Abstract
Competition is ubiquitous in plant communities with various effects on plant fitness and community structure. A long‐standing debate about different approaches to explain competition is the controversy between David Tilman and Philip Grime. Grime stated that the importance of competition relative to the impact of the environment increases along a productivity gradient, while Tilman argued that the intensity of competition is independent of productivity. To revisit this controversy, we assumed that the effects of plant–plant interactions are additive and applied the new competition indices by Díaz‐Sierra et al. (2017) in a field experiment along a productivity gradient in S‐Germany, using the rare arable plant Arnoseris minima as a study species. The ‘target technique' was applied, to separate the effects of root and shoot competition. The study plants were exposed to five competition treatments with three replicates in 18 sites, respectively. We investigated the expectation that root competition is more intense in unproductive sites than shoot competition. Additionally, we predicted survival to be less affected by competition than growth‐related plant parameters. Using the biomass of individuals without competition as a proxy for site productivity there was a positive relationship with competition importance but no relationship with competition intensity when plants experienced full competition. Survival of the target plants was unaffected by competition. Root competition was the main mechanism determining the performance of the target plants, whereas the effect of shoot competition was relatively low albeit increasing with productivity. We conclude that when considering plant–plant interactions additive both Grime's and Tilman's theories can be supported.
Highlights
Competition is a common phenomenon in plant communities with well-known effects on plant fitness and community structure (Aschehoug et al 2016)
Competition importance (NImpA), only differed between treatments with and without root competition, being significantly lower in absolute values for the shoot competition treatment compared to full, root and reduced competition (Table 1); for mean values per site see Supporting information
Using the rare arable plant species Arnoseris minima, we addressed fundamental principles of competition along a productivity gradient
Summary
Competition is a common phenomenon in plant communities with well-known effects on plant fitness and community structure (Aschehoug et al 2016). The significance of competition was already described by Darwin (1859), and empirical studies on this phenomenon date back to the rise of modern ecology (Clements 1929). Various experimental and modelling approaches have been performed to better understand the patterns and mechanisms of plant competition, among them some classic controversies between contrasting theories and the scientists behind them (Grace 1990). Many ecologists would define competition as ‘the process by which two or more individuals acquire resources from a potentially common, limiting supply’ (Craine et al 2013). The main resources plants compete for are water, nutrients and light
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
