Modelling decomposition of standard plant material along an altitudinal gradient: A re-analysis of data of Coûteaux et al. (2002)

Braakhekke, W.G.; Bruijn, Arjan M. G. de

doi:10.1016/j.soilbio.2006.06.018

Cited by 8 publications

(9 citation statements)

References 19 publications

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“…However, we found that increased respiration under warming in the early part of incubation is best modeled with an increase in the size of the active pool (C a ) with warming, whereas the decay constant (k a ) for that pool stays relatively constant (Table S1) in the Duke soils (flux data from Aspen soils did not fit the model). This pattern has been found in many studies, and it has resulted in an ongoing debate about whether temperature dependence can be in both the pool size terms and the rate constant (18)(19)(20).…”

Section: Resultsmentioning

confidence: 78%

Warming accelerates decomposition of decades-old carbon in forest soils

Hopkins

Torn

Trumbore

2012

Proc. Natl. Acad. Sci. U.S.A.

127

105

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Global climate carbon-cycle models predict acceleration of soil organic carbon losses to the atmosphere with warming, but the size of this feedback is poorly known. The temperature sensitivity of soil carbon decomposition is commonly determined by measuring changes in the rate of carbon dioxide (CO 2 ) production under controlled laboratory conditions. We added measurements of carbon isotopes in respired CO 2 to constrain the age of carbon substrates contributing to the temperature response of decomposition for surface soils from two temperate forest sites with very different overall rates of carbon cycling. Roughly one-third of the carbon respired at any temperature was fixed from the atmosphere more than 10 y ago, and the mean age of respired carbon reflected a mixture of substrates of varying ages. Consistent with global ecosystem model predictions, the temperature sensitivity of the carbon fixed more than a decade ago was the same as the temperature sensitivity for carbon fixed less than 10 y ago. However, we also observed an overall increase in the mean age of carbon respired at higher temperatures, even correcting for potential substrate limitation effects. The combination of several age constraints from carbon isotopes showed that warming had a similar effect on respiration of decades-old and younger (<10 y) carbon but a greater effect on decomposition of substrates of intermediate (between 7 and 13 y) age. Our results highlight the vulnerability of soil carbon to warming that is years-to-decades old, which makes up a large fraction of total soil carbon in forest soils globally.climate feedback | soil organic matter | soil respiration | radiocarbon | soil incubation T he potential for carbon stored on land to become a source of carbon dioxide (CO 2 ) to the atmosphere in the 21st century is a key uncertainty in predictions of future climate. Global warming increases the rate of decomposition of soil organic carbon (C), a major loss pathway of C from the land surface to the atmosphere, thus contributing to the increase in atmospheric CO 2 and hence, global temperatures. However, how much of the estimated 3,000 Pg C (1) stored in soils globally is vulnerable to enhanced decomposition with warming is highly uncertain and difficult to assess (2). In particular, the temperature sensitivity of C cycling on decadal timescales is a key uncertainty controlling the size of potential soil C responses to warming (3). Although there are no global estimates of decadal-aged C, it makes up the majority of C in mineral soils in temperate forests (4). We took advantage of a decade-long, whole-ecosystem C-isotope label to isolate the effect of warming on decomposition of decades-old C in a laboratory incubation experiment.The temperature sensitivity of decades-old C is difficult to observe using traditional approaches, such as response of CO 2 flux to experimental warming, because respiration is dominated by soil C cycling on fast timescales of 1 y or less. Previous studies using C isotopes to identify older C and assess it...

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Section: Resultsmentioning

confidence: 78%

Warming accelerates decomposition of decades-old carbon in forest soils

Hopkins

Torn

Trumbore

2012

Proc. Natl. Acad. Sci. U.S.A.

127

105

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“…MOMOS allowed us to adequately predict total and microbial 14 C dynamics during the decomposition of a standard plant material (wheat straw) in six extremely contrasting tropical environments using only one parameter specific to each site ( k resp ) instead of the two or three site specific parameters necessary in previous analysis using the same database to predict only total 14 C by two exponential models [ Coûteaux et al , 2002; Braakhekke and de Bruijn , 2007]. Furthermore, only this parameter k resp is related to soil properties.…”

Section: Discussionmentioning

confidence: 99%

“…Eighteen parameter values were necessary to describe 14 C mineralization along the gradient, and only 30% of the between‐site variability could be ascribed to climatic differences. Braakhekke and de Bruijn [2007] reanalyzed the same data to reduce the modeling complexity but had to maintain different mineralization rates for each site, and 13 parameter values were again necessary to predict the whole total 14 C data. The Transalt data were never used before to predict the 14 C transfer processes both in humus and atmosphere and validate models of organic matter in soil.…”

Section: Introductionmentioning

confidence: 99%

Modeling organic transformations by microorganisms of soils in six contrasting ecosystems: Validation of the MOMOS model

Pansu

Sarmiento

Rujano

et al. 2010

Global Biogeochemical Cycles

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[1] The Modeling Organic Transformations by Microorganisms of Soils (MOMOS) model simulates the growth, respiration, and mortality of soil microorganisms as main drivers of the mineralization and humification processes of organic substrates. Originally built and calibrated using data from two high-altitude sites, the model is now validated with data from a 14 C experiment carried out in six contrasting tropical ecosystems covering a large gradient of temperature, rainfall, vegetation, and soil types from 65 to 3968 m asl. MOMOS enabled prediction of a greater number of variables using a lower number of parameter values than for predictions previously published on this experiment. The measured 14 C mineralization and transfer into microbial biomass (MB) and humified compartments were accurately modeled using (1) temperature and moisture response functions to daily adjust the model responses to weather conditions and (2) optimization of only one parameter, the respiration rate k resp of soil microorganisms at optimal temperature and moisture. This validates the parameterization and hypotheses of the previous calibration experiment. Climate and microbial respiratory activity, related to soil properties, appear as the main factors that regulate the C cycle. The k resp rate was found to be negatively related to the fine textural fraction of soil and positively related to soil pH, allowing the proposition of two transfer functions that can be helpful to generalize MOMOS application at regional or global scale.

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“…For instance, the "equal-time" approach always leads to great discrepancies in the degradation of fast-vs. slow-turnover C pools among samples along with increasing incubation temperature and time, while the "equal-C" approach can underestimate the contribution of more recalcitrant substrates (Hamdi et al, 2013). Although a first-order model has been applied to disentangle the C mineralization process to quantify the sizes of various labile and recalcitrant pools as well as their decomposition rate constants, the temperature sensitivity of the abovementioned kinetic parameters of C mineralization has seldom been investigated (Braakhekke and de Bruijn, 2007;Bracho et al, 2016;Rey et al, 2008;Sun et al, 2016). Although Rey and Jarvis (2006) found that the labile C proportion (a 0 ) did not vary among 4, 10, 20 and 30°C, their experimental data were only derived from upper mineral soils, whose estimated labile fraction from the two-compartment model might be too small (1-9%) to detect substantial differences.…”

Section: Introductionmentioning

confidence: 99%

“…Although Rey and Jarvis (2006) found that the labile C proportion (a 0 ) did not vary among 4, 10, 20 and 30°C, their experimental data were only derived from upper mineral soils, whose estimated labile fraction from the two-compartment model might be too small (1-9%) to detect substantial differences. The C pool sizes were reported to vary with the substrate quality, the microbial community composition and the environmental conditions (Braakhekke and de Bruijn, 2007;CoÛteaux et al, 2002;Erhagen et al, 2015). In principle, a change in temperature can induce shifts in functional microorganisms and in enzyme activities, modify the primary resource decomposition pathways and the secondary material production, and, finally, affect the sizes of the labile or recalcitrant C pools (Dalias et al, 2001;Razavi et al, 2016Razavi et al, , 2017.…”

Section: Introductionmentioning

confidence: 99%

Q10 values vary with different kinetic properties of C mineralization

Bai

Lin

et al. 2017

Pedobiologia

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A B S T R A C TTemperature response quotient (Q 10 ) is a critical parameter for evaluating global additional carbon (C) release with climate change. However, its value is usually derived from time span or instantaneous rate or cumulative amount of C flux, giving a very one-sided account of thermal sensitivity of C cycling. Through a 117-day laboratory incubation study, we estimated Q 10 values simultaneously with the labile (a 0 ) and recalcitrant C proportions and their rate constants, and then tested for any variances of these kinetic properties in different vegetation stands, soil horizons, aeration statuses, and thermal settings (i.e., diurnally-varying, constant low and constant high temperatures). A regularly varying temperature regime increased the exploitation of labile C resources (i.e., high a 0 ) and required longer time spans (i.e., low rate constants). The constant high temperature induced the exhaustive depletion of the labile C pool and motivated a very rapid and short-term C mineralization process. The constant low temperature treatment was characterized by the lowest a 0 but by medium rate constants because low temperature slowed the C mineralization processes but retained high level of the original C processing diversity. Therefore, a 0 and the rate constants showed discrepancies in their temperature sensitivities as revealed by pairwise comparisons of temperature regimes. Such discrepancies were also supported by pairwise comparisons of aeration statuses, forest stands and soil horizons. The Q 10 bias between C mineralization a 0 and rate constants in this laboratory experiment is attributed to the inherently distinct properties of these two parameters, as a 0 and its Q 10 are closely correlated with the sizes of the easily available C pool, while rate constants and their Q 10 variances explain the temporal scale of the same C mineralization process. Our findings suggest a combined application of a 0 and rate constants for exploring the temperature sensitivity of C mineralization in future studies.

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Modelling decomposition of standard plant material along an altitudinal gradient: A re-analysis of data of Coûteaux et al. (2002)

Cited by 8 publications

References 19 publications

Warming accelerates decomposition of decades-old carbon in forest soils

Warming accelerates decomposition of decades-old carbon in forest soils

Modeling organic transformations by microorganisms of soils in six contrasting ecosystems: Validation of the MOMOS model

Q10 values vary with different kinetic properties of C mineralization

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