Plant ecology's guilty little secret: understanding the dynamics of plant competition

1.Plant competition has been studied for decades. Yet, it is still an elusive concept that means different things to different people, is resistant to direct study and is shrouded in semantic and statistical complexity. We still lack basic information about many competitive mechanisms, processes and outcomes and their relationship to other ecological processes, and about how local interactions between individuals are propagated through communities. We suggest here that two critical issues have been overlooked in previous studies.
2.First, there is a need for direct measurements of the process of competition as opposed to indirect mechanisms of competitive outcomes. Biomass has become the ‘industry standard’ for measuring competition, but we suggest that biomass cannot provide unambiguous insights into plant competition because it is the product of too great a range of factors and processes.
3.Second, the use of a single measure of competition at an arbitrarily assigned end point of an experiment misses much of the complexity of dynamic interactions between competing plants and can lead to erroneous interpretations. Here, we suggest approaches to handle these difficulties, using new techniques or the application of well-known methods in a novel way. We also provide examples of systems or questions where the improved understanding these approaches could bring would be of particular benefit.
4.Ultimately, we suggest the need for a major shift in the way in which we consider and measure plant competition to identify broadly agreed rules for variation in its importance, its role in different communities and habitats, and how and whether it influences or drives patterns of species diversity and abundance.