An analysis of post-fire regeneration at William Upton Hewett Memorial Reserve and the place of restoration ecology

Abstract

In New Zealand, the combination of flammable vegetation and an intensified fire regime has created new challenges for the management of fire-prone environments. As fires are due to become more prevalent within the New Zealand landscape, considerations need to be taken as to how best provide environmental defences, and aid in the regeneration of vegetation in a post-fire setting. However, there has been little research undertaken examining the use of planting as a restoration technique in post-fire landscapes. The purpose of this study was to (1) describe regeneration at a post-fire site in northern New Zealand with a history of recurrent fire and (2) analyse the use of plantings as an active restoration method in recently burnt landscapes. Vegetation and soils were sampled across three separate vegetation communities within the William Upton Hewett Memorial Reserve, which has had a history of recurrent fire events. The vegetation communities surveyed show three different successional stages, one successional stage is more mature vegetation that has not been impacted by the previous two fire events. The other two successional stages have occurred from the presence of two separate fire events (2014 and 1995), which destroyed two different areas of the reserve. In order to try to aid the regeneration of the areas burnt in 2014, active restoration in the form of plantings has been undertaken in parts of William Upton Hewett Memorial Reserve. Two different restoration planting efforts have been undertaken in 2017 and 2018, these plantings were surveyed for mortality rates. Compositional data collected from vegetation surveys, including vegetation dominance and presence/absence data, and soil cores were analysed using ordination and clustering analyses. Comparison of the different vegetation communities found significant differences between species richness across the three sites, as well as differences in dominant species cover. Soil characteristics show a significant difference across common soil elements, with the vegetation areas not impacted by fire having an overall higher level of all soil properties, than levels observed in post-fire soils. Cation exchange capacity, organic matter, and loss on ignition were all higher in the vegetation that had not been burnt during the last two fire events. Soil pH remained highly acidic across all three sites. Mortality surveys of the restoration plantings provide some insight into the likelihood of their success in the current landscape of William Upton Hewett Memorial Reserve.