Abstract:
The main aim of this study was to investigate the interactions between fire and vegetation on a patch of coastal dunes at Kaitoke, Great Barrier Island, New Zealand, that burned in January 2013. Vegetation surveys were undertaken in 2015 and 2017 using 30 plots in the burned area and six in the adjacent unburned vegetation. Each of these 36 5 × 5 m plots was divided into 25 1 × 1 m subplots within which each species present, its maximum height and reproductive status were recorded. Soil properties and associated environmental variables were also recorded and selected soil nutrients measured in the laboratory. These data were analysed based on vegetation composition and clustered using dissimilarity analysis; these analyses identified five distinct vegetation communities across the site. These communities represented a gradient of invasion, from at one end wholly indigenous communities reflecting pre-fire composition, to at the other end those fully dominated by invasive woody species. Correlative analysis of the vegetation and environmental conditions suggested that soil moisture and nutrients (C and N) acted as the strongest control on community type, with soil pH, slope, and rabbit abundance, as measured by pellet counts, having weaker influence. The vegetation across the burned area changed considerably over the period 2015 to 2017. The main trends over this period were the increased dominance of woody weed species where they were already dominant, and an increase in the extent of Pinus spp. across the post-fire landscape. Prospects for succession to mature indigenous forest at the site are minimal due to invasion, low-nutrient soils, and a lack of regional seed dispersal.