Human alteration of global macronutrient availability is well documented. Compared to pre-industrial levels, anthropogenic creation of biologically reactive nitrogen (N) has increased twelve fold (Galloway et al. 2008) and phosphorous (P) inputs to terrestrial systems have doubled (Carpenter and Bennett 2011). Additionally, it is well understood that N, P, and often the combination of the two (Elser et al. 2007), limit primary productivity globally from terrestrial to freshwater to marine systems. However, despite the large body of literature on co-limitation and multiple element limitation, few studies have explored beyond a two-nutrient approach to assess effects of other nutrients (e.g. K, Si, Ca) in limiting primary productivity. The goal of this study was, therefore, to push beyond the conventional N and P co-limitation framework to evaluate the additional effects of “micronutrients” on primary production. We performed a meta-analysis using 68 fertilization studies that test the effects of N, P, and other nutrient additions on primary productivity.
Results/Conclusions
We found that the “other” nutrients do in fact matter – often as much as N and P, across terrestrial and aquatic ecosystems. Additionally, we found that comparatively little is known about “other” nutrients and that only one marine study evaluated the effect of N, P and "other" nutrients together. These results suggest we broaden our analyses of nutrient limitation controls on primary production to include less abundant – but likely not less important – nutrients. Developing similarly robust analyses of global micronutrient deposition and availability across systems, as we have for macronutrients, will also be important to better understand implications for primary productivity.