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Bushfire 2016

The chemical signature of fire regime: implications for plant growth and nutrient demand

During his PhD studies, Orpheus Butler (pictured below during his field studies)  resolved to understand how fire regimes affect the levels of nutrients (nitrogen, phosphorus, etc.) in soil, and how these effects in turn influence the growth, chemistry, nutrient demands of plants. 

Orpheus found that fire consistently increases the levels of phosphorus (P) relative to nitrogen (N) and carbon in topsoil and leaf litter . This effect was consistent across a range of ecosystems around the world but is of particular significance in Australia, where many soils have very low levels of P. 

Image: Long term prescribed burning sites at Peachester in SEQ used for part of Orpheus studies. 

Then, Orpheus tested whether fire regime-induced changes in soil nutrient levels affect the growth and nutrient demand of Eucalyptus pilularis (Blackbutt) seedlings . To do so, he used soils from the long-term prescribed burning trial at Peachester in south-east Queensland. Levels of soil nutrients varied significantly among the biennially-burned, quadrennially-burned and long-unburned plots at Peachester. In particular, levels of N relative to P (i.e. N:P ratios) in soil were 43% lower in the biennially-burned plots compared to the long-unburned plots. However, this had no effect on E. pilularis growth rates. Further, E. pilularis growth tended to be enhanced by phosphorus fertilizer, but was never stimulated by nitrogen fertilizer, regardless of the soil’s history of fire exposure. These findings show that E. pilularis grows under a persistent state of ‘P-limitation’. This could offer a competitive advantage where levels of soil plant-available P are briefly enhanced (e.g. in ash-beds) or where levels of soil N are depleted (e.g. in frequently burned areas). 
Orpheus was based at Griffith University during his PhD and was a recipient of the SE Queensland Fire & Biodiversity Consortium student scholarship.

Papers related to Orpheus's work: 

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