The ecology of some alpine grasslands
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The study of the ecology of the alpine grasslands of New Zealand is in its infancy and one of the lesser-known kinds of grassland is that dominated by the short grass Chionochloa oreophila (Petrie) Zotov. This grass lives near the upper limit of alpine vegetation, usually in hollows where snow lies late into the summer (frontis-piece). The grasslands in which it is prominent are not very extensive in area compared with those dominated by other species but they are an interesting example of vegetation occupying a narrow niche between sites where harsh environmental factors limit plant growth and sites where taller grasses are vigorous to the exclusion of the short grass. The specific purposes of the present study and the general approaches to it are outlined in section I.2. The research embodied in this dissertation was carried out mainly in the field, from 1960 to 1966, in the western mountains of the South Island of New Zealand. Some greenhouse and laboratory study supplemented the field work. Grasslands dominated by Ch. Oreophila are found from about lat. 42°S. to lat. 46°S, mainly west of a line which approximates the eastern boundary of high precipitation (about 50 ins. annual average precipitation) (fig. 1.1). concentrated study was made in the alpine ecosystems at Lewis Pass (lat. 43°22’S. long. 172°23’E.) and Arthurs Pass (lat. 43°35’S. long. 171°34;E.) (fig. 1.2). The main study sites in Trovatore Basin, Lewis Pass and Rough Creek Basin, Arthurs Pass, are on or very near the main divide of the Southern Alps. Other field work was carried out in places between north-west Nelson and southern Fiordland (fig. 1.2). Throughout the dissertation, references to the alpine grasslands apply to these two sites unless specific mention of other places is made. The main study sites are at or above 5000 ft. of altitude on the mountainsides, whilst the valley floors are lower than 2500 ft. and separated from the sites by steep mountainsides. In both cases some 1500 ft. or more of forest was traversed before the alpine grasslands above timberline could be reached. All equipment was backpacked to these sites and samples of soil, plants etc. taken on the mountains were backpacked to the valley floor. Time was always short on visits to the study sites and bad weather often help up the work. Only on a few occasions could overnight stays be made near the sites. Difficulty of access thus placed considerable limitations on the amount of fruitful research effort which could be made. Many of the other sites visited were much more inaccessible.