XVI International Botanical Congess

Removing the outer layer of charcoal from the persistent leafbases of grasstrees reveals alternating cream and orange-brown bands corresponding to annual growth increments, and occasional black bands corresponding to fires. We hypothesised that the leafbases would store nutrients at levels corresponding to the conditions under which they were deposited up to 250 years ago. The levels of Ca, S, B, Mg, Cu, Fe and Mn varied seasonally. Fires resulted in a marked increase in levels of Ca, K, Mg, Mn, Zn, S, Cu and Zn, though leaching caused a return to base levels after the most recent fires for some highly soluble nutrients such as K. The technique shows promise of not only serving to provide accurate ages of grasstrees but also their fire history and the effects of season and fire on nutrient uptake patterns. The usefulness of the results depends on what part of the leafbase is examined and the solubility of the nutrient analysed. There is great scope for stable isotope analyses as well.