Date of Award

2004

Document Type

Thesis

Publisher

Edith Cowan University

Degree Name

Bachelor of Science Honours

Faculty

Faculty of Computing, Health and Science

First Supervisor

Dr Marcelle Buist

Second Supervisor

Dr Eddie van Etten

Abstract

Bold Park is a 437 hectare A class reserve with high conservation value. Bold park is located on the Swan Coastal Plain, approximately 11 km west of the Perth CBD. Bold park is one of the few remaining coastal bushland reserves on the Swan Coastal Plain. High levels of floristic and faunal diversity contribute to Bold Park's conservation value. Weed invasion in Bold Park is reducing floristic diversity and is modifying ecosystem processes. Principle in the modified ecosystem processes is fire. While fire is a natural disturbance event in the bushland of the south-west of Western Australia, altered fire regimes can lead to weed invasion. Fire events are important for the maintenance of the floristic diversity of bushland areas. Fire events also provide an opportunity for weed management activities to be implemented. A fire in December 2000 burnt over one third of the bushland area in Bold Park. This provided managers from the Botanic Gardens and Parks Authority with the opportunity to implement weed control activities. Three approaches to weed management were undertaken within the 2000 burn site. They are: 1. No management; 2. Control of the invasive weed Pelargonium capitatum with the broadleaf herbicides Aimtm and Rounduptm; and 3. Control of the invasive grass Ehrharta calycina with the grass-specific herbicide Fusiladetm, along with the two broadleaf herbicides. To determine whether the weed spraying was successful, vegetation surveys were undertaken in the treatment areas of the 2000 burn site to investigate floristic differences. Significant reductions in weed species cover were detected in sites receiving both types of herbicides. Native species richness was highest in sites in receiving some form of weed control. However, this was accompanied by an increase in the richness of weed species. There was a significant difference in the cover of P. capitatum and E. calycina in relation to weed control measures. Where Fusilade was used; the cover of E. calycina was significantly lower than areas not sprayed with the herbicide. Where Aim and Roundup were used; there was a significant reduction in the cover of P. capitatum. Weed control measures were also linked to increases in the diversity, abundance and survival of native species recruits. A second study provided supplementary information on weed management by investigating the germination ecology of three weed species, E. calycina, P. capitatum and Euphorbia terracina. The seeds of these species all fit broad generalisations about weed seeds. They all have high levels of viability, easily overcome dormancy mechanisms and high levels of germination. The results obtained in this research indicate that post-fire weed control had immediate and significant effects in the Bold Park bushland. The long-term benefits of effective weed control would be a continued reduction in weed cover in the 2000 burn site. This reduction would enhance native species recruitment, leading to improvements in the floristic and vegetative community structure. The potential for future fire events would be reduced due to the lower E. calycina cover, a sound reason for expanding management of this species. Finally, the germination ecology of the weeds studied enhances the understanding of the invasive capacity of these species.

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