Takahe Valley Hut: a focal point for weed invasion in an isolated area of Fiordland National Park, New Zealand

The role of backcountry huts as focal points for weed establishment and spread into New Zealand’s national parks has received little attention. In this study we describe the pattern of weed spread around Takahe Valley Hut, Murchison Mountains, Fiordland National Park. Established in 1948, the hut is located at 900 m a.s.l. at the ecotone between Nothofagus forest and valley floor shrubland/grassland. We recorded the distribution of vascular plants in quadrats (110) placed by restricted randomisation around the hut, and measured relative irradiance and distance from the hut. Nine exotic species, mostly grasses, were recorded, the most frequent being Agrostis capillaris (34%). The majority of occurrences of exotic plant species were located in the immediate vicinity (less than 5 m) of the hut but two exotic species (Agrostis capillaris and Dactylis glomerata) ranged more widely. Exotic species were present in well-drained shrubland and grassland but did not extend far into Nothofagus forest or onto infertile wetlands. The percentage of exotic species in quadrats declined significantly with distance from the hut. There was no linear relationship between the percentage of exotic species and relative irradiance. When forest quadrats were excluded, the number of native species in quadrats was negatively correlated with the number of exotic species, suggesting competitive displacement of native species by exotics in non-forest habitats. Long-term persistence of most exotic species at this site depends on physical disturbance and nutrient enrichment associated with human activities at the hut site. However the maintenance of this species pool has provided sufficient propagule pressure for some exotic species to disperse into the wider area. Weed accumulation around huts can be reduced by locating huts in vegetation types that are more resistant to invasion, and maintaining facilities to eliminate local weed infestations.