SOM and Microbes—What Is Left From Microbial Life

Kästner, Matthias; Miltner, Anja

doi:10.1016/b978-0-12-811687-6.00005-5

Cited by 29 publications

(28 citation statements)

References 137 publications

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“…Microorganisms are at the heart of two critical, contrasting mechanisms: not only reducing SOC stocks through mineralization to CO 2 but also increasing SOC stocks through the formation of microbial biomass and stabilization of its residues associated with minerals, within soil structures, or by incrustation with, for example, Fe or Si precipitates (Kästner & Miltner, ; Lehmann, Kinyangi, & Solomon, ; Liang et al, ). By now, it is readily accepted that SOC storage is heavily influenced by anabolic activities of microorganisms, emphasizing that the most persistent organic carbon in soil may not be composed of plant litter or their residues but carbon that has first passed through microbial biomass (Benner, ; Cotrufo, Wallenstein, Boot, Denef, & Paul, ; Liang & Balser, ; Lützow et al, ; Miltner, Bombach, Schmidt‐Brücken, & Kästner, ; Figure ).…”

Section: Introductionmentioning

confidence: 99%

“…This consideration is based on the fact that easily degradable and accessible molecules in SOM will be consumed by microorganisms and that even sorbed molecules can be degraded (Miltner et al, ; Schmidt et al, ). The molecules will then be partly mineralized for gaining energy (catabolism) and partly used for building microbial biomass (anabolism; Kästner & Miltner, ; Liang et al, ). After cell death and subsequent lysis and fragmentation, several organic cell compounds are still present and contribute, thus, to the pool of microbial necromass.…”

Section: Introductionmentioning

confidence: 99%

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Quantitative assessment of microbial necromass contribution to soil organic matter

Liang

Amelung

Lehmann

et al. 2019

Global Change Biology

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942

452

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Soil carbon transformation and sequestration have received significant interest in recent years due to a growing need for quantitating its role in mitigating climate change. Even though our understanding of the nature of soil organic matter has recently been substantially revised, fundamental uncertainty remains about the quantitative importance of microbial necromass as part of persistent organic matter. Addressing this uncertainty has been hampered by the absence of quantitative assessments whether microbial matter makes up the majority of the persistent carbon in soil. Direct quantitation of microbial necromass in soil is very challenging because of an overlapping molecular signature with nonmicrobial organic carbon. Here, we use a comprehensive analysis of existing biomarker amino sugar data published between 1996 and 2018, combined with novel appropriation using an ecological systems approach, elemental carbon–nitrogen stoichiometry, and biomarker scaling, to demonstrate a suit of strategies for quantitating the contribution of microbe‐derived carbon to the topsoil organic carbon reservoir in global temperate agricultural, grassland, and forest ecosystems. We show that microbial necromass can make up more than half of soil organic carbon. Hence, we suggest that next‐generation field management requires promoting microbial biomass formation and necromass preservation to maintain healthy soils, ecosystems, and climate. Our analyses have important implications for improving current climate and carbon models, and helping develop management practices and policies.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Quantitative assessment of microbial necromass contribution to soil organic matter

Liang

Amelung

Lehmann

et al. 2019

Global Change Biology

Self Cite

942

452

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“…Different microbial groups have diverse necromass structure and chemical composition (Kästner & Miltner, 2018; Kögel‐Knabner, 2002; Six, Frey, Thiet, & Batten, 2006), possibly resulting in different necromass mineralization rates. The cytoplasmic fraction of microbial tissue is highly labile and may be rapidly taken up by decomposer organisms (Drigo, Anderson, Kannangara, Cairney, & Johnson, 2012; Fernandez, Langley, Chapman, McCormack, & Koide, 2016), and efficiently used to build new biomass.…”

Section: Introductionmentioning

confidence: 99%

Elevated temperature increases the accumulation of microbial necromass nitrogen in soil via increasing microbial turnover

Wang

Cotrufo

et al. 2020

Global Change Biology

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Microbial-derived nitrogen (N) is now recognized as an important source of soil organic N. However, the mechanisms that govern the production of microbial necromass N, its turnover, and stabilization in soil remain poorly understood. To assess the effects of elevated temperature on bacterial and fungal necromass N production, turnover, and stabilization, we incubated 15 N-labeled bacterial and fungal necromass under optimum moisture conditions at 10°C, 15°C, and 25°C. We developed a new 15 N tracing model to calculate the production and mineralization rates of necromass N. Our results showed that bacterial and fungal necromass N had similar mineralization rates, despite their contrasting chemistry. Most bacterial and fungal necromass 15 N was recovered in the mineral-associated organic matter fraction through microbial anabolism, suggesting that mineral association plays an important role in stabilizing necromass N in soil, independently of necromass chemistry. Elevated temperature significantly increased the accumulation of necromass N in soil, due to the relatively higher microbial turnover and production of necromass N with increasing temperature than the increases in microbial necromass N mineralization. In conclusion, we found elevated temperature may increase the contribution of microbial necromass N to mineral-stabilized soil organic N.

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“…Long-term persistence of GDGTs could arise from their stabilization by soil minerals at greater soil depths. The amphiphilic nature of lipids, such as GDGTs with both polar and hydrophobic components, promotes the association with mineral surfaces and therefore may afford physical protection from degradation (Jandl et al, 2004;Kleber et al, 2007;von Lützow et al, 2008;Van der Voort et al, 2017). By comparison, in surface soils with high organic matter contents and less availability of reactive mineral surfaces, GDGTs are continuously produced and degraded, which results in a younger mean radiocarbon age and evidence for turnover on decadal timescales (Weijers et al, 2010).…”

Section: Radiocarbon Constraints On the Origin And Turnover Of Gdgts In Soilsmentioning

confidence: 99%

Millennial-age glycerol dialkyl glycerol tetraethers (GDGTs) in forested mineral soils: <sup>14</sup>C-based evidence for stabilization of microbial necromass

et al. 2021

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Abstract. Understanding controls on the persistence of soil organic matter (SOM) is essential to constrain its role in the carbon cycle and inform climate–carbon cycle model predictions. Emerging concepts regarding the formation and turnover of SOM imply that it is mainly comprised of mineral-stabilized microbial products and residues; however, direct evidence in support of this concept remains limited. Here, we introduce and test a method for the isolation of isoprenoid and branched glycerol dialkyl glycerol tetraethers (GDGTs) – diagnostic membrane lipids of archaea and bacteria, respectively – for subsequent natural abundance radiocarbon analysis. The method is applied to depth profiles from two Swiss pre-Alpine forested soils. We find that the Δ14C values of these microbial markers markedly decrease with increasing soil depth, indicating turnover times of millennia in mineral subsoils. The contrasting metabolisms of the GDGT-producing microorganisms indicates it is unlikely that the low Δ14C values of these membrane lipids reflect heterotrophic acquisition of 14C-depleted carbon. We therefore attribute the 14C-depleted signatures of GDGTs to their physical protection through association with mineral surfaces. These findings thus provide strong evidence for the presence of stabilized microbial necromass in forested mineral soils.

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SOM and Microbes—What Is Left From Microbial Life

Cited by 29 publications

References 137 publications

Quantitative assessment of microbial necromass contribution to soil organic matter

Quantitative assessment of microbial necromass contribution to soil organic matter

Elevated temperature increases the accumulation of microbial necromass nitrogen in soil via increasing microbial turnover

Millennial-age glycerol dialkyl glycerol tetraethers (GDGTs) in forested mineral soils: <sup>14</sup>C-based evidence for stabilization of microbial necromass

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SOM and Microbes—What Is Left From Microbial Life

Cited by 29 publications

References 137 publications

Quantitative assessment of microbial necromass contribution to soil organic matter

Quantitative assessment of microbial necromass contribution to soil organic matter

Elevated temperature increases the accumulation of microbial necromass nitrogen in soil via increasing microbial turnover

Millennial-age glycerol dialkyl glycerol tetraethers (GDGTs) in forested mineral soils: &lt;sup&gt;14&lt;/sup&gt;C-based evidence for stabilization of microbial necromass

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Millennial-age glycerol dialkyl glycerol tetraethers (GDGTs) in forested mineral soils: <sup>14</sup>C-based evidence for stabilization of microbial necromass