Dating Charred Soil Organic Matter: Comparison of Radiocarbon Ages from Macrocharcoals and Chemically Separated Charcoal Carbon

Eckmeier, Eileen; Borg, Klaas van der; Tegtmeier, Ursula; Schmidt, Michael W.; Gerlach, Renate

doi:10.1017/s0033822200055831

Cited by 21 publications

(13 citation statements)

References 33 publications

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“…About one-third of the soil organic matter in pit fillings and soil horizons consisted of charred organic matter, or black carbon. AMS 14 C data of charred organic matter from soil samples selected for this study (Table 1) indicated the occurrence of fires during Mesolithic to Neolithic periods (Gerlach et al, 2006;Eckmeier et al, 2009). The control samples were taken from the soil material (Bt-horizon of Luvisols) directly next to the pits from an identical soil depth.…”

Section: Methodsmentioning

confidence: 99%

Short-chain n-alkanes (C16–20) in ancient soil are useful molecular markers for prehistoric biomass burning

Eckmeier

Wiesenberg

2009

Journal of Archaeological Science

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103

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The incorporation of plant biomass into soil usually leads to long-chain n-alkanes with a relative predominance of odd carbon numbered homologues. Contrastingly, an increase in short-chain even carbon numbered n-alkanes was found in charred biomass with progressing temperatures. We applied lipid analysis to buried ancient topsoils that contained charred organic matter and to corresponding control soils, which were characterized by a lighter color and lower contents of charred materials. Commonly, the proportion of lipid extracts was found to be lower in the ancient soil than in the control samples, which indicated an enhanced degradation of organic matter, e.g., by thermal degradation. All samples displayed a particular pattern of short-chain and even carbon numbered n-alkanes (maximum at n-C16 or n-C18). The ratios CPI (carbon preference index) and ACL (average chain length) for the investigated soil samples matched the ratios found for maize and rye straw charred at 400 °C or 500 °C, respectively. These molecular ratios indicate the presence of charred biomass. The predominance of short-chain and even carbon numbered n-alkanes was a result of thermal degradation of biomass. The degradation products were preserved in ancient soils and could be applied as molecular markers in archaeological or palaeoenvironmental research.Author's personal copy b s t r a c tThe incorporation of plant biomass into soil usually leads to long-chain n-alkanes with a relative predominance of odd carbon numbered homologues. Contrastingly, an increase in short-chain even carbon numbered n-alkanes was found in charred biomass with progressing temperatures. We applied lipid analysis to buried ancient topsoils that contained charred organic matter and to corresponding control soils, which were characterized by a lighter color and lower contents of charred materials. Commonly, the proportion of lipid extracts was found to be lower in the ancient soil than in the control samples, which indicated an enhanced degradation of organic matter, e.g., by thermal degradation. All samples displayed a particular pattern of short-chain and even carbon numbered n-alkanes (maximum at n-C 16 or n-C 18 ). The ratios CPI (carbon preference index) and ACL (average chain length) for the investigated soil samples matched the ratios found for maize and rye straw charred at 400 C or 500 C, respectively. These molecular ratios indicate the presence of charred biomass. The predominance of short-chain and even carbon numbered n-alkanes was a result of thermal degradation of biomass. The degradation products were preserved in ancient soils and could be applied as molecular markers in archaeological or palaeoenvironmental research.

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Section: Methodsmentioning

confidence: 99%

Short-chain n-alkanes (C16–20) in ancient soil are useful molecular markers for prehistoric biomass burning

Eckmeier

Wiesenberg

2009

Journal of Archaeological Science

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103

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“…Our results are consistent with the hypothesis of Nocentini et al (2010) that the least stable CharC particles are the finest. However, CharC stability has also been proposed to increase with decreasing particle-size (Eckmeier et al, 2009).…”

Section: Stability Of Soc and Charcmentioning

confidence: 99%

“…If this is the case, the apparent contradictions indicated by studies reporting both fast and slow cycling charcoal may be resolved: at the soil surface charcoal is less stable, but in subsoils it can persist for millennia. Alternatively, charcoal stability has been linked with particle‐size and both coarse charcoal (Eckmeier et al , ) and fine charcoal (Nocentini et al , ) have been hypothesized as being the least stable fraction. Therefore, understanding the distribution and stability of charcoal in soils can provide the key to deciphering the black carbon cycle.…”

Section: Introductionmentioning

confidence: 99%

Vertical distribution of charcoal in a sandy soil: evidence from DRIFT spectra and field emission scanning electron microscopy

Hobley

Willgoose

Frisia

et al. 2014

European J Soil Science

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Summary This study uses diffuse reflectance infrared Fourier Transform (DRIFT) spectrometry and field emission scanning electron microscopy to investigate the vertical distribution of charcoal in a sandy soil from SE Australia. The soil was sampled to bedrock (120 cm) at varying depths and bulk samples were fractionated into three particle‐sizes: macro‐ (2000–200 µm), micro‐ (200–60 µm) and mineral‐associated organic matter (MAOM, < 60 µm). Charcoal was isolated from 0–30 and 30–60‐cm depths. Soil charcoal was detected by using a DRIFT band centred at 1590 cm−1 and scanning electron microscopy combined with energy dispersive spectroscopy. Charcoal content as a proportion of soil organic carbon (SOC) was estimated with linear regressions of cumulative DRIFT bands. At 0–30 cm, charcoal content as a portion of SOC did not differ significantly between particle‐size fractions, constituting 5–26% of SOC. At a depth of 30–60 cm, charcoal constituted 19–39% of SOC in the fractions. At 60–100 cm, charcoal was only detectable in the mid‐sized fraction, where it constituted about 17% of SOC. These results support our previous hypothesis of charcoal enrichment in the micro‐fraction inducing a greater SOC stability in this fraction as inferred from radiocarbon ages (Hobley et al., 2013). Our findings indicate that DRIFT spectra can be used to detect the presence and amount of charcoal in soil, which may prove to be a simple and low‐cost alternative to more laborious and costly detection methods.

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“…The chemistry of these molecules is heterogenous and can be represented as a "continuum" of compounds ranging from slightly charred biomass to highly condensed aromatic materials (Masiello, 2004;Bird et al, 2015), all of which are characterized by an increase in C concentration relative to their non-pyrolyzed precursors . Although part of the PyC pool is labile, PyC ages of 100s−1000s of years, and even up to 10,000 years have been reported in the top 1 m of soil, indicating that PyC can be one of the longest-lived C pools in terrestrial ecosystems (Schmidt et al, 2002Eckmeier et al, 2009). Therefore, conversion of biomass and soil C into long-lived PyC during fires may help mitigate a proportion of fire-induced C losses.…”

Section: Introductionmentioning

confidence: 99%

Quantifying Changes in Total and Pyrogenic Carbon Stocks Across Fire Severity Gradients Using Active Wildfire Incidents

et al. 2018

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Positive feedbacks between wildfire emissions and climate are expected to increase in strength in the future; however, fires not only release carbon (C) from terrestrial to atmospheric pools, they also produce pyrogenic C (PyC) which contributes to longer-term C stability. Our objective was to quantify wildfire impacts on total C and PyC stocks in California mixed-conifer forest, and to investigate patterns in C and PyC stocks and changes across gradients of fire severity, using metrics derived from remote sensing and field observations. Our unique study accessed active wildfires to establish and measure plots within days before and after fire, prior to substantial erosion. We measured pre-and post-fire aboveground forest structure and woody fuels to calculate aboveground biomass, C and PyC, and collected forest floor and 0-5 cm mineral soil samples. Immediate tree mortality increased with severity, but overstory C loss was minimal and limited primarily to foliage. Fire released 85% of understory and herbaceous C (comprising <1.0% of total ecosystem C). The greatest C losses occurred from downed wood and forest floor pools (19.3 ± 5.1 Mg ha −1 and 25.9 ± 3.2 Mg ha −1 , respectively). Tree bark and downed wood contributed the greatest PyC gains (1.5 ± 0.3 Mg ha −1 and 1.9 ± 0.8 Mg ha −1 , respectively), and PyC in tree bark showed non-significant positive trends with increasing severity. Overall PyC losses of 1.9 ± 0.3 Mg ha −1 and 0.5 ± 0

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Dating Charred Soil Organic Matter: Comparison of Radiocarbon Ages from Macrocharcoals and Chemically Separated Charcoal Carbon

Cited by 21 publications

References 33 publications

Short-chain n-alkanes (C16–20) in ancient soil are useful molecular markers for prehistoric biomass burning

Short-chain n-alkanes (C16–20) in ancient soil are useful molecular markers for prehistoric biomass burning

Vertical distribution of charcoal in a sandy soil: evidence from DRIFT spectra and field emission scanning electron microscopy

Quantifying Changes in Total and Pyrogenic Carbon Stocks Across Fire Severity Gradients Using Active Wildfire Incidents

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