DES Seminar by Valerie Densmore (PhD Candidate)

7 March 2014

Mechanisms underlying the patchy regeneration of woody legumes following bushfire


Woody legumes, such as Acacia spp. are found in almost every terrestrial ecosystem in Australia. Many species are able to fix atmospheric nitrogen (N), and higher phosphatase concentrations are often associated with their rhizospheres. These characteristics may indicate the potential of woody legumes to 'restore' soil N and 'remobilise' soil phosphorus (P) following bushfire, because many species often display rapid and widespread germination following moderate- to high-intensity bushfires. However, densities of regenerating populations typically vary several orders of magnitude over small distances, producing patchy distributions that are currently unpredictable. Moreover, some ecosystems recruit woody legume species without fire. The aim of this thesis was first to characterise soil properties and climate and geographic factors that significantly influence the densities of woody legumes following bushfire. Six representative species of woody legumes that germinated following the 2009 'Black Saturday' fires in Victoria were identified growing at two to three densities. Soil samples were collected, and ArcGIS was used to analyse topographic features before ordinal logistic regression was used to analyse edaphic and geographic variables. The best predictive model selected using discriminant analysis indicated factors that indicate fire severity and the availability of P. On the basis of this finding, fine roots were collected from field species and also following a glasshouse study varying P concentrations. PCR was then used to investigate whether these woody legume species possessed and expressed genes to increase available P. In addition, optimal temperatures to germinate species from different climate zones were compared. This study helps elucidate mechanisms underlying distributions of woody legumes following bushfire or other disturbances and may support land management decisions, particularly concerning hazard-reduction burns.

All welcome to attend

Time: 4-5PM

Location: Room 422, Biomedical Building (C81) ATP

Contact: Dr Uta Stockmann

Phone: 02 8627 1147

Email: 421b087629202a2505032e013e15070b0d2f354c5f5253136b513c