Biased 14C-derived organic carbon turnover estimates following black carbon input to soil: an exploration with RothC

Leifeld, Jens

doi:10.1007/s10533-008-9209-4

Cited by 13 publications

(16 citation statements)

References 23 publications

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“…For example, whereas most of their soils were only slightly contaminated, Jenkinson et al (1992) found three Rothamsted soils to have c. 500 g carbonised C m -2 , 10 times greater than the majority. Leifeld (2008) carried out simulations with the Roth-C 26.3 model (Coleman and Jenkinson 1999) of the effects of black carbon on apparent soil C turnover, and reported under-or over-estimation of C turnover rates by up to 30%, i.e. a similar magnitude to the results reported here.…”

Section: "Black Carbon" and Coalsupporting

confidence: 73%

Long-term organic carbon turnover rates in natural and semi-natural topsoils

et al. 2013

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Article (refereed) -postprintMills, R.T.E.; Tipping, E.; Bryant, C.L.; Emmett, B.A. 2014. Long-term organic carbon turnover rates in natural and semi-natural topsoils. Biogeochemistry,. 257-272. 10.1007/s10533-013-9928-z Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. We combined published and new radiocarbon and ancillary data for uncultivated topsoils 25 (typically 15 cm depth), to make two databases, one for the United Kingdom (133 sites), and 26 one global (115 sites). Forest topsoils are significantly higher in radiocarbon than non-forest 27 soils, indicating greater enrichment with "bomb carbon" and therefore faster C turnover, if 28 steady-state conditions are assumed. Steady-state modelling, taking into account variations 29 in atmospheric 14 CO 2 , including the effects of 20 th century nuclear weapons testing and 30 radioactive decay, was used to quantify soil carbon turnover rates. Application of a model 31 with variable slow (20 yr mean residence time, MRT) and passive (1000 yr MRT) carbon 32 pools partitioned the topsoil C approximately equally, on average, between the two pools 33 when the entire data set was considered. However, the mean slow:passive ratio of 0.65:0. Terrestrial soil organic matter (SOM) derived from dead biomass accounts for the largest 47 global pool of organic carbon, totalling 2300 Pg (Jobbagy & Jackson, 2000) and therefore 48 greater than both the oceanic pool of 1000 Pg, and the living terrestrial biomass pool of 600-49 1000 Pg (Falkowski et al., 2000). It comprises a range of organic material at various stages 50 of decomposition and stabilisation, from recently-deposited labile plant material and senesced 51 microbial biomass with fast turnover (seconds to years), to more stable material turning over 52 on decadal to millennial timescales (Trumbore 2000(Trumbore , 2009Amundson 2001). Quantification 53 of SOM turnover with respect to environmental conditions and litter quality and quantity is 54 crucial to understanding the resilience of soil C to perturbations such as climate change and 55 land use conversion in the longer term and at the global scale (Jenkinson et al, 1991; 56 Kirschbaum, 2000;Schlesinger & Adams, 2000;Smith et al., 2008; Schmidt et al, 2011). 57The response of topsoil SOM is of particular importance since it is in close contact with the 58 atmosphere and the least stabilised against decomposition. 59Much of the carbon entering soil is respired quickly, within months or a few years, and can 60 be studied with relatively short term experiments and observations, leading to detailed 61 understanding (Melillo et al., 1982;Berg and McClaugherty, 2008). However, the bulk of 62 soil carbon is in slowly-cycling SOM pools and far less amenable to experimental 63 investigation. The most generally-applicable approach at these longer timescales is the 64 determination ...

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Section: "Black Carbon" and Coalsupporting

confidence: 73%

Long-term organic carbon turnover rates in natural and semi-natural topsoils

et al. 2013

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“…However, the 13 C method can only be used when there are detectable changes in d 13 C after years of successive C 3 versus C 4 vegetation change, and 14 C dating could more accurately estimate C turnover of soil fractions when soils are under steady-state conditions or 14 C inputs derived from atmosphere and vegetation are well documented. It is noticeable that when using the 14 C dating method the presence of black C in soils could bias C turnover times of coarse organic matter, which is considered to be labile and has short turnover times (Baisden et al, 2002;Leifeld, 2008;Leifeld et al, 2015). Overall, these findings suggest that consideration should be given to methodological differences when using C turnover data to inform and parameterize soil C models.…”

Section: Discussionmentioning

confidence: 99%

Methodological uncertainty in estimating carbon turnover times of soil fractions

Feng

Shi

Jiang

et al. 2016

Soil Biology and Biochemistry

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C 14 C Incubation Fraction a b s t r a c t Improving predictions of soil organic carbon (SOC) dynamics by multi-compartment models requires validation of turnover times of different SOC pools. Techniques such as laboratory incubation and isotope analysis have been adopted to estimate C turnover times, yet no studies have systematically compared these techniques and assessed the uncertainties associated with them. Here, we tested whether C turnover times of soil fractions were biased by methodology, and how this changed across soil particle sizes and ecosystems. We identified 52 studies that quantified C turnover times in different soil particles fractionated either according to aggregate size (e.g., macro-versus micro-aggregates) or according to soil texture (e.g., sand versus silt versus clay). C turnover times of these soil fractions were estimated by one of three methods: laboratory incubation (16 studies), d 13 C shift due to C 3 eC 4 vegetation change (25 studies), and 14 C dating (19 studies). All methods showed that C turnover times of soil fractions generally increase with decreasing soil particle size. However, estimates of C turnover times within soil fractions differed significantly among methods, with incubation estimating the shortest turnover times and 14 C the longest. The short C turnover times estimated by incubation are likely due to optimal environmental conditions for microbial decomposition existing in these studies, which is often a poor representation of field conditions. The 13 C method can only be used when documenting a successive C 3 versus C 4 vegetation shift. C turnover times estimated by 14 C were systematically higher than those estimated by 13 C, especially for fine soil fractions (i.e., silt and clay). Overall, our findings highlight methodological uncertainties in estimating C turnover times of soil fractions, and correction factors should be explored to account for methodological bias when C turnover times estimated from different methods are used to parameterize soil C models.

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“…Depending on the amount and age of BC incorporated, mean ages estimated by the model may be biased by up to 30% (Leifeld 2008). It should also be noted that the mean age resulting from the steady-state turnover model as used here and in other soil science applications differs from the notation usually used for 14 C-dated samples and hence does not refer to calibrated or conventional 14 C age.…”

Section: Calculation Of Mean Carbon Agementioning

confidence: 99%

Age and Thermal Stability of Particulate Organic Matter Fractions Indicate the Presence of Black Carbon in Soil

Leifeld

Heiling

Hajdas³

2015

Radiocarbon

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Black carbon (BC) from incomplete combustion of organic materials is abundant in many soils. Its age is often higher than that of thermally unaltered soil organic carbon (SOC) owing to the presence of BC from fossil sources or to a high recalcitrance against microbial decomposition compared to that of plant residues. For a meaningful application of radiocarbon as an indicator for soil carbon age and turnover, the relative contribution of BC needs to be quantified, but BC is difficult to separate physically from soil. However, BC is thermally more stable than SOC, and hence thermal stability may provide a quantitative BC indicator. Here, we analyzed 30 light particulate organic carbon (POC) soil fractions for their thermal stability and for their 14 C signature. POC is particularly sensitive to "contamination" with BC, because it is obtained by combined size and density fractionation. A steady-state "bomb" 14 C model was used to derive mean POC ages. Soils from four sample sets, each consisting of six to eight individual POC samples and representing different field sites and POC types, were analyzed. Samples from one of the sets were virtually BC free, and their mean POC ages ranged from 60 to 100 yr. The 14 C signature of samples from the other three sets indicated the presence of very old carbon, with mean POC ages of several hundred and up to 3500 yr. Two indicators for thermal stability-(1) the amount of heat released at temperatures >450°C and (2) the amount of heat released at 500°C (the latter representing the peak temperature of heat released from charcoal isolated from soil)-correlated both significantly and nonlinearly with POC age, indicating that samples with high BC content were older than those with low BC content. It can be concluded that at an individual site with increasing abundance of BC, both the age and the thermal stability of POC increase. However, thermal stability proved to be a reliable predictor for BC in only one sample set, whereas thermal signals of the other two BC-containing sample sets were not significantly different from those of BC-free samples. Thermal stability thus gives no unequivocal indication for the presence of BC in POC across different sites.

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Biased 14C-derived organic carbon turnover estimates following black carbon input to soil: an exploration with RothC

Cited by 13 publications

References 23 publications

Long-term organic carbon turnover rates in natural and semi-natural topsoils

Long-term organic carbon turnover rates in natural and semi-natural topsoils

Methodological uncertainty in estimating carbon turnover times of soil fractions

Age and Thermal Stability of Particulate Organic Matter Fractions Indicate the Presence of Black Carbon in Soil

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