The conservation ecology of Teucridium parvifolium (Hook f.) on Banks Peninsula, New Zealand

Abstract

The distribution of the rare endemic shrub Teucridium parvifolium was investigated throughout New Zealand to determine the geographic distribution of the species, and specifically on Banks Peninsula. T. parvifolium is spread discontinuously throughout New Zealand and occurs in widely scattered, generally small populations. Aspects of the community ecology, including floristic composition, and community/physical site relationships, were studied to determine the habitat requirements of T. parvifolium on Banks Peninsula. T. parvifolium occurred in two plant communities that differed in species composition. The healthiest populations occurred in the marginal community characterised by Hoheria angustifolia and Urtica ferox rather than the community characterised by Macropiper excelsum and Melicope simplex. Data was gathered on the size and structure of populations, plant size, seed production and viability, seedbank, plant growth and the extent of browsing. Population structures were characterised by a large number of seedlings, fewer saplings, and very few adult plants. Adult plants were capable of producing large numbers of seeds and many of these entered the soil to form a seedbank. Seedlings were capable of rapid growth under ideal conditions but growth was restricted in the wild by introduced herbaceous weeds. Agents of decline were identified as browsing animals, competitive introduced plant species, and habitat disruption. The continued decline in suitable habitat, the effects of introduced weeds, severe browsing, and the severely fragmented nature of the populations warrants the IUCN threat classification of Vulnerable. Management options include managed browsing to control introduced plant species, provision of suitable habitat, and active management to increase the size and frequency of small populations.