Hurricanes and Mangrove Regeneration: Effects of Hurricane Joan, October 1988, on the
Vegetation of Isla del Venado, Bluefields, Nicaragua
Author(s): Linda C. Roth
Reviewed work(s):
Source: Biotropica, Vol. 24, No. 3 (Sep., 1992), pp. 375-384
Published by: The Association for Tropical Biology and Conservation
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BIOTROPICA 24(3): 375-384
1992
Hurricanes and Mangrove Regeneration: Effectsof HurricaneJoan,
October 1988, on the Vegetation of Isla del Venado,
Bluefields, Nicaragua1
Linda C. Roth
Graduate School of Geography,Clark University,
Worcester,Massachusetts 01610, U.S.A.
ABSTRACT
Based on samplingof a hurricane-damaged
Caribbeanmangroveforest,stand structure
and compositionare charwas typicalof mangroveforests
acterizedforbothpre-and posthurricane
vegetation.Beforethestorm,standstructure
throughoutthe region,but poorlydevelopedcomparedto upland forestsin the same lifezone, as expressedin a
compositeindexof treeheight,basal area,stemdensity,and speciesdiversity.
The hurricaneinflicted
the mostsevere
damage upon the largesttreesand markedlyreducedthe complexityindex of the stand,but it appears to have
favoredthe establishment
of abundantregeneration
by all of the originalmangrovespecies.Periodicdestruction
of
Caribbeanmangroveforests
by cyclonicstormsis proposedas one explanationfortheircharacteristically
low structural
complexityas well as the lack of typical"climax" componentsin the vegetation.
RESUMEN
En base al muestreode un manglarcaribeiioafectadopor vientoshuracanados,se caracterizanla estructuray la
del rodalantesy despuesdel cicl6n.Antesdel huracan,esterodalpresentabaun desarrollo
composici6nvegetacionales
estructural
tipico de los manglarescaribenios
pero pobre en comparaci6ncon bosques de tierrafirmedentrode la
mismazona de vida, segunun indicebasado en la altura,area basal, densidady diversidadde los arboles.El huracan
provoc6los daniosmas severosentrelos arbolesmas desarrolladosy redujomarcadamenteel indicede complejidad
del rodal,peroparecehaberpromovidoel establecimiento
de regeneraci6n
abundantede todas las especiesde mangle
previamentepresentes.La destrucci6n
peri6dicade los manglarescaribenospor tormentas
cicl6nicasse proponecomo
una explicaci6nde su complejidadestructural
caracteristicamente
baja asi como la faltade un tipico componente
"climax" en esta vegetaci6n.
Keywords:
diversity;
foreststructure;
hurricanedamage;mangrove;
succession.
Nicaragua; regeneration;
DISTRIBUTION ALONG LOW LATITUDE SEACOASTS
1959, Craighead & Gilbert 1962, Sauer 1962,
inevitably
placesmangroveswampsamongtheter- Stoddart1963, Vermeer1963, Glynnet al. 1964,
restrialecosystemsmost prone to experiencethe Alexander1967, Heinsohn& Spain 1974, Bunce
passage of hurricanesand othertropicalcyclones. & McLean 1990, Wunderleet ail. 1992), but the
Because the frequency
of such stormsat any one accountsare, forthe mostpart,generaland qualsiteis commonlywell withinthepotentiallifetime itative.Virtually
completedefoliation
bywindand/
of individualtrees(Egler 1952, Stoddart 1963, or waves,shearingof branchesand trunks,uprootGentry1974, Lugo et ail. 1976, Neumann et ail. ing of some trees,damage to bark,and the depopre- sitionof sedimentand organicdebrisoftenproduce
1981, Boucher,in press),thesedisturbances
theselectionregimesofmangrove an initialimpressionof completedevastation.Redictablyinfluence
speciesas well as theircommunitydynamics.An cuperationof some of the strippedtreesmay take
understanding
of mangroveresponsesto hurricane place throughsproutingand refoliation
(Craighead
impactshouldassistin interpreting
thedistribution & Gilbert 1962, Sauer 1962); failureto recover
and structure
of theseecosystems
and in designing depends in part on speciescharacteristics
(Wadsappropriatemanagementstrategies.
worth & Englerth1959), topographicsituation
Numerous reportsof the ecologicaleffectsof (Craighead & Gilbert 1962), sedimentationand
hurricanes
mentiondamageto mangrovevegetation drainagepatterns(Craighead 1971, Heinsohn &
(Davis 1940, Egler 1952, Wadsworth& Englerth Spain 1974, Cintr6net ail. 1978), and proximity
to the hurricanetrack(Stoddart1963). Seedlings
I Received 1 March 1991, revisionaccepted25 Novemand saplingsoftensurvivethestormor appearprober 1991.
lifically
in subsequentmonths(Craighead& Gilbert
THEIR
375
376
Roth
LA
af~~~~~~~~~~~~~~~~~~
3
2
<
Lf
X~~~~~~~~~~DE
BLU E FI E LDSf
L~
~ ~ ~~~~~~~~/
IL
FIGURE 1. Compositemap locatingIsla del Venado ( 11?55'N; 83045'W) in relationto Bluefields,Nicaragua,
and indicatingmangrovecommunities(hatchedarea) and numberedsamplingtransects(0).
1962, Sauer 1962, Craighead 1964, Alexander
occur
1967, Wunderleetal. 1992), but exceptions
(Egler 1952, Stoddart1963). Long-termstudies
appear to be
tracingthe fateof this regeneration
ofmangrove
nonexistent,
and althoughtherecovery
iswidelyrecognized
(Lugo
ecosystems
after
hurricanes
& Snedaker1974, Jim6nezetal. 1985), theprocess
is poorlydocumented.
The presentsurveywas undertaken17 months
acrossan
aftera Caribbeanhurricane
sweptdirectly
extensivestand of mangroveforest.Objectivesof
thesurveywereto recorddamageand earlyrecovery
and to leave markedplots forcontinuingobservation, with the intentof exploringthe ecological
significance
formangrovevegetation.
of hurricanes
Nicaragua (Fig. 1). Its climatecorresponds
to the
tropicalwet life zone of Holdridge (1967). The
island extends15 km in a broad north-south
arc
and is close to 2 km wide throughoutits length;
itsbaywardside is fringed
in a band 0.1 to 1.0 km
wide withmangrovevegetationgrowingon a substrateof fine-grained
mineraland organicdeposits.
Althoughtopographic
reliefis negligiblewithinthe
mangroveareaand mostoftheislandmaybe subject
to occasionalflooding,the surfaceis not typically
overwashedat hightide.The mangroveswould be
categorizedas "'fringeforest"in the typologyof
eitherLugo and Snedaker(1974) or Cintr6net al.
(1985).
Movingwestwardat 15-16 km hr-I alongparallel 12?N, HurricaneJoan struckIsla del Venado
on 22 October 1988. Meteorological
data are not
STUDY SITE AND METHODS
availablefortheislanditself,but Bluefields,
located
Isla del Venado is an elongatedbarrierislandfront- directly
acrossthe bay, experienced
sustainedwind
ing theBay of Bluefieldson theCaribbeancoastof speedsof 2 17 km hr-Inearthecenterof thestorm
377
Mangrove Regeneration
TABLE 1.
Nicaragua.
striptransects,
Isla del Venado,Blliefields,
inposthuirricane
Trees(-2.5 cmDBH) encountered
Transect2
TransectI
Species
#
Avicenniagerminans
Lagunculariaracemosa
Pellicierarhizophorae
Rhizophoramangle
Total
6
10
0
13
29
Y
21
34
0
45
10(
#
17
8
0
1
26
Transect3
5
Y
65
31
0
4
100
Total
7
1
1
2
11
64
9
9
18
100
Y
30
19
1
16
66
45
29
2
24
100
is consideredunusual for
withgustsexceeding250 kmhr-I(INETER 1988). of Pellicierarhizophorae
Rainfallin Bluefieldstotaledmore than 400 mm the Caribbeanarea (Roth & Grijalva 1991).
Tree size and densityestimatesare summarized
forthe period of 21-23 October and tidal surge
therewas substantial(INETER 1988). Immedi- in Table 2. Stem densityand basal area varied
in thelarge
amongtransects
as reflected
atelyfollowingthe stormobserversreportedthat considerably
is associatedin part
thebay had been standarderrors.This variability
throughout
themangroveforests
killed; seven monthslater therewas no sign of withthe low numberof treesin transect3, nearly
otherthanthe one-halfof whosesurface(233 m2of 500 M2) was
visiblefrom50 m offshore
recovery
sp.) occupiedby a thickcoverofAcrostichum
sp. Values
largegreenfrondsof leatherfern(Acrostichum
among the apparentlyleaflesstrunksof the man- in Table 2 representminimumestimatesforthe
stand since theyexclude treesbroken
pre-existing
groves(pers. obs.).
On 16-17 March 1990 woodyvegetationwas below 1.3 m, of whichthreesproutingspecimens
werecounted;fallentrees,ofwhich
thedam- ofLagumncularia
crossing
sampledalongthreestriptransects
Rhizophora;
anyindividuals
aged mangrovefringeon Isla del Venado (Fig. 1). therewas one sprouting
The islandwas chosenas a studysitebecauseof its uprootedand blownfromthesamplearea,ofwhich
as well no evidencewas noted;and dead stemslyingacross
in thepathof thehurricane
locationdirectly
as the appearanceof ratheruniformphysicalcon- but not appearingto have been rootedwithinthe
fromrandomly strips.
ditionsalongitslength.Originating
To permitcomparisonwith mangroveforests
locatedpointson the island'swestshore,thesamdue magneticeasttodetect elsewhere,complexityindices (Holdridge 1967)
plingstripswereoriented
based on thesestripsare presentedin Table 3. The
possibletopographiczonationin thevegetation.
to
measured5 m x 100 m, or 0.05 indices,whichare compositevaluesproportional
Striptransects
ha each. All woodyvegetationrootedwithinthese species number,stem density,maximumheight,
areaswas recorded,in 2 categories.For individuals and basal area (totalstemcrosssectionalareaat 1.3
- 2.5 cm DBH (bole diameterat breastheight,or m above ground),ofstands,arerecordedhereboth
1.3 m above groundlevel), recordwas made of forthe standardtreecomponent(DBH - 10 cm)
(dm), species,DBH (cm) and using a smallerminimumdiameter(2.5 cm)
distancealongthetransect
measuredwithdiametertape, approximateheight as adapted formangrovevegetationby Pool et al.
(ocular estimateto nearestmeterby experienced (1977). Complexityindicesare computedforeach
doublingstemnumbersand basal
conditionof main stem(brokenvs not), stripseparately,
forester),
vs poorlyrefoliat- areasto conformto thestipulated0.10-ha transect.
class(wellrefoliated
and recovery
ed vs dead). For smallerindividualsonlyposition (Althoughsuch extrapolationnormallywould be
of
(as above), species,height(to nearesthalf-meter), problematicaldue to the nonlinearrelationship
and origin(sproutvs seedling)werenoted.Patches
ofdead wood
fernand accumulations
ofAcrostichum
TABLE 2. Structuralparamieters (? 1 SE) ofprehur;rcane
werealso recorded.
RESULTS
miangrove
forest, Isla clel Venado, Bliefieldls,
Nicaragua.
AverageDBH: 14 (?4) cm
PRE-EXISTINGSTAND.-There were 66 individuals Heiglhtof tallesttrees:25 m (incl I brokenat thislevel)
>-2.5 cm DBH (hereafterreferredto as "trees") in Tree density:440 (? 111) ha'
Basal area: 14.88 (+9.29) m' ha-'
Fourmangrovespecieswere Tree species:4
thethreestriptransects.
in Table 1; thepresence
as enumerated
represented,
378
Roth
TABLE 3.
Complexity
indicerof prehurricane
mangrovevegetation,Isla del Venado, Bluefields,Nicaragua,and of
fringe(F) and overwash(0) mangroveselsewhere.b
Complexityindex
Mangrovelocation
Isla del Venado, 1
Isla del Venado, 2
Isla del Venado, 3
Florida
Florida
Ceiba, PuertoRico
Aguirre,PuertoRico
Punta Gorda, PuertoRico
Isla Roscell,Mexico
Sta. Rosa, Costa Rica
Life zone'
T Wet
T Wet
T Wet
ST Moist
ST Moist
ST Dry
ST Dry
ST Dry
ST Dry
T Dry
Type
Trees
-2.5 cm DBH
Trees
- 10 cm DBH
F
F
F
0
F
F
F
F
0
F
14.3
7.9
0.2
3.4
9.6
16.2
29.9
0.9
10.1
4.9
6.2
2.7
0.1
0.8
1.4
0.2
5.6
0.0
5.7
3.6
Holdridge(1967).
Pool et al. (1977).
c T = tropical;ST = subtropical.
a
b
points.Locations
speciesnumberto samplingarea,it is unlikelywith- and at a widerangeofintermediate
in the mangrovecommunitythat largersampling of Avicenniaand Laguncularialikewiseextended
unitswould have includedadditionaltreespecies; fromthe 5 m pointto theinlandends of the tranleftunchangedin the sects,with no segregationevident.Variance-ratio
speciestotalsareconsequently
positiveor negative
weightings.)Complexityindicesreportedby Pool testsfailedto show significant
data) amongthethree
et ail. (1977) forfringeand overwashmangroves association(presence/absence
inFlorida,Puerto principalmangrovespeciesusinga rangeofquadrat
byhurricanes
disturbed
notrecently
> W >
Rico, Mexico, and Costa Rica are tabulatedfor sizesfrom25 m2 to 75 m2(X2005
95
those exceptthatAvicenniaand Rhizophorawere negatheiraveragescloselyapproximate
comparison;
ofprehurricane
Isla del Vena- tivelyassociatedat the25 m2 size.Abundancevalues
ofthereconstructions
of Avicennia and Rhizophoraexhibitednegative
do.
using25 m2 (Spearman'srank
No cleargroupingofspeciesintozonesor belts pairwisecorrelation
parallelto shorewas apparentfortheprehurricane r = -0.349, N = 33, 0.01 < P < 0.05) and 75
the mangrovemost commonly m2 (r = -0.713, N = 11, 0.01 < P < 0.05)
stand. Rhizophora,
band,was indeed quadrats.The singleadult of Pellicierawas found
an outermost
reportedas forming
foundin the first5 m of each transect;but it was 28.2 m fromthe water'sedge.
also encounteredas far fromshore (100 m, the
as anyoftheotherspecies DAMAGE TO PRE-EXISTING STAND-Trees in thesaminnerlimitofthetransects)
by the
heavydamageinflicted
ple stripsmanifested
hurricane;
severedbranchesand twigshad leftmost
specimenswith bare, open crowns.Trees of each
samples,Isla del
oftreesin mangrove
TABLE 4. Recovery
class and conspeciesare enumeratedby recovery
afNicaragua,17 months
Venado,Bluefields,
in
4
stem
Tables
and
dition
of
main
5. Forty-five
terHurricaneJoan.
percentof the treeshad brokentrunks,and only
Number of individuals
42 percentof individualswere found to be well
class
per recovery
in
refoliated17 monthsafterthestorm.Rhizophora
thesestripshad higherproportions
of dead, poorly
Well Poorly
refoli- refoliindividualsthan
refoliated,and broken-stemmed
Total
Dead
ated
ated
Species
were
Avicenniaor Laguncularia,butthedifferences
not statistically
significant
30
12
4
14
(X2 = 7.06, 4 df, 0.50
A. germinans
19
4
11
4
L. racemosa
> P > 0.10 forrecovery
category;X2 = 2.07, 2
1
0
1
0
P. rhizophorae
df,0.50 > P > 0.10 forstemcondition;Pelliciera
16
8
5
3
R. mangle
counts).
excludeddue to insufficient
66
24
14
28
Total
largerbasal diBrokentrunkshad significantly
Mangrove Regeneration
379
Dead treesconstituted
36 percentof all stems
Stemconditionof treesin mangrove
samples,
on samplestripsand averagedmorethantwicethe
Isla del Venado,Bluefields,Nicaragua, 17
months
afterHurricaneJoan.
diameterof treesthatsurvived(21 cm vs 10 cm;
TABLE 5.
two-sideda = 0.0175), leavingonly32 percentof
the basal area in live stemsafterthe hurricane.
Number of individuals
with main stem
Species
Broken
Entire
Total
11
10
0
9
30
19
9
1
7
36
30
19
1
16
66
REGENERATION.-Seventeen
monthsafter
HurricaneJoanstruckIsla del Venado,seedlingsof
the threeprincipalmangrovespecieswere found
growingplentifully
throughout
thedamagedstand
exceptwithinaggregations
ofAcrostichum
fern,from
whichtheywere virtuallyabsent (Table 6). Avicenniaseedlingswere most abundanton all samametersthanunbrokenones (21 cm vs 7 cm; two- pling stripsand constitutedover one-halfof this
sided a = 0.001 1); by implicationit was probably regeneration,
followedin totalnumbersby Lagunthe tallertreesof the prehurricane
standthatwere cularia and Rhizophora;but populationdensityesmost likelyto sufferbreakage.Averageheightat timates did not differsignificantly
among the
thetimeof samplingdid notdiffer
betweenbroken threespecies(8583 vs 3943 vs 2054 ha-' of fernand unbrokenstems,so the effect
of thewindwas freearea; F = 3.96, a = 0.0801). Ten seedlings
evidently
one ofleveling.This effect
was augmented of Pellicierarhizophorae
were recorded."Stump"
by survival,sincethemeanheightofwellrefoliated sproutswereuncommon,largelybecausemoststem
individualswas significantly
belowthatofremaining breakagehad occurred
at higherlevelson thetrunks;
dead trunks(5 m vs 10 m; two-sideda = 0.0044). thethreerecordedcasesof basal sprouting
involved
Recoveryclass forbrokentreesdid notvarysignif- Laguncularia.
icantlybydiameternorbyheightat whichthetrunk
Like the adults,the seedlingsshowedlittleevsnapped,but stembreakageitselfwas strongly
as- idenceof segregation
intozonesby species.No sigsociatedwith mortality(X2 = 18.43, 2 df, P <
nficantoverallorpairwiseassociationamongspecies
0.001).
occurrenceswas found in 25 m2 sectionsof the
Among the unbrokentrunks,thosewithgood samplingstrips,althoughabundancevaluesforLarefoliation
had smallerdiametersthanthosewhich gunculariaand Avicenniawerepositively
correlated
recoveredpoorlyor died (5 cm vs 8 cm vs 16 cm; withinthesesame sections(0.01 < P < 0.05). The
F = 11.83, a = 0.000 1). Theywerealso ofshorter speciesof a givenseedlingwas associatedwiththe
staturethan the unbrokentrunkswhichrecovered speciesof itsnearestadultwithinthesame strip(X2
poorlyor died (5 m vs 6 m vs 12 m; F = 4.4, a = 17.37, 4 df, P = 0.0016), but the narrowness
= 0.02).
of the stripsprecludedreliable determination
of
A. germinans
L. racemosa
P. rhizophorae
R. mangle
Total
TABLE 6.
SEEDLING
Mangrove
seedlingnumbers
and densities
byspeciesand striptransect,
Isla del Venado,Bluefields,
Nicaragua,
17 months
afterHurricaneJoan.
Number of individuals
Transect1
Species
A. germinans
L. racemosa
P. rhizophorae
R. mangle
Total
Transect2
%
155
141
5
66
367
42
39
1
18
100
Transect3
%
541
266
3
99
909
60
29
0
11
100
Total
%
235
49
2
56
342
69
14
1
16
100
%
931
456
10
221
1618
57
28
1
14
100
Seedlingdensity(individualsm-2)
Averagedover:
Entiretransect
Acrostichum-free'
area
Transect1
Transect2
Transect3
Mean (? 1 SE)
0.73
0.94
1.82
2.18
0.68
1.28
1.08 (?0.37)
1.51 (?0.37)
380
Roth
TABLE 7.
as a grouppreComplexity
indicesofposthurricane
mangrove 3). Instead,mangrovecommunities
lowerindicesthantypicalupland
vegetation
bystriptransect,
Isla del Venado, sentsubstantially
Nicaragua.
forests
withintheirsamelifezones(Holdridge1967,
Bluefields,
Complexityindexa
a
Transect
Trees
-2.5 cm DBH
Trees
-10 cm DBH
1
2
3
0.6
0.9
0.0
0.1
0.3
0.0
Holdridge(1967).
nearestadult neighbors.However,the seedlingcohortappeared thus farto be reproducingat least
the proportionsof speciesin the older stand; the
numberof seedlingsperstripof a givenspecieswas
significantly
withthenumberof prehurcorrelated
ricaneadultsof thatspecieson thesame strip(r =
0.78, N= 12, P < 0.01) and totalseedlingnumbers were positivelycorrelatedwith overalladult
totalsforthe fourspeciesas well (r = 0.95, N
4, P - 0.05).
Mean height of Rhizophora and Laguncularia
seedlingswas 1.5 m (to nearesthalf-meter),
with
Lagunculariaregeneration
fromtheother
differing
species in averaging2 m tall (F = 44.3, a <
0.0001). If all seedlingsbecame establishedafter
the hurricane,theirheightsrepresentan average
growthof at least 1 m yr-'. Seedlinggrowthrate
may be somewhatlower than heightsindicatein
thecaseofRhizophora,
whosepropagulesarealready
typicallya few decimeters"tall" beforebecoming
rooted.Fieldobservations
didnotdistinguish
whether
anyrootedseedlings
thestorm,
mighthaveweathered
but it is curiousthathistograms
of seedlingheights
forall of thethreeprincipalspeciesappearbimodal
with the small second peak at 3 m; if theseless
numeroustallerindividualswere not established
thentheirheightgrowthhad
priorto thehurricane,
exceeded2 m yr-'.
Complexityindicescalculatedforthe posthurricanestandare shownin Table 7. On theaverage,
theseare morethan an orderof magnitudelower
thantheirprehurricane
in Table 3.
counterparts
DISCUSSION
As reconstructed
usingHoldridge'sindex,thestructuralcomplexity
of themangroveforestexistingon
Isla del Venado priorto HurricaneJoan was comparableto thatof fringe
in the
mangroves
elsewhere
hemisphere,
withno differentiation
evidentin complexityindexaccordingto climaticlifezone (Table
Pool et al. 1977). Low speciesdiversity,
reflecting
the physiological
challengesof the mangrovehabitat,accountsin partforthis;but thetreesof mangroveswampsare also generallysmallerin height
and averagegirththan theirupland counterparts.
Therewould be no inherent
reasonto expectmangrovestands,givensufficient
time,to developsmaller treesthanotherforests
eveniftheirgrowthwere
slower;but a greaterfrequency
of perturbation
of
mangroveforestscould accountforsucha discrepancy.Periodictropicalcyclonescharacterize
thearea
occupied by mangroveecosystemsand have long
been proposedas a limitationto theseforests'development(Egler 1952). To the extentthatstorm
winds lose forcecrossingland, one would expect
theiroverallinfluenceupon upland ecosystems
to
be less pronounced.
HurricaneJoanset back standdevelopmenton
Isla del Venado by selectively
breakingand disproportionately
killingthe largertrees.Thirty-six
percentof thetreeson thesamplearea had died, representing
fully68 percentof the basal area of the
pre-existing
stand.Treesshowingbestrecovery17
monthsafterthe stormwerethoseof shortstature
and small diameter.These patternscontributed
to
the sharplydiminishedcomplexityindex forthese
forestsafterthe hurricane.
Similarresultsare reportedelsewhere.Wadsworth(1959) foundthat saplingstandsof white
and blackmangrove
suffered
negligible
damagefrom
a hurricane
whichkilled 59 percentof the treesin
neighboring
pole stands.Craighead(1971) noted
that individualsless than 2 m tall were the only
mangrovesto escapecompleteinitialdefoliation
by
inFlorida.Wunderleetal. (1992) found
hurricanes
thatdamage to mangrovesin JamaicafromHurricaneGilbertwas proportionately
greaterin the
trees.
larger-diameter
The implicitassumptionthat any dead trees
foundon Isla del Venado had succumbedto the
It was not possibleat
hurricanewarrantsscrutiny.
the timeof samplingto distinguish
betweenstems
killed by the stormand dead trunkswhichmay
have existedwithinthe stand priorto Hurricane
Joan.Data compiledbyJimenezetal. (1985) from
numerousmangrovestandsshow a highlyvariable
percentageof standingdead trunks,averaging26
The valto "normalmortality."
percent,attributed
ue of 36 percentofstemsfounddead in thepresent
studyis well withinthe cited range (z = 0.60);
however,the diameterclassesmost affecteddiffer
Mangrove Regeneration
381
considerably.As Jimenezand coworkers(1985)
impliesthatthe prehurricane
tionin the regrowth
interactions, standwas itselfearly-successional,
fromcompetitive
pointout, mortality
thenso mustbe
in all mangroveforestsin theregion,and truesuccesand diseasetendsto be concentrated
herbivory,
thesmallersuppressedstemsofa givenassemblage, sional changewould depend upon the mangroves
so that standingdead treesfromsuch "normal" eventuallyalteringtheirhabitatsin such a way as
causes averageonly 19 percentof the basal area of to permitestablishment
of a different
set of (nonthe standstheylist. The factthat dead stemson mangrove)species.Indeed,mostdiscussionofmanprimary
Isla del Venado had an averagegirthmore than grovesuccessionhas focusedon protracted
landbuilddouble thatof live ones and made up 68 percent successioninthecontextofhypothesized
that ing and spatial zones interpreted
as seres,not reof basal area on samplestripssuggestsstrongly
in sponseto canopyremovalby disturbance;but the
treemortalitytherewas primarilycatastrophic
appears more typicalof timescale of stormeffects
may tendto eclipsethe
origin.Chronicmortality
(Jim6nez
etal. 1985) andonesin influence
of moregradualgeologicprocessesas well
basinmangroves
etal. 1978) wheresalt as rendering
aridenvironments
(Cintr6n
maladaptiveforvegetationof tropical
stress
is likelyto be moreacute.
coaststhe traitstypicalof "climax" species.
forest,
blowdealttheformer
Despitethesevere
One would expectfrequentstormdisturbance
as a to favorspeciescapable of constantor timelyflowarenotthreatened
evidently
thesemangroves
densities ering,abundantseedingor sprouting,fastgrowth
seedling
giventhatestablished
community,
thestand.Silvi- in openconditions,
maturity.
and earlyreproductive
alreadyappearampleto restock
islim- The threeprincipalCaribbeanmangrove
mangroves
withAmerican
cultural
experience
speciesshare
has proveneffectivethese"early-successional"
ited,butnaturalregeneration
ofshade,
traits.Intolerant
ofstandsin Puerto theygrowquicklyas seedlings,as demonstrated
portions
in replacing
harvested
in
(LunaLugo silviculturalstudies (Marshall 1939, Wadsworth
1959)andVenezuela
Rico(Wadsworth
in SouthAsia 1959). Theirflowering
is precociousand all three
1976). Data fromseveralcountries
adequatetorepop- floweryear-round
considered
indicate
thedensities
(Marshall1939, Little& Wadsin worth1964), but withpeaks whichin Floridaand
theretheregeneration
ulatemangrove
forests;
"abun- Panama producecopiouspropagulesbetweenAuisconsidered
mangroves
restocked
naturally
from605 gust and October (Craighead 1971, Rabinowitz
densities
areanywhere
dant"ifseedling
ha-' (Liewetal. 1977, 1978a, Tomlinson1980)-precisely the seasonof
to over50,000individuals
re- greatesthurricaneprobability(Neumann et al.
laws requiring
FAO 1985). Threecountries'
postharvest1981).
regenerated
plantingof inadequately
of 1667 to
standsstipulatedensities
Fromthelittlecomparativeevidenceavailable,
mangrove
man- adaptationsto wind disturbanceseem to be dis10,000plantsha-' (FAO 1985).IfCaribbean
inthisrespect,
thentherange tributedamongthespeciesin an unevenbut rather
arecomparable
groves
ha-' overmostofthe compensatory
of9400 to 21,800 seedlings
fashion(Table 8). Thus Rhizophora
forthestand manglehas provenin some cases themostresistant
areashouldbe morethansufficient
The onlyapparent to wind damage (Wadsworth& Englerth1959,
on Isla del Venadoto recover.
whichcovered Wunderleet al., 1992), but its olderbranchesare
obstacleto thisis Acrostichum
fern,
spp. incapableof sproutingoncebroken(Noakes 1955,
of thesamplearea;Acrostichum
28 percent
in openareasofmangrove
for- Wadsworth 1959, Tomlinson 1980); the other
becomeestablished
intractable
weedsbyforestersmangrovespecies coppice well (Marshall 1939,
estsandareconsidered
worldwide
(FAO 1985).
on the
Wadsworth1959). Lagunculariaracemosa,
evidentin these other hand, is considered least wind-resistant
The processof regeneration
thusfarfromtheconventional(Wadsworth& Englerth1959) but is the superior
differs
mangroves
estab- sprouter(Wadsworth1959). L. racemosaseedlings
succession.
of secondary
Seedlings
portrayal
afterthestormwere appearto growfasterin theopen thanthoseof the
lishedin thefirst17 months
thesamepropor- otherspecies(Marshall1939, Ball 1980), but they
ofthesamespeciesandin nearly
tionsas thetreesof thepreviousstand;no new also have been foundthe mostintolerant
of shade
"pioneers"
hadappearedandno "later-succession(Egler 1952, Wadsworth1959, Ball 1980) and
standhad yetbeen therefore
al" speciesfromthe former
the least likelyto existbeneatha canopy
Giventhat at thetimeofa disturbance.
in theemerging
generation.
eliminated
Lagunculariaalso tends
age to suffer
communities
ofwhatever
thehighestpercentseedlingmortality
mangrove
(DaCaribbean
related
totheseanda fewclosely
species vis 1940, Rabinowitz1978c, Ball 1980). Avicenarelimited
speciescomposi- nia germinansis thoughtto be the least shade(Chapman1976), ifunchanging
382
Roth
TABLE 8.
Summary
ofreported
relativeattributes
ofthreeCaribbeanmangrove
speciesrelatedtopersistence
following
hurricanes(references
in text). Plus sign (+) indicatesthat data fromthepresentstudyaccordwiththe
generalization;
mninssign(-) indicatesapparentdisagreement;
asterisk(*) indicatesstatisticalsignificance
(P < 0.05) ofresultsin eithercase.
Attribute
Resistanceto windthrow
R. mangle
A. germnnans
L. racemosa
highest
intermediate
lowest
intermediate
lowest
intermediate
(+-)
highest
highest
(+-)
intermediate
(-)
Resistanceto breakage
highest
(-)
Sproutingfromdamaged trunk
Initialseedlingdensity
lowest
(+-)
lowest
(+-)
(+-)
Shade tolerance
intermediate
highest
Seedlinggrowthrate
intermediate
lowest
(+-)
lowest
(A-)
(A-)
Seedlingsurvivalrate
highest
(A-)
(+a)
intermediate
highest
(Aw)
lowest
(-)
intolerant
of thethree(Egler 1952) and to produce carefullydesignedfuturestudiescould lend additypicallyhighinitialseedlingdensities(Jim&nezet tionaldimensionsto Table 8 as well as providing
a!. 1985) but to show theslowestseedlinggrowth morerigoroustestsforits claims.
Timing of observationsis likelyto influence
(Marshall 1939). Such patternscan be interpreted
a rangeof nichesall compatiblewith perceivedpatternsas well: "poorlyrefoliated"inas illustrating
while"well
but orientedtoward dividualsmaydie orcontinuesprouting,
disturbance,
periodichurricane
facetsand stagesoftherecovery refoliated"treesmaylatersuccumb.Relativeseedsomewhatdifferent
lingdensitywill presumablyshiftat some pointin
process.
growthratesand survivalof
Sample averagesfromthe presentstudy ac- responseto differential
althoughsample initialpopulations;fromTable 8 one mightpredict
cordedwithmostofthesepatterns,
sizes were inadequatein most cases to projectthe thatAvicenniawill be surpassedin densityfirstby
reliably
toanylargerpopulation(Table Laguncularia and then by Rhizophora.Later on,
relationships
species can
8). Sproutingcapacity(based on percentrefoliation relativegrowthrates of the different
of brokentrunks),"initial" seedlingdensity(17 continueto change(Ball 1980), inwayswhichlongwill help to clarify.Althoughthe
monthsafterthe hurricane),and seedlinggrowth termmonitoring
assuming componentspecies remainthe same, competitive
rate(height17 monthsafterthehurricane
on a givensubstrate
mayeventually
lead
followedmostclosely interactions
simultaneousestablishment)
the predictedorderby species.Densitiesobserved to predominanceof one species,as Ball (1980)
indicatedthat positsof R. manglein intertidalzones of Florida,
duringa March 1991 reconnaissance
Rhizophoraseedlingswere survivingconsiderably untilfurther
disturbancerestoresthe earlierdiverbetterthan thoseof Lagunculariaand Avicennia. sity.Theseinteractions
arelittlestudiedand deserve
SuperiorshadetoleranceofAvicenniaseedlingswas closerattention.
albeitweakly,byitslargerinitialnumber
Posthurricane
standdevelopment
suggested,
in mangroves
of seedlings-3 m tall relativeto theotherspecies, is doubtlessmorerelevant
to theirmanagement
than
whichcouldbe due to a greater
densityofAvicennia changeswhichmay occuron a geologictimescale.
can- The communities
aroundBluefieldshave made use
seedlingshavinggrownin beneaththeformer
opy. Adult Rhizophoradid not show the lowest ofall fourlocal mangrovespeciesto varyingextents
proportionof broken stems; and examples of forfuel,carvedobjects,construction
materials,and
werescantforall species.Speciesattri- tanning,and evidencepersistson Isla del Venado
windthrow
butes and availabilityof propagulesundoubtedly of sporadicpast cuttingof selectedtrees.Fromthe
of storm initialresultspresentedhere it would appear that
interact
withotherfactorssuchas severity
and type of substratein producingposthurricane periodicsmallharvests,
ifadjustedin size,position,
patterns(Cintr6net al. 1978), so that and timingto encouragepatchesor stripsof regenregeneration
Mangrove Regeneration
383
erationof preferredspecies,representa "distur- trees,the resultsof such inquirywould seem more
bance" fromwhichmangrovestandsmightreadily pertinentto the conditionsin whichtheyactually
a desirablecombinationof regenerate.The west coast of Isla del Venado is
recoverwhile offering
are presentlyan enormouslightgap of a sortwhich
and productiveuse wherehurricanes
protection
frequent.Limitingthe size of the cut patchesand thesemangrovesappearwell adaptedto recolonize,
shouldhelppre- and the developmentof its standswill providea
avoidingAcrostichum
aggregations
of theirpostdisturbance
vent spread of the fern,and the periodicallyre- continuingdemonstration
plenishedgroupingsofseedlingsand saplingswould successionalprocesses.
afterfuturehurpresumablyspeed standrecovery
ricanes.Researchon the communityecologyand
ACKNOWLEDGMENTS
profwouldundoubtedly
ofmangroves
management
de Recursos
Direcci6n
it fromthe experienceof local resourceusers,who JorgeBrooksof theNicaraguan
lentthisproject
manyforms
y del Ambiente
in turnmightbenefitfromcollaborationin testing Naturales
MaribelPizzi,Laureana
Rivera,
and ofvaluablecooperation.
and refiningpossible silviculturaltreatments
yRecursos
oftheEscuelade Ecologia
andManuelRomero
erosionhazards.
monitoring
in
participated
Centroamericana,
Universidad
Naturales,
In a classicstudy,Rabinowitz(1978b) com- allaspectsofthesampling
de
Staff
oftheCentro
process.
de la CostaAtlantica
y Documentaci6n
pared seedlingsurvivaland growthof American Investigaciones
Thanks
inBluefields.
support
logistical
generous
mangrovespeciesbeneaththe canopiesof different provided
reviewer
areduealsotoD. JeanLodgeandananonymous
speciesof adults; but she suggestedthata logical forveryhelpful
ofthispaper.The
on a draft
comments
next step should be to examine theirgrowthin fieldwork
wassupported
byNSF grant#BSR-8917680
of these toJohnVandermeer.
treefallgaps. Given the shade intolerance
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