1.1 Location Of The Study Area In 1847, William Colenso, missionary, explorer, and botanist made his first crossing of the Rangipo Desert in foul weather: "At 3pm we crossed the sand desert called Te Onetapu (Rangipo)- a most desolate weird- looking spot, about 2 miles wide where we crossed it; a fit place for Macbeth's witches or Faust's Brocken scene!" Colenso (1884) was describing a landscape clothed by tussock, dunefields, barren gravelfields and deeply scoured watercourses. The Rangipo Desert is situated on the exposed south-eastern portion of Mount Ruapehu's ring plain. Mount Ruapehu is New Zealand's largest andesitic massif and its summit is the highest peak in the North Island, reaching 2,797m. To the east of the Rangipo Desert uplifted ranges of indurated sandstone, argillite, and conglomerate make up the Kaimanawa Range (Grindley, 1960). The field study was, in the main, confined to the west and south of the Whangaehu River, to the north of the Waihianoa Aqueduct, and to the east of Makahikatoa Stream (Fig. 1.1). The field area, therefore, covers about 40km2 , most of which was
gazetted to the New Zealand Army in 1943 (Birch, 1987). The altitude within the study area gradually increases from 910 metres above sea level at Waihianoa Aqueduct, to 1200 metres above sea level at the north-eastern margin of the study area. The landscape of the Rangipo Desert is unique for its contrasts within a few kilometres. In one area eroding light yellow tephra, colonized by only scattered hardy plants, abuts against healthy enclaves of N. solandri; while, in another area only a kilometer away, dunes colonized by Phyllocladus and Halocarpus bidwillii are interpersed across a grey lag pavement covered by scattered boulders and even fewer plants. These contrasting features make the task of delineating the landscape into discrete regions simple.