Download FIRESTARTERS AN OPEN AND SHUT CASE ADAPT OR FRY HOT

Veld & Flora FACTSHEET FIRE
Learning about Biodiversity
FIRESTARTERS
HOT FACTS ABOUT FIRE
Fires are most commonly
started by humans, but natural
fires can be started by lightning
during thunderstorms, and to
a lesser extent, spontaneous
combustion of coal seams,
volcanic eruptions and
earthquakes. Fires need oxygen
to combust flammable material
and there are several types of fires,
both underground and on the
surface. Surface fires include fastmoving fires that sweep over the
ground, consuming plant material
or ‘crown fires’ that sweep through the canopy of dense, woody vegetation and forests.
Occasionally, a fire will develop into a firestorm of immense proportions. Browne and
Bond’s Veld & Flora article (see reading list) describes it well. ‘Imagine a set of switches. To
get a ship or a plane moving, all those switches need to be on. If any switch is off, it will be
an “ordinary” fire or no fire at all. So, what are the switches for a severe fire event? South
Africa’s “Working on Fire” teams have come up with a memorable rule: “thirty, thirty, thirty
conditions”. This means that in addition to the “switches” of enough dry vegetation to
fuel the fire and ignition (e.g. a match), there must be air temperature greater than 30oC,
relative humidity less than 30% and wind speed greater than 30 km/hour. Fires during
these conditions cannot be contained.’
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ADAPT OR FRY
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Many grassland and savanna
plants are adapted to survive
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surface fires. Adaptations
include: subterranean
tubers; fire-resistant bark,
auxiliary buds situated at, or
just below, ground level; or,
fire-resistant seeds. Species
of Protea growing in fynbos
have serotinous flower heads
in which the bracts protect
the seeds from the heat of
the fires. A few days after a
fire, the bracts open and shed
their seeds, usually resulting
in synchronous germination
and growth of same-aged
seedlings. This excess possibly reduces the effects of predation on seeds and seedlings,
through ‘safety in numbers'. Some species, such as the Common Sunshine Conebush
(Leucadendron salignum) in the photo above, re-sprout from the base of the stem.
Some of these shrubs, therefore, could be hundreds of years old!
For many fynbos and grassland species, fire is an important stimulus for
flowering, producing seeds and seed germination. Many plants are wholly dependent
on fire, including the Fire Lily (see below).
Smoke also plays a role, awakening dormant seeds of certain grassland and fynbos
species and prompting them to germinate soon after a fire. The heat from fire can also
stimulate germination in some species
AN OPEN AND SHUT CASE
The effects of fire on the
environment vary. Sometimes fire is
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beneficial, maintaining the vitality of
the biotic component, or facilitating
the regeneration and stability of
plant and animal communities.
Sometimes it can cause wind and
water erosion, stripping away
valuable topsoil. Many animals die in
fires, while others are able to escape
and forage on carcasses and prey
flushed out after fire.
Fires remove plant cover,
allowing more light to reach the
soil. This stimulates the growth of heliopytes (light-loving plants) but inhibits the growth of
sciophytes (shade-loving plants). Nutrients and minerals are recycled and, although some
are lost to the atmosphere, overall the productivity of ecosystems increases after fire. Recent
research on fire ecology emphasises the feedback role of vegetation on fire regimes. In
many fire-prone ecosystems alternative vegetation types with quite different ‘flammabilities’
co-exist in landscapes: ‘open’ and flammable, e.g. grassland, vs ‘closed’ and non-flammable,
e.g. forest communities. The size and dynamics of these co-existing patches have been
changing over the millennia in response to changes in fire regime and the concentration of
atmospheric oxygen (O2) and carbon dioxide (CO2). Low CO2 and high fire activity favours
open ecosystems while high CO2 and low fire activity favours closed ecosystems.
READ MORE about fire as an ecosystem
driver in these articles in Veld & Flora:
Firestorms in savanna and forest
ecosytems: Curse or Cure? by Catherine
Browne & William Bond, Veld & Flora
97(2), pp. 62–63, June 2011; Why do
grasslands have no trees? by Julia
Wakeling, William Bond & Michael Cramer,
Veld & Flora 96(1), pp. 24–25, March 2010;
The long walk to treedom: A tale of the
African savanna by Glenn Moncrieff, Veld
& Flora 96(1), pp. 22–23, March 2010;
The devil of a job: Ecological restoration
trials on Cape Lowland renosterveld by
Penelope Waller, Veld & Flora 100(3), pp.
132–134, September 2014; Where there’s
smoke, there’s seed: Plant-derived
smoke is an important natural ‘cue’ for
the germination of fynbos seed by Neville
Brown, Philip Botha, Deon Kotze and
Hanneke Jamieson, Veld & Flora 79(3) pp.
77–79, September (1993).
FIREFLOWERS
'Fire has been a neglected process in Earth’s history and now it is time to reassess its role in shaping our world.' Andrew C. Scott.
Fires are usually seen as disasters that destroy ecosystems, but they
are actually ecological processes that influence structure and function in
ecosystems, particularly among plant communities. Scientists have shown
that fire may have been the catalyst for the evolution and expansion of
flowering plants (angiosperms) during the Cretaceous period. Similarly, the
expansion of C4 grasses during the Miocene was probably facilitated by fire in
extensive seasonally dry areas. These studies have contributed to an increasing
recognition that fire has been an ancient process on Earth.
Fynbos in the south-western Cape depends on regular fires in seven to thirtyyear cycles to ensure that old plant communities make way for new growth.
Grasslands also need fire to prevent encroachment by shrubs and trees.
Fire is commonly used in Africa for managing different ecosystem types (albeit
sometimes to the detriment of the ecosystem as in the case of forests being
cleared for agriculture). As Earth’s climate is rapidly changing, we urgently need
a better understanding of the way in which fire shapes the landscape in order to
plan for the future of the human species.
All 101 volumes of Veld & Flora, the journal
of the Botanical Society, are now available
online through Sabinet. The latest journals
(2008–2014) are only available to Sabinet
subscribers but from 1915–2007 they are
free online resources. To access the back
issues go to http://reference.sabinet.
co.za/sa_epublication/veld. To find an
issue or article, go to ‘Table of Contents’ a
little way down the page, and click on the
dropdown arrow next to ‘Archive’. Select
and click on the issue you want. Select
and click on the article in which you
are interested. On the right hand side
of the screen, click ‘Full text’. Articles
mentioned here are also freely available
at http://labpages.blogspot.com/.
INFORMATION on this poster was
taken from the book The Story of
Life & the Environment: An African
perspective by Jo van As, Johann du
Preez, Leslie Brown and Nico Smit,
Many flowers appear after fire
has destroyed the vegetation.
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In this way they receive the
full attention of pollinators.
An example is the Fire Lily
(Cyrtanthus ventricosus) that
only flowers after fire – its
blooms appearing within two
weeks of a fire. Remarkably,
this geophyte, together with
several other species in the
genus Cyrtanthus, is entirely
dependent on fire. Within two
weeks after fire, the flower
appears, after which the plant
remains in a vegetative state
underground, sometimes for up to 15 years or more. Unique to this and many other
Cyrtanthus species is the hollow scape (stem) which is structurally strong and light on
resources for its development. In effect, the hollowness of the scape may be the key to
enabling the plant to put forth flowers so promptly after fire. The Table Mountain Pride
butterfly (Aeropetes tulbaghia) frequently visits the flowers of the Fire Lily.
Struik/Nature, 2012 and the article Fire
and the spread of flowering plants in
the Cretaceous by William J. Bond &
Andrew C. Scott in New Phytologist 188,
1137–1150, 2010 (www.sciencedaily.com/
releases/2010/09/100907104246.htm);
as well as from the SANBI website www.
PlantZafrica.com. TEXT adapted from the
above sources by Caroline Voget.
PHOTOS: (clockwise from top left): 1
Burned slopes of Table Mountain by C.
Voget; 2 Firestorm in Hluhluwe, 2008
by Dirk Swart; 3 Re-sprouting Common
Sunshine Conebush (Leucadendron
salignum) by C. Voget; 4 Fire Lily
(Cyrtanthus ventricosus) by Mickey
Orrey and 5 A scorched Mountain Cedar
(Widdringtonia nodiflora) by C. Voget.
LINKS TO THE CURRICULUM
Life Sciences Grade 10, Strand 3,
Environmental Studies. Content:
Environment and Ecosystems.