Geothermal Plants

Waikite stream

Otamakokore geothermal stream flowing from the Te Manaroa spring at Waikite. Photo Credit: Karen Houghton.

In New Zealand, geothermal vegetation has been identified as an ecosystem of historically limited extent, and naturally rare, even in pre-human landscapes. Combinations of temperature, chemistry, hydrology, and localised protection from frosts, produce rare and unusual habitats for plants.

Heat flow through the soil is the most important factor in determining the vegetation that can thrive in geothermal areas. Plants also must tolerate highly acidic soils with little organic material, phosphorus and aluminium, but high concentrations of metals and trace elements, such as arsenic.

Sampling

Prostrate kanuka growing by a geothermal spring at Waimangu. This species dominates geothermally altered and heated soils in New Zealand. Photo Credit: Julie Deslippe.

Vegetation assemblages include lichenfield, mossfield, herbfield, fernland, scrub, shrubland, rushland, sedgeland, reedland, forest, wetland and open water habitats. They occur over a wide range of altitudes, from sea level to the summits of the Central North Island volcanoes and Mt Tarawera.

A number of plants found in geothermal sites in New Zealand are listed as threatened or at risk. These include orchids, grasses, ferns and prostrate kanuka.

What can I see?

Fern

Dicranopteris linearis (tangle fern) at Karapiti. This tropical fern only survives in New Zealand in warm geothermal areas. Photo Credit: Julie Deslippe.

Prostrate kanuka only occurs in geothermal habitats. It is low in stature, becoming shorter as soil temperatures increase, and has shallow roots that enable it to survive in geothermal areas. Groundcovers are often a turf of unusual mosses, liverworts, and lichens.

Other species that are usually found only in warmer climates can also survive in the higher temperatures found in geothermal areas. The constant presence of steam around hot springs, fumaroles and streams allows frost-sensitive species to survive. Some geothermal areas are home to rare tropical ferns and orchids that grow nowhere else in New Zealand.

Some plants that occur in non-geothermal areas can also adapt to tolerate conditions in geothermal habitats. Examples include the low fertility shrublands of mingimingi, manuka and monoao.