Dual controls on carbon loss during drought in peatlands

Abstract

Peatlands represent about a third of global soil carbon. Research now indicates that increased shrub cover following drought and warming can contribute to the build-up of phenolics, which suppress decomposition and soil carbon loss. Peatlands store one-third of global soil carbon1. Drought/drainage coupled with climate warming present the main threat to these stores1,2,3,4. Hence, understanding drought effects and inherent feedbacks related to peat decomposition has been a primary global challenge5,6. However, widely divergent results concerning drought in recent studies3,7,8,9,10,11 challenge the accepted paradigm that waterlogging and associated anoxia are the overarching controls locking up carbon stored in peat. Here, by linking field and microcosm experiments, we show how previously unrecognized mechanisms regulate the build-up of phenolics, which protects stored carbon directly by reducing phenol oxidase activity during short-term drought and, indirectly, through a shift from low-phenolic Sphagnum/herbs to high-phenolic shrubs after long-term moderate drought. We demonstrate that shrub expansion induced by drought/warming2,6,10,12,13 in boreal peatlands might be a long-term self-adaptive mechanism not only increasing carbon sequestration but also potentially protecting historic soil carbon. We therefore propose that the projected ‘positive feedback loop’ between carbon emission and drought in peatlands2,3,14,15 may not occur in the long term.

Cite this article

Wang, H., Richardson, C. & Ho, M. Dual controls on carbon loss during drought in peatlands. Nature Clim Change 5, 584–587 (2015). https://doi.org/10.1038/nclimate2643

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