Long-Term Phosphorus Addition Strongly Weakens the Carbon Sink Function of a Temperate Peatland

Peatlands are important nutrient-limited, carbon (C)-accumulating ecosystems where phosphorus (P) is one major limiting nutrient. An increase in P input to peatlands has been observed close to agricultural areas. However, the effects of P input on gross primary productivity (GPP), ecosystem respiration (ER) and net ecosystem exchange (NEE) of peatlands, especially in temperate Asia, have been rarely studied. We selected the P addition plots of a 12-year experiment simulating environmental change in a peatland in northeastern China to evaluate the effect of P addition (5 and 10 kg ha(-1) y(-1)) on carbon dioxide fluxes. Our results showed that the growth of Sphagnum was inhibited but that of vascular plants was facilitated by P addition, resulting in an unchanged GPP. P addition increased ER due to the increased activity potentials of N-acetyl-beta-glucosaminidase (NAG) and polyphenol oxidase (POX) that might, in turn, increase the metabolic rate of soil microbes and enhance the decomposition of peat. During the growing season, a mean net CO2 absorption of 0.002 mg m(-2) s(-1) was observed at high levels of P addition, which was much lower than that of 0.063 mg m(-2) s(-1) in the controls. The results suggest that long-term P addition will greatly weaken the C sequestration in peatlands by enhancing ER rather than reducing GPP. Our study highlights the importance of the response of vegetation and soil enzyme activities to P addition regarding peatland respiration and C sink function.

Automated summary

Phosphorus addition has significant effects on the respiration and carbon sequestration function of peatlands, reducing carbon sequestration by increasing ecosystem respiration.