Hobdy, R.

Loope, L.L.

Medeiros, A.C.

English

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78REMNANT NATIVE VEGETATION AT A LOWLAND SITE NEAR KIHEI, MAUlArthur C. Medeiros and Lloyd L. LoopeHaleakala National Park, Box 369, Makawao, HI 96768andRobert HobdyDepartment of Land & Natural Resources, Division of Forestry andWildlife, Box 1~15, Wailuku, HI 96793Native lowland vegetation of the Hawaiian Islands has been sogreatly altered by Polynesian colonizers between the 5th and 18thcenturies and by urbanization, agricultute, and e x6ticintroductions in the 19th and 2~th centuries that its originalstructure and composition are not known (Rock, 1913; Kirch, 1982;Olson and James, 1982a & b). We have recently explored an ar~aof remnant native vegetation in the lowlands of leeward East Mauiwhich is remarkably intact and which may be a good indication ofthe nature of the pre.Polynesian vegetation of the lower leewardslopes of Haleakala.LOCATION, GEOLOGY, SOILS, AND CLIMATEThe location of the major native lowland vegetation remnants isin the Keokea and Waiohuli districts east of Kihei (SW quadrantof USGS Puu 0 Kali quadrangle) at elevations between 2~~m and4~gm. Two lava flows originating on East Maui's southwest riftzone are minimally weathered downslope from Puu 0 Kali (RedHill), a conspicuous cinder cone reaching 452m (1481 ft)elevation. These flows, radiocarbon dated by Crandell (1983) at4~7~ and 865~ years old, support primarily native vegetation.Adjacent terrain with relatively deep soils is covered almostentirely with introduced vegetation. Foote et ale (1972)characterize these deeper, reddi~h-brown soils as extremely stonysilty clay loams and silt loams developed from volcanic ash, withdepths of 3~·75cm to fragmented ala.Median annual precipitation at four rainfall stations in thevicinity (within a 4km radius) at elevations of l2g-4g~m (4~0­130~ ft) ranges from 335mm to 475mm with 86%~10~% falling in theNovember-April period and 78-95% falling in the 4 month periodfrom December through March (State of Hawaii, 1982). January istypically the month of heaviest precipitation. Amounts ofprecipitation vary greatly from year to year. Kihei, with a meanannual rainfall of 350mm (and a November-April mean of 315 mm)had the following November-April precipitation totals in the sixyears from 1976-77 through; 1981-82: l55mm, 94mm, 589mm, 495mm,l4lmm, 624mm (U.S. Department of Commerce, 1976-82).VEGETATION AND FLORAErythrina sandwicensis (wiliwili) is the dominant tree species onthe Puu 0 Kali lava flows. Other native tree species are present79sporadically- Diospyros ferrea (lama), Myoporum sandwicense(naio), Acacia koaia (koaia), and Reynoldsia sandwicensis (ohe).Common native shrubs include Sida fallax, Lipochaeta rockii var.dissecta, Dodonaea eriocarpa-;--Chenopodium oafiuense, Achyranthessplendens, Nototricfiium sandwicense, Euphorbia celastroides var.mauiensis, Cassia gaudIchaudii, capparis sandwicfiiana, andWikstroemia sp. Rare shrubs include Abutilon menzies!i andHibiscus brackenridgei var. brackenridgei, as well as the vine-lIke shrubs Canavalia haleakalensis and Bonamia menziesii. Thenative vines Sicyos sp. (seasonal), Ipomoea congesta, andIpomoaea tuboides are abundant. Native grasses include PanicumxerophIlum, Panicum beecheyi, Panicum cfr. pellitum, Eragrostisvariabilis, and Heteropogon contortus. Argemone glauca, Plumbagozeylandica, and Peperomia leptostachya are native herbs. Thenative fern Doryopteris decipiens is common. Boerhavia diffusa, arambling shrub, is present below 25~m on the Puu 0 Kali flows.Waltheria indica, a plant which mayor may not be native (St.John, 1978), is common.Exotic plants common on the lava flows include the trees Prosopispallida, Acacia farnesiana, and Leucaena leucocephala; the shrubsIndigofera suffruticosa and Abutilon grandif;oliumr the vinesMerremia aegyptia, Momordica charantia, andCucumls dipsaceus;the forbs Bldens pilosa, Bldens cynapifolia, Galinsogaparvifolia, and Reichardia picroldes; and the grassesCenchrusciliaris and Rhyncheletrum repens. .On the deeper soils adjacent to the slightly weathered flows, theexotics Prosopis pallida (kiawe) and Cenchrus ciliaris(buffelgrass) domInate the ovei~tory and understory respectively.Sida fallax is the only commonly associated native species.PHENOLOGY AND LIFE CYCLES OF THE FLORAThe phenology and life cycles of the plants of lowland leewardEast Maui are keyed to a very severe and prolonged dry season anda variable wet season. The adaptations of Erythrinasandwicensis, the dominant tree, are representative of thoserequired. It is one of the few deciduous trees in the Hawaii~nflora. (Reynoldsia is another.) Erythrina is summer deciduous,flushing new leaves in November-December and losing leaves inApril-June. It flowers while leafless during the summer. Seedsmature and are dispersed primarily in late-fall and early winter,just as the winter rains normally begin. Seedlings must developdeep roots prior to cessation of rains in the spring if they areto survive.Some species of this habit~t are annuals, including the nativeSlcyos sp. and Panicum spp. and the exotic Bidens spp., survivingthe 6 month dry season as seeds and germinating with the firstmajor rains in November or December. Growth of Sicyos isluxuriant in years of ample rainfall, with abundant seed set.However, in growing seasons when early rains are meagre and arenot followed by later rains, ripe seed may not be produced80abundantly. Presumably, some mechanism exists to prevent allseeds from germinating simultaneously. Annuals may be extremelysusceptible to disturbance- especially fire, since most seedscould be destroyed by a fire at the beginning of the dry season~They are also highly susceptible to displacement by perennials orby faster-developing annuals.Ipomoea tuboides, I. congesta, and Boerhavia diffusa, areperennials which dieoack vegetatively during the dry season andrestore leaves and herbaceous stems when the wet season commences.REPRODUCTIVE STATUS OF NATIVE SPECIESIn most plant communities of leeward East Maui, reproductionofnative species is minimal (Medeiros, Loope, and Holt, 1984).Reproduction was observed for many of the native species on thePuu 0 Kali lava flows, including the following: Erythrinasandwicensis, Achyranthes splendens, Chenopodium oahuense,Dodonaea eriocarpa, Euphorbia celastroides, Hibiscusbrackenridgei, Lipochaeta rockii, Ipomoea congesta, Ipomoeatuboldes, Sicyos sp., Panicum pellitum, Canavalia haleakilensls(one seedling only), and Acacia koala (vegetative root suckersonly). This reproductive success of natives would undoubtedly bemuch greater were it not for displacement by Bidens and otherexotics. We tentatively attribute the notably high reproducti~esuccess of native plants on the Puu 0 Kali flows to the sparsityof browsing by introduced ungulates.COMPARISON WITH OTHER NATIVE VEGETATION REMNANTS ON EAST MAUlThe Puu 0 Kali flows have 33 native species, only three of whichwere not recorded elsewhere on leeward East Maui in a survey byMedeiros, Loope, and Holt (1984)- Abutilon menziesii, Achyranthessplendens, and Hibiscus brackenridgei. The Puu 0 Kali flows,apparently because of their protection from browsing, have anative vegetation much more intact than that at any other lowlandleeward site on East Maui. Yet not surprisingly, in view oftheir small area (total of no more than 300ha), their flora ismissing species found in the same elevational zone elsewhere. Thetotal extant native flora of leeward East Maui above the strandzone and below 400m elevation numbers about 45 species. Thosenot yet recorded from the Puu 0 Kali flows are Bidens mauiensis,Canthium odoratum, Cassytha filiformis, Cenchrus agrimonioides,Jacquemontia sandwicensis, Lipochaeta kamolensis, Lipochaetalavarum, Nothocestrum latifolium, Panicum torridum, Portulacacyanosperma, Portulaca sclerocarpa, and Rauvolfia mauiensis.DISCUSSIONNative vegetation has survived on the lava flows apparentlybecause of their unsuitability for Polynesian agriculture,partial or complete protection from fire by tracts of unvegetated81la~a~ and fortuitous protection from goats. Since no evidence ofPolynesian irrigation syst~ms is apparent in the area, ancientagricultural use would have involved dry land cultivation. Kirch(1982) suggests that almost all topographically suitable lowlandsites with more than 500mm of annual precipitation were used foragriculture by Polynesians. Although the area in questionaverages only 300-400mm of annual rainfall, we would speculatethat successful use for shifting agriculture was a possibilityduring the wet seasons of many wet years. Even if the nativevegetation of areas with deeper soil was not directly obliteratedby shifting cultivation, the use of fire (Kirch, 1982) inconjunction with shifting cultivation in moister areas upslopeundoubtedly led to conflagrations in the vicinity of Puu 0 Kali.Fires repeated at frequent intervals may have quickly led to theconversion of. the pristine native vegetation surrounding the lavaflows to grasslands dominated by Heteropoyon contortus (piligrass). In more recent times, domestic 1 vestock grazing hasinfluenced the vegetation and Prosopis, Cenchrus, and otherintroduced species have come to dominate.There are numerous lava flows at low elevations on the southslope of East Maui ~here native vegetation has not been subjectedto Polynesian fire and agriculture. However, these sites havebeen and continue to be browsed by herds of feral goats. Acrucial feature of the Puu 0 Kali site which has led toexceptional protection of the leeward low elevation native florahas been the sparsity of goat browsing pressure. At present,goats do not seem to be present in the area- undoubtedly becauseit is such a small tract of "wildland" surrounded by landsmanaged for cultivation, livestock grazing, and residential use.Cattle, although present, seem to generally avoid the rough lava.Axis deer (Axis axis), introduced to the area by the State. ofHawaii in ~early 1970's, are currently present only in lownumbers in the area. Browsing damage to native shrubs seemsminimal.The major deterrent to survival of native species on the flowscurrently may be displacement by exotic plants- especially Bidensspp., Cenchrus ciliaris~Rhyncheletrum repens, and Prosopispallida. Bidens pllosa, the most effective competitor in theshallow soils of the flows (along with the very similar B.cynapifolia), was collected in Hawaii as early as 1845-47 (St.John, 1973). Annuals are particularly susceptible to displace-ment by exotic herbs because of their frequently recurringrequirement for seed production and seedling reestablishment.The surviving vegetation and flora of the Puu 0 Kali lava flQwsmayor may not be highly indicative of the composition ofpristine (pre-Polynesian) vegetation of much of lowland leewardMaui. Since the habitat is extremely rocky and thus notrepresentative of most of Maui's isthmus and the lower west slopeof Haleakala, it may not be at all typical. The site mayrepresent a living botanical analogue of the fossil bird bonesanalyzed by Olson and James (1982a & b). It is entirely possiblethat numerous plant species were eliminated by polynesian82agriculture and fire as suggested by Olson and James (1982b).That many additional species were eliminated by grazing andbrow~ing of feral and domestic ungulates following arrival ofCaucasians is suggested by an interesting analysis by St. John(1978) of the earliest plant collections of David Nelson in 1779.Certainly any native lowland species which required a habitatwith deep soil was eliminated long ago. All that is certain isthat the vegetation of PUU 0 Kali is the best indication we haveof the nature of the pristine lowland leeward vegetation of EastMaui.LITERATURE CITEDCrandell, D.R. 1983. Potentialeruptions on the island of Maui,Misc. Investigations Map 1-1442.hazardsHawaii.from futureU.S. Geol.volcaniqSurvey,and F. Stevens. 1972. SoilMaui, Molokai and Lanai.in coop. with Univ.ofFoote, D.E., E.L. Hill, S. Nakamura,survey of the islands of Kauai, Oahu,U.S.D.A., Soil Conservation Service,Hawaii Agric. Expt. Sta. 232p. & maps.Kirch, P.v. 1982. The impact of the prehistoric polynesians onthe Hawaiian ecosystem. Pacific Science 36(1): 1~14.Medeiros, A.C., L.L. Loope, and R.A. Holt. 1984. Status of nativeflowering plant species on the south slope of Haleakala, EastMaui. Univ. Hawaii, Dept. of Botany, Cooperative Natl. ParkResources Studies Unit, Tech. Rept.Olson, S., and H. James. 1982a. Fossil birds from the HawaiianIslands: evidence for wholesale extinction by man before westerncontact. Science 217: 633-635.Olson, S.I and H. James. 1982b. Prodromus of the Fossil Avifaunaof the Hawaiian Islands. Smithsonian Contributions to Zoology,No. 365. 59p.Rock, J.F. 1913. The Indigenous Trees of the Hawaiian Islands.Reprinted in 1974 by Charles E. Tuttle Co., Tokyo, Japan. 548p.St. John, H. 1973. List and Summary of the Flowering Plants inthe Hawaiian Islands. Pacific Trop. Bot. Garden, Memoir 1, 519p.St. John, H. 1978.David Nelson in 1779.The first collection of Hawaiian plants byPacific Science 32(3): 315-324.State of Hawaii, Department of Land and Natural Resources. 1982.Median Rainfall, State of Hawaii. Division of Water and LandDevelopment. Circular C88. 44p. & maps.u.S. Department of Commerce. 1976-82~ Climatological Data, Hawaiiand Pacific. National O~eanic and Atmospheric Administration.Issued monthly.

Remnant native vegetation at a lowland site near Kihei, Maui

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Remnant native vegetation at a lowland site near Kihei, Maui

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