Nitrogen inputs accelerate phosphorus cycling rates across a wide variety of terrestrial ecosystems

TLDR

Human activities are altering the magnitude and pattern of nitrogen and phosphorus limitations that constrain plant growth and microbial functioning. The study investigates how nitrogen and phosphorus fertilization affect phosphatase enzyme activity across diverse terrestrial biomes. A meta‑analysis of 34 studies assessed phosphatase activity under N, P, or combined N×P fertilization. Nitrogen fertilization boosts phosphatase activity worldwide, while phosphorus fertilization suppresses it; plant phosphatases are more responsive than soil ones, indicating a tight N–P coupling that can delay phosphorus limitation of plant productivity.

Abstract

• Biologically essential elements – especially nitrogen (N) and phosphorus (P) – constrain plant growth and microbial functioning; however, human activities are drastically altering the magnitude and pattern of such nutrient limitations on land. Here we examine interactions between N and P cycles of P mineralizing enzyme activities (phosphatase enzymes) across a wide variety of terrestrial biomes. • We synthesized results from 34 separate studies and used meta-analysis to evaluate phosphatase activity with N, P, or N×P fertilization. • Our results show that N fertilization enhances phosphatase activity, from the tropics to the extra-tropics, both on plant roots and in bulk soils. By contrast, P fertilization strongly suppresses rates of phosphatase activity. • These results imply that phosphatase enzymes are strongly responsive to changes in local nutrient cycle conditions. We also show that plant phosphatases respond more strongly to fertilization than soil phosphatases. The tight coupling between N and P provides a mechanism for recent observations of N and P co-limitation on land. Moreover, our results suggest that terrestrial plants and microbes can allocate excess N to phosphatase enzymes, thus delaying the onset of single P limitation to plant productivity as can occur via human modifications to the global N cycle.