Iron-associated organic carbon as a major carbon sink in permafrost-affected peatlands of Northeast China

Permafrost peatlands are essential terrestrial reservoir of organic carbon with high sensitivity for climate change. The binding of iron minerals to soils carbon is the dominant protection mechanism in carbon storage, however, there have been limited studies on iron-associated organic carbon (Fe-OC) in these carbon-rich peatland ecosystems. Here, we conduct a field survey on permafrost- and non-permafrost peatlands in Northeast China, and employ both large-scale comparisons across major terrestrial ecosystems. We find that permafrost peatlands in anoxic environment contain near 5-fold higher Fe-OC abundance than non-permafrost peatlands. From oxic to anoxic gradients, Fe-OC associations in peatlands decreases precipitously, but the presence of permafrost mitigates the loss of above carbon pool. Taking this together, we suggest a major carbon sink of Fe-OC in permafrost-affected peatlands and iron minerals as ‘OC protectors’ may greatly boosts the rusty carbon sink in cryogenic ecosystems under climate change.