Massive peatland carbon banks vulnerable to rising temperatures

A M Hopple,S D Bridgham,R M Wilson,J Kostka,M Kolton,J K Keller,J P Chanton,C A Zalman,P J Hanson

doi:10.1038/s41467-020-16311-8

Abstract

Peatlands contain one-third of the world’s soil carbon (C). If destabilized, decomposition of this vast C bank could accelerate climate warming; however, the likelihood of this outcome remains unknown. Here, we examine peatland C stability through five years of whole-ecosystem warming and two years of elevated atmospheric carbon dioxide concentrations (eCO2). Warming exponentially increased methane (CH4) emissions and enhanced CH4 production rates throughout the entire soil profile; although surface CH4 production rates remain much greater than those at depth. Additionally, older deeper C sources played a larger role in decomposition following prolonged warming. Most troubling, decreases in CO2:CH4 ratios in gas production, porewater concentrations, and emissions, indicate that the peatland is becoming more methanogenic with warming. We observed limited evidence of eCO2 effects. Our results suggest that ecosystem responses are largely driven by surface peat, but that the vast C bank at depth in peatlands is responsive to prolonged warming.

Highlights

Peatlands contain one-third of the world’s soil carbon (C)
Our current results suggest that ecosystem responses remain largely driven by surface peat, but that following a relatively short lag, the vast C bank at depth in peatlands is responsive to warming
Ecosystem responses to prolonged Whole-ecosystem warming (WEW) and eCO2

Summary

Introduction

Peatlands contain one-third of the world’s soil carbon (C). If destabilized, decomposition of this vast C bank could accelerate climate warming; the likelihood of this outcome remains unknown. Located in an ombrotrophic peatland in northern Minnesota, USA (S1 Bog)[12], this study uses a regression-based experimental design that warms the vegetation and peatland soil profile to a depth of 3 m within ten, 12-m-diameter enclosures to five target temperature differentials (+0 to +9 °C above ambient), with duplicate enclosures subjected to ambient and ~+ 500 p.p.m.v. above ambient atmospheric CO2 concentrations (eCO2; Supplementary Fig. 1a).

Results

Conclusion