Publication Date:
2023-04-03
Description:
Vegetation shifts in circum-Arctic permafrost peatlands drive feedbacks with important consequences
for peatland carbon budgets and the extent of permafrost thaw under changing climate. Recent shrub
expansion across Arctic tundra environments has led to an increase in above-ground biomass, but the
long-term spatiotemporal dynamics of shrub and tree growth in circum-Arctic peatlands remain
unquantified. We investigate changes in peatland vegetation composition during the Holocene using
previously-published plant macrofossil records from 76 sites across the circum-Arctic permafrost zone.
In particular, we assess evidence for peatland shrubification at the continental scale. We identify
increasing abundance of woody vegetation in circum-Arctic peatlands from ~8000 years BP to present,
coinciding with declining herbaceous vegetation and widespread Sphagnum expansion. Ecosystem shifts
varied between regions and present-day permafrost zones, with late-Holocene shrubification most
pronounced where permafrost coverage is presently discontinuous and sporadic. After ~600 years BP, we
find a proliferation of non-Sphagnum mosses in Fennoscandia and across the present-day continuous
permafrost zone; and rapid expansion of Sphagnum in regions of discontinuous and isolated permafrost
as expected following widespread fen-bog succession, which coincided with declining woody vegetation
in eastern and western Canada. Since ~200 years BP, both shrub expansion and decline were identified at
different sites across the pan-Arctic, highlighting the complex ecological responses of circum-Arctic
peatlands to post-industrial climate warming and permafrost degradation. Our results suggest that
shrubification of circum-Arctic peatlands has primarily occurred alongside surface drying, resulting from
Holocene climate shifts, autogenic peat accumulation, and permafrost aggradation. Future shrubification
of circum-Arctic peatlands under 21st century climate change will likely be spatially heterogeneous, and
be most prevalent where dry microforms persist.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
Format:
application/pdf
Permalink