You are here: Tussock Grasslands MIS Site Contents Broad-leaved snow tussock
Select from: Identification Habitat Other spp. present Vegetation history Background management information Management options
Or return to communities indexes: || High altitude || Mid altitude || Low altitude || drylands ||

Broad-leaved snow tussock
Chionochloa flavescens

Diagnostic features for identification in the field

Descriptions of broad-leaved snow tussock are complicated by the fact that this species is now considered to form a complex with narrow-leaved snow tussock (C. rigida). There are five recognised taxa (including two narrow-leaved ones which are described under C. rigida) , which vary in locality and habitat. However, the general description below will differentiate the broad-leaved members of this complex from the other Chionochloa tussock species.

A large green or tawny green tussock, usually less than 150cm tall. Tussocks may be smaller with narrow leaves, where soil fertility is reduced or at higher altitudes.

Leaves are relatively broad, which droop. They are tough and glossy, and lack a conspicuous midrib above or beneath. The leaves tend to trail on the ground, so that the exposed soil shows a swept effect.

The sheaths are a lighter colour than other species, being pale green to light brown to orange, often purple tinted. Young sheaths are white-hairy, while dead sheaths break crosswise.

The flower heads are borne well above the leaves.

References:
  • Mark, A.F. and Adams, N. 1996: Alpine plants of New Zealand. Christchurch
  • Wilson, H.W. 1996: Wild plants of Mount Cook National Park, Manuka Press, Christchurch.

Description of community and habitat

Chionochloa flavescens occurs as a complex with narrow-leaved snow tussock (C. rigida), with five taxa being recognised. For further information on the taxa of the C. flavescens-C. rigida complex, see Wardle (1991). The broad leaved snow tussock taxa are considered together here.

It is the common tall snow tussock in the zone near tree line, between 900 - 1500m a.s.l., from the Tararua Range southwards.

East of the Main Divide, South Island
Broad-leaved snow tussock is common in the northern half of the South Island. However, it's southern limits are not known. It occurs on rocky coarse textured slopes, where soil nutrient status is relatively high. Colluvium or alluvium is commonly present. Broad-leaved snow tussocks commonly shares dominance with shrubs, such as Dracophyllum spp and Podocarpus nivalis.

In Canterbury, broad-leaved snow tussocks reach their most eastern limit around the Rakaia Valley, where it commonly occurs on sunny rubbly slopes. It can occur on shady slopes where coarse textured soils shallowly overlie sub-angular gravels, or where gravels predominate. Elsewhere, this grassland type is restricted to more inland and mountainous localities. Many broad-leaved snow tussock grasslands have been depleted due to grazing and burning, resulting in a reduction in tussock cover and abundance, and a dominance of mountain cotton daisy (Celmisia spectabilis) and mountain heath (Leucopogon colensoi).

Broad-leaved snow tussocks can also occupy steep rocky slopes to the east of the Divide in Fjordland.

West of the Main Divide, South Island
Broad-leaved snow tussock grasslands are also found to the West of the Main Divide, from the west Nelson mountains and Westland, through to northern Fjordland.

In the west Nelson mountains, broad-leaved snow tussock grasslands occur on subalpine slopes over marble, landslide debris, debris cones, recent soils, and older soils which have been enriched by flushing and downslope movement. Where these grasslands have been modified by fire and grazing, tussock cover is greatly reduced (to ~5%), and mid-ribbed or copper tussock become more common, depending on site drainage. Intertussock species tend to reflect the high fertility of such sites, e.g. white clover (Trifolium repens) and Kentucky blue grass (Poa pratensis).

On moderately steep slopes overlying marble and tertiary calcareous rocks, broad-leaved snow tussocks are also associated with mid-ribbed snow tussock. It also commonly occurs on fertile steeper slopes by sink holes or flushed ground, associated with copper tussock grasslands.

In Westland, broad-leaved snow tussocks occupy very steep troughs, where it is associated with Dracophyllum scrub and mid-ribbed snow tussock.

In Fjordland, it occupies wet leached soils, as well as more recent, well drained talus soils at low altitudes.

North Island
Broad-leaved snow tussock grasslands are found on leached soils of the Tararua and Rimutaka Ranges.

Reference:Wardle, P. 1991. Vegetation of New Zealand, Cambridge Press, Cambridge

Other species present (see Wardle, 1991)

 East of the Main Divide, South Island
In the Waimakariri Basin, Canterbury, broad-leaved snow tussocks are associated with shrub species such as Leucopogon colensoi, matagouri (Discaria toumatou), Gaultheria crassa, in addition to the common tussock grassland species (e.g. blue tussock (Poa colensoi), Leucopogon fraseri, fescue tussock (Festuca novae-zelandiae), and the exotics catsear (Hypochoeris radicata), sheeps sorrel (Rumex acetosella), sweet vernal (Anthoxanthum odoratum), brown top (Agrostis capillaris), and mouse-eared hawkweed (Hieracium pilosella). In the Rakaia catchment, Canterbury, shrub species can be less prevalent. Open tussock grasslands on sunny faces are associated with the common tussock grassland species, whilst Aciphylla colensoi, golden spaniard (Aciphylla aurea), mountain cotton daisy, Anisotome filifolia, Pterostylis australis orchids, and short tussock species are associated with mid-altitude semi intact grasslands on shadier faces.

West of the Main Divide, South Island
In the west Nelson mountains, the least disturbed grasslands are associated with mountain flax (Phormium cookianum), Dracophyllum longifolium, Aciphylla ferox, A. colensoi, Celmisia sessiliflora, and C. verbascifolia, grading into Dracophyllum longifolium and Phyllocladus alpinus scrub. Where grasslands have been modified by burning and grazing, tussock cover can be reduced to 5%, and mid-ribbed or copper tussock become dominant, depending on site drainage. The intertussock species at these sites are often exotic pastoral species such a white clover (Trifolium repens) and Kentucky blue grass (Poa pratensis). At lower altitudes hunangamoho (Chionochloa conspicua) becomes dominant. On moderately steep slopes overlying tertiary calcareous rocks, the intertussock species are characterised by avalanche grass (Poa cockayneana), Aciphylla ferox, everlasting daisies (Helichrysum bellidioides), and Ranunculus insignis, reflecting the good drainage and fertility of these sites. Where broad-leaved snow tussocks are associated with copper tussock, mountain flax (Phormium cookianum), Dracophyllum longifolium and Coprosma propinqua occur at low altitudes. Where there is poor drainage, false tussock (Schoenus pauciflorus), Empodisma minor, Carpha alpina and Microseris scapigera occur.

On coarse textures soils in Westland, broad-leaved snow tussocks occur with species characteristic of seral shrublands, including Olearia moschata, Coprosma rugosa, Coriaria plumosa and Uncinia divaricata. Where very steep troughs occur, broad-leaved snow tussock grassland occurs alternating with Dracophyllum uniflorum shrub-heath on the spurs. These tussocks occur to high altitudes with mid-ribbed snow tussocks e.g. steep north facing slope at over 1900m a.s.l.

Broad-leaved snow tussock is common at low altitudes on recent, well-drained talus, in Fjordland. Here, everlasting daisies (Helichrysum bellidioides), prickly shield fern (Polystichum vestitum),and thousand island fern (Hypolepis millefolium).

North Island
On the Tararua and Rimutaka Ranges, broad-leaved snow tussocks are associated with hook grass (Uncinia caespitosa), and Astelia nervosa. Where soils are more humic and less fertile, Pentachondra, Carpha and Astelia are common. Where subalpine beech forest is lacking, broad-leaved snow tussocks and wet-heath species descend broad ridges to as low as 760m.

Reference:Wardle, P. 1991. Vegetation of New Zealand, Cambridge Press, Cambridge

Vegetation History

Much of the mountainlands to the east of the Main Divide were covered in forests prior to 700 - 900 years ago. These were largely destroyed by natural and Polynesian fires prior to European settlement, leading to a migration of tussock species into previously forested areas. Initially, short tussock species are thought to have migrated from enclaves within the forest, upslope. This was followed by a slower migration of Chionochloa species (including C. flavescens) naturally occupying alpine areas above the timberline, downslope into penalpine, subalpine and even montane environments. Subsequent modification of these tall tussock grasslands in subalpine and montane zones, through pastoral activities (grazing and burning) has lead to a transformation to short tussock grasslands.

Those broad-leaved snow tussock grasslands found in wetter locations, on, or to the west of the Main Divide are less likely to have been modified by human activities, although some have been depleted as a result of browsing by feral animals, such as hares and deer.

Reference:Wardle, P. 1991. Vegetation of New Zealand, Cambridge Press, Cambridge



|| Back to site contents || Provide feedback on this page || Disclaimer ||