The Editors of the Journal of Ecology are pleased to honour Professor Mark Westoby in our continuing Eminent Ecologist virtual issue series. The virtual issue is available on the Journal of Ecology website.
Assistant Editor, Journal of Ecology
Watson, I.W., M. Westoby and A. McR. Holm. 1997b. Continuous and episodic components of demographic change in arid zone shrubs: models of two Eremophila species from Western Australia compared with published data from other species. Journal of Ecology 85: 833-846.
Vesk, P.A. and Westoby, M. 2004. Sprouting ability across diverse disturbances and vegetation types worldwide. Journal of Ecology 92:310-320
During my PhD I had been a research assistant in the US/IBP Desert Biome programme. From that program there developed a “pulse-reserve paradigm” (Noy-Meir 1973) for arid ecosystems. This emphasized the importance of episodic events rather than continuous balance between recruitment and mortality. Through the 1970s and 1980s the idea that ecosystems were heavily driven by episodic events and disturbances became a new orthodoxy (and this was a trend across ecology as a whole, not just for arid zones). Many anecdotes were available about mass recruitment in exceptional years giving rise to even-aged stands.
Ian Watson came to our lab from Western Australia Dept of Agriculture (WADA), bringing with him long-term plot data from the WA Rangelands Monitoring Scheme. Measurements in these data runs were yearly, and they spanned a serious drought and a year of exceptional rainfall, as well as more commonplace years. This made possible a serious quantification of the extent to which for recruitment and mortality were actually concentrated into episodes vs occurring continuously year to year (Watson, Westoby & Holm 1997a; b). The second of these papers also gathered together literature data to the extent possible. As might perhaps have been expected, both episodic and continuous processes were influential. For Eremophila for example, 50-70% of all recruitment was concentrated into high-recruitment years, meaning that 30-50% occurred more continuously.
Peter Vesk switched from his MSc in microscopy and freshwater biology in order to undertake a PhD with us on dynamics of terrestrial vegetation. He focused on resprouting or vegetative regeneration, especially after grazing and fire. He published a variety of papers from field experiments and data syntheses. Vesk and Westoby (2004) looked at percentages of individuals that resprouted following different types of damage in different settings. Plant species response to stem-killing fire was indeed dichotomous – as implied by the widely-used distinction between resprouters and obligate-seeders – but the most common outcomes were not at 100% and 0% of individuals surviving fire, but at 79% and 13%. Response to other types of damage such as windthrow were more of a continuum. It’s a continuing problem for plant growth models to deal satisfactorily with damage that falls short of mortality.
After completing his PhD, Ian Watson went back to WADA initially. Later he moved to CSIRO, where he is currently leader of their Tropical Landscapes Joint Venture (joint with James Cook U in Townsville). He says his main claim to fame is that son Jay plays synth with Tame Impala. Peter Vesk is now an Assoc Prof at U Melbourne, with focus on landscape reconstruction and environmental decisions, and a member of the J Ecol Editorial Board. David Eldridge (Eldridge, Westoby & Holbrook 1991) is a researcher in soil conservation and arid zone ecology with NSW Office of Environment and Heritage and is also honorary faculty at University of New South Wales.
Prof. Mark Westoby