Pedogenesis and vegetation trends in the elefulvic and eldefulvic zones of the north-east Ben Ohau Range, New Zealand : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in the University of Canterbury, Lincoln College

The Twin Stream catchment is one of several transverse valleys in the Ben Ohau Range which flows into the Tasman River. It is approximately 44 sq km in area and is bounded by the Whale Stream in the south and the Bush Stream in the north, with the Ben Ohau Range on the western boundary. The catchment forms part of the 19,000 ha station of Glentanner which is run by Mr I. K. Ivey. In 1965 the Grasslands Division of the Department of Scientific and Industrial Research established a field station at 800 m. Since then a further field station has been located at 1,400 m. These two field stations form the focal point for plant and ecological studies into the mid and high altitude grasslands. Reasons for the selection of Twin Stream and purpose of present study are: i) The area is located on a precipitation gradient between the humid and per-humid zones (1,500 - 3,000 m). This enables the study of the varying effects of moisture on the soils and vegetation within a relatively small area. ii) The area includes a set of well preserved ground surface of different ages and altitudes. iii) Access is relatively easy to mid-altitude by landrover tracks. The growing pressures on the demands of marginal lands for pastoralism, forestry, recreation and water resources have resulted in a land-use conflict which can only be resolved by the compilation and interpretation of land resource data and subsequent classification of land into its various uses in accordance with scientific findings. At present the widely used system of land use capability classification is based upon very meagre basic land resource data and in many instances information upon soils and vegetation is almost completely lacking. This applies particularly to extensive areas of mountainous terrain which are grouped under broad land use capability classes of VII, VIII even though they are very different in terms of erosion, revegetation potential, yield and quality of water. The overall purpose of this project therefore is to study the natural process which influence and control the development of soils and vegetation in the sub-alpine and the alpine zones of the Twin Stream catchment with the view of contributing more quantitative resource data from which reliable interpretations and evaluations can be made.