Direct estimates of C:N ratios of ectomycorrhizal mycelia collected from Norway spruce forest soils

Wallander, Håkan; Nilsson, Lars Ola; Hagerberg, David; Rosengren, Ulrika

doi:10.1016/s0038-0717(03)00121-4

Cited by 97 publications

(70 citation statements)

References 13 publications

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“…The minimum values found for MB C : N ratios (Table 4) were in the commonly accepted range, except at the high-altitude site A(3968), where CO 2 -C respiration was reduced by lower temperatures. This study shows that it is possible to model the climatic role in C and N storage: cold and wet climates cause the accumulation of C with high C : N values, in accordance to Wallander et al (2003) for Norway. Bottner et al (2006) showed that total respired CO 2 -14 C was lower for nitrogen-poor straw than for nitrogen-rich straw.…”

Section: Relationship Between N and C Cyclessupporting

confidence: 64%

“…The microbial cultures of Nicolardot et al (1986) had C : N ratios in the range 5.2-12.7, depending on the substrate C : N ratios used in their laboratory conditions. Other works such as that of Wallander et al (2003) found MB C-N ratios of between 18.5 (for a soil C : N ratio of 16.9) and 21.9 (for a soil C : N ratio of 30.4); Bottner et al (2006) measured MB 14 C : 15 N ratios of 7.9 ± 1.3 for a substrate 14 C : 15 N ratio of 26.8, and MB 14 C : 15 N ratios of 33.9 ± 7.5 for a substrate 14 C : 15 N ratio of 130 (2 × 10 measurements in two sites). The MB-C : N ratios found in this paper were close to the measured total C : N ratios (Table 1) for the six sites, suggesting that the quality of living and dead organic materials converge to similar values after long fallow periods.…”

Section: Relationship Between N and C Cyclesmentioning

confidence: 99%

“…However, other models and experimental data (e.g. Wallander et al, 2003;Bottner et al, 2006) allow the C : N ratio of MB to change with time in response to the substrate C : N ratio and changes in the microbial communities during decomposition.…”

Section: Introductionmentioning

confidence: 99%

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Modelling microbial exchanges between forms of soil nitrogen in contrasting ecosystems

Pansu¹,

Machado

Bottner

et al. 2014

Biogeosciences

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Abstract. Although nitrogen (N) is often combined with carbon (C) in organic molecules, C passes from the air to the soil through plant photosynthesis, whereas N passes from the soil to plants through a chain of microbial conversions. However, dynamic models do not fully consider the microorganisms at the centre of exchange processes between organic and mineral forms of N. This study monitored the transfer of 14 C and 15 N between plant materials, microorganisms, humified compartments, and inorganic forms in six very different ecosystems along an altitudinal transect. The microbial conversions of the 15 N forms appear to be strongly linked to the previously modelled C cycle, and the same equations and parameters can be used to model both C and N cycles. The only difference is in the modelling of the flows between microbial and inorganic forms. The processes of mineralization and immobilization of N appear to be regulated by a two-way microbial exchange depending on the C : N ratios of microorganisms and available substrates. The MOMOS (Modelling of Organic Matter of Soils) model has already been validated for the C cycle and also appears to be valid for the prediction of microbial transformations of N forms. This study shows that the hypothesis of microbial homeostasis can give robust predictions at global scale. However, the microbial populations did not appear to always be independent of the external constraints. At some altitudes their C : N ratio could be better modelled as decreasing during incubation and increasing with increasing C storage in cold conditions. The ratio of potentially mineralizable-15 N/inorganic-15 N and the 15 N stock in the plant debris and the microorganisms was modelled as increasing with altitude, whereas the 15 N storage in stable humus was modelled as decreasing with altitude. This predicts that there is a risk that mineralization of organic reserves in cold areas may increase global warming.

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Section: Relationship Between N and C Cyclessupporting

confidence: 64%

Section: Relationship Between N and C Cyclesmentioning

confidence: 99%

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Modelling microbial exchanges between forms of soil nitrogen in contrasting ecosystems

Pansu¹,

Machado

Bottner

et al. 2014

Biogeosciences

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“…Low C / N ratios, as found in the top 10 cm of both mofettes, reflect microbially degraded organic matter (OM) (Rumpel and Kogel-Knabner, 2011) and C / N ratios as low as 9 (top 10 cm of mofette 2) suggest a high contribution of microbial biomass to bulk SOM (Wallander, 2003). A significant contribution of microbial biomass carbon at these depths is Figure 3.…”

Section: Carbon Sources In Mofette Soilsmentioning

confidence: 99%

Autotrophic fixation of geogenic CO<sub>2</sub> by microorganisms contributes to soil organic matter formation and alters isotope signatures in a wetland mofette

et al. 2015

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Abstract.To quantify the contribution of autotrophic microorganisms to organic matter (OM) formation in soils, we investigated natural CO 2 vents (mofettes) situated in a wetland in northwest Bohemia (Czech Republic). Mofette soils had higher soil organic matter (SOM) concentrations than reference soils due to restricted decomposition under high CO 2 levels. We used radiocarbon ( 14 C) and stable carbon (δ 13 C) isotope ratios to characterize SOM and its sources in two mofettes and compared it with respective reference soils, which were not influenced by geogenic CO 2 .The geogenic CO 2 emitted at these sites is free of radiocarbon and enriched in 13 C compared to atmospheric CO 2 . Together, these isotopic signals allow us to distinguish C fixed by plants from C fixed by autotrophic microorganisms using their differences in 13 C discrimination. We can then estimate that up to 27 % of soil organic matter in the 0-10 cm layer of these soils was derived from microbially assimilated CO 2 .Isotope values of bulk SOM were shifted towards more positive δ 13 C and more negative 14 C values in mofettes compared to reference soils, suggesting that geogenic CO 2 emitted from the soil atmosphere is incorporated into SOM. To distinguish whether geogenic CO 2 was fixed by plants or by CO 2 assimilating microorganisms, we first used the proportional differences in radiocarbon and δ 13 C values to indicate the magnitude of discrimination of the stable isotopes in living plants. Deviation from this relationship was taken to indicate the presence of microbial CO 2 fixation, as microbial discrimination should differ from that of plants. 13 CO 2 -labelling experiments confirmed high activity of CO 2 assimilating microbes in the top 10 cm, where δ 13 C values of SOM were shifted up to 2 ‰ towards more negative values. Uptake rates of microbial CO 2 fixation ranged up to 1.59 ± 0.16 µg g −1 dw d −1 . We inferred that the negative δ 13 C shift was caused by the activity of autotrophic microorganisms using the Calvin-Benson-Bassham (CBB) cycle, as indicated from quantification of cbbL/cbbM marker genes encoding for RubisCO by quantitative polymerase chain reaction (qPCR) and by acetogenic and methanogenic microorganisms, shown present in the mofettes by previous studies. Combined 14 C and δ 13 C isotope mass balances indicated that microbially derived carbon accounted for 8-27 % of bulk SOM in this soil layer.The findings imply that autotrophic microorganisms can recycle significant amounts of carbon in wetland soils and might contribute to observed radiocarbon reservoir effects influencing 14 C signatures in peat deposits.

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“…Fungi generally have higher C:N ratios than bacteria. Microbial C:N ratio is usually estimated around four for bacteria, and ten for fungi (Moore et al 2005), but may even amount to 20 for the latter (Wallander et al 2003). Fungi may have lower N-requirements than bacteria because of their structure and slower life cycle, but also because they use carbohydrates as osmoregulators rather than amino acids (e.g., Measures 1975;Kuehn et al 1998).…”

Section: Soil Organisms and N-dynamicsmentioning

confidence: 99%

The relationship between N mineralization or microbial biomass N with micromorphological properties in beech forest soils with different texture and pH

2009

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To test relationships between net N-mineralization, organic matter and soil organisms, we combined micromorphology with laboratory incubation experiments over a soil gradient. Microbial biomass N generally increased with pH, and from sandy to loamy soil, but net N-mineralization showed the opposite, and was highest in acid, sandy soil. Twenty-two micromorphological characteristics were analyzed with principal component analysis. PC1 had high eigenvalue (0.70), and clearly separated fungi from earthworms, microarthropods and bacteria. PC2 was less important (0.15). Organic layer and sand content clearly correlated with the fungi-end of PC1, but pH and C-content of the Ah with the opposite. Microbial N also correlated with the earthwormbacteria end, but net N-mineralization did not. Efficiency of N-mineralization per unit microbe even correlated with the fungi end of PC1, in both organic layer and mineral topsoil. The results support the hypothesis that high (or low) litter turnover and biological activity can be counteracted by high (or low) microbial N-demand.

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Direct estimates of C:N ratios of ectomycorrhizal mycelia collected from Norway spruce forest soils

Cited by 97 publications

References 13 publications

Modelling microbial exchanges between forms of soil nitrogen in contrasting ecosystems

Modelling microbial exchanges between forms of soil nitrogen in contrasting ecosystems

Autotrophic fixation of geogenic CO<sub>2</sub> by microorganisms contributes to soil organic matter formation and alters isotope signatures in a wetland mofette

The relationship between N mineralization or microbial biomass N with micromorphological properties in beech forest soils with different texture and pH

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Direct estimates of C:N ratios of ectomycorrhizal mycelia collected from Norway spruce forest soils

Cited by 97 publications

References 13 publications

Modelling microbial exchanges between forms of soil nitrogen in contrasting ecosystems

Modelling microbial exchanges between forms of soil nitrogen in contrasting ecosystems

Autotrophic fixation of geogenic CO&lt;sub&gt;2&lt;/sub&gt; by microorganisms contributes to soil organic matter formation and alters isotope signatures in a wetland mofette

The relationship between N mineralization or microbial biomass N with micromorphological properties in beech forest soils with different texture and pH

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Autotrophic fixation of geogenic CO<sub>2</sub> by microorganisms contributes to soil organic matter formation and alters isotope signatures in a wetland mofette