Fire and Succulents
There are numerous articles that exist on succulents - before, during and after fires. A few Australian examples are cited here.
How important were Carpobrotus to Aborigines?
How important were Aborigines to Carpobrotus?
A range of questions could be asked in relation to this topic, and while I am far from an expert on aboriginal culture, it does not preclude me from postulating about their relationship with plants, animals and the land itself prior to European settlement. Often, fragmented, inconclusive records exist for many Aboriginal cultural practices-or the diversity and complexity within and between regional cultures.
I need to re-iterate that I am not well read on all aspects of Australian aboriginal culture, but would like to think I know a little and that my ideas here are worthy to write about until such time as an expert discounts or contests its content.
I was always of the understanding that the skin of Australian aborigines is dark. Also that they are highly skilled fire starters by rubbing two sticks together; carriers of fire from camp to camp in a little cradle and that they used fire to burn/clear vast areas of scrub to make hunting easier. A strategic scrub fire, managed primarily by the wind direction, would automatically reward hunters with downwind escaping kangaroos, wallabies, emus, plus a range of other animals fleeing the fire. Areas previously burnt were soon flush with new grass growth and new fresh plant shoots, favored by marsupials, which also was a well-known to indigenous hunters. It is obvious that the hunter's skin colour was probably of major benefit in previously burnt out forested areas for camouflage, as they could easily stand near and amongst larger blackened tree stumps, whether dead or alive and be unseen by their intended prey.
It is well documented that Australian Aborigines used fire, regularly as a very successful 'hunting tool'. Also that the arrival of these first humans to Australia, approximately 50,000 years ago, changed the landscape dramatically as a result of their intensive fire/hunting form of land management. Scientists have concluded that many plants have consequently adapted to coping with frequently being exposed to fire, often regenerating quickly and with improved survival of the species. Some native plants now rely more heavily on fire assisted conditions than otherwise, especially for seed germination.
Carpobrotus fruit are large, juicy and sweet and among the favourite of all indigenous food plants recorded. Where this plant grows, Aborigines traditionally ate or carried fruit long distances and dispersed the plants seed as a result. Carpobrotus seed can survive ingestion therefore spreading every time a human defecated after eating Carpobrotus fruit. If defecation took place while hunting, and in a recently burnt out area, seed of Carpobrotus would not only have an ideal sunny exposed situation, but also an exceptional mix of nutrients from ash and charcoal to manure from the human faeces.
The science paper/article by Robert Parsons from the Latrobe University in Victoria (referenced in the next written entry below dated 23.11.13) confirms that Carpobrotus modestus has great difficulty growing from seed and surviving, without the effects of fire on its habitat. Also that animal ingestion of its fruit aids germination success significantly.
I ponder how significant a role indigenous people played, directly or indirectly on the evolution of succulent plants in Australia. I can summarise that it was far greater than current scientific literature records, especially as C. modestus and C. rossi currently have up to 95% of their former habitats almost devoid of the plants. For more on Carpobrotus and traditional use by Aborigines see the booklet titled Australian Pigface and Pigweed, available from this website.
Response just in below:
Yes it's interesting too that Sarcozona and Disphyma appear to extend up the Murray-Darling River systems and their tributaries, forming populations on suitable habitat along the way. This occurs right up as far as Yelarbon. I strongly suspect that trade of fruits or plant material were responsible. I firmly believe that these plants originated in South Australia and moved northwards by way of indigenous trade. Then further spread by local birds. How can I prove this? I can't. It's just a feeling I have, based on the greater diversity of species and size of populations in the south of the continent.
It's a good article but will have to remain a bit theoretical and speculative, except for the indirect tests relating to germination. It could form a compelling argument.
I've pondered the same things re tuberous Portulacaceae, which always seem to coincide with former campsites. It may be simply that both preferred the same habitat, but you can find similar habitat where there is no evidence of regular Aboriginal camps and there are often no tuberous Portulacaceae to be found. I speculate that they loved the tasty tubers which contained moisture and sugars, so carried them around in dilly bags like treats. Dilly bags have lots of holes in them, yet the fibres can also trap seed. So whenever the dilly bags were dropped at the campsite and the contents pulled out, lots of seeds spilled out too.
23.11.13 UPDATE: On14 November 2013 I received a copy of relevant and interesting article from Robert Parsons of the Department of botany at Latrobe University, Melbourne. It was an article of his from The Journal of Arid Environments (1997) 37:453-459, titled, Carpobrotus modestus (Aizoaceae), a post-fire pioneer in semi-arid southern Australia. While the article covers primarily details of how this native Carpobrotus responds well to fire affected land, where it regenerates extensively and then slowly over subsequent years almost disappears from the vicinity. The article logically explains all the reasons for this and also discusses how seed of this plant failed to germinate repeatedly in propagation trials. Robert discusses how fire and heat in habitat broke down dormancy protection in seed. He also found greater germination in animal droppings. This all conclusively supports the theory that the Carpobrotus seed have long survival strategies and a very hard protective coating to last years, on or in the soil, waiting for the right conditions for germination. Therefore water, rain or your propagation trials even with a heat bed might fail. I have had many people contact me to say their seed has failed to germinate. Very useful information indeed!
Interestingly, I can only hypothesize that indigenous people who once prized Carpobrotus fruit, either carried fruit far and wide or inadvertently as 'droppings' also contributed greatly to the plants wide distribution range. This activity rarely occurs now.
13.8.12 - In the latest Cactus and Succulent Society of Australia Journal (August 2012), there is a short 2 page article with colour pictures of two species within the succulent genus Delosperma. Both plants featured have exceptional fire reduction attributes. While many shrubby mesembs like Lampranthus have woody stems and regular dieback, the two Delospema species have these features greatly reduced, and thereby reducing fuel loads of fires. Both delospermas are exceptionally low-growing shrubs that also prevent air from moving freely between stems. Live plants have at least twice the standard water content in each leaf than most shrubby mesembs. For a more detailed report on trials please contact me.
'Survival of Succulents After Fire in South Australia' by Frances and Brian Reay. (British Cactus and Succulent Journal vol 5 (1), 23 -26 (1987). This article details an 11 acre property landscaped with native and exotic succulents near Adelaide that was badly burnt by a severe grassfire. It lists plants that died, plants that scarred and those that died above ground but re-generated from basal shoots or below the ground. One of the most interesting facts was that 'the height of the fire can be estimated by the height of scorching on taller plants, as the scorching extends approximately 6 times the height of the flames' (Noble, I. R. (1986). Fire. Chapter v.2 in The Ecology of the Forests and Woodlands of South australia. Ed. H. R. Wallace. S. A. Government, 291pp.)
There are two other more recent articles below. Please scroll down.
from an Australian Plant Society home gardener and Native wildflower grower’s perspective.
I saw a house in the tall forest near Daylesford a few years ago that as part of their bushfire plan, planted succulents around the outskirts of their house.
Everyone knows that fires will absolutely burn everything, however plants that are full of moisture such as pigface, will not be as flammable as other garden favorites i.e. Lavender and plants with dry matter underneath and throughout the bush. The best approach is not to have a garden close to your house at all, if you can plan it that way and set it back a few metres at least, but for where people like plants nearby, this is an attractive alternative.
My friend told me about her observations about her pigface fence out at Dereel, south of Ballarat.
They were undertaking some fuel reduction burning around their pine tree and burnt some of the pine tree as well.
They used the pigface fence as a radiant heat barrier to shelter behind while observing the burn.
They found that when they stood up, the radiant heat was incredibly uncomfortable, when they ducked behind the 1 metre high pigface covered wire fence, it was cool and bearable. After the fire died down, they inspected the side of the pigface subjected to the worst of the fire and found a mushy gooey mess was left behind, rather than a burnt plant, just a melted one.
The pigface above is Carpobrotus chilensis. This is an exotic species however there are numerous native Carpobrotus that are just as useful. Whilst all members of this genus are usually groundcover plants, when given support they can climb (this picture is not the actual example mentioned in the article, but conveys the same idea).
I am in the process of replacing my garden completely around my house and am keen to plant Maireana and some of the other colourful succulents found native throughout Australia.
I live in a grassland / grassy woodland area, and ember attack would be our main concern. At the moment, we have many flammable plants near the front of the house, with lots of dry litter underneath - a huge hazard to our house.
Coming into autumn, I will replace these plants with a lower growing, moisture storing range of succulents. I am looking forward to the new challenge of colour and the new look of the house, which I believe will enhance it.
I also want to show people i.e. such as APS that Australian succulents may not be everyone’s cup of tea, but you can get some really interesting colours and form that can be just as impressive as an average native plant garden.
If I find anymore interesting case studies of where succulents have been used in fire prone areas in my travels, I will let you know.
Jennifer (an APS gardener)
This new hybrid xDisphyllum 'Sunburn' is a groundcover succulent that is extremely fire resistant. There are some short shrubby succulents that can be a problem, notably the genus Lampranthus, commonly known as Ice Plants or Livingston Daisies for their spectacular spring floral displays. These fast growing succulent shrubs quickly dry and die in a short life cycle of 1-3 years, at varying stages of deterioration they become an increasing fire hazard. Even plants that haven't died and totally dried out can still burn in hot conditions. Lampranthus are very popular and versatile and used widely around the world but in their drying state can almost explode in a fire. Embers fly some distance in the roar of a single plant going up - tested and recorded numerous times on 23.2.12. xDisphyllum 'Sunburn' grows closer to the ground in a tight compact growth habit, and has leaves and stems many times more succulent than Lampranthus.
Interestingly many mesembs similar to Lampranthus have leaves which are detachable. Leaves that detach easily whether dead or alive, are the most likely to contribute to the hazard of a fire spreading further. So in fact while many inexperienced gardners may be advised to plant succulents, a word of caution - even experienced and highly educated experts have been caught out with this point before. xDisphyllum 'Sunburn' has leaves that do not detach readily and likely to 'dissolve into jelly' rather than contribute to ember strike (ember strike is when small burning pieces of organic matter are swept up in the wind and spread the fire much further).
NEWS update: 17.7.12 - Testing a range of native plants and succulents in a fire. While this is not a definitive scientific experiment, I wanted to see how certain plants behaved when thrown into a burning hot fire. Enchylaena tomentosa - I have many plants growing, some surplus to my needs which were then thrown on the fire. They ignited slowly and didn't seem to have explosive resins within. Parts of plants that were more succulent persisted without ignition and just 'melted' away. This could indicate that this species has a low combustibility. I've taken time lapse photographs of this 'experiment' which was then repeated several times.
I have always been aware that the plant family Chenopodaceae (which includes Enchylaena)has members which have high levels of salt which can impede combustion of plants duriing fire. My fire was red hot coals and flames to a metre in 30 km winds when I did my trials. Could enchylaena be of benefit to gardeners who use native plants or live in fire risk areas?
18.7.12 - I've just been informed that the Arid Lands Botanic Gardens in South Australia has a huge sign with part of the text reading, '.....many Chenopods also possess fire retardant properties because of the high salt content of their sap and are useful as borders around highways, parks, and gardens in fire-prone areas'.
Also Enchylaena produce edible fruit for much of the year that is sought after by our native animals and birds.
It may be interesting to note that most Chenopods are grazed heavily by livestock and the plant family has had most of the highly palatable species eradicated due to overgrazing, which then allows ground spacings for introduced grasses and other more combustible plants. For much of the last century farmers and graziers had removed the sparse native vegeation and replaced it with more vigorous taller growing grasses - these add considerably to the fire's fuel load and burn more readily.