Dynamics of oxidized and reduced iron in a northern hardwood forest

Fuss, C. B.; Driscoll, Charles T.; Johnson, Chris E.; Petras, Robert J.; Fahey, Timothy J.

doi:10.1007/s10533-010-9490-x

Cited by 37 publications

(24 citation statements)

References 62 publications

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“…These Fe oxidizers that thrive in circumneutral pH environments take advantage of thermodynamic gradients at interfaces between low O 2 (where Fe (II) is stable) and higher O 2 (Konhauser et al, 2011). Oxidation of Fe in the early growing season has been well documented at redox transition zones in surface waters of first‐order watersheds (Emerson et al, 2010; Fuss et al, 2010; Knorr, 2013). It is also likely that the interior of soil aggregates serve as similar redox gradients, where these Fe‐oxidizing bacteria could facilitate oxidation of Fe (II) in the solid and dissolved phase within aggregates as soil drains through the early growing season.…”

Section: Discussionmentioning

confidence: 99%

Soil CO₂ and O₂ Concentrations Illuminate the Relative Importance of Weathering and Respiration to Seasonal Soil Gas Fluctuations

Hodges

Kim

Brantley

et al. 2019

Soil Science Soc of Amer J

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Soil CO2 and O2 cycles are coupled in some processes (e.g., respiration) but uncoupled in others (e.g., silicate weathering). One benchmark for interpreting soil biogeochemical processes affected by soil pCO2 and pO2 is to calculate the apparent respiratory quotient (ARQ). When aerobic respiration and diffusion are the dominant controls on gas concentrations, ARQ equals 1; ARQ deviates from 1 when other processes dominate soil CO2 and O2 chemistry. Here, we used ARQ to understand lithologic, hillslope, and seasonal controls on soil gases at the Susquehanna Shale Hills Critical Zone Observatory in central Pennsylvania. We measured soil pCO2 and pO2 at three depths from the soil surface to bedrock across catenas in one shale and one sandstone watershed over three growing seasons. We found that both parent lithology and hillslope position significantly affect soil gas concentrations and ARQ. Soil pCO2 was highest (>5%) and pO2 was lowest (<16%) in the valley floors. Controlling for depth, pCO2 was higher and pO2 was lower across all sites in the sandstone watershed. We attribute this pattern to higher macroporosity in sandstone lithologies, which results in greater root respiration at depth. We recorded seasonal variation in ARQ at all sites, with ARQ rising above 1 during July through September, and dipping below 1 in the early spring. We hypothesize that this seasonal fluctuation arises from anaerobic respiration in reducing microsites July through September when the soils are wet and demand for O2 is high, followed by oxidation of reduced species when the soils drain and re‐oxygenate. We estimate that this anaerobic respiration in microsites contributes 36 g C m−2 yr−1 to the soil C flux. Our results provide evidence for a conceptual model of metal cycling in temperate watersheds and point to the importance of anaerobic respiration to the carbon flux from forest soils. Core Ideas Hillslope position and lithology affect soil CO2 and O2 in humid temperate forests. The ratio of CO2 and O2 (ARQ) fluctuates over the growing season. The ARQ fluctuations indicate seasonal metal redox cycling at all hillslope positions. Anaerobic respiration is important to soil CO2 flux during the late growing season.

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Section: Discussionmentioning

confidence: 99%

Soil CO₂ and O₂ Concentrations Illuminate the Relative Importance of Weathering and Respiration to Seasonal Soil Gas Fluctuations

Hodges

Kim

Brantley

et al. 2019

Soil Science Soc of Amer J

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“…In contrast, in the annual grassland and drained peatland soils, where Fe reducing conditions likely occur only episodically for short durations following large rain events, Fe reduction rates peaked after three days. These hot moments can be important to overall ecosystem function as evidenced by higher-thanexpected Fe(II) concentrations in well-drained soils at the Hubbard Brook experimental forest (Fuss et al 2011), which contribute to soil C stabilization at that site.…”

Section: Discussionmentioning

confidence: 99%

High potential for iron reduction in upland soils

Yang

Liptzin

2015

Ecology

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Changes in the redox state of iron (Fe) can be coupled to the biogeochemical cycling of carbon (C), nitrogen, and phosphorus, and thus regulate soil C, ecosystem nutrient availability, and greenhouse gas production. However, its importance broadly in non-flooded upland terrestrial ecosystems is unknown. We measured Fe reduction in soil samples from an annual grassland, a drained peatland, and a humid tropical forest We incubated soil slurries in an anoxic glovebox for 5.5 days and added sodium acetate daily at rates up to 0.4 mg C x (g soil)(-1) x d(-1). Soil moisture, poorly crystalline Fe oxide concentrations, and Fe(II) concentrations differed among study sites in the following order: annual grassland < drained peatland < tropical forest (P < 0.001 for all characteristics). All of the soil samples demonstrated high Fe reduction potential with maximum rates over the course of the incubation averaging 1706 ± 66, 2016 ± 12, and 2973 ± 115 μg Fe x (g soil)(-1) x d(-1) (mean ± SE) for the tropical forest, annual grassland, and drained peatland, respectively. Our results suggest that upland soils from diverse ecosystems have the potential to exhibit high short-term rates of Fe reduction that may play an important role in driving soil biogeochemical processes during periods of anaerobiosis.

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“…In humid tropical forest soils, Fe reduction dominates anaerobic respiration in laboratory experiments (Chacon et al 2006), and Fe(II) was observed at relatively low moisture contents in the field (Hall et al 2013). Even in well-drained, seemingly oxic spodosols in temperate forests, the soil solution can contain up to 60 % Fe(II) (Fuss et al 2010). Redistribution of Fe(II) across persistent anaerobic-aerobic interfaces, creating redoximorphic features in the process (Jacobs et al 2002;Richter et al 2007;Fimmen et al 2008), provides further evidence for the importance of anaerobic Fe reduction in upland soils.…”

Section: Evidence For Anaerobic Metabolism In Upland Soilsmentioning

confidence: 99%

“…Nevertheless, Fe reduction is increasingly recognized as the quantitatively most important anaerobic respiratory pathway in a large range of upland soil ecosystems because of its abundance relative to other TEAs (Schuur and Matson 2001;Miller et al 2001;Chacon et al 2006;Fuss et al 2010;Thompson et al 2011;Hall et al 2013 Nutrients (e.g., N and P)…”

Section: Evidence For Anaerobic Metabolism In Upland Soilsmentioning

confidence: 99%

Are oxygen limitations under recognized regulators of organic carbon turnover in upland soils?

et al. 2016

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Understanding the processes controlling organic matter (OM) stocks in upland soils, and the ability to management them, is crucial for maintaining soil fertility and carbon (C) storage as well as projecting change with time. OM inputs are balanced by the mineralization (oxidation) rate, with the difference determining whether the system is aggrading, degrading or at equilibrium with reference to its C storage. In upland soils, it is well recognized that the rate and extent of OM mineralization is affected by climatic factors (particularly temperature and rainfall) in combination with OM chemistry, mineral-organic associations, and physical protection. Here we examine evidence for the existence of persistent anaerobic microsites in upland soils and their effect on microbially mediated OM mineralization rates. We corroborate long-standing assumptions that residence times of OM tend to be greater in soil domains with limited oxygen supply (aggregates or peds). Moreover, the particularly long residence times of reduced organic compounds (e.g., aliphatics) are consistent with thermodynamic constraints on their oxidation under anaerobic conditions. Incorporating (i) pore length and connectivity governing oxygen diffusion rates (and thus oxygen supply) with (ii) 'hot spots' of microbial OM decomposition (and thus oxygen consumption), and (iii) kinetic and thermodynamic constraints on OM metabolism under anaerobic conditions will thus improve conceptual and numerical models of C cycling in upland soils. We conclude that constraints on microbial metabolism induced by oxygen limitations act as a largely unrecognized and greatly underestimated control on overall rates of C oxidation in upland soils.

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Dynamics of oxidized and reduced iron in a northern hardwood forest

Abstract: Iron (Fe) is ubiquitous in forest ecosystems and its cycle is thought to influence the development of soil, particularly Spodosols (podsolization), and the biogeochemistry of macro-

Cited by 37 publications

References 62 publications

Soil CO₂ and O₂ Concentrations Illuminate the Relative Importance of Weathering and Respiration to Seasonal Soil Gas Fluctuations

Soil CO₂ and O₂ Concentrations Illuminate the Relative Importance of Weathering and Respiration to Seasonal Soil Gas Fluctuations

High potential for iron reduction in upland soils

Are oxygen limitations under recognized regulators of organic carbon turnover in upland soils?

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Dynamics of oxidized and reduced iron in a northern hardwood forest

Abstract: Iron (Fe) is ubiquitous in forest ecosystems and its cycle is thought to influence the development of soil, particularly Spodosols (podsolization), and the biogeochemistry of macro-

Cited by 37 publications

References 62 publications

Soil CO2 and O2 Concentrations Illuminate the Relative Importance of Weathering and Respiration to Seasonal Soil Gas Fluctuations

Soil CO2 and O2 Concentrations Illuminate the Relative Importance of Weathering and Respiration to Seasonal Soil Gas Fluctuations

High potential for iron reduction in upland soils

Are oxygen limitations under recognized regulators of organic carbon turnover in upland soils?

Contact Info

Product

Resources

About

Soil CO₂ and O₂ Concentrations Illuminate the Relative Importance of Weathering and Respiration to Seasonal Soil Gas Fluctuations

Soil CO₂ and O₂ Concentrations Illuminate the Relative Importance of Weathering and Respiration to Seasonal Soil Gas Fluctuations