Arid areas are often overgrazed and dysfunctional with poor recruitment of desirable species, diminished control over resources and altered soil properties. Restoration ecology re-establishes these valued processes. State-and-transition models summarise knowledge of vegetation dynamics and tools for restoration, and encourage the incorporation of new information. The model developed here for semi-arid woodlands of north-west Victoria highlighted the unknown cause of observed, natural recruitment and the need for a technique, other than direct seeding and handplanting, for enhancing the recruitment of desirable species. I pursued these knowledge gaps for two dominant, woodland trees: Allocasuarina luehmannii and Casuarina pauper. Natural recruitment of juvenile C. pauper was found to be limited and primarily from root suckers. Extensive recruitment of A. luehmannii was shown to be mostly seedlings established following substantial reductions in grazing pressure since 1996. Seedlings were associated with areas devoid of ground flora near a female tree. The importance of competition between seedlings and ground flora, spatial variation in soil moisture and individual variation in the quantity of seed produced deserves further investigation to enhance future restoration success. Root suckers of both C. pauper and A. luehmannii can be artificially initiated, albeit in low numbers and this was found to be a feasible, new tool for restoration. Suckers are preceded by the growth of callus tissue on exposed or damaged, living, shallow roots. Both male and female trees can produce suckers and spring treatments may be more successful. Genetic fingerprinting of mature A. luehmannii and C. pauper trees in six populations did not identify any clonal individuals indicating that recruitment in the past has been from seedlings. Despite this, the high level of gene flow suggests that the impact of introducing small numbers of root suckers into existing populations is unlikely to impact negatively on the population genetics of these species. / Doctor of Philosophy
| Identifer | oai:union.ndltd.org:ADTP/266077 |
| Date | January 2005 |
| Creators | Murdoch, Fiona |
| Publisher | University of Ballarat |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
| Rights | Copyright Fiona Alys Murdoch |
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