Subalpine and alpine vegetation of granite ranges in western Nelson, New Zealand

Abstract

Twenty two vegetation units, derived subjectively from qualitative field notes, are described from several glaciated granite mountains and ranges in western Nelson: Lead Hills in the north, Herbert Range, Kendall Ridge, and Scarlett Range north of Little Wanganui Saddle, the adjacent western part of Allen Range south of the saddle, and Glasgow Range on the western side of the Mokihinui River. Their area sums to about 190 km².

The ranges all have high rainfall (4800-6400 mm), high cloud cover, and very infertile granite soils. The main cover is Nothofagus menziesii forming the timberline, scrub dominated by Olearia colensoi and Dracophyllum uniflorum, tussocklands of Chionochloa pallens ssp. pallens, C. rubra ssp. occulta, and C. australis, and Oreobolus pectinatus — Donatia novae-zelandiae cushion-herbfield.

Vegetation units characteristic of more fertile soils in other parts of western Nelson are uncommon, e.g., Chionochloa flavescens ssp. lupeola tussockland and Hebe topiaria scrub. Calcicoles are rare on granite and are confined to dry rock overhangs, e.g., Asplenium lyallii.

Several conspicuous species are not found on all ranges. Some differences are because Kendall Ridge has a more extensive alpine zone and several species that are rare or absent from other granite ranges are found there, e.g., Chionochloa oreophila and Raoulia subulata. Other differences are possibly related to the position of the ranges with respect to the prevailing moisture-laden westerlies, e.g., the absence of Celmisia spectabilis from the Glasgow Range. However, for several conspicuous species there is no ready explanation for their distribution patterns, e.g., Aciphylla hookeri and a large unnamed Gentiana taxon.

Anomalous distribution patterns of Nothofagus forest on the Glasgow Range that do not appear to be related to geology or fire history factors require investigation.

Keywords:

• alpine and subalpine vegetation
• granite mountains
• western Nelson