Abstract
Ombrotrophic peatlands are a globally important carbon store and depend on atmospheric nutrient deposition to balance ecosystem productivity and microbial decomposition. Human activities have increased atmospheric nutrient fluxes, but the impacts of variability in phosphorus supply on carbon sequestration in ombrotrophic peatlands are unclear. Here, we synthesise phosphorus, nitrogen and carbon stoichiometric data in the surface and deeper layers of mid-latitude Sphagnum-dominated peatlands across Europe, North America and Chile. We find that long-term elevated phosphorus deposition and accumulation strongly correlate with increased organic matter decomposition and lower carbon accumulation in the catotelm. This contrasts with literature that finds short-term increases in phosphorus supply stimulates rapid carbon accumulation, suggesting phosphorus deposition imposes a threshold effect on net ecosystem productivity and carbon burial. We suggest phosphorus supply is an important, but overlooked, factor governing long-term carbon storage in ombrotrophic peatlands, raising the prospect that post-industrial phosphorus deposition may degrade this carbon sink.

Schillereff, D.N., Chiverrell, R.C., Sjöström, J.K., Kylander, M.E., Boyle, J.F., Davies, J.A.C.,Toberman, H. & Tipping, E., 2021. Phosphorus supply affects long-term carbon accumulation in mid-latitude ombrotrophic peatlands. Communications Earth & Environment: 2, 241.

https://doi.org/10.1038/s43247-021-00316-2

We collated P, N and C concentration data for 23 mid-latitude sites (crosses; Supplementary Figs. 1 and 2), of which 11 also provided accumulation rates (diamonds). Red stars represent the locations of regional monitoring stations for P deposition used in the analysis, originally reported by Tipping et al. and Brahney et al. The distribution of peatlands is taken from the PEATMAP of Xu et al.