Anthropogenic nitrogen (N) enhancement has considerably altered plant growth, soil chemistry and other ecosystem functioning, but its impact on the cycle of another important nutrient, phosphorus (P), has not been well synthesized. We conducted a comprehensive meta-analysis including 288 independent study sites from 192 articles to evaluate global patterns and controls of 18 variables associated with ecosystem P cycle in response to N additions.
Results/Conclusions
Overall, N additions increased plant biomass production (+27.0%) and the P sequestration in plant tissues (+14.5%), while decreasing plant P concentration (-7.3%) and soil total P (-4.1%). N additions did not change soil labile P and microbial biomass P, but enhanced phosphatase activity (+31.0%). The response of ecosystem P cycle to N additions varied among different ecosystems, without significant effect of N source type. The P cycle in the tundra was not influenced by N additions, but in the tropical forest, N additions decreased both plant P concentration (-3.5%) and soil labile P (-20.3%). The shift in soil labile P with N additions was positively correlated with soil pH value in the control sites. In addition, plant P concentration decreased more with the increase in total N load, and phosphatase activity initially increased with N load, but declined when N load was beyond a certain threshold value. These results suggest that as anthropogenic N enhancement continues in the future, it could induce P limitation in terrestrial ecosystems, particularly in the tropical forest.