Co-limitation of plant production by multiple resources has recently been shown to be widespread in aquatic and terrestrial systems. Recognition of synergisms between multiple limiting resources represents a paradigm shift away from a traditional focus on identifying the “main” limiting resource for a given system. Such interactions suggest potential fundamental stoichiometric adaptations to multiple environmental constraints that are generally shared by photosynthetic organisms, and point to potential mechanisms underlying resource limitation. We present results from a meta-analysis of over 650 factorial experiments that manipulated nitrogen (N) and phosphorus (P) in marine, freshwater or terrestrial systems. We used several alternative approaches to characterize multiple nutrient limitation. In particular, we classified studies into one of eight categories based on the form of the interaction between N and P.
Results/Conclusions

We found that interactions between N and P were common, and that the form of the interaction varied, with the majority showing super-additive co-limitation. We also found evidence for the importance of nutrients other than N and P, despite a dearth of such studies.  Understanding the potential impacts of increasing anthropogenic N and P deposition to biodiversity and ecosystem function will require a mechanistic understanding of nutrient co-limitation and the potential interactive effects of other limiting factors.