Positive interactions between plants are commonly termed ‘facilitation’. The concept of facilitation is not new (Went 1942 ), but since Bertness & Callaway ( 1994 ) proposed that facilitation and competition shift in relative frequency with stress, i.e. the stress‐gradient hypothesis (SGH), incorporation and innovations in the theory of facilitation have been extensive and rapid (McIntire & Fajardo 2014 ; Bulleri et al. 2016 ). Nonetheless, there are some pitfalls or gaps in our capacity to use these innovations. There are at least three practical opportunities to more effectively advance and promote application of facilitation by avoiding each pitfall. (1) Detection of facilitation in a high‐stress ecosystem does not necessarily support the SGH per se but does suggest that facilitation is present, even in harsh ecosystems (Michalet et al. 2014 ). (2) Facilitation in a system does not necessarily preclude concurrent competition (Holmgren & Scheffer 2010 ; Sheley & James 2014 ). And, (3) context – including species specificity – matters (Chamberlain et al. 2014 ). Collectively, these opportunities can be best described as a ‘Fix‐it Felix’ effect. Fix‐it Felix was a fictional character in the movie ‘Wreck It Ralph’ wherein this character can only fix things, regardless of the context. Conversely, the other main character, Ralph, can only wreck things. Fix‐it Felix is good, and Ralph is bad. Felix can only fix things within the game (in the movie), and Ralph can only wreck. So, similar to the facilitation literature and maybe plant ecology at large at times, it is convenient but not correct to assume that a species does only one thing all the time . The above opportunities illuminate the limitation of undue simplifications and binary assumptions on the role of facilitation (and competition). There is an opportunity to design better experiments and empirically test for a Fix‐it Felix effect, i.e. does facilitation always promote ‘better’ outcomes or are there gradients, net interactions (positive and negative) and contexts that mediate the outcome? In applied vegetation science, two critical, global issues benefit from this contemporary facilitation framework – invasion by non‐native species (Badano et al. 2015 ; Barney 2016 ) and restoration ecology (Gomez‐Aparicio et al. 2004 ; Noumi et al. 2015 ; Badano et al. 2016 ). Rydgren et al. ( 2017 ), in this issue of Applied Vegetation Science , explore all dimensions of the Fix‐it Felix effect perfectly, highlighting a modern facilitation perspective by empirically incorporating plant facilitation as a restoration tool.

Application of theory

Rydgren et al. (2017) clearly examine the role that net interactions, competition and facilitation play in mediating the outcome of restoration in a high‐stress, arctic‐alpine ecosystem. The experimental design is fully randomized and orthogonal testing mixture/monoculture by substrate type both in the field and in a greenhouse via seed addition for three different species common to the region. This design is novel because it explores facilitation in the context of mixtures vs monocultures without using a nurse plant model. This design clearly embodies a modern and necessary view of applied facilitation using an expanded toolbox (Lortie et al. 2016). Active restoration vs passive recovery is likely needed in high‐stress environments such as the arctic‐alpine. All bare ground or open microsites, however, are not created equal. Rydgren et al. show that arctic‐alpine substrate is a critical consideration for active restoration selection and best not oversimplified to ‘open’. Shifts in plant–plant interactions are important, and this study also demonstrates the need to test context – whether mixtures improve restoration efforts through facilitation in high‐stress environments, and if net interactions vary by substrate. There is rich theory associated with the recent innovations to facilitation, and this experiment sets up and clearly tests the modern paradigm by not assuming a Fix‐it Felix effect.

The primary findings advance facilitation and restoration theories. Interactions are species‐specific, and species respond uniquely to substrates. Seed mixture/monoculture and substrate treatments did not significantly interact, suggesting that each factor functions independently – this will be important because it simplifies active restoration decisions for this system. Facilitation is not necessarily the driving force in all contexts and for all species within this relatively high‐stress environment. It is present, but the specifics need to be tested. This is a salient reminder that net interactions are the most powerful heuristic when considering plant–plant interactions, and experiments must be designed with the capacity to detect both positive and negative net outcomes (Lortie et al. 2016). Rydgren et al. show that context includes not just the environment but also the biotic components supporting an expanded concept of context dependency (Chamberlain et al. 2014). Facilitation was a consistent net outcome. Substrate differences, such as organic vs mineral soil, changed the mechanistic pathway of facilitation and shifted the net outcome to more positive for some species, suggesting that, similar to many other systems, the mechanistic pathway of can change at the microhabitat or neighbourhood scale (Malanson & Resler 2015). Finally, net interactions established priority effects within the microhabitats. The rapid short‐term outcome of net interactions can thus amplify different potential restoration goals, and this work further suggests that facilitation does not necessarily set the stage for benefits to all species equally.