Charles Darwin University

CDU eSpace
Institutional Repository

 
CDU Staff and Student only
 

Assessing the invasiveness of Calotropis procera (Aiton) W.T. Aiton in northern Australia

Menge, Enock Ondeyo (2017). Assessing the invasiveness of Calotropis procera (Aiton) W.T. Aiton in northern Australia. Doctor of Philosophy Thesis, Charles Darwin University.

Document type: Thesis
Citation counts: Google Scholar Search Google Scholar
Attached Files (Some files may be inaccessible until you login with your CDU eSpace credentials)
Name Description MIMEType Size Downloads
Download this reading Thesis_CDU_61441_Menge_E.pdf PDF version generated by student application/pdf 8.09MB 12
Reading the attached file works best in Firefox, Chrome and IE 9 or later.

Author Menge, Enock Ondeyo
Title Assessing the invasiveness of Calotropis procera (Aiton) W.T. Aiton in northern Australia
Institution Charles Darwin University
Publication Date 2017-02
Thesis Type Doctor of Philosophy
Supervisor Bellairs, Sean M.
Subjects ENVIRONMENTAL SCIENCES
Abstract Rubber bush (Calotropis procera) was recognised during industry and expert weed prioritisation processes as an important economic and environmental weed in northern Australia. It establishes at high densities hindering pastoral management and reducing range productivity. It is estimated to infest 1.8-3. 7 million hectares of northern Australia, however, the drivers of its spread are not well known. This thesis documents various aspects of its reproductive biology and ecology, seed ecology, competitiveness and distribution in Australia; and how these attributes contribute to its invasiveness. A combination of greenhouse, field, laboratory, observational and computer simulation studies, covering the competitive ability, reproductive biology and ecology, seed ecology and species habitat modeling were performed at multiple locations in the Northern Territory and Queensland over three and a half years. This work addressed the question whether rubber bush invasions are a symptom of rangeland management practices or a consequence of natural biological interactions with native species. The results demonstrated that rubber bush is not a strong competitor of native grasses and its invasion is dependent on anthropogenic disturbance. The spread of rubber bush is facilitated by a self-compatible breeding system and an ability to recruit new pollinators during range expansion. Additionally, it exerts considerable propagule pressure through prolific wind-dispersed and highly germinable seeds in Australia compared to native environments. The seeds are quiescent under unfavourable temperature conditions but germinate rapidly when conditions improve. Species habitat modeling showed that it has not saturated the current suitable area, and its suitable area will expand under future climate scenarios. These abilities combine with ruderality to make rubber bush a high risk weed in northern Australia. Nevertheless, because feasibility of control is low, targeted control and protection of priority areas is recommended. Given the important role of disturbance in the spread of rubber bush, careful management of disturbance regimes on rangelands is necessary to limit the spread of rubber bush across northern Australia. For greater effectiveness, it is recommended that policy frameworks regarding the management of rubber bush be harmonised across affected Australian States and Territories.
Additional Notes Please note that articles in this thesis have been removed due to copyright restrictions.


© copyright

Every reasonable effort has been made to ensure that permission has been obtained for items included in CDU eSpace. If you believe that your rights have been infringed by this repository, please contact digitisation@cdu.edu.au.

 
Versions
Version Filter Type
Access Statistics: 22 Abstract Views, 12 File Downloads  -  Detailed Statistics
Created: Fri, 06 Apr 2018, 09:13:46 CST by Jessie Ng