Botany Of Whangapoua Wetlands And Dunes North Eastern .

50 rn) dominated by Selliera glasswort andTriglochin. Beard grass {Polypogon monspeliensis)Lobelia anceps Isolepis cernua saltwater paspalum{Paspalum vaginatum) Samolus repens and glaucous goosefoot {Chenopodium glaucum) are alsopresent. Although all these species are seenelsewhere in the estuary especially along the tidalparts of the drains in the northern "paddocks" thisis the most extensive saltmeadow present. Similarareas also exist on the western estuary boundary(C. Green pers. comm.). Such areas would only bereached by extreme high water spring tides thatoccur about every 3 weeks. The margins of theupper tidal drains are lined with Triglochin andLobelia. Bachelors button {Cotula coronopifolia)Isolepis cernua sea rush mangrove and Apium"white denticles" are occasionally present in thedrains. {Apium "white denticles" appears to be anundescribed species widespread in New Zealandsalt marshes and it is unknown whether it is nativeor adventive to New Zealand.)imately 1.5 rn tall. Commonly associated with thesespecies is the scrambling vine pink bindweed{Calystegia sepium) kiokio {Blechnum novaezelandiae) swamp willow weed {Polygonum salicifolium) Epilobium pallidiflorum and various sedgese.g. Eleocharis acuta Carex lessoniana C. virgataand giant umbrella sedge {Cyperus ustulatus). Twoexotic species lotus {Lotus pedunculatus) andMexican devil {Ageratina adenophora) are alsofrequent. Locally New Zealand flax {Phormiumtenax) and Baumea teretifolia are presenteThis wetland crosses the road and continueseastward to a series of "paddocks" which have beenpartially drained. Before reaching these drains thecomposition of the wetland is similar to above butis more open with rough pasture adjacent to itdominated by rush species e.g. soft rush {Juncuseffusus) giant rush {1 pallidus) and Juncus gregiflorus and a sedge Carex virgata. Common alongthe open swamp margin is Ranunculus urvilleanusamongst globe sedge {Cyperus brevi folius) andvarious rushes {Juncusspp.).In places the saltmarsh is contiguous with amanuka {Leptospermum scoparium) shrubland (e.g.by the Sandspit and near the airstrip). In suchplaces tangled shrubs of marsh ribbonwood{Plagianthus divaricatus) are occasionally presentalong this interface. A single 2 rn tall shrub ofcoastal tree daisy {Olearia solandri) is also presentin this zone near the airstrip. Coastal tree daisy islocally common by the tidal creek 1 km east of theOkiwi School. Apart from these two localities it wasnot seen elsewhere within the estuary. Clumps ofneedle tussock {Stipa stipoides) are locally frequentalong the upper estuarine zone on both mud orsand. The shrublands on the western side of theestuary are tall (2 6 rn high) and usually comprisedof an equal mix of manuka and kanuka {Kunzeaericoides). Dally pine {Psoralea pinnata) isfrequently present in these shrublands. Additionalsaltwater species are present in the dune hollows(see Appendix 1).The series of fenced partly drained "paddocks"down to the upper estuarine zone is an extensiveopen wetland dominated by giant rush about 1.5 rntall. Most of this area has been severely modifiedover the last decade by drainage channels rotarymowing and grazing. It is now (1992) mostly beingleft to regenerate. Nine other rush species arepresent; especially common ones being soft rushand Juncus gregiflorus. Lotus is common and exoticgrasses are uncommon apart from sweet vernal{Antho xanthum odoratum) and kikuyu grass{Pennisetum clandestinum). Occasionally present isswamp millet Centella uniflora Pseudognaphaliumleuteoalbum raupo (not dense) and fleabane{Conyza albida). Locally there are more open areasof Isolepis proliferMercer grass {Paspalumdistichum) wind grass {Lachnagrostis filiformis)danthonia {Rytidosperma racemosum) and lowrushes {Juncus articulatus J. acuminatus). Giantrush decreases in height to about 1 rn tall and seaaster {Aster subulatus) is frequent approaching theupper estuarine zone. Although fenced cattledroppings are present throughout this area.Freshwater wetlandsFreshwater wetlands surround the estuary. Theybegin in the higher forested land traverse therough paddocks and drain into the estuary. In 1992they varied from totally grazed to partially drainedto a few that lacked recent modification. The bestfreshwater wetland seen is on the north side ofMabeys Road just west of the start of the TePaparahi Track. It is long narrow and surroundedby 3 5 rn tall manuka with the occasional cabbagetree {Cordyline australis) and regenerating kahikatea {Dacrycarpus dacrydioides). The swamp isdominated by raupo {Typha orientalis) Schoenoplectus tabernaemontaniand swamp millet{Isachne globosa) which are dense and approx-By the north end of Okiwi airstrip behind theestuarine zone or dunes are a series of narrowsilty freshwater depressions. These are dominatedby Schoenoplectus tabernaemontani Eleocharisacuta and swamp willow weed. Small herbs ofCentella Lilaeopsis novae zelandiae sneezewort{Centipeda minima) and Ranunculus amphitrichusare present on the bare mud amongst the tallerspecies. Leptinella tenella was collected from thishabitat in 1980 by Ogle. Behind these hollows is60

rough grazed pasture dominated by knee highrushes e.g. soft rush and Juncus sarophorus.Another freshwater wetland studied is on the southside of the Fitzroy Harataonga Road opposite theOkiwi airport building. This is a totally grazedwetland on private land which runs through apaddock draining the steep forested land to thesouth. Common here is swamp millet Isolepisprolifer Mercer grass globe sedge Schoenoplectustabernaemontani Baumea rubiginosa and variousrushes e.g. Juncus articulatus J. prismatocarpusand soft rush. Native pond weed {Potamogetoncheesemanii) and the exotic creeping buttercup{Ranunculus repens) are present. This wetlandcrosses the road and continues down to a small bayeast of the airstrip near the estuary mouth.On the north side of the Fitzroy Harataonga Roadopposite the entrance to the Okiwi RecreationReserve is a beautiful raupo swamp {c. 120 rn by80 rn) dominated by 6 8 rn tall cabbage trees. Pinkbindweed and New Zealand flax are present. On theswamps north eastern side is kanuka a ver/ tallkahikatea and a nikau {Rhopalostylissapida).pumila Selliera radicans Lobelia anceps andLilaeopsis novae zelandiae are common. Occasionally present are Limosella lineata oioi and jointedrush {Juncus articulatus) Isolepis cernua beardgrass hawkbit {Leontodon taraxacoides) andsaltwater paspalum. Most of these species are alsopresent in the estuarine zone.Inside the spit near the mouth is a band of oioi andsea rush (10 30 rn wide) and locally a low sandyturf of saltwater paspalum Samolus repensglasswort Selliera radicans Carex pumila occursand then bare sand flats below this zone.The small dune at the end of the Okiwi airstrip isabout 300 rn long by 25 rn wide. Three quarters ofit is dominated by spinifex and the balance by Carexpumila. Other dune species present include sandwind grass shore bindweed harestail Zoysiapauciflora woody root oxalisbuffalo grass{Stenotaphrum secundatum) (locally common) treelupin and a single clump of pingao. Stock grazingand vehicle tracks were evident.Threatened speciesNationally threatened species (see Cameron et al. 1995)Austrofestuca littoralis an Australasian sand grass(Status: Rare; Regionally Endangered)on theWhangapoua Beach fore dune it is one of the lastcolonies of this native grass in the Auckland region.In the 19th century it was more widespread butthere have been no records for over 50 years of thisspecies in the Auckland region apart from the eastcoastbeaches ofGreatBarrierIsland(Whangapoua Kaitoke and Medlands Beaches). Thecause of this plants decline is unknown but it isprobably due to grazing animals and humanmodification of dune areas. Only two clumps wereThe mobile foredunes of Whangapoua Beach aredominated by pingao {Desmoschoenus spiralis and seen on the Whangapoua dunes in 1992; in 1999spinifex {Spinifex sericeus). Mats of shore bindweed Phil Todd and Geoff Stone recorded two adult and{Calystegia soldanella) are occasionally present and twelve juvenile plants from the same area (P. Toddtwo tussocks of Austrofestuca littoralis were seen. pers. comm.). In January 1999 about 60 plantswere recorded on Kaitoke Beach and six plants atIn the more stable sites behind the mobile dunes onthe Sandspit tauhinu {Ozo thamnus leptophylla) Medlands Beach (RJ. Stanley pers. comm.). Thewire vine {Muehlenbeckia complexa) kikuyu grass abundance of pingao (a declining New Zealanddune species) and spinifex in the absence of theharestail {Lagurus ovatus) pampas grassintroduced sand binding marram grass {Ammophila{Cortaderia selloana) and tree lupin {Lupinusarenaria) means that the three native sand bindingarboreus) are frequent. Less common speciesmonocots can be seen (and studied) togetherinclude Isolepis nodosa woody root oxalis {Oxalisrubens) Zoysia pauciflora and wildling radiata pines without marram affecting their ecology. (Note that{Pinus radiata). The small radiata pine plantation on a single clump of marram was seen onWhangapoua Beach in October 1992. It appearedthe lee of the spit was cut down in 1986 87 butto have been recently washed ashore and wasseveral were resprouting. Browsing on the pingao isdestroyed.)apparent presumably by rabbits.DunesThere are two separate dunes areas. By far thelargest is at the back of Whangapoua Beach andextending over the sandy spit to the northern sideof the estuary mouth. The last (southern) 1 km ofthis spit is low (less than 10 rn asl) and containsopen low vegetation. North of this open spit areconsolidated dunes (up to 60 rn asl.) which arecovered in 2 4 rn tall manuka. The smaller dune ison the southern side of the estuary mouth at thenorthern end of the Okiwi airstrip.The low down dune hollows contain a differentflora all herbaceous estuarine species. CarexCentipeda minima (Status: Local) since 1903there have only been five collections (based on AK61

Auckland region over the last 100 years L. tenellahas only been collected at Little Barrier Island andtwo mainland sites (northern Manukau Harbour andnear Albany). Regionally listed as Declining.and AKU herbaria) of this herb in the Aucklandregion: three at Whangapoua and one each at LittleBarrier and Kawau Islands. All Whangapouacollections came from damp areas by the Okiwiairstrip where it was locally frequent in 1986 and1992 as low clumps up to 30 cm across. It wasseen there again in 1999 by P. J. de Lange (P. Toddpers. comm.).Ditch millet {Paspalum orbicular)Great BarrierIsland is the regional stronghold for this speciesbut it may be an early Polynesian introduction toNew Zealand (see Cameron 1998). Status Declining.Atriplex billardierei (Status: Endangered) the onlyGreat Barrier records are Kirk (1869) and two Kirkcollections: "Whangapoua Sands" on 19 December1867 (WELT 51801) and the other December 1867which has no specific Great Barrier locality (WELT51806). This northern North Island entity may bedifferent from the Australasian A billardiereis.sXx.(PJ. de Lange pers comm.) which now onlysurvives on the coast just south of North Cape.Threatened and other species that are likely to bepresent or were likely once to be presentBotanically the Whangapoua area has not been fullystudied and other species will no doubt bediscovered with further fieldwork. For example twospecies which are easilyoverlookedareAmphibromus fluitans (Status: Nationally Critical)and Carex litorosa (Status: Regionally threatened).The discovery of the Australasian freshwater grassA. fluitans in 1989 by Peter de Lange (1990) in asmall dune pond near Claris was a new record forGreat Barrier Island (AK 199925). Similar habitatsexist at Whangapoua. The endemic New Zealandsedge Carex litorosa grows in estuarine zones andis very local in the North Island. Kirk recorded it forGreat Barrier (Kaiarara) last century (AK 11179) andit may well be present in the Whangapoua estuaryas well.Pomaderris hamiltonii (Status: Rare) although theadjacent shrublands to the Whangapoua estuaryare excluded for this article it is worth noting thatP. hamiltonii occurs around the western and northwestern fringes of the estuary by Mabeys Roadwhere it was first discovered on Great Barrier in1992 (see Cameron 1992).Regionally threatened or uncommon species (seede Lange et al. 1999)Ranunculus urvilleanus initially this species waslisted nationally as "Vulnerable" (Wilson & Given1989) but later deleted from the nationalthreatened list because it was more common thanpreviously thought (Cameron et aL 1993) and morerecently its deletion further supported by de Lange& Gardner (1997). However it is listed as regionallyDeclining (de Lange et al. 1999). The discoveryduring this 1992 survey of a large population of thisnorthern endemic New Zealand buttercup on themargins of swampy ground near Mabeys Road wasimportant as it is one of the largest populationsknown in the Auckland region. Although de Lange &Gardner (1997) state that ". so long as low leveldisturbance of R. urvilleanus habitats continues thespecies will very likely be able to maintain itself." Ifeel they have over looked the threat of weedcompetition in these open habitats such as fromkikuyu grass {Pennisetum clandestinum) andtherefore these populations should be monitored tosee if the species can maintain itself in the longterm under the increasing weed threat.Pimelea arenaria is a sand dune shrub (Status:Nationally Local) once occurring throughout theNorth South and Chatham Islands. I am only awareof two Great Barrier collections and neither have alocality cited for the island: Kirk 1867 (WELT52995) and Matthews & Carse 1919 (AK 101201).The Whangapoua dunes would be an ideal habitatfor this species that now appears to be extinctthroughout the Auckland erable)first discovered on Great Barrier inJanuary 1999 at Kaitoke Beach by Bec Stanley(Stanley 1999 AK 236524). The only other regionalsite it is known from is Whatipu west Auckland. Atboth sites it grows on wet sand and it is possiblethat suitable sites occur at Whangapoua.Euphorbia glauca (Status:Nationally Rare;Regionally Declining) sand dunes are a commonhabitat of this species which was recorded by Kirk(1869) for Great Barrier (no specimen located) andalso seen there (1975 1980) by the late J.K.Bartlett but no locality given (Bartlett & Gardner1983). It used to be wide spread in the Aucklandregion and is now only known from Motukorea(Browns) and Little Barrier Islands.Leptinella tenella the presence of the small NewZealand endemic daisy (found by C. Ogle in 1980AK 169712) in a silty depression by the Okiwiairstrip is another important record. All Leptinellaspecies are very local or scarce in northern NewZealand. Apart from this Great Barrier record in theEpilobium pallidiflorum (Status: Declining).62

Sand coprosma {Coprosma acerosa) although thisis not considered to be a threatened species it hasdisappeared or decreased (mainly due to humanimpacts) from many dune areas in the region. Kirkrecorded it on the east coast of Great Barrier and itstill grows there today at Kaitoke Beach (AKU14170). The Whangapoua dunes are an idealhabitat for this species and it would have almostcertainly once have grown there.ConclusionsBotanical values of WhangapouaThe main botanical values of the area are its largesize the lack of recent modification itsrepresentativeness of north eastern New Zealandestuarine vegetation the unbroken sequences ofdifferent vegetation types and the species present.Extensive areas exist of different vegetation typesthat change and integrade along a salt gradient anda substrate gradient (mud to sand). Nationally (seeCameron et al. 1995) and regionally threatenedspecies (see de Lange et al. 1999) are present inthe wetlands and dunes and others are likely to bepresent. On botanical values alone it is nationallyimportant.One of the most important features of theWhangapoua estuary is the general lack of recentground disturbance in the whole estuary catchment.(Note the Mabey farm in the north mainly drainsseparately to the sea). In places the sequence fromforest on the upper catchment slopes down throughfreshwater wetlands (flanked by manuka kanukashrublands) to estuarine vegetation to the sea isvirtually unbroken via dominantly native vegetation(though reduced to mostly narrow strips across thefarmland zone). Dune vegetation also intermingleswith saltmarsh and freshwater wetlands.Apart from a couple of old drainage channels in thesouth west corner and extensive drains in thenorthern freshwater/saltwater "paddocks" theestuary is relatively unmodified. The northern drains(dug in 1979 80 in an attempt to drain and farmthis area) are filling in with sediment andmangroves are starting to establish in the moreshallow drains.The absence of all Spartina species and possums{Trichosurus vulpecula) on Great Barrier increasesthe botanical value of Whangapoua estuary. ManyNew Zealand estuaries are grossly modified bythese adventive intertidal grasses and possums canheavily browse accessible mangrove vegetation.It has been fortunate during the 1980s that lowimpact farming was carried out on the surroundingOkiwi Station. Intensive farming with fertilisers andhigh stock numbers would directly influence thewetland vegetation.The importance of the Whangapoua estuary andsurrounds is highlighted in an article on settingpriorities for threatened New Zealand species byDavies et al. (1992): The habitats most importantfor threatened plants namely lowland coastalherbfields and freshwater wetlands are the mostseverely reduced in area and are under representedin the conservation estate. . . In order to maintainits biodiversity New Zealand must protect sites thatare rich in species and have diverse ecosystems."All of the natural areas of Whangapoua stronglyqualify for preservation under these criteria. Thereis no other opportunity in north eastern NewZealand to control virtually the whole catchment ofan estuary approaching this size and in such goodcondition.Future ManagementFortunately few aggressive weeds are present thatwould potentially dominate the vegetation. Pampasgrass is one that does require immediate controlotherwise it will cover much of the dune areas.Wildling pines and tree lupin need to be kept incheck as well. Dally pine is locally common in thewetter areas behind the north west part of theestuary. This weed needs to be monitored to see ifit is increasing its range. Marram grass should notbe allowed to establish on the dunes.Stock needs to be totally excluded from thewetlands and dunes and rabbits need to bemanaged on the dunes. More farmland should beretired to develop wider bush and wetland corridorsbetween the forest and estuary as well as providea wider buffer area around the estuary. The estuarybuffer is particularly narrow along the western andsouthern boundaries. If widened it would achieve abetter gradation from saltmarsh to shrublandinstead of changing abruptly from saltmarsh tofarmland as much of it currently is. The upperestuarine zone of marsh ribbonwood is absent inmost places and the coastal tree daisy is extremelylocal.The proximity of the manuka kanuka shrublands toa good seed source

These sparse mangroves (area type 2) account for a further 36 ha within the estuary. Mangroves are absent in the sandy areas by the estuary mouth but low mangroves are present in the shelter of the small bay just east of Okiwi airstrip. At the upper mangrove level there is an abrupt cha