The demography of Epacris pauciflora A. Rich. on two contrasting pakihi terraces, North Westland, South Island

Abstract

Epacris pauciflora is one of the few woody plants that commonly grows in shrub/rushfernland vegetation (pakihi) on poorly drained terraces in North Westland. Terraces west of the coastal ranges have more extensive open areas and a higher floristic diversity than terraces in the inland basins. This study investigated whether the apparent differences in the vigour of E. pauciflora on contrasting terraces in these localities are caused primarily by differences in the size and age structures of the patches or by some unspecified environmental factor.

On the western terrace (German Terrace) stands had a mean age of 9 years and those with dead patches of E. pauciflora were of similar age to those without dead patches. However, plants were significantly smaller and stem growth rates lower in open areas with a lower cover of Baumea teretifolia and Gleichenia dicarpa and a greater diversity of small herbs. On the inland terrace (Dublin Terrace) stands had a mean age of 15 years and the vegetation was relatively uniform. There were no dead bushes and no significant differences in stem growth rates between the stands. Overall, differences in stem parameters between the two terraces, such as stem growth rates and stem densities, are not significantly different. Stand self-thinning was not a cause of bush death because of the low stem density, and neither were the dead bushes the oldest. The dead patches were probably caused by unidentified environmental factors such as seasonal variation in depth of the water table. Whatever the cause, the slow growth and death of patches of Epacris pauciflora may he one process maintaining the greater diversity of herbaceous species on the western terrace.

Keywords:

• pakihi
• wetland
• Epacris pauciflora
• growth rates
• Westland