Sheunesu Ruwanza

Current research

My research interests are invasive alien plants and restoration practises in degraded environments. My interests in invasion and restoration ecology were stimulated by the restoration studies that I conducted during my time at SANBI. Therefore the core issues of this PhD are the management and control of Eucalyptus species along the Berg River as well as the recovery and restoration of fynbos riparian species.

To address these issues I will adopt a novel approach in restoration ecology applying alternative ecosystem state models. Models of alternative ecosystem states incorporate systems thresholds and feedbacks and suggest ways in which restoration can identify, prioritise and meet constraints.

Invaded ecosystems move between alternative ecosystem states. To classify different ecosystem states in the Berg River region, which is heavily invaded by eucalypts, I will investigate invaded sites compared to previously cleared sites. Furthermore I will test a combination of treatments including clearing and active restoration. Clearing will entail fell and removal, and fell and burn, whilst active restoration will involve the broadcast-sowing and cuttings of native species. The success of these treatments will result in a healthy river system that fulfils various important ecological functions including both use and non-use values. Constraints for restoration after Eucalyptus invasion i.e. allelopathy and low water resources which are both known to inhibit re-growth of natural vegetation, will also be tested with the view of understanding how Eucalyptus out-competes native plant species. Results of the two studies on constraints will help to advise restoration managers on which native species can better out-compete the invaders, and thus provide guidelines for their most effective active restoration treatment. This PhD hopes to identify the most effective clearing strategy which leads to suppression of Eucalyptus re-invasion while at the same time initiating the recovery of native riparian vegetation structure, diversity and composition. Lastly I hope to develop simple management and restoration plans that can be used for clearing and restoring riparian systems.

Previous research topics