What’s happening on the Claris fire scar?
by Riki Taylor (School of Environment, University of
The 2013 fire at the Kaitoke dunes was an important event for the
Barrier, burning through 116 hectares of regenerating scrub, putting
much of Claris at risk, and requiring a large and expensive response by
the fire service. But the fire also presented a valuable research
My thesis, entitled ‘Post-Fire Community Dynamics in a Disturbed
Landscape, Great Barrier Island’ aimed to take advantage of this
opportunity, using it as a case study for the increasingly significant
role fire is taking in New Zealand forests, especially where exotic
fire-loving invasive plant species are present.
The initial aim of the research was to survey the post-fire vegetation
at Claris to see if different plant communities had formed, and if so,
to determine the main influences on the species that had become
established. The results show a range of distinct communities have
regenerated across the fire scar area, from relatively uninvaded areas
dominated by mānuka (Leptospermum scoparium) regrowth, to plant
communities comprised almost exclusively of exotic invasive woody
species, either pine species or brush wattle (Paraserianthes
Mānuka and a range of sedge species emerging among
standing remains of mānuka that burned in 2013. This is one of the
least-invaded communities at the Kaitoke dunes.
major invasive species present included hakea (both Hakea sericea and
H. gibbosa) and berry heath (Erica baccans), with gorse (Ulex
europaeus), and Banksia species seen in lower numbers. Common to all
of these invasive plant and tree species are fire-tolerant traits that
gave them a competitive advantage following the fire (see
A secondary aim of the research was to determine the major influences on
the establishment and composition of post-fire communities. The most
influential factor was topographic position and the associated closeness
of the surface to the groundwater table. For example, the mānuka-dominated
community only occurred in low-lying areas inundated with water during
winter. Alongside soil moisture soil nutrient levels were also
influential, with high moisture and fertility associated with the most
resilient areas where no invasive plants were found. Soil conditions of
low moisture and fertility were consistent across the rest of the site,
with the distribution of plant communities controlled mainly by the
presence (or absence) of an invasive species prior to the fire.
Another aim was to assess change in community composition from before
the fire, to two, and four years afterwards. This work revealed changes
in the make-up of plant communities with important implications for the
risk of future fire at the site.
A dense stand of brush wattle emerging beneath mature Pinus spp.
This is the most-invaded community at the Kaitoke dunes.
Of particular interest was that all of the major woody species appeared
to have increased distributions across the site, implying a
corresponding increase in flammable plant material which could fuel a
fire. Brush wattle distribution expanded the most, and in especially
The intensity of another fire in this area is likely to be higher than
the last one, with the continued spread of woody exotic invasive plant
species (weeds) the ultimate outcome.
Looking forward, a range of management responses could be considered.
Felling and removal of pine and wattle is an option which could be done
now, although it is highly labour-intensive. More complex efforts
involving replanting and control of pest mammals would require more
planning, but less labour overall and could better incorporate community
Ultimately, the vegetation in the fire scar area will only return to a
pre-fire state (that can act as part of the ecosystem of the island), if
management efforts are made alongside consistent vigilance in preventing
fire from occurring again.
Fire tolerance in plants
Several species of exotic invasive plants established in New
Zealand have fire tolerant characteristics, influenced by the
frequency of fires in their native ranges. Fire tolerance is
exhibited through bark thickness and other vegetative
insulation, above-ground re-sprouting, and underground roots and
Bark thickness provides resistance to fire damage.
Thick bark reduces the heat in the growing tissue beneath the
bark. Species, such as pine, with thick bark do not catch fire
or burn easily. Other plants are able to grow new shoots
after fire from buds in parts of the plant that are below ground,
such as Banksia species. Heat from a fire can also
stimulate seed release from woody capsules. Seeds of many
species of Casuarina, Hakea, Banksia,
Leptospermum and Eucalyptus are encased in woody
capsules capable of remaining dormant for years and resisting
seed predation. Germination occurs after the seed coat is
damaged in some way, such as through fire. Some species
respond positively to chemicals in smoke. Species with this
type of regeneration response are common in plant communities
established after a fire.
was an infrequent and relatively small part of the disturbance
regime in New Zealand forests until the arrival of humans over
700 years ago - very few indigenous plants show clear
adaptations to fire1. Post the arrival of humans in
the mid-13th century, fire had a dramatic impact on the New
Zealand landscape, reducing forest cover from around 90% to
25%. Perhaps unsurprisingly, fire-adapted species in our flora
tend to be of Australian origin and are fast growing, including
mānuka (Leptospermum scoparium), kānuka (Kunzea
ericoides), bracken (Pteridium esculentum) and
matagouri (Discaria toumatou).
The numerous fire-resistant seedpods of Hakea gibbosa,
which open days after the death of the tree.
G.L.W., Wilmshurst, J.M., and McGlone, M. S. 2014. Ecology and
long-term history of fire in New Zealand. New Zealand Journal of
Ecology 38(2): 157-176.
Environmental News Issue 38