The Botany of Bushfires

Australia is going through a severe heatwave at the moment. So severe that the Australia’s Bureau of Meteorology has added two new colours to their temperature scale for forecasts. Along with the record heat, there are a number of large out of control fires that are wreaking devastation across parts of Australia.

[youtube http://www.youtube.com/watch?v=U-jLXrrr4gY&w=500 ]

The Bushfire Cooperative Research Centre is trying to understand more about how bushfires work and how the environment responds to them. With sadly appropriate timing their recent research paper, Relationship between leaf traits and fire-response strategies in shrub species of a mountainous region of south-eastern Australia has just become a free access paper at Annals of Botany.

The idea of fire response by plants might seem a bit odd. Surely their response is they either burn or they don’t? In fact a freshly burned area is an ecological niche that plants can exploit. For some plants in hot and dry regions it’s simply a matter of time before they burn. This means that the ones best equipped to recover after the fire have a reproductive advantage.

Varying fire-response strategies and co-occurring traits
Part of the SE Australia region studied by Vivian and Cary.
There are four categories of response for a plant. Two are obligate seeders and obligate sprouters. Obligate seeders respond to fires by dying. This is not a survival strategy for the plant, but it is for the species. Before the fire, the plant puts a its resources into producing seeds. When the fire comes the plants die, but the seeds can be triggered to germinate. They take advantage of the newly cleared landscape to spread.

Obligate sprouters are different. They put resources into creating buds and a strong root system. After the fire the plant is able to shoot again from this new buds and take immediate advantage of the cleared area.

There are facultative sprouters, which can both sprout and grow from seed after fire. The final response type is fire intolerance. These plants simply die.

Lyndsey Vivian and Geoffrey Cary have been investigating to see how these different strategies affect the plants. What they’ve found is that Australian plants are different to other known plants, and the relationship between leaves and fire-response is more complex than simple correlations between environment and response.

It’s not a convenient finding, but it’s an important one. By discovering that there is within-species variation in plant, the Bushfire CRC is helping build maps with much richer information. It means firefighters can prioritise their resources much more effectively. If the death toll from the fires remains low then it’ll be partly due to botanists giving firefighters information so they’re not wasting their efforts and ignoring danger areas.

The Bushfire CRC has a lot of outreach material that you can find from their website at http://www.bushfirecrc.com. You can read Relationship between leaf traits and fire-response strategies in shrub species of a mountainous region of south-eastern Australia by Lyndsey Vivian and Geoffrey Cary at http://dx.doi.org/10.1093/aob/mcr263 for free.