Fire disturbance favours exotic species at kaituna wetland, bay of plenty

Abstract

Fires regularly occur in New Zealand wetlands, affecting ecological indicators and conservation values such as native plant species richness. Following a small fire at the Kaituna Wetland, Bay of Plenty, foliage cover was measured and biodiversity indices determined on eight occasions over 48 months. Visual percentage estimation of species cover in six height classes showed that grasses (especially naturalised exotic species) were early colonists, although plots were subsequently dominated by the exotic Japanese honeysuckle (Lonicera japonica) and the native common twig rush (Machaerina rubiginosa). At 48 months, there were 14 exotic vascular species in burnt plots compared to 10 in unburnt plots; conversely 10 native species were found in burnt plots, compared to 18 in unburnt plots. Mean species richness, Shannon-Weiner diversity, and total vegetation cover increased in the burnt quadrats over time, with exotic plant species having a greater relative increase in these measures than native species. Without proactive management, fire does not confer conservation benefits to the Kaituna Wetland. Disturbance events such as fires can be used as natural experiments to measure restoration and rehabilitation initiatives post-perturbation.