Long-term ecosystem dynamics of an ice-poor permafrost peatland in eastern Eurasia: paleoecological insights into climate sensitivity

Abstract. Northern peatlands are carbon-rich ecosystems highly sensitive to climate change, with nearly half of their carbon stocks associated with permafrost. Peat-based paleoecological records provide insights into the complex responses of permafrost peatlands to long-term climate variability, but most studies were conducted in ice-rich permafrost peatlands in Europe and North America. Here, we use multiple active-layer cores to reconstruct the ecosystem history of an ice-poor permafrost peatland in eastern Eurasia, near the southernmost limit of circumpolar permafrost but outside the circumpolar thermokarst landscape.

Our results show that the peatland, which developed on a floodplain since the late Holocene cooling, underwent a major phase of lateral expansion during the Little Ice Age. A fen-to-bog transition occurred in recent decades, with dry-adapted Sphagnum mosses replacing herbaceous vegetation across the site and having rapid surficial peat accumulation. Carbon isotope ratios of Sphagnum macrofossils, a proxy for surface wetness, indicate that Sphagnum mosses initially established under very dry conditions but that their habitats have since become gradually wetter.

Synthesizing these findings, we highlight that: (1) permafrost aggradation during climate cooling may promote new peatland formation over permeable mineral substrate by impeding drainage; (2) anthropogenic climate warming and active layer deepening can induce an ecosystem-scale regime shift, but ice-poor permafrost peatlands generally exhibit stability and homogeneity due to the absence of dynamic surface morphology (such as frost heave and thermokarst collapse); (3) recent wetting may result from surface adjustment–hydrology feedback and vegetation–hydrology feedback, demonstrating the internally driven resilience of ice-poor permafrost peatlands in maintaining their hydrology and carbon accumulation; and (4) ice-poor permafrost peatlands are likely to remain persistent carbon sinks under ongoing and future climate change.