Now for the third instalment of The Fire Regime Delivery Truck. Old-mate Koala has his box of matches, he’s got Jimi cranked up to eleven, and this time he’s heading north to look at some real sensitive trees…..
Callitris intratropica to be precise – Arnham cypress pine. So let’s head to Australia’s tropical savannas – a very flammable landscape – and let’s see what this very very fire-sensitive species can tell us about how fire regimes have changed in this landscape.
Now this species is in a little bit of strife, and we think its decline is due to a shift in the fire regime – from patchy mosaic burning to large unmanaged wildfires.
By looking at the population dynamics of this species, Clay and his colleagues were testing the hypothesis that population stability of Callitris depends upon a regime of frequent, low-intensity fires maintained by Aboriginal management.
Now this crew did the lot – demographic surveys of a large study area, analysed vital (growth, survival, etc.) rates, modelled population behaviour, modelled patch dynamics relative to fire, combined that with condition of Callitris grove, and predicted change under different fire scenarios….. So after all that, did they find support for their hypothesis?
Yep. Put most simply, closed-canopy groves of Callitris were essentially where all recruitment (population growth) was taking place. Degraded groves and singleton trees were where all the mortality was occurring. So population persistence and growth is all dependent on the ability of these closed-canopy groves to exclude fire.
Under current fire conditions (repeated high-intensity unmanaged wildfires) this is not going to happen and the models predicted significant declines if this was to continue. However, under an Aboriginal managed, low-intensity patchy fire regime, Callitris persistence and growth is a go!
For the actual science of this story, you should definitely read the paper and contact the authors if you have any questions.
Trauernicht C, Murphy BP, Prior LD, Lawes MJ & Bowman DMJS (2016) Human-imposed, fine-grained patch burning explains the population stability of a fire-sensitive conifer in a frequently burnt northern Australian savanna. Ecosystems DOI:10.1007/s10021-016-9973-2 [early view]
K!E#21 by Luke S. O’Loughlin