TANE 23, 1977

VEGETATION AND FLORA OF THE ISLAND GROUP, NORTHLAND,

by A.E.Wright

Department of Botany, University of Auckland, Private Bag, Auckland

SUMMARY Vegetation descriptions and plant species lists are presented for the vegetated islands and rocks in the Moturoa Island Group, Northland, New Zealand. The vegetation of the largest island, Whale Island, has been dominantly modified and is regenerating through several different communities to manuka (Leptospermum scoparium) scrub and coastal scrub. The remaining islands support dense "petrel scrub", a low shrub community dominated by taupata {Coprosma repens) and Hymenanthera novae-zelandiae. A total flora for the Moturoa Island Group of 103 taxa indicates the lack of habitat diversity and the exposed conditions prevalent on the islands.

INTRODUCTION

The Moturoa Islands (centred on latitude 34° 47' S and longitude 173° 22' E) lie to the north and northeast of the Karikari Peninsula in Northland (Fig. 1). They are composed of indurated intrusive rocks of Cretaceous age and range in area from less than one hectare to 12 hectares. The observations on which this paper is based were made during the Auckland University Field Club scientific camp on the islands from 8-16 May, 1976.

VEGETATION HISTORY

The island group is Maori owned, although infrequently visited of later years. Despite the lack of evidence of any sizeable prehistoric occupation of the island, the present owners state that the early Maori people utilised the islands' large seabird populations for food, a practice that has continued into recent years. Thus intermittent burning of the vegetation is likely to have occurred. The largest island, Whale Island, has been modified to the greatest extent. It was the site of an early whaling station and was partially cultivated in the 1950s and early 1960s. During the cultivation period, domestic pigs (Sus scrofa) were liberated on the island, the last being removed about 1966 (Mr McC. Matiu pers. comm.). All these uses have resulted in considerable modification of the vegetation and the establishment of a variety of communities and stages of development within these communities. By comparison, the remaining islands have been little disturbed. Apart from mutton birding and a short period in the early twentieth century when soil was removed from Moturoa Island, they

11 MOTUROA ISLAND GROUP

Hoturoa Island 'Trig Rock' Rocky Island ^>

Cape Karikari Green Island

Sugar loaf Island

Island ^\J*>r

0 km 2

Fig. 1: Location and Distribution of the Moturoa Islands off the Karikari Peninsula and of New Zealand. Informal names denoted by inverted commas. appear to be unmodified. Firing of the vegetation could not be recalled by spokesmen for the present owners. No published account of the vegetation of the islands exists. However two unpublished reports can be found in the Department of Internal Affairs File 46/29/133. The first followed a brief inspection of the islands by Sir Robert Falla in October 1967. In September 1968, two members of the Wildlife Branch, Department of Internal Affairs, spent 10 days in the island group, working mainly on the avifauna, although preliminary accounts of the vegetation and plant species lists were prepared.

VEGETATION DESCRIPTIONS

WHALE ISLAND

As would be expected of the largest island (12 hectares), Whale Island presented a more varied plant cover and a larger flora than the other islands in the group. As previously indicated, the nature of the vegetation was very different to that found on the other islands. The major plant communities have been mapped (Fig. 2) and detailed notes on the plant groupings in defined localities have been made to allow easy comparison in future surveys. The description of the island's vegetation is divided into three parts: immediate coastal vegetation from high water to the top of the coastal slope; the plateau-like summit of the island; and the three small islets occurring around the coast. As could be predicted, the most modified vegetation occurred around the main landing point, Commodore Bay. The hillside above the beach was covered in a dense sward of buffalo grass {Stenotaphrum secundatum). Scattered amongst the buffalo grass were young mingimingi (Cyathodes fasciculata), manuka (Leptospermum scoparium), cabbage trees (Cordyline australis) and the fern Doodia media. Towards the ridge between Commodore and Driftwood Bays, flax {Phormium tenax) bushes became more common. The eastern slopes of Commodore Bay supported the most advanced vegetation on the island. It was dominated by taupata (Coprosma repens) and Hymenanthera novae- zelandiae with lesser amounts of cabbage tree, flax and hangehange (Geniostoma ligustrifolium). Further east between Commodore and Annie Bays a clear zonation pattern in the vegetation emerged. Samolus repens and Paspalum distichum grew in rock crevices just above high water; these were followed by a belt of Leptocarpus similis, with grasses such as sand wind grass {Deyuexia billardieri) and paspalum {Paspalum dilatatum) scattered amongst it. Behind the Leptocarpus belt was a dense growth of flax bushes with large clumps of the ferns Asplenium lucidum and A. flaccidum spp. haurakiense on the coastal margin. Also amongst the flax bushes were the remains of extremely large plants of inkweed {Phytolacca octandra), often 2 metres tall, and with woody bases over 5cm in diameter. Within Annie Bay, dense swards of flax came right down

13 to the boulder beach. The ground was largely bare beneath the flax bushes, although small numbers of the ferns kiokio (Blechnum capense), Hypolepis tenuifolia and turawera (Pteris tremula) were found. Between Annie Bay and the easternmost point of the island flax, cabbage tree and purple pampas grass (Cortaderia jubata) dominated the vegetation. Several areas of bare soil adjacent to highwater supported a thick growth of seedling grasses, shore groundsel (Senecio lautus) and New Zealand harebell (Wahlenbergia gracilis). On the

14 eastern headland, a few small clumps of Astelia banksii occurred, flowering profusely. Along the northeastern coast, a dense shrub community dominated by taupata, karamu (Coprosma robusta) and manuka occurred. Below this was a belt of Leptocarpus, followed by scattered Paspalum distich, Samolus repens and glasswort (Salicomia australis) in the rock crevices. Evidence of a very interesting phenomenon which had considerable bearing on the composition of the vegetation and flora of the islands during our visit was found in the small gut east of Annie Bay, but on the northeast coast of the island. A small valley-like depression lies parallel to the coast, ending in high seacliffs to the north. The valley was evidently damp at most times, supporting a mat of raupo (Typha orientalis) and Leptocarpus with scattered young pohutukawa (Metrosideros excelsa) on the rocky sides. The interesting fact was that the whole of the vegetation was completely flattened and lying downslope. The top of this little valley was measured to have an altitude of 20 metres above sea level at minimum. It was obvious that waves had broken right over this valley and that tremendous volumes of water had flowed down to flatten the vegetation so completely. 30cm high new leaves showed that regrowth of the raupo had just begun. Coupled with reports from local fishermen of an enormous storm several weeks prior to our stay on the island, this provided an explanation for the absence of the more tender herbaceous weeds in any state other than seedlings or dead remains. Evidence of considerable saltburn was found even on hardy native species on the summit of the island. On the central northern coast, the shrub community was replaced by a dense sward of the native grass Zoysia pauciflora. Occasional shrubs of mingimingi, manuka and dune tauhinu (Cassinia retorta) were scattered through the grassland, as were areas of patotara (Cyathodes fraseri). On the eastern headland, a small patch of the fern Cheilanthes sieberi was found. The eastern side of Driftwood Bay supported healthy coastal scrub (taupata and Hymenanthera). Within Driftwood Bay itself were the greatest concentration of pohutukawa trees and seedlings on the island. Numbers of this species have increased considerably since the 1963 survey. The ridge between Driftwood and Trypot Bays was covered in poor taupata/ Hymenanthera scrub, with masses of flowering New Zealand morning glory (Ipomoea palmata) scrambling through it. The remaining coastline between Trypot and Commodore Bays was characterised by a strongly developed belt of halophytes. Above high water were scattered patches of glasswort, Samolus and Paspalum distichum in the crevices; followed by a dense mat of iceplant (Disphyma australe) and pure stands of Leptocarpus.

The summit of the island appeared to take the form of plateau remnants. A small flat area atop the island between Commodore, Driftwood and Trypot Bays was primarily covered by Zoysia with varying amounts of flax. This community continued east along the ridge, with the addition of scattered shrubs of mingimingi, manuka and cabbage trees. The northern area of the main summit plateau of the island was clothed in a meadow of the native grass Poa seticulmis. Amongst the Poa were the remains of a large variety of adventive species. The central area was covered in open shrub dominated by large clumps of flax,

15 cabbage trees, manuka and mingimingi. Open ground between the shrubs supported a variety of herbaceous seedlings and tangled masses of dead Lotus spp. The southeastern edge of the summit plateau supported the largest manuka on the island - an almost impenetrable hedge one or two plants thick and 2.5 to 3 metres tall. The possibility that these manuka were planted by the Maori people who formerly cultivated the plateau cannot be discounted. The slope down to the eastern ridge was densely vegetated by flax, cabbage trees, purple pampas grass, manuka and Melianthus major, a large semi-succulent garden escape that is also well-established on the nearby mainland. The eastern ridge supported low flax/manuka scrub interspersed with weeds e.g. fleabanes (Erigeron spp.). The least modified vegetation occurred on the three small islets around Whale Island. Two were capped by well-developed soil and vegetation while the third (in Driftwood Bay) supported a variety of plants growing on small accumula• tions of soil in rock crevices. The vegetation on this latter islet was centred around one large and healthy pohutukawa tree covering an area of approxi• mately 6 metres diameter. Beneath the pohutukawa were masses of 3-4cm high Hymenanthera seedlings. Further out on the island, several clumps of flowering Astelia banksii were found, stunted but apparently thriving. Scirpus nodosus and Samolus were common in rock crevices and large areas of rock were colonised by Pyrrosia serpens. Perhaps the most interesting little plants were several dozen tiny sun-orchids (Thelymitra longifolia) with stunted, tightly curled leaves 3-5cm long. A second very small islet in Commodore Bay was capped by permanent vegetation. The lower slopes supported iceplant, renga lily (Arthropodium cirratum) and the fern Asplenium obtusatum spp. northlandicum in crevices. The upper slopes were more or less covered in windshorn clumps of wire vine (Muehlenbeckia complexa). The summit of the islet, approximately 5 metres across, supported low shrubs of taupata and Hymenanthera, a large number of purple pampas grass tussocks, a patch of Carex flagellifera with masses of old elongated culms lying about, two clumps of blue wheat grass (Agropyron scabrum) and further thickets of wire vine. The third islet, also the largest, lay west of Trypot Bay. Because it was better separated from the main island it carried a more mature and varied flora (presumably due to less frequent burnings and human interference). Lower areas were carpeted with dense mats of iceplant and conspicuous clumps of renga lily. The crown of the island was clothed in a dense shrubbery of taupata and Hymenanthera. 94 taxa of vascular plants were found on Whale Island and they are listed in Table 1. Of the total flora listed, only 30% are adventive species, which on a small, modified island relatively close to the mainland, would imply considerable winter dieback and a larger and more varied introduced weed flora over the summer months. As it was, several weed species were identified from completely dead remains. Adams (unpublished report 1968) listed 37 species for Whale Island, 3 of which were not found during the present survey. Bachelor's button (Cotula coronopifolia) was not found despite extensive searching. Pomaderris phylicifolia is very probably a case of mis-identification of the similar Cassinia

16 retorta common on the island. The third species, Hibiscus trionum is more exciting. This was found on the islet off Trypot Bay by Adams who noted several plants. Due to extensive bird burrowing, the islet was not searched during the present survey. In general, coastal areas of Whale Island appeared to be regenerating towards dense taupata and Hymenanthera scrub in most places. The summit of the island was regenerating into a more varied, manuka-dominant scrub.

Table 1: Species list of vascular plants found on Whale Island. Nomenclature follows Allan (1961), Moore and Edgar (1970) and New Zealand Weed and Pest Control Society (1969). The abundance of each species has been estimated in one of the following classes: a - abundant, c = common, u = uncommon, r = rare. * indicates adventive species, f indicates that specimens were found washed up on the beach (presumably fron Rangaunu Harbour).

TREES AND SHRUBS Avicennia resinifera\ mangrove u Cassinia retorta dune tauhinu c Coprosma repens taupata a C. robusta karamu u Cordyline australis cabbage tree a Cyathodes fasciculata mingimingi u Ficus carica* fig tree r Geniostoma ligustrifolium hangehange u Hymenanthera novae-zelandiae a Leptospermum scoparium manuka a Melianthus major* c Metrosideros excelsa pohutukawa u Phormium tenax flax a Phytolacca octandra* inkweed a Pimelea prostrata Strathmore weed u

FERNS Adiantum hispidulum rosy maidenhair c Asplenium Flaccidum spp. haurakiense makawe c Asplenium lucidum huruhuruwhenua c A. obtusatum spp. northlandicum c Blechnum capense kiokio u Cheilanthes sieberi r Dix>dia media a Hypolepis tenuifolia r Pteridium aquilinum var. esculentum bracken a Pteris tremula turawera u Pyrrosia serpens u

GRASSES Agropyron scabrum blue wheat grass u Cortaderia jubata* purple pampas grass a Deyeuxia billardieri sand wind grass c

17 Lachnagrostis filiformis NZ wind grass c

L. cf. Littoralis u Oplismenus undulatifolius r Paspalum dilatatum* paspalum c P. distichum c Poa seticulmis a Polypogon monspeliensis* beard grass r Sporobolus africanus* ratstail a Stenotaphrum secundatum* buffalo grass a Zoysia pauciflora a

SEDGES Baumea juncea u Carex flagellifera u Cyperus congestus* c C. ustulatus a Scirpus cernuus a S, nodosus a

MONOCOT HERBS Arthropodium cirratum renga lily c Astelia banksii u Leptocarpus similis a Thelymitra longifolia sun orchid r Typha orientalis raupo r Zostera muelleri\ eelgrass a

DICOT HERBS Anagallis arvensis* scarlet pimpernel c Apium australe Maori celery r Calystegia sepium agg. greater bindweed c C. soldanella shore bindweed u Crepis capillaris* hawksbeard u Centaurium erythraea* centaury c Centella uniflora centella c Coronopus didymus* twin cress u Cyathodes fraseri patotara a Dichondra repens Mercury Bay weed c Disphyma australe NZ iceplant c Epilobium rotundifolium creeping willow herb r Erigeron canadensis* Canadian fleabane r E. floribundus* broad-leaved fleabane a Geranium molle* dovesfoot u Gnaphalium luteoalbum agg. Jersey cudweed c G. spicatum* cudweed c G. sp. cudweed r Gunnera strigosa r Haloragis erecta shrubby haloragis u Hypochoeris radicata* catsear a

18 Ipomoea palmata NZ morning glory u Lobelia anceps c Lotus pedunculatus* lotus major c Muehlenbeckia complexa wire vine Orobanche minor* broomrape c Oxalis corniculata c Plantago hirtella* swamp plantain u Portulaca oleracea* wild portulaca 11 Rhagodia triandra c Sagina procumbens* pearlwort r Salicornia australis glasswort a Samolus repens u Senecio lautus shore groundsel a Silene gallica* catchfly c Solanum nodiflorum small-flowered nightshade a Sonchus oleraceus* sowthistle c Spergularia marginata sea spurrey 11 Tetragonia trigyna NZ spinach c Trifolium glomeratum* clustered clover c T. repens* white clover c T. resupinatum* reversed clover c Wahlenbergia gracilis NZ harebell a

MOTUROA ISLAND

With an area of 10 hectares, Moturoa is the second largest island in the group. From out to sea this island appeared to be the largest in the group; however, when one attained the summit and ascertained how narrow the island was it was easy to see how the considerable length and height (40m) deceived in this way. Moturoa Island was probably the most interesting and least modified of the islands; where the remaining islands could be relatively easily circumscribed on foot, this island could not. Very steep cliffs impeded coastal travel and the vegetation was extremely dense and difficult to pass through. In addition, the island was greatly burrowed by seabirds. The vegetation is mapped in Figure 3. Extreme coastal vegetation was dominated by Scirpus nodosus, glasswort, Mercury Bay weed (Dichondra repens), Rhagodia triandra and Paspalum distichum. Extensive mats of iceplant had developed in many coastal areas, often several metres wide. In some areas, cliffs were so steep that soil accumulation was confined to crevices, where numerous seedlings of the small-flowered nightshade (Solanum nodiflorum), shore groundsel (Senecio lautus) and New Zealand pellitory (Parietaria debilis) were found. Much of the interior of the island was covered in Hymenanthera and taupata scrub with varying dominance. For example, an entire belt across the island from the small beach on the west coast was clothed in taupata only, while 200 metres north the scrub was almost entirely Hymenanthera. However, the majority of the scrub was mixed.

14 Fig. 3: Vegetation map for Moturoa Island.

Scattered throughout the scrub were open areas with flax, poroporo (Solarium aviculare) and Cyperus ustulatus. In a few coastal areas, particularly the cliffs around the small beach and on the summit ridge of the island, scattered small karo (Pittosporum crassifolium) trees were found. The only variation from the

20 vegetation so far described occurred in one small area in the northwest of the island. Despite an apparently even canopy height, small valleys occurred on Moturoa Island where the ground dropped away and the plant cover became correspondingly taller. One such valley contained several new plant records for the Moturoa Island Group viz. karaka (Corynocarpus laevigatus), houpara (Pseudopanax lessonii) and one plant of Coryline pumilio. The karakas were 5 metres tall with trunks 25cm in diameter lm above the ground. Leaf size was considerably reduced in the harsh conditions prevailing. Only one specimen of mature houpara was seen, although several seedlings were found amongst the groundcover of Asplenium lucidum and taupata and Hymenanthera seedlings. From the summit ridge, a distinct difference in the condition of the vegetation on each side of the island was visible. The mainland (western) side of the island had a very much better developed, greener vegetation than the exposed seaward side. A flora of 29 species is listed in Table 2. This includes many new records for the island; however three species listed by Adams in his unpublished report were not found - black nightshade (Solanum nigrum — probably equivalent to S. nodiflorum in this report), bachelor's button and Hibiscus trionum.

Table 2: Species list of vascular plants for Moturoa Island. See Table 1 for explanation of abbreviations.

TREES AND SHRUBS Coprosma repens taupata a Cordyline pumilio r Corynocarpus laevigatus karaka r Hymenanthera novae-zelandiae a Phormium tenax flax a Pittosporum crassifolium karo u Pseudopanax lessonii houpara r Solanum aviculare poroporo u

FERNS Asplenium lucidum huruhuruwhenua a A. obtusatum spp. northlandicum c

GRASSES Cortaderia jubata* purple pampas grass c Paspalum distichum u

SEDGES Cyperus ustulatus a Scirpus nodosus c

MONOCOT HERBS Arthropodium cirratum renga lily c

21 DICOT HERBS Dichondra repens Mercury Bay weed u Disphyma australe NZ iceplant a Lotus corniculatus* u L. pedunculatus* lotus major u Muehlenbeckia complexa wire vine a Parietaria debilis NZ pellitory c Rhagodia triandra a Salicornia australis glasswort c Samolus repens c Senecio lautus shore groundsel a Solatium nodiflorum small-flowered nightshade a Sonchus oleraceus* sowthistle c Spergularia marginata sea spurrey u Tetragonia trigyna NZ spinach u

TRIG ROCK

This small vegetated rock lies to the southeast of Moturoa Island (Figs. 1, 3). Although small in area it was relatively elevated and had a well-developed vegetation cover (Fig. 4). A landing was made on the northeast side of the island which rose steeply to a narrow summit flat. The northeastern side of the island was comprised of steep soil and rock rubble screes clothed in iceplant with occasional clumps of Rhagodia, sea spurrey, Cyperus and glasswort. Immediately below the summit was a thicket of Hymenanthera, wire vine and taupata. The narrow summit plateau was dominated by purple pampas grass with lesser amounts of iceplant, sea spurrey, Cyperus and Scirpus nodosus. The adventive species listed in Table 6 were commonly found in sheltered hollows on the summit. One of the most interesting features of the vegetation of Trig Rock was the abundance of karo shrubs on and about the summit. Both Asplenium lucidum and Asplenium obtusatum ssp. northlandicum grew beneath the karo in considerable quantities, despite their scarcity on nearby Moturoa Island. The southwestern side of the island was dominated by precipitous cliffs, apparently unvegetated.

SUGARLOAF ISLAND

Although less than one hectare in area, Sugarloaf Island had a well-developed vegetation cover. The name of the island was derived from the conical appearance of the island from a distance. A long, low bare rock lies off the northeastern side of the island, affording some protection from storms and forming a tiny harbour into which dinghys could be manoeuvred. The plant cover is mapped in Figure 5.

22 O m«tret 50

Hymenanthera - Muehlenbeckia - taupatar bore rock • • Pittosporum individuals • highest point Edge summit plateau A old trig marker

Limit of vegetation • landing point Al Asplenium lucidum Ao A. obtusatum

Fig. 4: Vegetation map for Trig Rock.

Table 3: Species List of Vascular Plants for Trig Rock, Moturoa Island Group. See Table 1 for explanation of abbreviations.

TREES AND SHRUBS Coprosma repens taupata c Hymenanthera novae-zelandiae c Pittosporum crassifolium karo c

FERNS Asplenium lucidum huruhuruwhenua c A. obtusatum spp. northlandicum c

GRASSES Cortaderia jubata* purple pampas grass c

23 SEDGES Cyperus ustulatus c Scirpus nodosus c

DICOT HERBS Crepis capillaris* hawksbeard I Disphyma australe NZ iceplant c Muehlenbeckia complexa wire vine c Rhagodia triandra u Salicornia australis glasswort u Solatium nodiflorum small-flowered nightshade u Sonchus oleraceus* sowthistle r S. sp. (cf. littoralis t Spergularia marginata sea spurrey r

Fig. 5: Vegetation maps for Sugarloaf and Green Islands.

24 The vegetation of the island fell into distinct zones from highwater to the summit. The coastal margin was made up of scattered plants of glasswort, Mercury Bay weed and Paspalum distichum growing in rocky crevices. Continuous vegetation began with a dense mat of iceplant, followed by Rhagodia and numerous seedlings of New Zealand pellitory, shore groundsel and New Zealand spinach {Tetragonia trigyna). The Rhagodia mat continued some distance under the next vegetation zone, taupata shrubs up to 2 metres tall. This covered the majority of the island and was characteristically defoliated. The ground beneath the taupata was largely bare soil apart from occasional plants of poroporo, Cyperus, small-flowered nightshade and inkweed. A small colony of Hymenanthera grew on the summit of the island, with thick tangles of wire vine throughout it and a dense groundcover of small-flowered nightshade and poroporo beneath it. In contrast to the taupata, the Hymenanthera was vigorous, healthy and possessed thick foliage. It appeared that seabirds landed in the taupata, thus knocking off almost all the leaves except the very youngest and forming a rich humus which developed into a friable soil. The vast majority of avian burrows were found beneath the taupata. The vegetation of the southwestern portion of the island was in poor condition. Some areas were totally lacking the normal taupata cover while others possessed a few dead stumps and very unhealthy specimens. This side of the island was the most intensively burrowed and also the most exposed to storms and a combination of these two factors would be responsible for the death of the taupata. These areas supported a dense meadow of two or three week old seedlings of Poa annua, small-flowered nightshade and shore groundsel with occasional scarlet pimpernel (Anagallis arvensis) and sowthistle (Sonchus oleraceus). A flora of 23 species was found on Sugarloaf Island and is listed in Table 4. The indigenous species are typical of the island group. Of the species found by Adams (unpubl.), two were not seen during the present survey. Bachelor's button was missing (in common with the other islands) while flax was searched for and was definitely not present during the current survey. It was very disturbing to note a well-established patch of kikuyu grass (Pennisetum clandestinum) on the northeastern side of Sugarloaf Island. Efforts should be

Table 4: Species List of Vascular Plants from Sugarloaf Island. See Table 1 for explanation of abbreviations.

TREES AND SHRUBS Coprosma repens taupata a Hymenanthera novae-zelandiae a Solanum aviculare poroporo u

GRASSES Cynodon dactylon* Indian doab u Paspalum distichum c Pennisetum clandestinum* kikuyu r

25 SEDGES Cyperus ustulatus c Scirpus nodosus u

MONOCOT HERBS

Arthropodium cirratum renga lily u

DICOT HERBS Anagallis arvensis* scarlet pimpernel u Dichondra repens Mercury Bay weed u Disphyma australe NZ iceplant a Muehlenbeckia complexa wire vine a Parietaria debilis NZ pellitory c Phytolacca octandra* inkweed c Rhagodia triandra a Salicornia australis glasswort c Samolus repens c Senecio lautus shore groundsel a Solanum nodiflorum small-flowered nightshade a Sonchus oleraceus* sowthistle u Spergularia marginata sea spurrey u Tetragonia trigyna NZ spinach u made to remove this serious threat to the indigenous vegetation before it spreads any further.

GREEN ISLAND

This island of six hectares was notable for its steep and rocky shoreline preventing easy access from boats. The whole of the interior of the island was dominated by steep slopes culminating in sharp ridges. As with its size, Green Island's vegetation was intermediate between that found on Moturoa and Sugarloaf Islands. The plant cover is shown in Figure 7. Lack of time prevented a thorough coverage of the island and species such as kawakawa (Macropiper excelsum), ngaio (Myoporum laetum) and karo recorded in earlier surveys were not seen. The iceplant mats around the perimeter of the vegetation appeared to be more extensive than on any other islands in the group and also continued to a greater altitude where they were extensively burrowed. As with Sugarloaf Island, the Hymenanthera were more healthy than the taupata which were severely defoliated. Lower soils were rich and humic, while higher on the island these soils did not appear to accumulate and the weathered country rock was exposed at the surface. Although burrows occurred in this harder substrate, they were considerably less common than in the lower soils. The fern Asplenium lucidum was common in damper spots in sheltered valleys, while the purple pampas grass dominated exposed ridges and headlands. In one locality on the southwest side of the island, low, windshorn Hymenan-

26 thera came right down to seaward vegetation limits. A flora of 23 species is recorded in Table 5.

Table 5: Species List of Vascular Plants for Green Island. See Table 1 for explanation of abbreviations.

TREES AND SHRUBS Coprosma repens taupata a Hymenanthera novae-zelandiae a Phormium tenax flax a Solanum aviculare poroporo c

FERNS Asplenium lucidum huruhuruwhenua c A. obtusatum ssp. northlandicum u

GRASSES Cortaderia jubata* purple pampas grass a Dactylis glomerata* cocksfoot u Paspalum distichum c Poa annua u

SEDGES Cyperus ustulatus a Scirpus nodosus c

MONOCOT HERBS

Arthropodium cirratum renga lily u

DICOT HERBS Dichondra repens Mercury Bay weed u Disphyma australe NZ iceplant a Muehlenbeckia complexa wire vine a Phytolacca octandra* inkweed c Rhagodia triandra a Salicornia australis glasswort a Samolus repens c Senecio lautus shore groundsel a Solanum nodiflorum small-flowered nightshade c Spergularia marginata sea spurrey u

ROCKY ISLAND

Rocky Island was extremely exposed and had a correspondingly reduced vegetation cover. A small area of windshorn Hymenanthera/taupata scrub occurred on the upper western slope, with clumps of purple pampas grass and Cyperus on the summit. Lower on the island were isolated patches of iceplant, glasswort, Mercury Bay weed, Samolus, sea spurrey and Paspalum distichum

27 growing in crevices and on the margins of small pools of salty water. 16 species were recorded for Rocky Island and these are listed in Table 6.

Table 6: Species List of Vascular Plants for Rocky Island. See Table 1 for explanation of abbreviations.

TREES AND SHRUBS Coprosma repens taupata c Hymenanthera novae-zelandiae c

FERNS

Asplenium obtusatum ssp. northlandicum c

GRASSES Cortaderia jubata* purple pampas grass u Paspalum distichum u SEDGES Cyperus ustulatus c Scirpus cernuus u S. nodosus u

DICOT HERBS Dichondra repens Mercury Bay weed u Disphyma australe NZ iceplant c Muehlenbeckia complexa wire vine c Rhagodia triandra u Salicomia australis glasswort u Samolus repens u Solatium nodiflorum small-flowered nightshade r Spergularia marginata sea spurrey r

DISCUSSION

The vegetation of the islands in the Moturoa Group falls into two distinct classes: the dominantly modified grassland and coastal scrub of Whale Island, regenerating towards taupata/Hymenanthera scrub on the coast and manuka dominated scrub inland; and the taupata/Hymenanthera dominated "petrel scrub" of the remaining islands. The complete absence of vermin from the islands is somewhat surprising considering the variety of past uses. This absence has a beneficial effect on the lizard and bird life on the islands, but no immediately discernible effect on the vegetation. From a botanical point of view, the islands are not particularly exciting, although they do represent a vegetation type that is very restricted in distribution today. Their chief value lies in the lizard and seabird populations and for these reasons they should be strictly preserved.

28 Fig. 6: Looking south at the westernmost point of Sugarloaf Island. Shrub zone is taupata with scattered clumps of Cyperus. C = Cyperus; D = iceplant; P = Paspalum distichum; S = Samolus.

REFERENCES

Allan, 11.11. 1961: "Flora of New Zealand". Volume 1. Government Printer, Wellington. 1085pp. Moore, L.B. & Edgar, E. 1970: "flora of New Zealand". Volume 2. Government Printer. Wellington. 354pp. New Zealand Weed and Pest Control Society 1969: "Standard Common Names for Weeds in New Zealand". Editorial Services, Wellington, 141pp.

29