Fire does not stimulate flowering of the grasstree Xanthorrhoea latifolia subsp. latifolia in central Queensland

Many species of grasstree, genus Xanthorrhoea, flower profusely after fire, but little is known about responses to fire by northern Australian species. After noticing flowering in an unburnt population of Xanthorrhoea latifolia (A.Lee) Bedford subsp. latifolia in central Queensland, we tested the hypotheses that (1) X. latifolia latifolia flowers annually in the absence of fire and (2) fire has no effect on the percentage flowering. Flowering in the absence of fire consistently occurred every February-April (late summer-autumn) from 2006 to 2008. A manipulative experiment with two treatments, namely (1) burnt in spring 2009 and (2) an unburnt control, showed that the percentage flowering did not differ significantly between treatments in 2009 (before the experimental treatment was burnt) or from 2010 to 2012. There was a significant negative correlation between the percentage flowering and rainfall before each flowering season. This population may be extremely resilient to fire. Flowering occurred with or without fire, plants resprouted after fire and mortality in the burnt treatment was 2.75%. Our findings emphasise that every species within a 'fire-dependent' or 'fire-tolerant' genus cannot be assumed to respond in the same way to fire; some may require fire management at the population level.