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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.
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Evaluating permanganate oxidizable carbon (POXC)’s potential for differentiating carbon pools in wetland soils
Soil carbon (C) storage is a globally important ecosystem service with the potential to contribute to climate change mitigation. Wetlands are heavily researched hot spots for soil C storage. Despite the growing number of wetland soil C inventories, most studies focus only on total C quantification; there is limited application of methods that evaluate differences in C stability and vulnerability to mineralization within the C pool. Permanganate oxidizable C (POXC) is a well-established soil health indicator in agriculture shown to be sensitive to changing conditions or management regimes and may prove equally informative in wetland studies. This research quantified POXC in six diverse wetland soils that differed greatly in organic matter content and spanned both freshwater and saltwater habitats, then evaluated the relationship between POXC and basic soil C properties, microbial indicators, and physical and chemical fractionation metrics. Results showed POXC averaged ∼ 37 times greater in wetlands than upland agricultural soils, but was less robust in differentiating between individual wetlands than total C or organic matter content. Rather, the ratio of POXC to soil organic C may be a more informative metric for evaluating the proportion of slightly processed C in wetland soils. Significant correlations were found between POXC and almost all other soil properties measured, suggesting POXC could be a rapid, reliable, and economical proxy for other analyses. Overall, POXC shows potential for providing novel information about wetland soil C stability, but requires additional research to improve interpretability. Applying POXC analysis in time series data collection and before-after-control impact experiments may be particularly informative for wetland management.
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- Award ID(s):
- 2149866
- PAR ID:
- 10609848
- Editor(s):
- NA
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Ecological Indicators
- Volume:
- 167
- Issue:
- C
- ISSN:
- 1470-160X
- Page Range / eLocation ID:
- 112624
- Subject(s) / Keyword(s):
- Potassium permanganate Soil health indicator Wetland Soil carbon Mineral associate organic matter
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.ecolind.2024.112624
