Heathlands occur on very infertile soils. These widespread soils are found on diverse landforms, in areas from subtropical Northland to the cool-climate subantarctic islands. They support low-growing (1–2-metre-tall) plants, mainly evergreen shrubs with small, hard leaves (sclerophylls). Many of these belong to the heath family (Ericaceae). In other countries, this type of vegetation is known as heathland. In New Zealand it is also called gumland and pakihi.
Mānuka is usually present, often dominating or sharing the canopy with one or more species of Dracophyllum. The understorey plants are usually grass-like sedges and rush-like plants from the restiad family.
Where to find heathlands
- gumlands on podzol soils – Northland
- heathlands on peat – Waikato lowlands, southern South Island, Stewart Island, Chatham, Campbell and Auckland islands
- heathlands on young volcanic materials – central Volcanic Plateau
- heathlands on wet mineral soils – mountains, glacial outwash surfaces, hill country.
Fire and heathlands
Many heathlands, especially in lowland areas, formed and expanded after Polynesian and European settlers cleared forests using fire.
In dry periods, heathlands are susceptible to fire. Most heathland species are poorly adapted to frequent fires, although mānuka seeding is promoted by burning, and mountain flax, sedges and some ferns can resprout from underground root stocks.
Gumlands are areas where kauri forests previously grew, and were named after the valuable kauri gum found in their soils. In 1840 gumlands covered about 300,000 hectares of northern New Zealand – but today few remain, as most have been converted to farmland.
In gumlands mānuka is the dominant plant, along with kūmarahou (Pomaderris kumeraho), sedges, and heath shrubs (Dracophyllum lessonianum, Leucopogon fasciculatus and Epacris pauciflora).
Peat bog heathlands
Heathlands developed on peat bogs in the Waikato, but most have been burnt or drained and turned into farmland. They carried a cover of mānuka and bamboo rush (Sporodanthus ferrugineus), under which grew Schoenus brevifolius, Baumea teretifolia and wire rush.
The peat bog heathlands of the Chatham, Auckland and Campbell islands are dominated by Dracophyllum species.
Volcanic Plateau heathlands
Mānuka and Dracophyllum dominate on young volcanic soils in the central North Island, which have been burnt many times. The soils dry out in summer, summer frosts are frequent, and forest is slow to regenerate. The introduced Scotch heather, Calluna vulgaris, dominates in the north-western part. Since the 1920s, heathlands on the Volcanic Plateau have been greatly reduced through pine planting and agriculture.
Subalpine and alpine heathlands
Dracophyllum scrub grows in wet mountain areas of both main islands, above the treeline. It often forms a mosaic with tall tussock grasslands, or a richer subalpine scrub of conifers, shrub daisies, coprosma and hebe species, mountain flax and shrubs, depending on the location.
The wet, leached soils of the western South Island support an open shrub vegetation known as pakihi – a Māori word that originally meant open country.
Pakihi vegetation is similar to that of the northern gumlands. Mānuka grows above a layer of sedges, ring ferns and wire-rush. Some sites are long-standing, while others developed after forests were burnt and cleared. A taller shrubland of celery pine, mānuka, silver pine, kāmahi and Quintinia often develops at the margin between forest and pakihi.