Characterization of soil organic matter

Denef, Karolien; Plante, Alain F.; Six, Johan

doi:10.1017/cbo9780511711794.007

Cited by 23 publications

(20 citation statements)

References 302 publications

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“…Recent studies have also highlighted the importance of the long-term stabilization of N-containing compounds (proteins, amino acids, peptides, chitin) and polysaccharides to soil organic C stabilization in arable soils (Kiem and Kögel-Knabner, 2003). These findings imply a preservation of microbial-derived C and indicate the greater importance of microbial processing of organic matter over intrinsic biochemical recalcitrance for the long-term stabilization of C (Denef et al, 2009; Gentile et al, 2010; Kogel-Knabner, 2002). Although a proportion of organic matter-C is respired during microbial processing, we maintain that more microbial activity is a prerequisite for greater C sequestration, in absolute terms (i.e., increased C respiration is not necessarily contradictory to increased C stabilization).…”

Section: Introductionmentioning

confidence: 83%

Microbial community composition and carbon cycling within soil microenvironments of conventional, low-input, and organic cropping systems

Kong

Scow

Córdova-Kreylos

et al. 2011

Soil Biology and Biochemistry

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167

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This study coupled stable isotope probing with phospholipid fatty acid analysis (13C-PLFA) to describe the role of microbial community composition in the short-term processing (i.e., C incorporation into microbial biomass and/or deposition or respiration of C) of root- versus residue-C and, ultimately, in long-term C sequestration in conventional (annual synthetic fertilizer applications), low-input (synthetic fertilizer and cover crop applied in alternating years), and organic (annual composted manure and cover crop additions) maize-tomato (Zea mays – Lycopersicum esculentum) cropping systems. During the maize growing season, we traced 13C-labeled hairy vetch (Vicia dasycarpa) roots and residues into PLFAs extracted from soil microaggregates (53–250 μm) and silt-and-clay (<53 μm) particles. Total PLFA biomass was greatest in the organic (41.4 nmol g-1 soil) and similar between the conventional and low-input systems (31.0 and 30.1 nmol g-1 soil, respectively), with Gram-positive bacterial PLFA dominating the microbial communities in all systems. Although total PLFA-C derived from roots was over four times greater than from residues, relative distributions (mol%) of root- and residue-derived C into the microbial communities were not different among the three cropping systems. Additionally, neither the PLFA profiles nor the amount of root- and residue-C incorporation into the PLFAs of the microaggregates were consistently different when compared with the silt-and-clay particles. More fungal PLFA-C was measured, however, in microaggregates compared with silt-and-clay. The lack of differences between the mol% within the microbial communities of the cropping systems and between the PLFA-C in the microaggregates and the silt-and-clay may have been due to (i) insufficient differences in quality between roots and residues and/or (ii) the high N availability in these N-fertilized cropping systems that augmented the abilities of the microbial communities to process a wide range of substrate qualities. The main implications of this study are that (i) the greater short-term microbial processing of root- than residue-C can be a mechanistic explanation for the higher relative retention of root- over residue-C, but microbial community composition did not influence long-term C sequestration trends in the three cropping systems and (ii) in spite of the similarity between the microbial community profiles of the microaggregates and the silt-and-clay, more C was processed in the microaggregates by fungi, suggesting that the microaggregate is a relatively unique microenvironment for fungal activity.

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Section: Introductionmentioning

confidence: 83%

Microbial community composition and carbon cycling within soil microenvironments of conventional, low-input, and organic cropping systems

Kong

Scow

Córdova-Kreylos

et al. 2011

Soil Biology and Biochemistry

Self Cite

167

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“…Our findings provide partial support for the mass ratio hypothesis in that M. vimineum biomass was positively related to SOC content in the urban matrix. However, if increased detrital inputs were driving the accrual of SOC in the urban matrix, we would expect most of this C to accumulate in the POMC pool, which primarily consists of recently plant-derived C (Denef et al 2009). Koteen et al (2011) invoked this mechanism to explain why SOC was lower under an invasive annual grass that had low productivity relative to the native perennials that it replaced.…”

Section: Discussionmentioning

confidence: 99%

“…Likewise, Liao et al (2008) suggested that higher soil C under N-fixing invasive species may be due to the positive effects of increased N availability on plant productivity. However, if increased detrital inputs were driving the accrual of SOC in the urban matrix, we would expect most of this C to accumulate in the POMC pool, which primarily consists of recently plant-derived C (Denef et al 2009). Instead, we found that the POMC pool was consistently lower (25% on average) under M. vimineum, and higher SOC was mainly attributable to the MAOMC, or microbe-derived, pool.…”

Section: Discussionmentioning

confidence: 99%

Grass invasion effects on forest soil carbon depend on landscape‐level land use patterns

Craig

Pearson

Fraterrigo

2015

Ecology

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Plant invasions can alter the quality and quantity of detrital and root-derived inputs entering a system, thereby influencing the activities of microbial decomposers and affecting the soil carbon cycle. The effect of these inputs on soil carbon storage is often conflicting, suggesting strong context dependency in the plant-decomposer relationship. Whether there is a generalizable pattern that explains this dependency remains relatively unexplored. Here, we (1) examine how invasion by the exotic grass Microstegium vimineum affects carbon cycling across a land use gradient, and (2) evaluate the importance of inorganic nitrogen availability and other environmental variables for explaining patterns in soil carbon. Using paired invaded and uninvaded plots, we quantified invasion effects on belowground carbon pools, extracellular enzyme activities, and native leaf litter decomposition in forests embedded in an urban, agricultural, or forested landscape matrix. Compared to the urban matrix, invasion-associated declines in total soil organic carbon in the forested and agricultural landscapes were 3.5 and 2.5 times greater, respectively. Inorganic nitrogen availability and M. vimineum biomass interacted to explain these patterns: when both nitrogen availability and M. vimineum biomass were high, invaded soils exhibited higher total organic carbon, unchanged particulate organic matter carbon, and higher mineral-associated organic matter carbon compared to adjacent uninvaded soils. Consistent with these patterns, activities of carbon-mineralizing enzymes were lower in invaded than in uninvaded soils when both nitrogen availability and M. vimineum biomass were high. By contrast,. decomposition of native leaf litter was faster when inorganic nitrogen availability and M. vimineum biomass were high. Our findings suggest that, although this invader may accelerate carbon cycling in forest soils, its effects on soil carbon storage largely depend on nitrogen availability and invader biomass, which can be altered by landscape-level patterns of land use. Additional research is needed to determine whether land use or other broad-scale processes such as atmospheric nitrogen deposition can explain context dependence in plant invasion effects on other ecosystem processes.

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“…Overall, soil fractionation approaches have well-known limitations (e.g. von Lützow et al 2007;Denef et al 2009) but may still be useful to parameterize modelable pools (e.g. Smith et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Distribution of Radiocarbon Ages in Soil Organic Matter by Thermal Fractionation

Plante

Beaupré²,

Roberts³

et al. 2013

Radiocarbon

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ABSTRACT. Radiocarbon analysis is an important tool in quantifying soil organic matter (SOM) dynamics within the terrestrial carbon cycle. However, there is increasing appreciation that representing SOM as a single, homogeneous pool with a single, mean 14 C concentration is inadequate. We investigate whether the differing patterns in CO 2 release during rampedtemperature oxidation reflect organic matter of different ages, and hypothesize that thermally labile SOM (combusting at low temperatures) consists of younger carbon than thermally resistant organic matter. Topsoil samples under contrasting land uses (native vegetation and long-term cultivation) were selected for 14 C analysis before and after acid fumigation for the removal of carbonates. Results of bulk 14 C analyses showed a significant shift in 14 C age from 0.944 Fm under native vegetation to 0.790 Fm under cultivation. Four to 5 "fractions" associated with different CO 2 -evolution regions were identified by thermal analysis and analyzed for 14 C via modifications to NOSAMS' established "programmed temperature pyrolysis system," in which discrete CO 2 fractions evolved during ramped-temperature oxidation were isotopically characterized by a microwave gas ion source (GIS) continuous-flow AMS (CFAMS) system. Results showed that while acid fumigation removed soil carbonates, the treatment also significantly altered the thermograms and inferred SOM composition. While direct attribution of 14 C values to individual peaks is somewhat confounded by overlapping temperature ranges for oxidation of unique populations of carbon, in general, thermally stable fractions of SOM appear to be 14 C-depleted compared to thermally reactive (low temperature) fractions regardless of pretreatment.

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Characterization of soil organic matter

Cited by 23 publications

References 302 publications

Microbial community composition and carbon cycling within soil microenvironments of conventional, low-input, and organic cropping systems

Microbial community composition and carbon cycling within soil microenvironments of conventional, low-input, and organic cropping systems

Grass invasion effects on forest soil carbon depend on landscape‐level land use patterns

Distribution of Radiocarbon Ages in Soil Organic Matter by Thermal Fractionation

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