Sunday, 4 August 2013

Students completing in 2013

Changes in the stand dynamics and composition of a long-unburned coastal woodland - effects of drought, fire and herbivory

My honours research assessed changes in vegetation structure and composition in a woodland at Ocean Grove, Victoria using data from three points in time (1971, 1996, 2012). Previous assessments of the site had documented the replacement of Eucalyptus with the mid-storey species Black She-Oak in the long absence of fire. In my study, changes in the continued absence of fire were assessed, as well as whether these changes could be reversed with the re-introduction of fire.
Long-unburned coastal grassy woodland at Ocean Grove Nature Reserve
I identified that in the continued absence of fire, Black She-Oak had consolidated dominance, with declines in tree density compensated for through an increase in basal area, while all other trees, as well as small shrubs in the understorey, declined markedly.  Where fire had been re-introduced, the structure of the woodland had opened up, creating large canopy gaps and killing many Black She-Oak trees. Surprisingly, trees did not recruit in open areas created by fire, most likely a consequence of wallaby browsing. Small shrubs that had declined in the absence of fire failed to recover with the re-introduction of fire, nor were these species found in the germinable soil seed bank. Changes that did occur with the re-introduction of fire were largely characterised by the proliferation of grass cover.
Burnt coastal woodland at Ocean Grove Nature Reserve. While the canopy has
opened up, fire did not recover once common native shrubs.
Thus, the changes that had occurred in the long absence of fire were found to be non-reversible with the re-introduction of fire.