Setting a reference for wetland carbon: the importance of accounting for hydrology, topography, and natural variability
Setting a reference for wetland carbon: the importance of accounting for hydrology, topography, and natural variability
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Date
2023-05-19
Authors
Stewart, Graham A.
Kottkamp, Anna I.
Williams, Michael R.
Palmer, Margaret A.
Advisor
Citation
Graham A Stewart et al 2023 Environ. Res. Lett. 18 064014.
Abstract
Wetland soils are a key global sink for organic carbon (C) and a focal point for C management and
accounting efforts. The ongoing push for wetland restoration presents an opportunity for climate
mitigation, but C storage expectations are poorly defined due to a lack of reference information
and an incomplete understanding of what drives natural variability among wetlands. We sought to
address these shortcomings by (1) quantifying the range of variability in wetland soil organic C
(SOC) stocks on a depressional landscape (Delmarva Peninsula, USA) and (2) investigating the
role of hydrology and relative topography in explaining variability among wetlands. We found a
high degree of variability within individual wetlands and among wetlands with similar vegetation
and hydrogeomorphic characteristics. This suggests that uncertainty should be presented explicitly
when inferring ecosystem processes from wetland types or land cover classes. Differences in
hydrologic regimes, particularly the rate of water level recession, explained some of the variability
among wetlands, but relationships between SOC stocks and some hydrologic metrics were eclipsed
by factors associated with separate study sites. Relative topography accounted for a similar portion
of SOC stock variability as hydrology, indicating that it could be an effective substitute in
large-scale analyses. As wetlands worldwide are restored and focus increases on quantifying C
benefits, the importance of appropriately defining and assessing reference systems is paramount.
Our results highlight the current uncertainty in this process, but suggest that incorporating
landscape heterogeneity and drivers of natural variability into reference information may improve
how wetland restoration is implemented and evaluated.