The Spread of Heather, Calluna vulgaris (L) Hull, into Indigenous Plant-Communities of Tongariro National-Park

The vegetation of 10 quadrats from each of 26 sites, in and around the Tongariro National Park, which contained the introduced dwarf shrub, Calluna vulgaris (L.) Hull, was analysed using Reciprocal Averaging and Indicator Species Analysis. Six major plant communities were recognised and related to previous mapping units: tussockland with shrubs and herbs (red tussock tussockland); heathland with tussock and Dracophyllum subulatum (monoao-red tussock tussock-shrubland); communities of herbfield and scoria slopes ([mountain inaka] gravelfield); Calluna-dominated tussock or heathland (heather- red tussock tussock shrubland and heathland shrubland); Gleichenia/Empodisma bog (red tussock/wire rush-gleichenia rushland); and weed/scrub communities of disturbed ground (unmapped). An ordination of the sites showed that the major directions of variation in the vegetation were associated with altitude and soil moisture. Calluna had increased in extent since the area was mapped in 1960, and has been observed to have increased further since this survey was completed in 1984. Calluna has a potential to spread in all the recognised communities, although increases have been greatest in tussock grassland and on disturbed ground at lower altitudes and least in boggy areas. Calluna thus remains a threat to the natural vegetation of the Park, although some areas may be equally liable to succeed to taller vegetation. It is suggested that future research should be directed towards the effective control of heather within the Park.