19e2l PARTOMIHARDJO ET AL.: ONCOSPERMA ON KRAKATAU

Principes,36(1), 1992, pp. 7-17

Ecology and Distribution of Nibung(Oncosperma tigillarium

within the Krakatau Islands, Indonesia

T. PenroumARDJo, E. MmueNro, S. RISwAN AND R. J' .WuIrrexon'

"Herbarium Bogoriense," Research and Deuelopment Centre for Biology,

Ind.onesian Institute of sciences, Jalan Ir. H. luanda 22-24, Bogor 16122, Indonesia and

School of Geography,' Uniaersity of Oxford, Mansf'eld Road' Oxford', OXl 3TB, LK

ABSTRACT

A study of the distribution and ecology ol Onco'sperma tigillailum (Jack) Ridl. (nibung) within the

Krakatau Islands, Indonesia, was conducted to gain

an understanding of factors controlling location and

dynamics of populations. The history of its coloni

zation and that of other palm species is also briefly

examined. Four plots were established at different

sites on the three main islands.Reconnaissance throughout the islands between

1979 and, 1989 revealed that nibung grows in the

lowlands below 150 m altitude, but away from the

immediate vicinity of the sea. Populations were stud-

ied within a number of diferent forest types (as

described by Whittaker, Bush and Richards 1989),

and it was concluded that the palm appears to be

relatively insensitive to comunity characteristics and

to between-island differences in disturbance histories.Examination of seed, seedling and sapling densities

in relation to parent trees revealed a large number

of propagules failing to disperse, and in consequencetendencies toward clumped distributions, The seed-

lings tend to grow best in hollow and,/or moister sites.

The Krakatau islands remain poor in palm species(eight) and numbers of individuals, however, the evi'

dence from this study, exemplified by nibung, is of a

slow but steady increase in their presence.

Nibnng (Onc o s p errna tigillarium (J ack)Ridl.), is one of eight palm species knownfrom the Krakatau Islands (below). Thetree is tall, clustering and spiny with dis-tinct crown shafts and pinnately dividedleaves. Nibung may reach in excess of 25m in height and clusters may have up tol0 major stems. Based on the collectionsat Herbarium Bogoriense and other avail-able information (e.g., Seeman 1856, Eth-

elbert Blatter 1926), nibung is widely dis-tributed throughout Sumatra, Kalimantan,Peninsular Malaysia, and Java. The spe-cies is generally confined to forest below50 m above sea level, in near-costal local-ities (Steenis 1935, Backer and van denBrink 1968, House 1984).

Recently this palm tree has becomethreatened in many places, especially nearthe coast, due to utilization for "bagang"

poles. Stems of nibung are also used as amajor building component, the leaf sheathsin basket making and the heart or cabbageis eaten raw or cooked in a coconut sauce(Dransfield 1976, House 1983). Seeman(1856) quotes Low as stating it to be "the

most esteemed of all the excellent vege-tables of Borneo,'o with a very sweet nuttyflavor. According to local fishermen, it cur-rently sells in Lampung for about 20,000rupiahs per stem. Despite the economicvalue of the plant, little is known aboutthe ecology and distribution of this palm.By studying it in a habitat protected frommarked human disturbance, we hope to beable to make a small contribution to anunderstanding of the autoecology of thespecies.

The Krakatau islands provide a classicsite for the study of primary colonizationand ecosystem regeneration in the humidtropics, a context in which palms are arelatively neglected component. In focus-ing on the history and dynamics of nibung

P R I N C I P E S [Vor. 36

within these islands it is intended to providea simple case study, hopefully provokingfurther interest in the subiect.

Study Area and Methods

The Krakatau Islands are situatedapproximately in the middle of the SundaStraits, between West Java and SouthSumatra (Fig. 1). The group consists offour small islands: Rakata or KrakatauBesar, Sertung or Verlaten, Panjang orLang (Rakata Kecil), and Anak Krakatau(the smallest island with an actiye crater).The Islands are mostly forest-covered withthe exception of Anak Krakatau, themajority of which still consists of open bareareas of black ash. The group was com-pletely sterilized in the eruptions of lBB3,but now supports a variety of secondaryforest communities. The history of recov-ery and current forest types are describedby Whittaker, Bush, and Richards (1989).

The soils of Rakata have developed ontop of a thick layer of white volcanic ashproduced by the l8B3 eruptions, but thoseof Sertung and Panjang are developed fromcomplex series of mainly post- 1930 ejecta(RJW, work in progress). These were pro-duced by Anak Krakatau, which emergedin the center of the group over the period1927 to 1930, and which has been inter-mittently active since. Particularly severeeruptions occurred in 1930, 1932, 1934/5, 1952/3, 196l and around 1970; ineach of these cases (and doubtless others)Sertung and/ or Panjang has been affected(reviewed in Whittaker et al. 1989). Itappears that little, if any, of either islandhas escaped from serious damage at onetime or another. The forests of both islandsare consequently ecologically immature andspecies-poor in comparison to Rakata. Inaddition, their soils are less developed andthe surface horizons are coarser textured,being typically 80-90% sand fraction(Newsome 1986, M. Saunter, unpubl.data). Erosion by fluvial action has pro-duced pronounced ridge and gully systems,

particularly on Rakata, with most majorgully-forming activity probably taking placein the initial unvegetated period. Theshorelines of the three older islands havealso been eroded by wave action, such thatthe majority of the coastline consists ofsteep ash walls with many hanging valleys(Bird and Rosengren 1984). The coastlineis quite dynamic and although the majorprocess has always been erosion, areas ofaccretion (and hence colonization ofthalas-sochorous species) exist on each island. OnSertung there is a quite pronounced spit,fed by longshore drift from the erodingcliffs (see Fig. l). In short, inland parts ofRakata have been relatively stable sincevery shortly after the eruptions of lBB3,but the vegetation of Panjang and Sertunghas experienced significant disturbance byvolcanic events in the past sixty years.Coastal and near-coastal populations havealso been variously affected by geomorphiccnange.

Reconnaissance was undertaken todetermine the nibung distribution withineach island. The data presented in TableI were then collected using a plot basedmethod. Three plots of i0 x 100 m andone of l0 x 120 m were set up underselected parent nibung trees. Two plotswere established on Rakata and one ploteach on Sertung and Panjang. All treeswith trunks of >10 cm dbh and saplingsof 2 cm diameter at I m above groundlevel were measured. Data recorded werediameter, total height and bole height inall sub-plots of l0 x l0 m. Ground coverwas sampled from further subplots of 2 x2 m, which were set up systematicallywithin each i0 x t0 m sub-plot. Voucherspecimens were collected for identificationof all taxa present. The fallen seeds ofnibung under the selected parent nibung.trees were counted systematically, withinconcentric contours.

Prior to the analyses of these data, wefirst review the historical data for the col-onization of the islands by Nibung and otherpalms. Surveys of the islands have not been

r9921 PARTOMIHARDJO ET AL.: ONCOSPERMA ON KRAKATAU

1. Known distribution oI Oncosperma tigillarium in the Krakatau Islands, Indonesia. NB. Site locations areapproximate. algSS/4 plots in which O. tigillariun was recorded (after Whittaker et al. l9B9); A 1989 study

sites; O other locations in which O. tigillarium was recorded in 1989.

it

particularly systematic and have been ofvarying frequency and intensity throughtime. Whittaker et al. (1989) group thesurvey data into the following oocollection

periods," which broadly indicates the pat-tern: 1886, 1897, 1908, 1920, 1922,1924, 1929, 1932, 1934, r95r , L979,1982, 1983. In addition, we report pre-viously unpublished finds of 1989.

Results and Discussion

History of palm colonization of theKrakatau Islands. Nibune is one of seven

palm species recorded for the KrakatauIslands post-I883 by Whittaker et al.(1989). One of rhese, Nypa fruticansWurmb has been observed only as a seed-ling on Anak Krakatau in the early 1930s,and did not survive the eruptions of thatperiod. The remaining species are Cala-mus unifarius Bl., Calamus aiminalisWilld., Cocos nuciferaL., Corypha utanLam., and Licuala spinosa Thunb., all ofwhich have been recorded during the sur-veys of I979-1989. However, specimenscollected in l9B9 and provisionally iden-tified as Licuala spinosa, were later found

0 0.5 1 1.5 2 2.5

WEST JAVA

t 0 P R I N C I P E S

Table 1. Sample plot data recorded in 1989.

lvor. 36

R2R1

I.V.No.I .VNo.I .V.No.I .V .No.

Tree Layer

Neonauclea calycinaTerminalia cdtappaFicus futulosaTimonius compr essicaulisVillebrunea rubescensMacaranga tanariusFicus fuIztaFicus ampelasFicus septicaD y s oxylum guadic haudia numFicus tinctoriaOncosper ma tigillariumAr t hr o p hyllum j ao anicumBridelia monoicaGlochid,ion borneenseAntid,esma montanumPipturus argenteusTarenna fragransGnetum gnemonHernandia peltataMorinda citilfoliaArtocarpus elasticus

Shrub/Sapling

Leea sambucinaFicus f.stulosaAntidesma tnontanumTimonius compr essicaulisDy s o xylum gaudic haudianumNeonauclea calycina

. Leucosyke capitellataArt hr o p hy llum j an t anicumTarenna fragransVillebrunea rubescensFicus ampelasBuchanania arborescensFicus septicaFicus tinctoriaBrid,elia nonoicaFicus fuluaMorinda citrifoliaC alo p hyllum ino p hyllumMussaenda frond,osaArdisia humilisFicus pubineruisMacaranga tanariusPipturus argenteusSyzygium polyanthumLitsea sp.Glochid.ion borneenseM elast o ma malab athr icuntGnetun gnemon

2 t 2 . t 57 50.72

3r t t8 .83

j 'y'

, *.t,6 26.983 18.33r 6.07

87.85 r 2.6s20.68 4 7.Os3 l .482.25 I I 2A.86

4 6 .7032.55 2 7.77I I . I U

8.52I4.097.53

14.38 | 2.648.688.9 I8.074.267.O4 6 13.63

I 2 .813 8.56

| 2 .79

*r I i.no2.792.232.042.042.Or

202 167.73

t0 58.296 55.828 49.655 29.653 15 .752 I 3 . r 92 12 .692 11.782 I 1 .36I 6 .4 rI 6.3,37 6 .31

2r 108.033 21.643 22.06

_ � - i

- risz

2 15 .0421 83.48

] 7.85

s 18.99I ?.09

82t 222 ..

t

l 91.246

I O46425

32

9 '80 .49

; ni.ez

r 8.09

I 8.0e

4 36.32

j '*'

r i '

I r ,u

29.6523.20a a A 1

3.4151.0616.26

7.56

2.9812.3827.33

26.O9

8.242.28

2.733.698.447.09

8.20

5.825.705 . O J

5.62

64 54.8330 34.3438 33.2926 27 .73t2 25.3218 24.5018 22.6315 I 5 .788 I r .015 7 .326 7 . t 44 6.263 5.08J + . + J

3 4.363 3 .952 3 .722 3 .03I I .82I 1 .57I r .47

t 87

20I

J I

6

J

I6

l 8

7

I

I2t

J

4

r9921 PARTOMIHARDJO ET AL.: ONCOSPERMA ON KRAKATAU

Table 1. Continued.

1 l

R2R1

I.V.No.I .V.No.I .V.No.I .V.No.

Hernandia peltataOncosperrna tigillariumArtocarpus elasticusTerninalia catappaMangifera indica

Seedling and Herb

Neonauclea calycinaMussaenda frond,osaAntidesma montanumSyzyzium polyanthumMacaranga tanariusNephrolepis hirsutulaBridelia monoicaAngiopteris eaectdTe t r a s t i g na lanc e ola r iunTerminalia catappaFlagellaria indicaHoya d.ioersifoliaFicus tinctoriaFicus f,stulosaTylophora asthmaticaLeea indicaOncosperma tigillariurnSnilax zeylanicaDrynaria quercifoliaTectaria melanocaulaD y s o xylurn g aud,ic haudia nu mLygodium f,exuosumFicus septicaBuchanania arborescensNephrolepis biserrataTeciaria dissectaGlochidion borneenseMicrosoriurn punctatunFicus fuluaAr htro p hyllum j au anicumTacca palmataTarenna fragransMycetia jauanicaPteris aittataCayratia trifoliaLeucosyke capitellataFicus ampelasC alo p hyllum i no p hy llumHernandia pehataGnetum gnemonStenachlaena palustrisArdisia humilisDicranopteris linearisElaeagnus latifoliaMicrosorium nigrescensArtocarpus elasticus

129 9r.4r25 28.9629 26.6rt4 23.2513 19.26I I I I . 3 O6 I I .006 9.355 8 . r 05 7 .77a 7 r l

r I 7 .057 6.562 6 . 5 rJ J . O J

3 3 .83l 3.822 3.482 3.363 2 .722 2 . r 4| 2 .02r 2 .02I T . 7 9

I 5 .84I 5 .84

r 7 .23B 2r .90

4 7.86

I 5 .84

I 5.84

I 5.84

1 5 .8480 149.52

8 26.863 23.663 20.09I 5.84

l0 32 .21I 9.30r 3.24

J

I O

i

5 l3I

I2I4

I 22

I27

2207I2222tI2

24.47r4.402.64

6

2,

;5

I

3I

9I 7

462

I

27

I

3.78

20.r7

2 .77

68.723.982.77

r2 .633 . r 72 .77

r0.7613.243 . 1 7

2.57J 4 . J I

3.7828.88I0 .216.475.955.95J . J q

5 .014.474.41J . J I

2.772.572.572.57

o

8I

13 .54

5.003.40

9.09

3.24

41.09

20.89I 9 . 6 It3.29

J 5 . U D

6.62

8.78

3.39

5 6 . 1 5

4.64

3.39

8.78

P R I N C I P E S

Table 1. Continued.

lvor. 36

Total number of Oncosperma tigillarium seedlings recorded within study plots: Plot Rl : 130' R2 : 215' S: I I , P : 4 7 .

Site details

SitePlot size (m2)Altitude (m)

SitePlot size (m2)Altitude (m)

SitePlot size (m2)Altitude (m)

SitePlot size (m2)Altitude (m)

No. : number of individuals.I.V. : importance value (Relative dominance * relative density * relative frequency. For seedlings, dominance

was calculated from cover values.)

R I1200

I O

R2r000

50

S1000

20

Pr000r20

LocalitySlope (')Vegetation

LocalitySlope (')Vegetation

LocalitySlope (')Vegetation

LocalitySlope (")Vegetation

S.E. Rakata20Te r minalia- N e o naucle a

S.E. Rakata30Neonauclea

N.W. SertungI J

Timonius-Terminalia

Central Panjangt 0Timonius-Neonauclea

to belong to Corypha utan (J. Dransfield,pers. comm.). It is thought most parsi-monious that the only previous record ofL. spinosa, in 1982, was also a misiden-tification of C. utan. In the 1989 surveya further species, Salacca zalacca(Gaertn.) Voss, has been provisionallyidentified from Rakata and a confirmedidentification of another Calarnus has alsobeen made, C. polystachys Becc. (J.Dransfield, pers. comm.). Thus, excludingthe Licuala, there are eight palm speciesknown from the Krakatau Islands, of whichseven may be regarded as successful col-onists.

The first palm species recorded on thegroup was Cocos nucifera L., found in1897 on Rakata and Panjang. The nextrecord is for nibung in 1920, by Doctersvan Leeuwen. He found a very young spec-imen growing in a "wilderness" of Hibis'cus tiliaceus L. on the sandy spit at thenorthern end of Sertung. It was mentionedthat the soil there was moist but not salty(Docters van Leeuwen 1936). Given his

frequent visits to Rakata and occasionalvisits to Sertung during the 1920s, it isunlikely that it colonized the former, orspread markedly in the latter during thisperiod, as he would typically have record€dsuch events. The next record of this spe-cies is not until 1932, when he found itat two places on Panjang. He did notobserve it in his first brief visits to Panjangin 1928/29, but in 1932 he found threeyoung specimens in a mixed wood in thenortheast of the island, behind the strand-bank and about l0 m from the coast. Healso observed some specimens in one ofthe highest ravines on the south-east sideof the island, about 90 m above sea level.The specimens were well-developed androse with their leaves above the surround-ing vegetation, but were not yet flowering(Docters van Leeuwen 1936). The otherpalms present at this time in the group,Cocos nucifera arrd Corypha tltan, wererespectively slightly more common andslightly less common than nibung. The his-tory of the first fifty years of ecosystem

ree2)

recovery on Krakatau is thus one of anextreme poverty of palms, both in numbersof species (three) and in numbers of indi-viduals (e.g., contrast with House I984).

Borssum Waalkes (1960) failed to re-cord. Oncosperm.a tigillarium during hisbotanical observations on the KrakatauIslands in l95l and 1952, but it shouldbe noted that he spent only a few hourson Panjang and Sertung, in comparison toabout 9 days on Rakata. In the more inten-sive sampling efforts of 1979-1989, thepalm has been recorded on each of thethree main islands but it has not yet beenfound on Anak Krakatau (Whittaker et al.1989: appendix I and 2*).

Present Distribution of Nibung

Of 35 vegetation sites (average sizeapproximately 900 m') enumerated by theKrakatoa Centenary Expedition in 1979and l9B3l84, nibung was recorded in six(Bush and Whittaker 1986), as follows.Their Rakata site I I was located at 15 maltitude, in near-coastal Neonauclea caly-cina-Terminalia catap p a ecotone foreston the south side of the island. The palmwas large enough to be recorded as partof the tree layer, with 2.7Vo csa (cross-sectional area). On Sertung, it was foundin sites Ser l0 (2.63% csa) and Ser l l(present but <30 cm girth), respectivelyat 35 m and 80 m altitude. The formersite was in the Terminalia catappa*Timonius cornpressicaulis forest, the lat-ter in Timonius compressicaulis forest.Both sites were at the northern end of themain part of Sertung. In Panjang, nibungwas present in sites Kec I (Kecil : Pan-jang), Kec 2, Kec 5, each as individualsof less than 30 cm girth, and respectivelyat altitudes of 90 m, ll5 m, and 90 m,in the northern half of the island (Fig. l).

Durine the l9B2 and l9B3 Kaeo-

* See for taxonomic authorities of species mentionedin this paper. unless given here.

PARTOMIHARDJO ET AL.: ONCOSPERMA ON KRAKATAU t 3

shima,/Bogor expeditions, the first author(TP), also observed several clusters of flow-ering and fruiting nibung on Panjang, Ser-tung and Rakata. In 1989 particular atten-tion was paid to this species, and patchesof seedlings and trees were observed scat-tered within the three islands (Fig. I). Fouradditional sites were selected for detailedstudy (above). In these plots (Rl, R2, S,and P), 34 arboreal species were recorded,belonging to 28 genera and 17 families(Table I).

The two Rakata plots, RI and R2, werelocated on the gentle slope of south-eastRakata at altitudes of l0 m and 50 mabove sea level. The vegetation of bothsites was dominated by Terminaliacatappa and Neonauclea calycina (Fig.2 and Table I), with the former providingthe tallest trees, of about 35 m height. Thesecond layer consisted of a mixture, prin-cipally of Tinonius compressicaulis, N.calycina, Dysoxylurn gaudichaudianumand nibung itself. The data in Table I areentirely compatible with the coastal andnear-coastal yegetation types described forRakata by Whittaker et al. (1989). Thenibung clusters consisted of about 7 stemsin the first plot and 2I stems in the secondplot. Most of the nibung trees were flow-ering and fruiting. In the third layer, therewere several shrub species, such as Anti-desma tnontanum, Leea indica, Leuco-syke capitellata and Villebrunea rubes-cens. The ground vegetation layer wascharacterized by Tetrastigrna lanceolari-um, Nephrolepis biserrata, Lygodium

f,exuosurn and nibung. The latter occurredas seedlings in both sites, most numerouslyin R2, in which the species was clearlybetter established (Table l).

Plot S was placed within the Timoniuscompressicaulis forest on the west side ofSertung island (Fig. I , Table I ). The emer-gent trees consisted of Terminalia catappeand Hernandia pehata, reaching heightsup to about 30 m (Fig. 3). The main can-opy was characterized by T. compressi-

I 4

caulis and, to a lesser extent, Neonaucleacalycina.In this less mature forest nibunggrew as an emergent tree, in a cluster ofB stems. There were some saplings ofnibung in the second layer, but it was dom-inated by Gnetum gnemon (common atthis end ofSertung). In general the groundvegetation was sparse, due to the relativelydense arboreal cover. However, a smallnumber of nibung seedlings were observedin hollow sites near to the parent trees(Table l).

The last plot (site P) was established onth'e central ridge of Panjang, which sup-ported a Timonius compressicaulis com-munity unusually rich (for Panjang) in

[Vor. 36

m

20

Neonauclea calycina, such that it mightbe termed a patch of Tirnonius-Neonau-cleaforesr. The shrub,/sapling data (Table

l) indicate this site to be transitional toDysoxylurn gaudichaudianun forest, apathway described by Whittaker et al.(1989). As in plot S, the forest had arelatively thin, broken canopy (Fig. 4)'typical of T. cornpressicaulis, allowinghealthy growth of the nibung, the crownsof which were an important component ofthe main forest canopy layer. Althoughrequiring shade in the early stages ofgrowth, Oncosperma tigillariurn is knownas a facultative light demanding specieswhen approaching reproductive maturity;

'100

P R I N C I P E S

2. Profile diagram and map of trees within plot R2. x : seedling of nibung. ot _: parent tree' ' : other tree

species Bm : Bridelia minoica, Fs : Ficus septica, Ft : Ficus tinctoria, Nc : Neonauclea calycina,

Pa : Pipturus argenteus, FI : Ficus f,stulosa, Trc : Terminalia catappa' Tl : Tarenna fragrans'

? n

o l

a .

@ 'r a

r a

aa

. a

a

a

) a

o r

a

\ tU o .

a a

a

a ' '

aa

a a

a

E A

3. Profile diagram and map of trees within plot S. Key as for Fig. 2, pl's Ae : Artocarpils elasticus, G-g:

Gneturn gnei.on, Hp = Iierrand.ia pebati, Mc : Morind.a citrifotia, Tme : Timonius compressicaulis-

* * ; . { *

, ox

a

a

t a a

s

a r !

a t '

a

a

I

a

oX

a

@a

a

o

r O xa

x a x

a x a

a

0 5 0 1 0 04. Profile diagram and map oftrees within plot P. Key as for Figure 3, plus: Dg : Dysoxylum gaudichaudianum,

Ff : Ficus fulua. Mt : Maearanga tanarius.

t9921

howevero exposure is needed gradually forits development into the mature tree (House

1984). This was reflected by the occur-rence of several small clusters of nibuneunder quite dense forest canopies (e.g.. seeFig.2). The data presented here are inter-preted as showing nibung to be insensitiveto community type within these near-coastal forests and to have no obvious asso-ciat ion with other plant species.

Distribution of Nibung in Relationto Environment

In mainland Java, Sumatra and Kali-mantan, nibung is generally known frombrackish swampy areas or behind the tidalforests (Steenis I 935). Backer and van denBrink (1968) mention that nibung can befound at altitudes between I and 50 mabove sea level, extensively associated withnear-coastal localities, salt water swampsand "denudated rocks." Interestingly,Hommel (I987) describes an Orucospermatigillarium- S alacca edulis (: $. zalacca)vegetation community from a lowland flu-vio-alluvial plain within Ujung Kulon (west

Java). It is described as secondary in statusand is near-coastal in location, but its dis-tribution explicitly does zo, include thecoastal plains, swamps and beaches. It isnot stated, however, whether O. tigillari-um itself is similarly restricted. In the rel-atively aseasonal climate of Siberut (140km west of Sumatra) another member of

PARTOMIHARDJO ET AL.: ONCOSPERMA ON KRAKATAU

m

2 0

0

the genus, Oncosperm,a horrid.um (Gritr.)Scheff., occurs commonly in the interior,but is replaced by O. tigillarium near thecoast on sandy beach-derived deposits andalong the tidal stretches of large rivers(House 1984). House found on Siberutthat both species show a preference forcoarse-textured, well-drained soils, of lowfertility, and that these conditions weremore often met with on slooes rather thanin hollows. On Krakatau, iuch conditionsare more or less ubiquitous and indeeddrought conditions in the dry season aremore likely to be limiting than is water-Iogging.

Within Krakatau, nibung has been foundin Rakata, Sertung and Panjang at alti-tudes between 2 and 150 m above sealevel. Although the young plants of Onco-sperma tip;illarium are reported to tol-erate saline conditions (Koebernik 1966),no seedlings were recorded close to theshore line during the present study. Theclosest individual of nibune to the shorewas about I0 m from an erodine coasL.We conclude therefore that at least in theSunda Straits area, it behaves as a near-coastal but not strand-line species.

Dispersal and Regeneration

The fruits of nibung are globular andabout 12 mm in diameter. At first theyare dark green but they turn black-purpleon ripening (Backer and van der Brink

P R I N C I P E S [Vor-. 36t 6

1968). Docters van Leeuwen (1936) wasof the view that they had been brought to

the islands by birds, probably the pigeonMyristiciuora bicolor, which occurred atthat time in large numbers. In support ofthis he cites observations of Ridley (1930)

that the fruits are taken by other pigeonsand, the facts that the young plants stoodtogether in groups within woodland somedistance from the beach.

The maximum distance that seeds werefound from the parent trees within thestudy plots was about l0 m. A detailedcount of the number of seeds in the vicinityof selected parent trees is shown in Table2. House (1984) states that the closelyrelated Oncosperma horridum does notgerminate in open, sunny conditions but

that the shade requirement for establish-ment and early growth is gradually lost asthe palm grows into the main tree canopy.Nibung may well have a similar autoecol-ogy, requiring shady, humid conditions in

the early stages. This is supported by ourfield observations that seedlings of nibungtended to be found in largest numbers in

the moister sites within the study plotsexamined. In addition to seed production,nibung clumps also increase by the pro-duction of new buds at the base of thetrunks of mature Plants.

The distribution and population dynam-ics of nibung on the Krakatau Islands maybe influenced by many factors. Strongwinds, unconsolidated substrates and heavyrain all contribute to tree-fall. This meansthat canopy structures are relativelyunstable. As important, the forests of Pan-jang and Sertung have been significantlydisturbed by volcanic action on severaloccasions (above). It is hard to judge theimpact on the nibung populations of theseprocesses. The populations have spread aswell on the more disturbed islands Panjangand Sertung as on Rakata, on which, how-ever, it arrived most recently. The knowndistribution of the species within the islandssuggests that most seed falls close to theparent trees, but that populations on each

Table 2. Densities of nibung seeds perm2 on the study plots.

Distance Nibung seeds

fromparent

tree (m, AverageR I R 2 S

0- ll-22-33-44-J

..)-o

6-77-88-99-10

o

8827I0000

00000

s (+4 .6)6 (+6 .8)8 (+6 .7)3 .3 (a2 .3)4 (+2 .6)0 .5 1+9.6 ;0 . 5 ( + 1 . 6 ;0 .3 (+0 .5)0 (+0 .0)0 (+0 .0)

island have gradually spread from the ini-

tial colonization point, presumably aidedby occasional animal-dispersal of seeds intosuitable sites. Although nibung is not knownas a true gap exploiter, it needs canopyspace for successful flowering and fruiting.The seed falling very close to the parenttrees is effectively o'wasted," as the effectsof continuous shading from the dense arrayof palm crowns, the damage caused byfalling palm fronds and competition withparent plants leads to poor prospects ofsurvival. The apparent ineffectiveness ofdispersal agencies (Table 2) may thus bea limiting factor on the spread of the spe-cies, although the proportion of seed pro-duction involved is unknown. On the otherhand, the buds shooting from the base ofthe trunk will generally be protected fromthe fallen palm leaves since nibung stems(especially the outer side of the clusters)tend to be a bit bent. As the palm' whenfull grown, is often taller than the sur-rounding trees, particular clumps may thuspersist well. It may be that the main factor.iirnititrg the spread of nibung is low levelsof soil moisture, particularly in the dryseason. Comparison of data in Tables Iand 2 indicates better initial germinationand establishment rates in the deeper shadeand more mature forests of Rakata;

I l I1 4 I1 7 66 4J J

0 ln t

O I0 00 0

r9921

although this remains something of a mat-ter for speculation. It was also noted, how-ever, that the development of the nibungpopulation appears to be threatened byillegal cutting on each island.

Conclusions

l. In the first fifty years of recoveryfollowing sterilization in 1883 only threepalms species were recorded on Krakatau,Oncosperrna tigillarium being one ofthem.

2. After 106 years, eight palm speciesare known, all but one of these havingestablished a continued presence. Nibunghas now established a scattered distributionin near-coastal vegetation, below 150 maltitude and away from the strandline.

3. Nibung appears from our data to berelatively insensitive to the between-islanddifferences in vegetation, soil developmentand disturbance histories within the Krak-atau islands.

4. Its spread appears to be limited bythe effectiveness of local dispersal agenciesand quite possibly by soil moisture condi-tions. Nonetheless it forms an occasionalcanopy component in all three originalislands of the group.

5. We hope that this paper, althoughleaving many unanswered questions, mayserve to awaken further interest in theecology ofpalm colonization within tropicalforest successions.

Acknowledgments

This paper is Krakatau Research Proj-ect Publication No. 34. We thank all thosewho participated in the project, and whohelped the project in any wayo financial orotherwise. The major part of the field workwas conducted on the joint Oxford Uni-versity, Ohio State University, and Her-barium Bogoriense l9B9 expedition toKrakatau. Major financial support wasprovided by The Royal Society of London,The British Ecological Society, The RoyalGeographical Society, The Percy Sladen

PARTOMIHARDJO ET AL.: ONCOSPERMA ON KRAKATAU T7

Fund, Meyer International PLC., SmeeTimber Importers (UK), Oxford Univer-sity, and BP.

LrrrReruRn Clrno

Becrsn, C. A. e.No R. C. BAKHUTZEN VAN DENBRINK, JR. 1968. Flora of Java. Vol. III.N.V.P. Noordhoff, Groningen.

BrRD, E. C. F. & N. J. R0SENGREN. 1984. Thechanging coastline of the Krakatau Islands,Indonesia. Zeitschrift fur Geomorphologie N.F,28:347 366.

BoRssurr.r WerrrEs, J. ve.N. 1960. Botanical obser-vations on the Krakatau Islands in l95l and1952. Annales Bogoriensis 4: l, 64.

Busu, M. B. AND R. J. Wurrrernn. 1986. Thevegetation commmities of Sertmg, Rakata Keciland Rakata. Chapter 3. In:M.8. Bush, P. Jones,and K. Richards (eds.). The Krakatoa CentenaryExpedition: 1983 final report. MiscellaneousSeries No. 33, Department of Geography, University of Hull, pp. 14 49.

DocreRs vAN LEEUwEN, W. M. 1936. Krakatau1883-1933. Annales du Jardin Botanique deBuitenzorg 46-47.

Dn,tNsrIntn, J. 1976. Palms in the everyday lifeof West Indonesia. Principes, 20(2): 39-47.

ETHELBERT Brerrrn, S. J. 1926. The palms ofBritish India and Ceylon. OUP: London.

Hottunr, P. W. F. M. 1987. Landscape-ecologyof Ujung Kulon (West Java, Indonesia). 206 pp.Published by the author, Wageningen.

Housn, A. P. N. 1983. The use of palms by manon Siberut island, Indonesia. Principes 27(I):t 2 - 1 7 .

I984. The ecology of Oncosperma hor-ridum on Siberut Island. Indonesia. Princioes28(2): 85-89.

KorsnnNIr, J. 1966. Salt tolerance in yomg palms.Pr incipes I0(4) : 130-132.

NEwsour, D. I986. Aspects of soil surface char-acteristics on Rakata and Anak Krakatau. Chap-ter 9. In: M. B. Bush, P. Jones, and K. Richards(eds.). The Krakatoa Centenary Expedition: 1983final report. Miscellaneous Series No. 33,Department of Geography, University of Hull,pp . r 34 -156 .

RIDLEY, H. N. 1930. The dispersal of plantsthroughout the world. Reeve, Ashford, England.

SrnlraN, B. 1856. Popular history of the palms.London, Lovell Reeve.

Srnnnrs, C. G. G. J. vAN. 1935. Maleische Vege-tatieschetsen. Tijdschr. Kon. Aardrijksk. Ge-nootschap. Serie II vol. LII.

WHTTTAKER, R. J., K. RrcH,cnls, exl M. B. Busn.1989. Plant recolonization and vegetation suc-cession on the Krakatau Islands. Indonesia. Ecol.Monosr. 59: 59-123.