Yoshinaga, Alvin Y.

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387EXOTIC PLANTS IN KIPAHULU VALLEY: 1945-1980Alvin Y. YoshinagaDepartment of Botanyuniversity of Hawaii at ManoaHonolulu, Hawaii 96822The Kipahulu Valley District of Ha1eakala National Park isknown for the exceptional quality of its native montane rainforest vegetation. In recent years there has been concern aboutdamage to native plant communities from feral pig (Sus scrofa L.)activities and invasion by exotic plant species. The numberof exotic plant species noted by scientific parties betweenthe Haleakala Crater rim and the lower edge of the forest hasincreased steadily. In 1945, the first such party reported fivespecies between the upper tree line arid Pa1ikea (Fagerlund 1945).In 1967, Lamoureux (1967) reported 22 species within that z~ne.During the present. study (1978-1980), we have recorded 55 spe-cies of exotics and new weedy natives. Each succeeding partysurveyed a wider area more intensively than the previous party.If the 1945 party had retraced its route on the same schedule,it might have noted about 13 exotic species in 1967 and 18 today.In 1945, only *Maui pa'makani (Eupatorium adenopho~um) was com-com. At present, 20 species are either widespread or abundant.Exotics are most abundant in the koa (Acacia koa Gray) forestbelow 1200 m (3940 ft). Some exotics occur-WIthin the 'ohi'a(Metrosideros) forest above 1200 m (3940 ft) but none are commonbeneath the canopy.Appendix I lists exotic and weedy native plant s~eciesreported from KIpahulu Valley between 6l0m (2000 it) and theHaleakal~ Crater rim. Grasses, sedges, and composites make up aparticularly large part of the list. Characteristics shared bymany species on this list are: Small size, light propagules,herbaceous growth form, and tropical origin. Most are ruderalspecies which readily colonize disturbed habitats. Species whichare now especially abundant or appear to be spreading include thefollowing:*Ageratum conyzoidesCU2hea carthageneQsisCyperus brevifolisC. haspanC. kyllingaEupatorium adeno~horumHydrocotyle vertlcillataExotic species.Maile honohonoPuakamoliKyllingaKyllingaMaui pa'makaniPohepohe388 , ;Ludwigi~ ~~tivalvisPaspalum conjugatum,P. orbiculare~sidium cattleianum'Rhynchoseo~a lavaru~Rubus rosaefolius 'SaccioleBis indicaStachyta~pheta jamaicensisYoungia japonica'KamoleHilo g,rassRicegrassStrawberry guavaKuolohiaThimbleberry,Glenwoodg r assOiOriental hawksbeardTh! t~o agerits most commonly accused of spreading exoticsinto Kipahulu Valley are man and feral pigs. The argument fOI!wholesale man-caused vegetation change is not strong. Most ofthe spread of exotics occurred during periods of very littl~human activity, frequently i~ areas far from any activity. Com~parison of 'the most heavily used trail for the p~'esent projectwith an otherwise s im il at' tr ail used. only for 1 i,gh t downhilltraffic (counter to the direction of spt:ead of most:' exotics) sug ...gests some small-scale dispersal from human activity, but nolarge-scale mass movement. Many of the exotics havepropaguleswhich are readily dispersable independently. 'Feral pigs are known to disp~rse some exotics, such as*s~rawberry guava, and to attack certain natives, such as lcbe-liads and hapu'u (Cibotium sp.). Probably more important istheir role in habitat modification, particularly by rooting.Most of the widespread exotics are ruderal species, well~adaptedto disturbed habitats. By contrast, ~ew 01 the natives are~ thefew whith have increased or become established since 1967 aremostly weedy sedges~A series ofexclosutes have be~n e~tablished at 670 m(2200 ft), 960 m (3150 ft), and 1430 m (4700 ft) to study ~heeffects of pig exclusion on vegetation. The lower two are in ko~forest heavily invaded by exotics, the uppermost is in relativelyuninvaded 'ohi'a forest. The exclosures range from 0.04 ha(0.1 acre) to 0.12 ha (0.3 acre). Frequencies of plants in 1 m2quadrats along fixed transects both inside and outside the exclo-sures are recorded.So far there have been few changes in vegetation. In thelongest established exclosure, at 670 m (2200 ft), the averagenumber of plant species per 1 m2 quadrat in 'September 1978 was2.9 inside the exclosure' and' 2.6 outside. In Febrtiary, theaverage was 3.0 inside, and 2.8 outside. The. most noticeabledifference between the inside and the outside in 1980 was the'more continuous leaf litter layer inside.There is special concern about *strawber~y guava, which hasspread rapidly since 1967. In KIpahulu Valley, the red varietypredominates, although the yellow spherical variety occurs also.Unlike most of the other exotics, *strawberry guava is a treewhich is relatively long-lived and shade~tolerant. It formsdense stands from which natives may be excluded.389To study its establishment mechanism, all *strawberry guavawas cleared from 20 m X 20 m sites at 640 m (20g0 ft), in an areawith ca. 2900 trees of 2 cm or greater diamete~ at breast height(dbh) per ha; at 820 m (2700 ft); near the current upper edgeof heavy infestation; and at 950 m (3120 ft), where *strawberryguava is currently scattered and uncommon. A 10 m X 10 m griddedplot was laid out in the center of each site so that recordscould be kept of individual seedlings as they emerged. Pigrootings and droppings were also recorded.The average rate of seedling appearance at the 640 m(2090 ft) site has been 0.4 seedling/m2 /year .. Seedling den-sity 14.5 months after initial clearing was 0.2 seedling/m2 ;this implies a new seedling has a 20% chance of surviving oneyear~l At the 820 m (2700 ft) site, appearance rate has been0.6 seedling/rn2 /year; density 13.5 months after clearing was0.2 seedling/m2 , implying a survivorship rate of 8% per year. Noseedlings have appeared within the 950 m (3120 ft) site, whichhad no mature tr~es to begin with. The latter observation sug-gests that the seedlings arise from dormant seeds rather thanfrom seeds brought in by animals. No. seedlings have arisen with-in the plots from pig droppings, although they are known to do soelsewhere. Most have arisen on undisturbed moss or leaf litter.Observations of other marked *strawberry guava seedlingsshow low mortality once the seedlings reach around 10 cm height.Of 27 such seedlings marked in February 1979, 23 were still alivein July 1980, for an 89% annual survivorship rate. Seedlingsare common beneath mature plants below about 900 m (2950 ft).Above that elevation, they are practically absent beneath matureplants, and occur elsewhere· mainly in scattered clumps. Thissuggests that at these elevations it becomes established mainlythrough animal dispersal.Assuming that: (1) All seedlings have been counted; (2) seed~lings appear at a constant rate; and (3) the death rate isuniform for seedlings of all ages throughout the year, thesurvivorship rate for one year can be found by solving for "a"in the following equation:t = total elapsed timex = (seedling density at t)(annual appearance rat~)which is readily determined numerically.whereTh i s gives at - 1LNa390LITERATURE CITEDBeeking, R. 1970. Report of the Kipahulu valley trip. Reportfiled at Haleakala Nationa1 Park (unpublished). 14 pp.Fagerluna, G. O. 1945.Valley~ Reportlished). 8 pp.An account of an inspection offiled at Haleakala National ParkKipahulu(unpub-Lamoureux, C. 1967. The vascular plants of Kipahulu Valley,Maui. Pages v + 184 in R. E. Warner, ed. Scientific Reportof the Kipahulu ValleYExpedition. The Nature Conservancy,Arlington, VA.Yoshinaga, A. 1980. Upper Kipahlu valley weed survey. CPSU/UHTech. Rep. 33 (Dept. of Botany, University of Hawaii).391APPENDIX IList of Exotic and weedy Native Plant SpeciesReported from KIpahulu ValleySPECIES REPORTED UP TO 1945 (Fagerlund 1945; Lamoureux 1967):Coix lachryma-jobi L.Eupatorium adenophorum Spreng.Musa sp.polygonum glabrum Willd.Rubus rosaefolius Sm.Setaria palmaefolia (Koen.) StapfJob's tearsMaui pa1makaniBananaKamoleThimbleberry. Palmgrass ?ADDITIONAL SPECIES REPORTED IN 1967 (Lamoureux 1967):Adiantum cuneatum Langs. & Fisch.Cordyline terminalis (L.) KunthCuphea carthagenensis (Jacq.) MacBrideCyperus brevifolius (Rottb.) Hassk.Drymaria cordata (L.) Willd.**Eleocharis obtusa (Willd.) Schult.Erechtites valerianaefolia (Wolf) DC.Geranium carolinianum L.var. australe (Bent~.) Fosb.Holcus lanatus L.Hydrocotyle verticil~ata Thunb.Hypochaeris radicata L.Ludwigia octivalvis (Jacq.) RavenOplismenus hirtellus (L.) Beauv.Paspalurn conjugaturn Berg.Prunella vulgar!s L.Psidium cattleianum SabineP. guajava L.Rumex acetosell~ L.Sacciolepis indica (L.) Chase**Solanum nigrum L.Youngia japonica (L.) DC.Maidenhair fernTiPuakamoliKyllingaPipiliP.ipi waiHino hanaCarolina crane's billVelvetgrassPohepohe'GosmoreKamoleHonohono-kukuiHilo grassSelf-healStrawberry guavaGuavaSheep sorrelGlenwoodgrasspopoloOriental hawksbeard392ADDiTIONAL SPECIES REPORTED BY 1980 (Becking 1970; Yoshinaga1980) :Ageratum conyzoides L.Axonopus compressus (Sw.) Beauv.Castilleja arvensis Schlecht.Commelina diffusa Burm. f.Cyperus haspan L.C. kyllinga Endl.Digitaria sanguinalis (L.)Heist. in Scop.Erigeron canadensis (L.) Cronq.Eugenia jambos L.Eupatorium riparium RegelFestuca sp.Fimbristylis dichotoma (L.) VahlMelinis minutiflora Beauv~paspalum dilatatum Poir.P. orbiculare Forst. f.R. urvillei Steud.**Rhynchospora lavarum Gaud.Senecio vulgarts L ..Setaria geniculata (Poir.) Beauv.Spathodea campanulata Beauv.Spathoglottis plicata Bl.Stachytarpheta iamaicensis (t.) VahlAnd several species not yet identified.Maile honohonoBroad-leavedcarpetgrassField Indian paintbrushHonohonoKyllingaKUkaipua1a ?IliohaRose appleHamakua pamakaniFescueTall fringe rush'Molassesgrass?Dallis grassRicegrassVaseygrassKuolohia ?Common groundselPerennial foxtailAfrican tulip treeMalayan groun~ orchidOi**?Native or possibly native.Questionable identification.

Exotic plants in Kipahulu Valley: 1945-1980

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Exotic plants in Kipahulu Valley: 1945-1980

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