Simulated Hydrological Dynamics and Coupled Iron Redox Cycling Impact Methane Production in an Arctic Soil

Abstract

Permafrost regions contain enormous soil organic carbon (C) stocks (Hugelius et al., 2014). The fate of this vast C pool is critical to the global climate system because of the potential for decomposition of permafrost organic matter (OM) and C release into the atmosphere as greenhouse gases (Schuur et al., 2015;Turetsky et al., 2020). Because thawing permafrost often drives physical collapse and flooding, anoxic processes are an important component of permafrost OM decomposition. Major uncertainties in current understanding of permafrost thaw include the amount of C that will be mineralized and the relative amounts of CO 2 and CH 4 that will be produced by decomposition of OM in thawing permafrost soils (

Subsurface Redox Interactions Regulate Ebullitive Methane Flux in Heterogeneous Mississippi River Deltaic Wetland

“…Although this complex redox network includes the major subsurface redox reactions, there are other important reactions which may influence the ratio of a specific gas in the bubbles but are not included in this network (i.e., H 2 ). Additionally, this model configuration does not include pH impacts on the redox reactions, but pH dynamics can be critical processes or controlling factors for subsurface soil and coastal water environments and it is suggested to evaluate pH dynamics in future modeling effort (B. N. Sulman et al., 2022). Finally, our model framework used a highly simplified representation of plant carbon inputs to the subsurface, which were simulated as a constant input rate of sediment organic matter in the top sediment layer.…”

“…A new complex reactive network of key redox reactions were defined in the chemical reaction solver—PFLOTRAN (G. E. Hammond et al., 2014; Glenn E. Hammond & Lichtner, 2010), including soil organic matter decomposition, sulfate (SO 4 2‐ ) reduction, iron (Fe) reduction, nitrification, denitrification, methanogenesis, and methanotrophy along with dissimilatory nitrate reduction to ammonium (DNRA) and abiotic mineral formation such as mono‐sulfide‐iron precipitation (Tables 1 and 2). Soil organic matter decomposition in PFLOTRAN follows previous implementations in land models with modifications over decomposition rates and C:N ratios (B. N. Sulman et al., 2022; Tang et al., 2016). The DNRA includes a fermentative pathway and an autotrophic pathway with hydrogen sulfide (H 2 S) or methane (CH 4 ) as the electron donors.…”

Modeling strategies and data needs for representing coastal wetland vegetation in land surface models

“…However, for some specific sites or estuaries, sulfide exerts significant influence over vegetation dynamics and plant–soil feedbacks (Ingold & Havill, 1984; Chambers et al ., 1998; Alldred et al ., 2020; Lagomasino et al ., 2021). Work is progressing on coupling redox‐explicit biogeochemistry models with LSMs, so opportunities exist to explore sulfate reduction and sulfide phytotoxicity in sites where coupled carbon and sulfur cycling is relevant (Tang et al ., 2016; Sulman et al ., 2022). To make progress on representation of fine‐scale geochemistry, measurements of sulfide with geochemical context (iron, DOC, etc.)…”

“…Data on redox potential or rates of radial oxygen loss by species, life cycle, flooding regime, and photoperiod are likely to be useful. Coupling between vegetation models and biogeochemical models will be important for capturing productivity and decomposition of plant matter and will benefit from comprehensive biogeochemical datasets in terrestrial–aquatic interfaces, including organic carbon, oxygen, nitrogen species, iron and sulfur species, methane, and pH in addition to building on existing model coupling frameworks (Tang et al ., 2016; Sulman et al ., 2022). Ideally, these measurements will be co‐located with measurements of vegetation growth, meteorology, and gas fluxes.…”

“…Reactive transport models can also simulate production, consumption, and transport of salts, nutrients, and phytotoxins, allowing for representation of flushing effects that interact with plant responses to salinity ('Salinity tolerance' in the Vegetation functional types and traits section) or sulfide ('Sulfide tolerance' in the Vegetation functional types and traits section). While current LSMs are not generally capable of direct coupling to reactive transport models, ongoing research efforts are building the groundwork for advances in this direction (Tang et al, 2016(Tang et al, , 2022Sulman et al, 2022).…”