Responses of Indigenous Vegetation to Contrasting Trends in Utilization by Red Deer in 2 Southwestern New Zealand National- Parks
- Department of Botany, University of Otago, P.O. Box 56, Dunedin, New Zealand
The responses of rain-forest vegetation on Secretary Island (Fiordland National Park) which was subjected to low but sustained browsing by red deer, are compared with those of the full range of mountain vegetation in Mt Aspiring National Park where deer numbers had been reduced substantially from previously high numbers.
On Secretary Island the most palatable species have continued to decline. Woody plants are debarked by chewing or antler rubbing, and herbs are grazed. Accessible parts of palatable trees and shrubs continue to be heavily browsed, while stems of some species continue to be distorted because lateral buds substitute for removed terminal shoots. Some unpalatable species have increased. In Mt Aspiring National Park, marked sites in five major vegetation types were assessed three times during 1970-1986 when deer numbers were kept low. The order of increasing recovery of communities has been: high- alpine fellfields and snowbanks through forests, subalpine shrublands, valley grasslands and low-alpine snow tussock grasslands. In the last, midribbed snow tussock grassland and many associated species recovered dramatically whereas previously prominent unpalatable or tolerant species have become less conspicuous.
Vegetation has not yet stabilised in either Park. Possible future trends are evaluated in relation to changing management. For Secretary Island these include more effective lures with improved 1080 poison gel formulation; for Mt Aspiring a continuing decline in the commercial return from hunting.