Above: White trunks of fire-adapted Mountain Ash from Otway National Park (left). Banksia pods in the Blue Mountains near Katoomba (right).

Looking around the charred remains of the landscape, while we wait for a ranger to arrive to confirm the whether the road to our study site is/is not closed, I am reminded that not all animals are made equal when is comes to escaping a fire. For example, what chance does a land-snail have? No legs, no wings, no burrow, no-where to go.

Above: the shells of native land snails litter the ground after a small grass fire has passed through Davies Creek National Park

Snails and other leaf-litter dwelling critters provide crucial ecosystem services, reincorporating carbon from leaf litter into the soil. Perhaps the best adaptation these animals have to cope with fire is to be most active when fire is least likely to occur: in winter or in the wet season (depending where you live in Australia). Microbes are among the list of critters integral to soils and soil function that are not going to be fleeing from fire. Whilst lower reaches of the soil may be buffered from the impact of burning, big fires, like the Black Saturday fires that decimated Marysville and King Lake in Victoria in 2009 burnt so hot that PVC piping buried 1 m below the ground, was found melted. Not much could have survived that. So how are soils recolonised after fire? Where does the new generation of microbes and other soil-dwelling critters come from? How long does it take to rebuild these communities?.

Above: Images King Lake National Park landscape recovering from the 2009 bush fires, taken in 2012

Studies on this question may be particularly important when thinking about fuel-reduction burning which typically occurs in winter when the ground is damp. While this is to be sure a safest time to burn-off leaf litter and ensure the fire will remain under control, this is also the time of year that soil microbes – and all the other soil-dwelling critters – are most active. So how is a soil community that gets burnt during summer, when insects and microbes have effectively shut up shop for the year, impacted by fire and is it different from how communities react to being brunt when they are in full swing, defenses down, during the wet? I suspect it matters a lot.

Rainforest soils provide and interesting tangent upon which to take these musings. Rainforests are not meant to burn. In fact, they are notoriously resistant to fire. But as the climate changes some rainforests are becoming dryer (others will become wetter) and they are starting to burn. This year fire brunt 440 ha of sub-tropical rainforest in Lamington national park. There are multiple lines of evidence to suggest that soil microbes have an important role to play in creating the impressive levels of diversity seen in rainforest plant communities. We don’t know exactly which microbes or microbial functions are key to creating plant diversity, but we do know that diversity plant-microbe interactions occur among seedling and small saplings (Green et al. 2014). Given that the entire ecosystem is not fire adapted, it seems likely (to me at least) that the microbes that carry out these processes will not be adapted to fire either. So when a rainforest burns, and it comes time for plants to regenerate and recolonize the space, will the diversity return to the rainforest or will disrupting processes in the soil have profound flow-on effects for the whole ecosystem? We’re optimistic that the research we are here to conduct will in part begin answering this very question. We’ll be looking at how drought impacts microbial soil-function and whether this has flow-on effects for plant-microbe interactions that govern rainforest diversity. Provided, of course, we are able to access our site.

A quick sat-phone call to the local ranger confirms that the road is indeed closed for today due to fire, but we’ll be right tomorrow to access our site. Have a day off.