This type of alpine vegetation occupies a zone about 500 m wide above the treeline where soils of adequate depth are present. The term 'herb-field' as applied to northern hemisphere mountains is defined as a complete cover of herbaceous alpine plants, but in New Zealand the page 172modified term tussock herbfield is preferred. This is because the dominant and conspicuous large tussock grasses belonging to the genus Chionochloa (Figs. 95, 96), although they lack woody tissues, are often as tall as or taller than some of the alpine shrubs.