Vegetation of the Aorangi range,Southern Wairarapa

Abstract

SUMMARYIn primeval times the Aorangi Range supported an almost continuous forest cover broken only by occasional slips and young stream terraces. Forest still forlT15 the mo.,t extensive cover in the area. It can be broadly classified into four main types: mahoe-hinau-rewarcwa forest en the more stable slopes and flats up to an altitude of 1,700-1,900 ft; black b(;ech forest on the drier, more exposed spur sites up to 1,600 ft; red beech forcst on the mid slopes between 1,400 ft and 1,900 ft; and silver beech forc.~t along the ridges between 2,000 ft and the highest points of the range.In recent times the vegetation of the area has been modified by fire, browsing, and erosion. Erosion has favoured the extension of seral plant communities such as are found on slips, in gully heads, and on aggrading river terraces. Burning has given rise to tall kanuka scrub at lower altitudes and to subalpine scrub and tussock grassland at higher altitudes. Browsillg mammals have considerably altered the composition of cach forest type and have modified Succc.~sion on bared areas.The first section of this paper hriefly describes the physical nature of the range; the second deals with the distribution, structure, and composition of the main forest types, and the third descrihes how erosion. fire. and hrowsing have altered these to produce the present seral and suhclimax communities. I NTRODII('TIONThe greater part of the Aorangi Range (commonly referred to as the "Haurangis") lies within permanent State forest. The total area of State forest is approximately 34.000 acres. divided into a northern and a southern section by a strip of hilly grazing country lying to the true left of Turanganui River (Fig. I).The range is comparatively low. the two highest peaks being Mt Ross 0.226 ft) in the southern section. and Mt Te Munga (3.211 ft) in the northern section. It constitutes a major block moving between two transcurrent fault zones which trend in a NE-SW direction. The present sharp ridges of the range resulted from extensive southward movement of the block during the Tertiary period (Wellman. 1956;Kingma. 1959) 1967]North ISland N Z. [MARCH movement caused the development of a series of minor faults and consequent large-scale internal deformation. Many of these minor faults are still active (Fig. 2). The drainage pattern of the range is largely influenced by the pattern of fault lines and shatter zones. and is of a somewhat trellised nature. As a result downcutting by the streams is rapid and the valleys are typically V -shaped and steep walled. with numerous gorges. The parent rock is predominantly grey wacke. dating from the Aptian and Neocomian stages of the Cretaceous (Grindley. Harrington. and Wood, 1959). Minor volcanics. probably of Jurassic age (Wellman, (956), border the south-western margin. and towards the north-east there are pockets of limestone resulting from movement during the Kaikoura diastrophism (Kingma. 1959). The Aorangi Range. and the mountain ranges to the north-east. are a continuation of the ranges of the ...

Integrating earth and life sciences in New Zealand natural history: The parallel arcs model

“…Examples include cliff and scree plants in Scrophulariaceae, including fault-scarp colonisers such as Hebe cockayneana (Fig. 13c, 22d), the diverse swamp forests running along the Alpine Fault Zone, Griselinia-Fuchsia forests growing on steep faultscarps around Dunedin, and the Nothofagus forests of Wellington, where Wardle (1967) has illustrated the dramatic effects on plant communities of even minor fault movement.…”

Biogeographic disjunction along the Alpine fault, New Zealand

“…J. Wardle (1967) has also illustrated the dramatic effects of fault movement on New Zealand vegetation, and P. Wardle (1980) suggested that a major earthquake in 1730-40 led to the establishment of even-aged stands of Metrosideros and Wknmannia in Westland (cf. Stewart & Veblen, 1982).…”

Effects of possum browsing on northern rata, Orongorongo Valley, Wellington, New Zealand

“…Northern rata is now absent from the nearby Aorangi Range (Wardle 1967) and has declined dramatically in abundance in the southern Ruahine Range as a result of possum and ungulate impacts (Batcheler 1983).…”