Vegetation

Silver beech "goblin forest" on Mitre in the Tararua Forest Park.
Silver beech "goblin forest" on Mitre
in the Tararua Forest Park

If you think the vegetation of the Tararua Range is just gloomy bush, impenetrable leatherwood, and wet snow tussocks on the mist-shrouded tops you will be pleasantly surprised if you look closer. There is a fascinating and subtle pattern to the vegetation. This diversity stems from a whole host of site factors: exposure to wind, the depth and drainage of the soil, changes in altitude (affecting temperature and rain/snowfall) and aspect (whether the plants occur on the sunny or shady side of a ridge).

There is now very little forest left below the 350 m contour, because most of the forest margins of the range were cleared long ago for farming. With increasing altitude from the edge of the park, the visitor passes from lowland podocarp/tawa or podocarp/kamahi forest, through montane podocarp/beech, then subalpine pure beech (forming a sharp treeline), to alpine tussock grasslands. This beech treeline is usually around 1000 m but can be as high as 1300 m in the east. A very different pattern occurs where beech is absent. Here, the treeline is much lower (around 800–900 m) and consists of montane podocarp/kamahi forest which passes gradually into a leatherwood shrubland.

Alpine tussock grasslands

Above the treeline (or ‘shrubline’), the tops are covered in alpine tussock grasslands and herbfields. Two tall tussocks are the conspicuous Chionochloa flavescens (broad-leaved snow tussock) which tends to occupy the damper, more sheltered sites and C. pallens (mid-ribbed snow tussock) on the more exposed sites. In spring and early summer, the delicate flowers of many alpine herbs, such as Celmisia (mountain daisy), Ranunculus (buttercup), Gentiana (gentian) and Leucogenes (edelweiss) shelter among the tussocks or in rock crevices. Here you may find the endemic Tararua harebell (Wahlenbergia pygmaea subsp. tararua) and a species of speargrass also unique to the Tararua Range (Aciphylla dissecta).

Subalpine shrublands

The subalpine shrubland ('leatherwood') belt is a very distinctive feature of the central and northern Tararua Range. In the north and west (where miro/kamahi, rather than beech, forms the treeline), the leatherwood band can extend across more than 400 m of altitude, a very trying vegetation barrier to travellers. In the south and east, where silver beech forms the treeline, the leatherwood band is much narrower, usually no more than 150 m.

The main leatherwood shrubland species is Olearia colensoi with its thick, stiff, saw-toothed leaves. It is the same impenetrable shrub that is the bane of trampers in the southern Ruahines, the westernmost ranges of the South Island and Stewart Island/Rakiura. 

Another common tree daisy is O. lacunosa, sometimes termed the ‘lancewood leatherwood’ because its leaves are long, leathery and spiky like a juvenile lancewood.

Other common shrubs are mountain fivefinger and needle-leaved species of Dracophyllum (especially D. filifolium and D. uniflorum); everywhere, the crown fern mountain kiokio (Blechnum montanum) and prickly shield fern tend to form a dense ground cover. It is amongst these shrublands you may find the locally endemic   – a species only found in the Tararua Range.

Montane miro/kamahi forest

In the northern third of the range where beech is absent, the mid-slope to treeline forests (600-900 m altitude) consist of a kamahi canopy with emergent podocarps (miro and mountain totara). The gnarled trunks of kamahi, miro and mountain totara festooned with hanging moss, and the open understorey  dominated by horopito and toro, all combine to create an eerie ‘goblin forest’ feeling. This is the cloud forest belt, found on other very wet ranges such as Mount Taranaki, where the rainfall and mist is so prevalent that the forest is literally wreathed in pale green moss. It is here that you may find a newly described locally endemic tree, Myrsine umbricola, only recently discovered on Mt Holdsworth and on ridges near Waiopehu Hut.

Beech forests

The beech forests of the central and southern Tararua Range are the most widespread and best-known to trampers in the park. This group contains one or more of the Nothofagus species (silver, red, hard and black beech). Silver and red beech are the most common, yet curiously they are completely missing from the northern part of the range and from the Akatarawa uplands. The most likely explanation is that they were eliminated during earlier unfavourable warmer climatic conditions and have not yet managed to reinvade.

Silver beech is most prevalent at higher altitudes (600 -1000 m) and generally forms the treeline. The stunted, gnarled, moss-festooned silver beech straddling Marchant Ridge or Cone Ridge have just as much character as the silver beech of Fiordland.

Near the treeline, the silver beech trees become quite stunted, the canopy being only 4-5 m above ground level. Here, the forest can be quite open, with occasional shrubs of broadleaf, haumakaroa (Raukaua simplex), horopito, occasional bush tussocks (Chionochloa conspicua) and the ubiquitous Blechnum ferns. On the mid-slopes of the valleys, red beech and kamahi join silver beech in the forest canopy. Red beech are generally larger in stature, with massive trunks and attractive translucent foliage, combining to give the forest interior a lighter, more dappled feeling; red beech tend to occupy the more fertile sites, especially those with deeper soils closer to the valley floors.

In December, it is worth keeping an eye out for the red and scarlet mistletoes (Peraxilla tetrapetala and P. colensoi) that parasitise beech trees and produce copious flowers during early summer months. In the past these were far more abundant in the Tararua Range - their decline being attributed to possum browse.

Lowland broadleaf forest (with emergent podocarps)

Kamahi is the most widespread tree in the Tararua Range, absent from only the highest and driest forest sites. In the north, along the western slopes, and in the Akatarawa catchment of the southwest, the forest canopy consists of kamahi, with scattered emergent rimu and miro.  Other common species are totara, hinau, toro, rewarewa, mahoe and pigeonwood. In the valley floors and lower slopes below 350 m, northern rata can be a distinctive feature, towering above the canopy, but rimu (and sometimes miro) is still the main tree emerging above the canopy. A well known and superb example of this type of forest, completely unlogged, surrounds the Hutt and Pakuratahi Rivers in the vicinity of Pakuratahi Forks (see Kaitoke Regional Park). 

In the lower western foothills of the Tararua Range (where frosts are limited), tawa is the main forest canopy tree. This forest has very much of a ‘rainforest’ feeling to it, with dense thickets of tree ferns (ponga, mamaku and wheki), supplejack and kiekie and epiphytes on the larger trees. Good examples of tawa-dominated rainforest can be experienced at the entrance to most of the western valleys of the park; the Ohau River, Makaretu Stream, Waikawa Stream and the Mangaone Track through the upper Waikanae River. Closer to the coast at lower altitudes, kohekohe and nikau palms can become a major component, particularly in the forests behind Waikanae township.

Many forest remnants remain outside the park on the Hautere, Manawatu and Wairarapa Plains. Around river margins and in sand plains, where soils can be wet for long periods, swamp forest (kahikatea, pukatea and swamp maire) can be found. On the higher stony river terraces, the soils are freer-draining and support more drought-tolerant trees such as totara, matai and titoki. These trees remain as the attractive forest remnants that dot the farmed Hautere Plains, passed through en route to Otaki Forks. Closer to the coast, pockets of ngaio, mahoe, kohekohe, wharangi, karaka, rewarewa, akeake and titoki remain among the sand dunes.

Alert

If you find a threatened species of plant or animal, please do not collect it but report your discovery to your local Department of Conservation office, noting the location and if possible providing a photograph.

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