seedling establishment

Adult mortality, seed production, and seedling establishment of two species of New Zealand broom (Carmichaelia juncea and C. vexillata) were studied in exclosure trials to determine the level of threat posed by herbivory by introduced mammals. While no effect on mortality was observed for either species, herbivory by hares drastically reduced seed production and subsequent seedling establishment in C. juncea. C. vexillata seemed less vulnerable to herbivore damage due to its plant architecture, as well as the timing and intensity of the herbivore impact.

Quantitative and qualitative studies of understorey regeneration in a mature kohekohe-taraire dominated forest remnant were undertaken before and after the extensive replanting and species reintroduction programme on Tiritiri Matangi, a northern New Zealand island. The changes in regeneration patterns of taraire and kohekohe within this remnant before the restoration programme, and twenty years later, are described.

Two indigenous small tree and shrub species, kanuka (Kunzea ericoides) and manuka (Leptospermum scoparium), have potential as reforestation species in New Zealand as they are forest pioneer species that can invade grassland naturally from present seed sources. The aim of this study was to determine if establishment of kanuka and manuka from seed in grassland distant from stands of these species might be constrained by lack of appropriate mycorrhizal fungi.

Large areas of mountain beech (Nothofagus solandri var. cliffortioides) forest in the South Island of New Zealand have been destroyed by fire and replaced by grassland or shrubland. Mountain beech regenerates into grassland or shrubland mainly by slow spread from forest margins, though instances of long-distance spread into manuka (Leptospermum scoparium) shrubland have been recorded.

Norway rats (Rattus norvegicus) were eradicated from Ulva Island, Rakiura National Park, in 1996. The aim of our work was to determine if seedlings and saplings increased in density and/or species richness following this eradication. In 2003, we took advantage of eight permanent plots (5 × 5 m) that had been established on Ulva Island in 1991, by counting seedlings and saplings of woody species, including tree ferns. Over this period, total numbers of woody seedlings (< 30 cm tall), and saplings (30 cm – 2 m tall) did not increase significantly (P > 0.05).