TANE 25, 1979

VEGETATION AND FLORA OF PONUI ISLAND, ,

by E.A. Brown Botany Department, University of , Private Bag, Auckland

SUMMARY

A total of 202 species of vascular (178 of which are indigenous to New Zealand) are recorded for Ponui Island. The major indigenous communities are discussed in detail. The composition of the flora is briefly discussed and compared with other areas. Remnants of the island's probable former cover of kauri ( australis) forest are present in the southern half of the island. However much of the kauri present is probably secondary forest that developed after milling in the early 1900's. Also present, both in coastal valleys and in valleys within the kauri forest, are remnants of taraire (Beilschmiedia tarairi) dominated broadleaf forests.

INTRODUCTION

If Ponui Island (1770 hectares) lies 30km east of Auckland (Fig. 1) and is the most eastern of the Inner Gulf island (latitude 36° 55' S, longitude 175 ° 11' E). The terrain is hilly for the most part and the southern half is dominated by a large ridge that runs roughly north south. Most of the northern half of the island with the exception of one large valley (Fig. 1), several areas of teatree (Leptospermum) scrub and the steep coastal cliffs is in pasture. The survey was therefore concentrated on the southern end of the island where there are remnants of the kauri and broadleaf forests that probably once covered the island. Studies on the vegetation of Ponui Island were carried out during the Auckland University Field Club scientific trip to the island, 26 August-2 September, 1978.

VEGETATIONAL HISTORY

Accounts of the vegetation of Ponui Island are extremely scarce (Cockayne 1904, 1905; Atkinson 1959) and virtually no material has been published. The extent of the forests in pre-European and even early- European times is unknown. There is abundant evidence of Maori occu• pation which suggests considerable areas of the natural vegetation may have been cleared or modified prior to European occupation. The diary of Frederick Chamberlin for 1853 tends to support this view as it mentions

5 wild pigs being shot and scrub burned (Maddock and Whyte 1966). In the following eighty years the vegetation was further modified by the introduction of gorse (Ulex europaeus), the actions of gumdiggers, the mill• ing of kauri in the Trig area and the periodic firing of the danthonia (Rytidosperma spp.) pastures. At present two thirds of the island is in pasture and many bushed areas, particularly the coastal valleys, are grazed. The remaining kauri forest and regenerating areas nearby are largely kept clear of cattle and sheep (except during harsh winters). Efforts to control gorse and eradicate it from the pastures have been, to a large extent, successful and invasion of other habitats has remained at a minimum.

PLANT COMMUNITIES

Leptospermum (kanuka/manuka) scrub This occurs on dry, often quite steep slopes throughout the island. Most of the areas observed are fairly heavily grazed and opened up by cattle. Kanuka (Leptospermum ericoides) and manuka (L. scoparium) up to 4m tall form the canopy. Where subcanopy and/or ground cover are present prickly heath (Cyathodes juniperina), mapou (Myrsine australis), Coprosma rhamnoides, Doodia media and Oplismenus imbecillus are occa• sional with introduced grasses forming the dominant ground cover. Scrub is present in a number of areas adjoining the kauri forest. The youngest scrub lies just north of the trig and is dominated by manuka (l-2m). Common species include mingimingi, prickly heath, tauhinu (Pomaderris phylicifolia var. ericifolia), bracken (Pteridium aquilinum var. esculentum), heather (Erica lusitanica) and gorse. A few emergent tanekaha, towai, mapou, ponga and mamangi (Coprosma arborea) are present. On the south-eastern reaches of the kauri forest the scrub is older and more open. Kanuka and Olearia spp. are the dominant with occasional stands of mamangi/mapou/kanuka. Ground cover is sparse but includes Gahnia, Morelotia affinis, comb (Schizaea fistulosa) and Lindsaea linearis. Kauri rickers are present in the older kanuka/Olearia scrub while podocarps are more common in mamangi dominated stands.

Kauri forest South of the Trig (Fig. 1) there is an area of healthy, relatively young kauri (Agathis australis) forest. Milling in the early 1900s removed many of the larger specimens; most of the remaining trees have a diameter at breast height of 0.7-1.0m. Many species commonly associated with kauri are pres• ent: Gahnia spp., Kirk's daisy (Senecio kirkii), hoihoi (Alseuosmia macrophylla), ponga (Cyathea dealbata) and hangehange (Geniostoma ligustrifolium). However kauri grass (Astelia trinerva) is absent and the miniature tree fern Blechnum fraseri was found in only one place (covering 7 an area of some 3m2). Young towai (Weinmannia silvicola), rimu (Dacrydium cupressinum), miro (Podocarpus ferrugineus), matai (Podocarpus spicatus) and tanekaha (Phyllocladus trichomanoides) are present in varying quantities. With the exception of tanekaha few specimens of these species are larger than striplings. Common understorey species include lancewood (Pseudopanax crassifolius), mingimingi (Cyathodes fasciculata), white maire (Nestegis lanceolata) and clinging rata (Metrosideros perforata); while ground cover is provided by the orchids Acianthus reniformis, Pterostylis brumalis and Bulbophyllum pygmaeum and a number of ; mangemange ( articulatum), hound's tongue (Phymatodes diversifolium), Lindsaea spp. and filmy ferns (Trichomanes spp., Hymenophyllum spp.). In many areas the kauri forest grades into gumland scrub while numerous valleys within the forest are clad in broadleaf species. Three hard beech (Nothofagus truncata) saplings were found on one ridge (immediately SE of the trig).

Coastal cliffs Pohutukawa (Metrosideros excelsa) is the most common tree on the unstable greywacke cliffs. Houpara (Pseudopanax lessonii), karo (Pittosporum crassifolium), akepiro (Olearia furfuracea), mahoe (Melicytus ramiflorus) and mapou most frequently form the sparse subcanopy. Wharawhara (Astelia banksii) is a prominent ground dweller; renga lily (Arthropodium cirratum), N.Z. flax (Phormium tenax), Coprosma rhamnoides and Mercury Bay weed (Dichondra repens) are also present in vary• ing quantities.

Younger scrub (2-3m) consists of dense stands of manuka, wharawhara, houpara, karo, mapou, hangehange, taupata (Coprosma repens), koromiko (Hebe stricta var. sticta), bracken and gorse. In several places pohutukawa and houpara form a more important part of the cover. Near Motunau Bay radiata pine (Pinus radiata) and macrocarpa (Cupressus macrocarpa) form self sown colonies. South of Shell Bay boxthorn (Lycium ferocissimum) has similarly escaped from cultivation.

Broadleaf forest Broadleaf forest is present in many coastal valleys and also in some of the wetter valleys associated with the kauri forest. Taraire (Beilschmiedia tarairi) and karaka (Corynocarpus laevigatus) are the most common members of the canopy. Puriri (Vitex lucens) and kohekohe (Dysoxylum spectabile) are present in smaller amounts, as are tawa (Beilschmiedia tawa), white maire and mamangi. Most of the broadleaf forest is heavily grazed thus a subcanopy is rarely present. Ponga and mamaku (Cyathea medullaris) are occasional. Several ferns are commonly present near the small seasonal streams: Blechnum filiforme, B. membranaceum, heruheru (Todea hymenophylloides) and

8 Doodia media. Epiphytes include kokaha (Collospermum hastatum), iwituna (Lycopodium billardieri), Earina mucronata, makawe (Asplenium flaccidum subsp. flaccidum) and Pyrrosia serpens. Kauri and rewarewa ( excelsa) are frequently found in the well drained headwaters of the larger valleys.

Raupo/Cyperus swamp Two swampy areas on Ponui Island were incompletely surveyed. The largest area lies inland from Motunau Bay (Fig. 1). Cyperus ustulatus is the main species present with cabbage tree (Cordyline australis), wheki (Dicksonia squarrosa) and ponga also occurring. The absence of raupo (Typha orientalis) suggests that during the summer months the water level in the swamp becomes quite low. The second, very small swamp is situated behind Rabbit Bay. Raupo is dominant in the swamp with Cyperus ustulatus occuring on the drier margins. Several herbs e.g. a native willow herb Epilobium pallidiflorum, celery leaved buttercup (Ranunculus sceleratus) and starwort (Callitriche stagnalis) are abundant on the swamp margins.

Minor plant communities There are several microhabitats on Ponui Island. On the headland south of Rabbit Bay gorse has invaded the pasture. In one place (Fig. 1) mamangi has established itself on a cleared slope. The young stand is extremely dense and at present no other species occurs in significant numbers within this community. Associated with the kauri forest there is a swampy valley. Kiekie (Freycinetia banksii) grows abundantly around the edges with kotukutuku (Fuchsia excorticata), nikau (Rhopalostylis sapida) and hangehange grow• ing in the wetter areas. Kiokio (Blechnum capense), wheki, heruheru, A thy Hum australe, A. japonicum, Carex dissita and C. virgata are also present in great profusion. Further down this valley the king fern (Marattia salicina) grows in and beside the small stream. This fern may have originally been planted by the Maori (A. Wright pers. comm.) and has survived only because the valley sides are too steep to permit the entry of cattle and sheep.

VASCULAR PLANT SPECIES LIST

Both native and adventive species are listed. As no attempt has been made to include pasture and garden species the adventive flora is incomplete. Nomenclature of indigenous plants follows Allan (1961) and Moore and Edgar (1970) except where otherwise referenced. Adventive plants are named according to various sources e.g. Clapham et al. (1962). Well known common names are given, and where applicable follow "Standard Com• mon Names for Weeds in N.Z.". Families are ordered according to Vol. I & II of the "Flora of N.Z.". 9 Those families not native to N.Z. are listed at the end of each section. Genera are listed alphabetically within families, as are species within genera. * denotes adventive species ** denotes adventive family t collected by G.P. Adams tt recorded during visits by the Auckland Botanical Society (Hastings 1956)

PSILOPSIDA Psilotaceae Tmesipteris elongata subsp. elongata Chinnock (1975) T. elongata subsp. robusta T. tannensis LYCOPSIDA Lycopodiaceae Lycopodium billardieri iwituna I. deuterodensum clubmoss I. volubile waewaekoukou, .•limbing clubmoss FILICOPSIDA Marattiaceae Marattia salicina para, king tern Osmundaceae Todea hymenophylloides heruheru Schizaeaceae Lygodium articulation mangemange Schizaea fistulosa Hymenophyllaceae filmy ferns Hymenophyllum demissum H. flabellatum H. multifidum H. rarum H. revolutum H. sanguinolentum Trichomonas elongation T. reniforme T. venosum Dicksoniaceae Dicksonia squarrosa wheki Cyatheaceae Cyathea dealbata ponga C. medullaris mamaku Polypodiaceae Phymatodes diversifolium hound's tongue P. scandens Pyrrosia serpens Grammitidaceae Grammitis billardieri G. ciliata G. heterophylla Thelypteridaceae Thelypteris pennigera Lindsaeaceae Lindsaea linearis L. trichomanoides var. lessonii Davalliaceae Arthropteris tenella Pteridaceae Pteridium aquilinum var. esculentum bracken Pteris conians^ P. macilenta P. tremula turawera Aspleniaceae Asplenium bulbiferum var. bulbiferum hen and chickens A. flaccidum subsp. flaccidum makawe

10 A. lucidum A. obtusatum subsp. obtusatum A. polyodon (Brownsey 1977) Blechnaceae Blechnum capense kiokio B. filiforme B. fraseri B. lanceolatum B. membranaceum B. norfolkianum Doodia media Dryopteridaceae Ctenitis decomposita C. glabella Polystichum richardii Rumohra hispida Athyriaceae Athyrium australe A. japonicum Adiantiaceae Adiantum cunning/iamb maidenhair A. fulvum maidenhair SPERMATOPSIDA GYMNOSPERMAE Dacrydium cupressinum rimu Phyllocladus trichomanoides tanekaha Podocarpus dacrydioides kahikatea P. ferrugineus miro P. spicatus matai Araucariaceae A gal his australis kauri Cupressaceae Cupressus macrocarpa* macrocarpa Pinaceae Pinus radial a" radiata pine ANGIOSPERMAE: DICOTYLEDONESi Lauraceae Beilschmiedia tarairi taraire B. tawa large-leaved tawa Monimiaceae Hedycarya arborea pigeonwood Ranunculaceae Clematis paniculata clematis Ranunculus hirtus R. sceleratus* celery leaved buttercup Piperaceae Macropiper excelsum kawakawa Peperomia urvilleana Violaceae Melicytus ramiflorus mahoe Droseraceae Drosera auriculata sundew Aizoaceae Disphyma australe NZ iceplant Polygonaceae Muehlenbeckia complexa pohuehue, wirevine Rumex brownii* hooked dock Chenopodiaceae A triplex has la la * orache Salicornia australis glasswort Geraniaceae Geranium sp. Oxalidaceae Oxalis corniculata oxalis Haloragaceae Haloragis erecta shrubby haloragis Onagraceae Epilobium pallidiflorum Fuchsia excorticata kotukutuku Callitrichaceae Callitriche stagnalis starwort Thymelaeaceae Pimelea tomentosa Knightia excelsa rewarewa Coriariaceae Coriaria arborea tutu Pittosporaceae Pittosporum crassifolium karo Myrtaceae Leptospermum ericoides kanuka

11 L. scoparium manuka Metrosideros diffusa M. excelsa pohutukawa M. perforata clinging rata Elaeocarpaceae Elaeocarpus dentatus hinau Tiliaceae Entelea arborescens whau Cunoniaceae Weinmannia silvicola towai Escalloniaceae Quintinia serrata tawheowheo Rosaceae Acaena anserinifolia piripiri Rubus cissoides bush lawyer Papilionaceae Carmichaelia aligera NZ broom Sophora microphylla kowhai Ulex europaeus* gorse Fagaceae Nothofagus truncata hard beech Corynocarpaceae Corynocarpus laevigatus karaka Santalaceae Mida salicifolia maire M. salicifolia var. myrtifolia Rhamnaceae Pomaderris phylicifolia var. ericifolia tauhinu P. rugosa Meliaceae Dysoxylum spectabile kohekohe Sapindaceae Dodonaea viscosa akeake Araliaceae Pseudopanax crassifolius P. crassifolius x lessonii t horoeka, lancewood P. lessonii Schefflera digitata houpara Umbelliferae Apium australe pate, sevenfinger Centella uniflora NZ celery Ericaceae Erica lusitanica* heather Epacridaceae Cyathodes fasciculata mingimingi C. juniperina prickly heath Myrsinaceae Myrsine australis mapou Oleaceae Nestegis cunninghamii^^ N. lanceolata white maire Loganiaceae Geniostoma ligustrifolium hangehange Apocynaceae Parsonsia heterophylla kaiwhiria, NZ jasmine Caprifoliaceae AIseuosmia macrophylla hoihoi Alseuosmia x quercifolia Rubiaceae Coprosma arborea mamangi C. australis raurekau C. macrocarpa coastal karamu C. repens taupata C. rhamnoides Compositae Brachyglottis repanda rangiora Erigeron floribundus* broad-leaved fleabane Gnaphalium sp. Olearia furfuracea akepiro O. rani heketara Senecio hispidulus Sonchus oleraceus* sowthistle Primulaceae Anagallis arvensis* scarlet pimpernel Samolus repens Plantaginaceae Plantago lanceolata* narrow-leaved plantain Solanaceae Lycium ferocissimum* boxthorn Solanum aviculare poroporo S. nigrum* black nightshade 12 S. nodiflorum small-flowered nightshade Convolvulaceae Dichondra repens Mercury Bay weed Scrophulariaceae Hebe stricta var. stricta koromiko Veronica arvensis* V. plebeja* Australian speedwell Myoporaceae Myoporum laetum ngaio Verbenaceae Vitex lucens puriri Avicenniaceae Avicennia resinifera manawa, mangrove Labiatae Mentha sp.* Papaveraceae** Fumaria muralis* scrambling fumitory Phytolaccaceae*' Phytolacca octandra* inkweed MONOCOTYLEDONES Zosteraceae Zostera capricorni seagrass Liliaceae Arthropodium cirratum renga lily Astelia banksii wharawhara Collospermum hastatum kokaha Dianella nigra turutu Smilacaceae Ripogonum scandens supplejack Agavaceae Cordyline australis cabbage tree Phormium tenax NZ flax Juncaceae Juncus gregiflorus Restionaceae Leptocarpus similis oioi, jointed rush Typhaceae Typha orientalis raupo Palmae Rhopalostylis sapida nikau Pandanaceae Freycinetia banksii kiekie Orchidaceae Acianthus fornicatus var. sinclairii A. reniformis Bulbophyllum pygmaeum Corybas sp. spider orchid Dendrobium cunninghamii Drymoanthus adversus Earina mucronata Microtis unifolia microtis Pterostylis brumalis greenhood Thelymitra intermedia T. longifolia Cyperaceae Baumea juncea Carex dissita C. virgata Cyperus ustulatus Gahnia lacera G. setifolia Lepidosperma australe square stemmed sedge Morelotia affinis Schoenus tendo Scirpus nodosus Uncinia banksii hooked sedge Gramineae Agrostis tenuis* browntop Anthoxanthum odoratum* sweet vernal Cortaderia jubata* purple pampas grass Dactylis glomerata* cocksfoot Deyeuxia billardieri sand wind grass Echinopogon ovatus hedgehog grass Oplismenus imbecillus Poa anceps 13 Sporobolus africanus * ratstail Stenotaphrum secundatum * buffalo grass Stipa teretifolia needle grass

DISCUSSION

Past vegetation cover Large kauris were removed from the Trig area earlier this century. This together with the presence of a flourishing, relatively young kauri forest (possibly the result of secondary forest development (Atkinson 1959) after milling) suggests that, in the past, kauri forest clad the higher ground. Broadleaf forests would have dominated the inland valleys (taraire-tawa- kohekohe-puriri) and coastal valleys (taraire-karaka-kohekohe). The absence of mature podocarps, if natural rather than man induced, would suggest that the kauri/podocarp mixtures found in several areas are a recent (0-150 years) occurrence.

Composition of the flora The native flora of Ponui Island is not large and varied. The floras of similar sized, and even much smaller islands, are larger by up to 30 % (Table 1). In this respect Ponui is floristically more similar to the mainland kauri forest of Waipoua. The ferns and fern allies (pteridophytes) make up 32% of Ponui's indigenous flora; the island is also well represented by filmy ferns. It has been suggested (Wright 1976) that the latter, together with a high propor• tion of ferns, is indicative of a flora formerly more diverse and extensive. This would appear to be true on Ponui, where many ferns are present only in small isolated pockets within the kauri forest. Comparison of the number of indigenous species with those from other areas (Table 1) reveals a high ratio of monocotyledons to dicotyledons. Both Tiritiri Matangi (Esler 1978) and Great Mercury (Wright 1976), where vegetation has been extensively modified, have similarly high ratios. It can perhaps be concluded (Wright 1976) that the dicotyledonous element of the flora is less tolerant of changes than its counterparts; susceptibility to habitat changes, diaspore motility and seed dispersal mechanisms are but a few of the possible barriers to survival and/or re-establishment that may exist. Atkinson (1959) mentions that a single stand, and some scattered trees of hard beech are present on the southern slopes of Ponui. Although several saplings were found in the kauri forest no other sightings were made during our visit. It would be interesting to know if these specimens are still present, as hard beech is not commonly found in the Auckland region. An unusual feature of the kauri forest is the almost complete absence of the two more notable kauri associates, kauri grass and Blechnum fraseri. The apparent absence of kauri grass, a bird dispersed species which occurs 14 Table I. The distribution and percentage (in brackets) of the indigenous vascular floras of Tiritiri Matangi I. (Esler 19781. Little Bar• rier I. Hamilton and Atkinson iw.li. Waipoua Forest {Cockayne 1*081. Kapiti I. (Cockayne 1907). Great Mercury I. (Wright 1976) and Ponui I. according to plant groups.

Tiritiri Link Barrier Waipoua Kapiti Great Mercury Ponui

Area (in hectares) 220 3 020 9 310 2 000 1 850 1 770 Species/hectare 0.85 0.12 0.11 0.14 0.10

Pteridophytes 31(16.5) 90 (24.5) 63 (26.0) 43 (19.5) 63 (25.0) 56 (31.5) Gymnosperms 1(0.5) 9(2.5) 11(4.5) 2(1.0) 2(1.0) 6(3.0) Dicotyledons 92 (49.0) 187 (51.0) 122 (50 5) 126(58 0) 113 (44,5) 76(43.0) Monocotyledons 64 (34.0) 82 (22.0) 45(19.0) 47(215) 75 (29.5) 40(22.51 TOTAL 188 368 241 218 253 178

on nearby , is particularly hard to explain, unless ii is palatable and has been exterminated by stock. On Ponui Island the relatively low topography and few permanent streams with the consequent lack of habitat diversity delimits the potential flora. Although indirect evidence such as the monocotyledon/dicotyledon ratio suggests that the flora may have been larger it probably never has had the diversity of nearby Waiheke (Kirk 1878) or Waipoua.

ADDENDA

Mr A.E. Wright has supplied 9 additional taxa which are recorded in the collecting notebook of Mrs P. Hynes.

Hymenophyllaceae Hymenophyllum scabrum Trichomonas endlicherianum Cyatheaceae Cyathea smithii ?? Dennstaedtiaceae Hypolepis distans Pteridaceae Paesia scaberula scented fern Aspleniaceae Asplenium flabellifolium A. hookerianum A. lamprophyllum Adiantaceae Adiantum hispidulum rosy maidenhair

ACKNOWLEDGEMENTS

There are many people I would like lo thank; all the members of A.U.F.C. involved in the planning and preparation for the trip, the Chamberlin family for their hospitality and help, Mr Arthur Calvert for the use of his boat, A.E. Wright for his help in identifying a number of specimens and Associate Professor J.A. Rattenbury for critically reading this manuscript.

REFERENCES

Allan. H.H. 1961; "Flora of New Zealand". Volume I. Government Printer, Wellington. 1085pp. Atkinson, l.A.F. 1959: Forest vegetation of the inner islands of the Hauraki Gulf. Proceedings of the New Zealand Ecological Society 7: 29-33. Brownsey, P.J. 1977: Asplenium hybrids in the New Zealand flora. New Zealand Journal of Botany 15: 601-637. Cheeseman, T.F. 1925: "Manual of the New Zealand Flora". Second Edition. Government Printer, Wellington. Chinnock, R.J. 1975: The New Zealand species of Tmesipteris (Psilotaceae). New Zealand Journal of Botany 13: 743-768. Clapham, A.R., Tutin, T.G. & Warburg, E.F. 1962: "Flora of the British Isles". Second Edition. Cambridge University Press. 1269pp. Cockayne, L. 1905: Notebook 21, In Leonard Cockayne manuscript collections (Ms 74), Auckland Institute and Museum Library, Auckland. Cockayne, L. 1907: Report on a botanical survey of Kapiti Island. Appendix to the Journal of the House of Representatives of New Zealand C8. 23pp. Cockayne, L. 1908: Report on a botanical survey of the Waipoua Kauri Forest. Appendix to the House of Representatives of New Zealand CI4, 44pp. Edgar, E. 1973: Names in Pseudopanax . Koch (Araliaceae). New Zealand Journal of Botany II: 171-172. 354pp. Esler, A.E. 1978: Botanical features of Tiritiri Island, Hauraki Gulf, New Zealand. New Zea• land Journal of Botany 16: 207-226. Hamilton, W.M. & Atkinson, I.A. 1961: Vegetation. In Hamilton, W.M. (Ed.): Little Barrier Island (Hauturu). New Zealand Department of Scientific and Industrial Research Bul• letin 137. Government Printer, Wellington. 198pp. Maddock, S. & Whyte, D. 1966: "Islands of the Gulf". Collins, Auckland and London. 286pp. Moore, L.B. & Edgar, E. 1970: "Flora of New Zealand". Volume II. Government Printer, Wellington. New Zealand Weed and Pest Control Society 1969: Standard common names for weeds in New Zealand. Editorial Services, Wellington. 141pp. Wright, A.E. 1976: The vegetation of Great Mercury Island. Tone 22: 23-49.

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