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Invasion and Restoration: The Yin and Yang of Ecology

Mediterranean-type environments are famous for their geophyte diversity but what intrigued Prof. Karen Esler (C·I·B core team member) on a recent visit to Western Australia was to see just how many native South African species have become successful invaders there. Species such as Hesperantha falcata, Babiana stricta, B. disticha, Ornithogalum thyrsoides, Ferraria crispa, Watsonia bulbillifera (amongst others) are a common sight in spring and in many places. They are so competitive that the native flora (including indigenous orchids) is threatened. The irony is that while we in South Africa conduct detailed experiments trying to “reconstruct” or restore our native flora including our geophyte diversity, similar types of experiments are being conducted by Prof. William Stock, (Director, Centre for Ecosystem Management, Edith Cowan University), colleagues and students in Western Australia in an attempt to reduce the competitive upper hand of South African geophytes.

On both continents, researchers are concerned with how geophyte communities are assembled, disassembled and reassembled. The tools and their uses are essentially the same – manipulating biomass and flowering times using or excluding herbivory, mowing, herbicides or fire. This is a good example of how invasion and restoration might be interpreted as the yin and yang of ecology – insights from both may lead us to a greater understanding of the processes that architect communities.

Above: Experiments using herbivory exclusion (mostly Kangaroos) and fire attempt to control Romulea rosea and Morea flacida (Irdidaceae) by stimulating mast flowering. These South African geophytes are weeds in degraded Eucalypt woodlands of Western Australia . Pictured here are Prof William Stock (right) and Dr Tony Verboom, UCT Botany (left). [Photo: Karen Esler ]

Above: The sweet smelling hybrid Freesia alba x leichtlinii can establish itself in dense populations of natural bushland in western Australia . In the background are indigenous grass trees – Xanthorrhoea preissii (Xanthorrhoeaceae)