Carbon Sequestration Potential of Restored Peatlands in Temperate Ecosystems
DOI:
https://doi.org/10.5281/zenodo.22792415Keywords:
peatland restoration, rewetting, net ecosystem carbon balance, eddy covariance, methane flux, chronosequence, blanket bog, fen, carbon sequestration, greenhouse gas balanceAbstract
Drained temperate peatlands are among the most concentrated terrestrial sources of soil carbon loss, and rewetting
is now widely promoted as a climate mitigation measure, yet the timescale over which a rewetted peatland is
expected to return to net carbon sink status, and the size of the methane cost incurred along the way, remain poorly
constrained by direct flux observation. We instrumented nine temperate peatland sites in the Netherlands, Germany
and the United Kingdom spanning a restoration chronosequence from 2 to 32 years since rewetting, plus two
drained and two near-natural reference sites, with eddy covariance towers measuring CO2 and CH4 exchange
continuously over two full annual cycles (2019-2021), supplemented by manual chamber measurements at 24
collars per site and continuous water table monitoring. Net ecosystem carbon balance (NECB), combining eddy
covariance CO2 exchange with CH4 flux expressed as CO2-equivalent, shifted from a mean source of 410 g
CO2-eq m-2 yr-1 at the drained sites to a mean sink of -185 g CO2-eq m-2 yr-1 at sites rewetted for more than 15
years, with the sign of the NECB crossing from net source to net sink at a median of 9 years post-rewetting.
Methane emissions rose sharply within the first 3 years after rewetting, averaging 38 g CH4 m-2 yr-1 across newly
rewetted sites, roughly six times the flux measured at drained sites, and remained elevated relative to near-natural
reference sites even in the oldest restoration cohort, indicating a persistent rather than purely transient methane
cost. Water table depth was the strongest single predictor of both CO2 and CH4 flux magnitude across the
chronosequence, with sites maintaining a mean growing-season water table shallower than 10 cm below the
surface showing consistently stronger net carbon sinks than more variably flooded sites regardless of restoration
age. These results indicate that restored temperate peatlands can become net carbon sinks on a roughly decadal
timescale, but that early-successional methane emissions partially offset the climate benefit of avoided CO2 loss for
a period long enough to matter for near-term mitigation accounting, and that sustained, stable rewetting of the water
table is a more reliable determinant of restoration outcome than restoration age alone.
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