How do plant community ecologists consider the complementarity of observational, experimental and theoretical approaches?

Background and aims - A large variety of methods are used by ecologists for studies at plant community level. While early works were mainly descriptive, more manipulative experiments are now being undertaken because they provide a better functional understanding and a greater insight into underlying mechanisms. Mathematical models are also being increasingly used, in particular for predicting biodiversity under global change. The aim of this study is to highlight the strengths, limitations, and advantages of these three approaches, namely observational, experimental and theoretical modelling. Methods - We assessed 149 papers published during the last four years in three specialized disciplinary journals (DJ) and 151 papers in three generalist high impact journals (HIJ) dealing with plant ecology, and checked the methods that were used. We asked participants of the ECOVEG7 meeting held in Switzerland (Lausanne, April 2011) whether observational, experimental and theoretical modelling approaches can, or should, be used alone or in combination when studying plant communities and ecosystem functioning in the context of global change. Key results - About 50% of articles published in both journal types used only a single approach. Nevertheless, papers in HIJ used the approaches in similar proportions, while articles in DJ had eight times more observational than modelling studies. Combined approaches represented only 8% in DJ, while this percentage was more than double in HIJ. Conclusion - Plant community ecologists favour a combination of several approaches, but for practical difficulties (communicating among people using different approaches and publication strategies), singleapproach studies are generally preferred. A combination of the three highlighted approaches seems to be the most appropriate way to respond to future challenges in plant community ecology such as biodiversity loss and impact of climate change as such studies require work on different temporal and spatial scales.