The paradox of assessing greenhouse gases from soils for nature-based solutions

Vargas, Rodrigo; Le, Van Huong

doi:10.5194/bg-20-15-2023

Cited by 12 publications

(15 citation statements)

References 53 publications

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“…Third, future studies should consider implementing long‐term automated measurements of diverse trace gas fluxes to identify patterns and controls at multiple temporal scales (Capooci & Vargas, 2022b). Finally, the appropriate measurements in time and space of trace gas fluxes constitute a science frontier when reporting carbon budgets and assessments of nature‐based solutions (Vargas & Le, 2023).…”

Section: Discussionmentioning

confidence: 99%

Physiochemical Controls on the Horizontal Exchange of Blue Carbon Across the Salt Marsh‐Tidal Channel Interface

Fettrow,

Jeppi,

Wozniak

et al. 2023

JGR Biogeosciences

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Tidal channels are biogeochemical hotspots that horizontally exchange carbon (C) with marsh platforms, but the physiochemical drivers controlling these dynamics are poorly understood. We hypothesized that C‐bearing iron (Fe) oxides precipitate and immobilize dissolved organic carbon (DOC) during ebb tide as the soils oxygenate, and dissolve into the porewater during flood tide, promoting transport to the channel. The hydraulic gradient physically controls how these solutes are horizontally exchanged across the marsh platform‐tidal channel interface; we hypothesized that this gradient alters the concentration and source of C being exchanged. We further hypothesized that trace soil gases (i.e., CO2, CH4, dimethyl sulfide) are pushed out of the channel bank as the groundwater rises. To test these hypotheses, we measured porewater, surface water, and soil trace gases over two 24‐hr monitoring campaigns (i.e., summer and spring) in a mesohaline tidal marsh. We found that Fe2+ and DOC were positively related during flood tide but not during ebb tide in spring when soils were more oxidized. This finding shows evidence for the formation and dissolution of C‐bearing Fe oxides across a tidal cycle. In addition, the tidal channel contained significantly (p < 0.05) more terrestrial‐like DOC when the hydraulic gradient was driving flow toward the channel. In comparison, the channel water was saltier and contained significantly (p < 0.05) more marine‐like DOC when the hydraulic gradient reversed direction. Trace gas fluxes increased with rising groundwater levels, particularly dimethyl sulfide. These findings suggest multiple physiochemical mechanisms controlling the horizontal exchange of C at the marsh platform‐tidal channel interface.

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Section: Discussionmentioning

confidence: 99%

Physiochemical Controls on the Horizontal Exchange of Blue Carbon Across the Salt Marsh‐Tidal Channel Interface

Fettrow,

Jeppi,

Wozniak

et al. 2023

JGR Biogeosciences

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“…We encourage the publication of these data sets in a way that facilitates meta-analysis, in order to improve our understanding of seasonal dynamics and uncertainty in this kind of data. Furthermore, although regular sampling helps elucidate broad seasonal patterns and the effects of agricultural practices, weekly sampling, or other fixed-time interval approaches are limited in their ability to capture influential storm events (Vargas and Le 2023). The effect of highflow events on wetland phosphorus retention is most likely underrepresented in most studies (Audet et al 2020).…”

Section: Areas For Further Researchmentioning

confidence: 99%

Source or sink? Meta-analysis reveals diverging controls of phosphorus retention and release in restored and constructed wetlands

Ury,

Arrumugam,

Herbert

et al. 2023

Environ. Res. Lett.

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Wetland restoration is a popular nutrient management strategy for improving water quality in agricultural catchments. However, a wetland’s ability to retain phosphorus is highly variable and wetlands can sometimes be a source of phosphorus to downstream ecosystems. Here, we used a meta-analysis approach to explore the source and sink capacity of 139 wetlands for both total phosphorus (TP) and the more bioavailable form, phosphate (PO43-), at seasonal and annual timescales. Median retention efficiency across all studies is 32 % for TP and 28 % for PO₄³⁻, however the range is extremely broad. We found that wetlands are often sinks for TP (84 % of site-years) and PO₄³⁻ (75% of site years). The median TP retention within wetlands that are sinks (2.0 g∙m-2∙year-1) is greater than release by wetlands that are sources (-0.5 g∙m-2∙year-1). In contrast, for PO₄³⁻, median retention within wetlands that are phosphorus sinks (0.8 g∙m-2∙year-1) is of similar magnitude to that released by wetlands that are phosphorus sources (-0.7 g∙m-2∙year-1). We found that phosphorus release from wetlands coincides with higher hydraulic loading rates, lower influent phosphorus concentration, and legacy soil/sediment phosphorus. Phosphate releases were especially common in wetlands used for treating municipal wastewater, as well as restored and constructed wetlands with flashy, precipitation-driven flow. We found that experimental design may inherently bias our understanding of wetland performance for phosphorus retention as studies conducted in mesocosms outperform other wetland types. Analysis of monthly data demonstrated significant temporal variability in wetland phosphorus dynamics, often switching from retention to release many times within a year, but with no generalizable seasonal trends. Our results highlight the value of restoring wetlands for phosphorus retention and point to ways of furthering their utility towards improving water quality by simultaneously targeting retention enhancing measures and release avoidance.

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“…Savage et al, 2014). This may bias the functional relationships researchers estimate between Rs and soil temperature or moisture as well as the calculation of annual flux estimates (Bond-Lamberty et al, 2019;Giasson et al, 2013;Vargas & Le, 2023;M. Xu & Shang, 2016).…”

Section: Methodological Advancesmentioning

confidence: 99%

“…(2014) suggest that high‐frequency data capture short‐duration shifts and pulses in the Rs response, increasing the variance of the data (cf. Vargas & Le, 2023). This emphasizes the importance, noted above, of consistently treating and reconciling these different measurement strategies.…”

Section: In Situ Measurements and Manipulationsmentioning

confidence: 99%

“…This approach is laborious, however, and for convenience researchers often measure once a month (Jian et al., 2018), likely biasing their observations to days and times when conditions are best for fieldwork (Cueva et al., 2017). Such sampling may not capture temporal trends (Vargas & Le, 2023) and inadequately samples Rs pulses driven by rain or atmospheric pressure (Bain et al., 2005; Lee et al., 2004; Leon et al., 2014; Pumpanen et al., 2010; K. Savage et al., 2014). This may bias the functional relationships researchers estimate between Rs and soil temperature or moisture as well as the calculation of annual flux estimates (Bond‐Lamberty et al., 2019; Giasson et al., 2013; Vargas & Le, 2023; M. Xu & Shang, 2016).…”

Section: In Situ Measurements and Manipulationsmentioning

confidence: 99%

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Twenty Years of Progress, Challenges, and Opportunities in Measuring and Understanding Soil Respiration

Bond‐Lamberty,

Ballantyne,

Berryman

et al. 2024

JGR Biogeosciences

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Soil respiration (Rs), the soil‐to‐atmosphere flux of CO2, is a dominant but uncertain part of the carbon cycle, even after decades of study. This review focuses on progress in understanding Rs from laboratory incubations to global estimates. We survey key developments of in situ ecosystem‐scale Rs observations and manipulations, synthesize Rs meta‐analyses and global flux estimates, and discuss the most compelling challenges and opportunities for the future. Increasingly sophisticated lab experiments have yielded insights into the interaction among heterotrophic respiration, substrate supply, and enzymatic kinetics, and extended incubation‐based analyses across space and time. Observational and manipulative field‐based experiments have used improved measurement approaches to deepen our understanding of the integrated effects of environmental change and disturbance on Rs. Freely‐available observational databases have enabled meta‐analyses and studies probing the magnitude of, and constraints on, the global Rs flux. Key challenges for the field include expanding Rs measurements, experiments, and opportunities to under‐represented communities and ecosystems; reconciling independent estimates of global respiration fluxes and trends; testing and leveraging the power of machine learning and process‐based models, both independently and in conjunction with each other; and continuing the field's tradition of using novel experiments to explore diverse mechanisms and ecosystems.

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The paradox of assessing greenhouse gases from soils for nature-based solutions

Cited by 12 publications

References 53 publications

Physiochemical Controls on the Horizontal Exchange of Blue Carbon Across the Salt Marsh‐Tidal Channel Interface

Physiochemical Controls on the Horizontal Exchange of Blue Carbon Across the Salt Marsh‐Tidal Channel Interface

Source or sink? Meta-analysis reveals diverging controls of phosphorus retention and release in restored and constructed wetlands

Twenty Years of Progress, Challenges, and Opportunities in Measuring and Understanding Soil Respiration

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