The Alpine Zone:

Mountain Beech Gertrude Valley Fiordland This is often the tree that grows at tree line in the South Island

The Alpine zone is the area between the upper limit of trees and the lower limit of permanent snow. In New Zealand the upper limit of trees is around 1500m in the North lowering to 900m at the bottom of the South Island. The variation is caused mainly by latitude and also due to distance from the coastline. The upper limit of treeline occurs as a result of average temperature conditions
Treeline is probably a result of the length of time available for winter hardening of shoots at suitable temperatures. It is also probably a result of at higher altitudes winter dieback becomes greater than summer growth. In areas where Beach forest grows (Nothofagus spp.), tree line occurs as a very clear and sudden transition. However in areas where Beech forest does not grow due to deforestation or glaciation etc. treeline is not very obvious with a slow transition from trees and shrubs to lower growing shrubs and increasing tussocks etc.
The alpine zone is devided into several zones based on a system by Wardle 1964 for New Zealand.

Short tussock growing in the low alpine area near Lake Lyndon Canterbury. This vegetation is caused by grazing and burning, through farming.

Low alpine
Each zone has its characteristic vegetation. The low alpine is characterised by the tall tussocks Chionochloa spp. These form a continuous canopy with a few smaller herbs and shrubs growing in between. Bunched grasses are a characteristic growth habit for tropical high mountains and oceanic alpine areas. They are present in South America, Papa New Guinea and New Zealand. They are absent from Northern Hemisphere Mountains, that are usually more continental (inland)
The higher one goes in the low alpine zone the less dominant the tussocks become and the more bare ground and rocky patches occur until the so called grassline is reached. This is not so clear as the treeline but is still a relatively consistent feature.

High alpine herb species growing at 1900m Remarkables Range on a rock ledge Dracophyllum muscoides the dominent species of Central Otago High alpine cushion fields

High alpine zone:
The high alpine zone which is the zone above continuous grassland is further divided into five community types: Fell field, Scree or tallus slopes, Cushion field, Snow bank and Herb field. Another less important type occurs in permanently wet areas: wetlands. The higher in this zones one goes the less vegetation occurs and the more bare rocky areas dominate. The length of snow lie is an important determinant of vegetation makeup.