Our September
speaker’s address on “Fire in the Landscape” couldn’t be more timely or
relevant to the past 16 months. But rather than speak about the raging wildfires
of last summer, Craig Welden explained the numerous elements involved in
successful controlled burns, and the plant and animal responses to them when
carried out with due consideration.
As a Senior
Scientist at Healthy Land and Water and coordinator of the Queensland Fire and
Biodiversity Consortium, Craig has developed extensive skills and knowledge in
fire management, weed and pest control, and flora and fauna surveying.
He spoke of quite a few critical
considerations and questions to be answered for successful “burns” and results.
Different areas
require site specific planning for their vegetation and fauna, for example, dry
vine thicket; brigalow, riparian and rainforest areas do not tolerate fire well
at all. Are there exotic weeds in the mix that need intense concentration; how
much heat will the native plants tolerate to regenerate; when was it last burnt;
what are the expected flora and fauna results if there is no fire and will a
plant or animal species become overly dominant, stifling diversity? Other
factors to consider include seasonal and weekly weather predictions, the need
to vary the months for burning, and nearby areas
needing to be left unburnt to offer food and habitat while the burnt areas
recover; so much to consider!
Craig also explained
some of the unique interactions between Australian native plants and animals
with fire: i.e. certain fungi will sprout on black burnt logs; hakeas and
banksias release their seeds due to fire heat and smoke; some insects lay their
eggs in (sometimes warm!) ashes; frogs and others escape by burrowing into the
soil or under logs; birds feed on
insects escaping from ground flames.
The plants that
regrow after fire are generally divided into “seeders” and/or “resprouters”,
and the latter can be from lignotubers, rhizomes, or epicormic shoots under
tree bark. Most eucalypt shoots emanate from deep under the bark and can
therefore withstand more radiant heat and flame than other species. Some
species require (are obliged to have) fire to sprout and so are called “obligate
seeders”. Most of these adult species are killed by fire and their new
seedlings are vulnerable to a second fire occurring too soon.
The takeaway message was that wisely
controlled fire is integral to the Australian landscape, has been practised for
centuries, and affords the recovery and continuation of a vast number of flora and
fauna species.
Craig brought
copies of two issues of excellent
fire information booklets entitled “Living With Fire: Fire Ecol-ogy”, and “Fire
Regimes”, which feature many photos taken by Craig himself, and from which I
will include here a few major points and observations.
“Fire Regimes”
describes 10 broad vegetation types in southeast Queensland, and outlines the
recommended frequency, area, season, and intensity of controlled burns for each
one. 80°C is a temperature which enables hard coated seeds to crack open, while
120°C kills most seeds and species. Post fire regrowth can be quite positive,
especially following rain, with seed germination, seedling growth, and some
prolific plant flowerings.
“Fire Ecology”
covers the effect fires have on the burnt flora, fauna (including insects) and
soil biota. One major negative side effect on native animals is that open clear
burnt understory terrain allows easier feral animal predation. On the other
hand, some native fauna prefers the resultant new vegetation after cool fires. But
it seems reptiles are more abundant in areas of fewer fires. With frogs, some prefer
burnt sites (Litoria frycineti), others (Litoria olongburensis)
do not. Ants of 16 taxa showed up strongly in areas burnt annually which was
shown by research north of Gympie, along with long-horned beetles at those
frequently burnt sites.
Fire also affects, alters, and changes the soil. It burns away surface organic matter, alters nutrient availability and the pH, depletes soil nitrogen, and moisture retention, so rain run-off erosion is more likely. However, indications are that many fungi, soil fauna, and bacteria do recover fairly quickly after a low intensity fire, although that can be quite variable depending on remaining leaf litter.
(Report by Lauren
Marlatt)