review of Microbial decomposition processes and vulnerable Arctic soil organic carbon

2018 ◽  
Author(s):  
Anonymous
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Microbial Decomposition ◽  
Arctic Soil ◽  
Decomposition Processes

scholarly journals Soil Organic Carbon and Nitrogen Decomposition in Fecal Manure of Cattle Fed Browse/Maize Silages

2014 ◽  
Vol 3 (3) ◽  
pp. 50
Author(s):  
Habib Kato ◽  
Robert Mulebeke ◽  
Felix Budara Bareeba ◽  
Elly Nyambobo Sabiiti
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
The Other ◽  
Organic N ◽  
Calliandra Calothyrsus ◽  
Maize Silage ◽  
Protein Nitrogen ◽  
Microbial Decomposition ◽  
Organic C ◽  
Soil Microbial

<p>Soil organic carbon (C) and nitrogen (N) decomposition in fecal manure of cattle fed browses of Calliandra (<em>Calliandra calothyrsus</em>), Gliricidia (<em>Gliricidia sepium</em>) and Leucaena (<em>Leucaena leucocephala</em>) browse/maize silage mixtures and maize (<em>Zea mays</em>) silage alone when applied to the soil were investigated in a pot experiment in comparison to the corresponding silages fed. Maize silage alone had the lowest N and a larger C: N ratio, making it a poor quality compost when applied to the soil, but compared to the browse/maize silage mixtures it had the highest level of soluble N as non-protein nitrogen (NPN) which makes much of its N available for soil microbial decomposition of its organic C. Calliandra browse/maize silage mixture had the highest level of fiber-bound N (ADFN), which reduces N availability for soil microbial decomposition of its organic C in spite of its high N content and a narrower C: N ratio. Fecal manure from maize silage alone had a lower level of N and a wider C: N ratio than fecal manure from the other silages fed which would affect its decomposition in the soil, but it had the lowest level of ADFN and much of its N is made available for soil microbial decomposition of its organic C. Soil samples after 12 weeks of the experiment showed that Calliandra browse/maize silage mixture maintained the highest level of C in the soil, while maize silage alone maintained the lowest level. Also soils treated with fecal manure from the other browse/maize silage mixtures maintained higher levels of C than fecal manure from maize silage alone. Organic C levels were lowest at 8 weeks of the experiment for all treatments and rose to the original levels at 12 weeks which could have been as a result of biotic and hydrologic factors coupled with soil aggregation. Decomposition of organic N followed a similar trend as organic C. The two elements are linked in both plant inputs in the soil and in the eventual soil humic substances. The soils treated with browse/maize silage mixtures maintained C: N ratios that were similar to that of the control soil and higher than those of the fecal manure treatments. Thus, in spite of the added silage materials to the soil, rapid decomposition of organic C could not occur to reflect benefits of adding the silage materials to the soil. Thus, fecal manure, particularly from feeding animals on browse/forage diets is more beneficial in the soil as it would decompose more readily releasing the plant nutrients they contain.</p>

Soil thinning and thickening: the fate of soil organic carbon

2020 ◽  
Author(s):  
Andrew Tye ◽  
Daniel Evans
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Depth ◽  
Significant Proportion ◽  
Deep Soil ◽  
Microbial Decomposition ◽  
Organic Carbon Fractions ◽  
The Stability ◽  
The Uk ◽  
The Impact

&lt;p&gt;The redistribution of soil by humans has been demonstrated to rival that of geologic events. Moreover, the impact of some conventional, agricultural techniques has been shown to redistribute a significant proportion of soil organic carbon. On the more erosive areas of hillslopes, the resulting thinning of soil could make deep soil carbon more accessible and, ultimately, more susceptible to destabilisation. However, downslope colluviation can thicken soil profiles such that subsoil carbon pools become inaccessible to microbial decomposition. The fate of soil thinning and thickening on soil organic carbon has not been studied in the UK until now. In this work, we studied the distribution of organic and inorganic carbon down profiles surveyed at three landscape positions (midslope, backslope, and toeslope) on Mountfield Farm, in Somerset, UK. In this poster, we present the results of thermogravimetric analysis and laser-induced fluorescence spectroscopy, both of which we used to investigate the stability of soil organic carbon down each profile. We explore the relationships between soil depth and the stocks and stability of soil organic carbon fractions at each position, and suggest the implications of continued upslope soil thinning and downslope soil thickening. &lt;/p&gt;

scholarly journals Substrate quality alters the microbial mineralization of added substrate and soil organic carbon

2014 ◽  
Vol 11 (17) ◽  
pp. 4665-4678 ◽  
Author(s):  
S. Jagadamma ◽  
M. A. Mayes ◽  
J. M. Steinweg ◽  
S. M. Schaeffer
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Stearic Acid ◽  
Quantitative Polymerase Chain Reaction ◽  
Model Fitting ◽  
Gene Copy ◽  
Microbial Decomposition ◽  
Substrate Quality ◽  
Copy Numbers ◽  
Gene Copy Numbers

Abstract. The rate and extent of decomposition of soil organic carbon (SOC) is dependent, among other factors, on substrate chemistry and microbial dynamics. Our objectives were to understand the influence of substrate chemistry on microbial decomposition of carbon (C), and to use model fitting to quantify differences in pool sizes and mineralization rates. We conducted an incubation experiment for 270 days using four uniformly labeled 14C substrates (glucose, starch, cinnamic acid and stearic acid) on four different soils (a temperate Mollisol, a tropical Ultisol, a sub-arctic Andisol, and an arctic Gelisol). The 14C labeling enabled us to separate CO2 respired from added substrates and from native SOC. Microbial gene copy numbers were quantified at days 4, 30 and 270 using quantitative polymerase chain reaction (qPCR). Substrate C respiration was always higher for glucose than other substrates. Soils with cinnamic and stearic acid lost more native SOC than glucose- and starch-amended soils. Cinnamic and stearic acid amendments also exhibited higher fungal gene copy numbers at the end of incubation compared to unamended soils. We found that 270 days were sufficient to model the decomposition of simple substrates (glucose and starch) with three pools, but were insufficient for more complex substrates (cinnamic and stearic acid) and native SOC. This study reveals that substrate quality exerts considerable control on the microbial decomposition of newly added and native SOC, and demonstrates the need for multi-year incubation experiments to constrain decomposition parameters for the most recalcitrant fractions of SOC and complex substrates.

scholarly journals Substrate quality alters microbial mineralization of added substrate and soil organic carbon

2014 ◽  
Vol 11 (3) ◽  
pp. 4451-4482 ◽  
Author(s):  
S. Jagadamma ◽  
M. A. Mayes ◽  
J. M. Steinweg ◽  
S. M. Schaeffer
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Stearic Acid ◽  
Quantitative Polymerase Chain Reaction ◽  
Model Fitting ◽  
Gene Copy ◽  
Microbial Decomposition ◽  
Substrate Quality ◽  
Copy Numbers ◽  
Gene Copy Numbers

Abstract. The rate and extent of decomposition of soil organic carbon (SOC) is dependent on substrate chemistry and microbial dynamics. Our objectives were to understand the influence of substrate chemistry on microbial processing of carbon (C), and to use model fitting to quantify differences in pool sizes and mineralization rates. We conducted an incubation experiment for 270 days using four uniformly-labeled 14C substrates (glucose, starch, cinnamic acid and stearic acid) on four different soils (a temperate Mollisol, a tropical Ultisol, a sub-arctic Andisol, and an arctic Gelisol). The 14C labeling enabled us to separate CO2 respired from added substrates and from native SOC. Microbial gene copy numbers were quantified at days 4, 30 and 270 using quantitative polymerase chain reaction (qPCR). Substrate C respiration was always higher for glucose than other substrates. Soils with cinnamic and stearic acid lost more native SOC than glucose- and starch-amended soils, despite an initial delay in respiration. Cinnamic and stearic acid amendments also exhibited higher fungal gene copy numbers at the end of incubation compared to unamended soils. We found that 270 days was sufficient to model decomposition of simple substrates (glucose and starch) with three pools, but was insufficient for more complex substrates (cinnamic and stearic acid) and native SOC. This study reveals that substrate quality imparts considerable control on microbial decomposition of newly added and native SOC, and demonstrates the need for multi-year incubation experiments to constrain decomposition parameters for the most recalcitrant fractions of SOC and added substrates.

The effect of soil texture and roots on the stable carbon isotope composition of soil organic carbon

Soil Research ◽  
2003 ◽  
Vol 41 (1) ◽  
pp. 77 ◽  
Author(s):  
M. Bird ◽  
O. Kracht ◽  
D. Derrien ◽  
Y. Zhou
Keyword(s):  
Particle Size ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Microbial Decomposition ◽  
Δ13c Values ◽  
Size Fractions ◽  
Particle Size Fractions ◽  
Δ13c Value

This study examines the distribution of soil organic carbon and carbon-isotopes with depth and among particle size fractions in 2 forest soil profiles of contrasting texture from Cape York Peninsula, Queensland, Australia. The profile on sand has a comparatively low inventory of carbon (557 mg/cm2 from 0–100 cm) and exhibits comparatively small variations in δ13C value. In contrast, the clay-rich profile has a much larger inventory of soil organic carbon (1725 mg/cm2 from 0–100 cm) and large variations in δ13C value occur both with depth in the profile and between different particle size fractions. The considerable differences in carbon inventories and δ13C values between the sites appear to be largely due to soil textural differences. In�the absence of fine minerals the trend in δ13C value with decreasing particle size is to similar or lower δ13C values, due to an increase in the relative abundance of low δ13C compounds in the residue left by microbial decomposition. In the presence of fine minerals, the trend is to higher δ13C values due to the stabilisation of the products of microbial decomposition by the fine minerals. Thus, the bulk δ13C value of soil organic carbon appears to be determined as much by the abundance of fine minerals in a soil profile as by isotope fractionation effects accompanying degradation. It is further postulated that an initial rapid rise in δ13C value in the upper soil layers is due to an increase in the relative importance of higher 13C, root-derived carbon immediately below the soil surface.

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