Vegetation studies on the Humboldt Mountains Fiordland, part 1: The alpine tussock grasslands
- Botany Department, University of Otago, Dunedin
- Present address: Botany School, University of Melbourne, Australia
Values for frequency and percentage dominance are given for 105 species in alpine tussock grassland from six sites located between timber line at about 1,000 m. and the upper limit of closed vegetation at about 1,640 m. on the western slope of the Humboldt Mountains in northern Fiordland. On the basis of physiognomy, three distinct communities can be recognised: (1) A low alpine scrub dominated by the tall tussock Chionochloa flavescens and subalpine shrubs, particularly Dracophyllum uniflorum, extending for about 75 m. above treeline; (2) a low alpine snow tussock grassland in which C. flavescens and the shorter C. crassiuscula co-dominate, extending continuously from about 1,100 m. to 1,530 m., but above this being replaced in snow pockets by (3) a high alpine grassland of the dwarf tussocks C. oreophila and Poa colensoi together with Celmisia hectori.
Floristic affinities between the sites indicate an altitudinal gradient, but justify treatment of the snow tussock-scrub as a separate community. Moreover, they suggest the possibility of recognising two communities within the low alpine snow tussock grassland, one below 1,530 m. and one above. In the lower, Chionochloa flavescens and C. crassiuscula share dominance, whereas the upper is marked by a reduction in the importance of C. crassiuscula, a corresponding increase in Poa colensoi, and the appearance of Celmisia hectori.
Vegetation patterns in the alpine grasslands are compared with those previously described for the forest on the lower slopes of the range.