa Rica Author(S): Teri J
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Tree Damage and Annual Mortality in a Montane Forest in Monteverde, Costa Rica 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 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://www.jstor.org/page/ info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. The Association for Tropical Biology and Conservation is collaborating with JSTOR to digitize, preserve and extend access to Biotropica. http://www.jstor.org 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,Puntarenas-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 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 442 Matelson, Nadkarni,and Solano 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) 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 443 100 TABLE 2. The numberof treessustaining damage by 90 seasonexpressed