Phosphorus supply affects long-term carbon accumulation in mid-latitude ombrotrophic peatlands

Daniel N Schillereff,Richard C Chiverrell,Edward Tipping,Jessica A C Davies,Hannah Toberman,John F Boyle,Jenny K Sjöström,Malin E Kylander

doi:10.1038/s43247-021-00316-2

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.

Highlights

Ombrotrophic peatlands are a globally important carbon store and depend on atmospheric nutrient deposition to balance ecosystem productivity and microbial decomposition
We compile the first database of P:N:C stoichiometry from deep mid-latitude ombrotrophic peatlands spanning continents to test the idea that, over millennia, differences in local P input to individual bogs is a key driver of the biogeochemical cascade from surface vegetation to burial in the catotelm
We propose that our finding that bogs that accumulate more P are characterised by higher N:C ratios, indicative of more efficient decomposition, is a widespread and largely overlooked biogeochemical characteristic of ombrotrophic peatlands

Summary

Introduction

Ombrotrophic peatlands are a globally important carbon store and depend on atmospheric nutrient deposition to balance ecosystem productivity and microbial decomposition. We compile the first database of P:N:C stoichiometry from deep mid-latitude ombrotrophic peatlands spanning continents to test the idea that, over millennia, differences in local P input to individual bogs is a key driver of the biogeochemical cascade from surface vegetation to burial in the catotelm.

Results

Conclusion