Introduction

Subalpine scrub is widespread on the New Zealand mountains, especially in the wetter districts. The strange life forms and unusual floristic composition have excited the curiosity of botanists; but the inaccessibility and impenetrability of the scrub have prevented any detailed studies. Cockayne (1928) gave broad floristic descriptions and Zotov (1939) related the distribution of scrub and beech forest in the Tararua Range to the occurrence of fog.

One of the functions of the Forest and Range Experiment Station of the New Zealand Forest Service will be the study of mountain ecology; the subalpine scrub is receiving particular attention. The ecological survey of the Hokitika catchment which was carried out during the summer of 1957–58 gave me the opportunity of gathering the material for this preliminary paper on the subalpine scrub communities, in an area representative of the Westland botanical district. A week's visit in July, 1959, enabled me to see the vegetation under winter conditions. The bulk of the work was done in the basin at the head of the Toaroha river (Locality map, Fig. 1.). The subalpine scrub there is fully representative of the Hokitika catchment and the configuration of the basin is such that its parts can be reached easily from the hut, which is situated at 2,900 feet above sea level.

In ascending the Hokitika River, one crosses alluvial valleys, terraces and foothills, for a distance of 12 to 15 miles. This rather broken “plain” halts abruptly against a mountain wall, which rises, often precipitously, to some 5,000ft. The Hokitika and its tributaries head into the mountains through successions of gorges, waterfalls and narrow valleys. Most of the larger tributaries are fed by the snowfields and glaciers of the main divide which, in the southern corner of the catchment, includes peaks over 8,000ft in height.

The bulk of the mountainous part of the Hokitika catchment is underlain by schist, but the greywackes which compose the Canterbury mountains generally begin