Rapid vegetation succession and coupled permafrost dynamics in arctic thaw ponds in the Siberian lowland tundra

While dead shrubs and open water are associated with permafrost degradation (lower surface elevation, high active layer thicknesslarger thaw depth), sites with sedge and in particular Sphagnum display indications of permafrost recovery. Recruitment of Betula nana on Sphagnum carpets in ponds indicates a potential recovery towards shrub dominated vegetation, although it remains unclear if and on what timescale this occurs.

Our results suggest that thaw ponds display potentially cyclic vegetation succession associated with permafrost degradation and recovery. Thaw pond formation and initial colonization by sedges can occur on subdecadal timescales, which is relatively fast compared to rates known for ice wedge degradation (subdecadal to century-scale). The rates of formation and recovery of small-scale thaw ponds have implications for the greening/browning dynamics and carbon balance of this ecosystem.

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