Organic carbon pools and organic matter chemical composition in response to different land uses in southern Brazil

2020 ◽  
Author(s):  
Clever Briedis ◽  
Jeff Baldock ◽  
João C. de Moraes Sá ◽  
Josiane B. dos Santos ◽  
Janine McGowan ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
Organic Carbon ◽  
Carbon Pools ◽  
Land Uses ◽  
Southern Brazil

Soil organic matter formation is controlled by the chemistry and bioavailability of organic carbon inputs across different land uses

2021 ◽  
Vol 770 ◽  
pp. 145307
Author(s):  
Mohammad Bahadori ◽  
Chengrong Chen ◽  
Stephen Lewis ◽  
Sue Boyd ◽  
Mehran Rezaei Rashti ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Organic Carbon ◽  
Land Uses ◽  
Soil Organic Matter Formation

The effects of cultivation on the composition of organic-matter and structural stability of soils

Soil Research ◽  
1995 ◽  
Vol 33 (6) ◽  
pp. 975 ◽  
Author(s):  
A Golchin ◽  
P Clarke ◽  
JM Oades ◽  
JO Skjemstad
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
Organic Carbon ◽  
Organic Materials ◽  
Aggregate Stability ◽  
Soil Samples ◽  
Modulus Of Rupture ◽  
Dispersible Clay ◽  
Different Soils

Soil samples were obtained from the surface horizons of five untilled sites and adjacent sites under short- and long-term cultivation. The soil samples were fractionated based on density and organic materials were concentrated in various fractions which enabled comparative chemical composition of the organic materials in cultivated and uncultivated sites by solid-state C-13 CP/MAS NMR spectroscopy. Changes in the nature of organic carbon with cultivation were different in different soils and resulted from variations in the chemistry of carbon inputs to the soils and a greater extent of decomposition of organic materials in cultivated soils. Differences in the chemical composition of organic carbon between cultivated and uncultivated soils resided mostly in organic materials occluded within aggregates, whereas the chemistry of organic matter associated with clay particles showed only small changes. The results indicate a faster decomposition of O-alkyl C in the cultivated soils. Wet aggregate stability, mechanically dispersible clay and modulus of rupture tests were used to assess the effects of cultivation on structural stability of soils. In four of five soils, the virgin sites and sites which had been under long-term pasture had a greater aggregate stability than the cultivated sites. Neither total organic matter nor total O-alkyl C content was closely correlated with aggregate stability, suggesting that only a part of soil carbon or carbohydrate is involved in aggregate stability. The fractions of carbon and O-alkyl C present in the form of particulate organic matter occluded within aggregates were better correlated with aggregate stability (r = 0.86** and 0.88**, respectively). Cultivation was not the dominant factor influencing water-dispersible clay across the range of soil types used in this study. The amount of dispersible clay was a function of total clay content and the percentage of clay dispersed was controlled by factors such as clay mineralogy, CaCO3 and organic matter content of soils. The tendency of different soils for hard-setting and crusting, as a result of structural collapse, was reflected in the modulus of rupture (MOR). The cultivated sites had significantly higher MOR than their non-tilled counterparts. The soils studied had different MOR due to differences in their physical and chemical properties.

The chemical and physical stability soil organic carbon in the top 1 m of the soil profile under different land uses in the UK

2020 ◽  
Author(s):  
Dedy Antony ◽  
Jo Clark ◽  
Chris Collins ◽  
Tom Sizmur
Keyword(s):  
Land Use ◽  
Organic Matter ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Profile ◽  
Soil Depth ◽  
Physical Stability ◽  
Silty Clay ◽  
Land Uses ◽  
Total N

<p>Soils are the largest terrestrial pool of organic carbon and it is now known that as much as 50% of soil organic carbon (SOC) can be stored below 30 cm. Therefore, knowledge of the mechanisms by which soil organic carbon is stabilised at depth and how land use affects this is important.</p><p>This study aimed to characterise topsoil and subsoil SOC and other soil properties under different land uses to determine the SOC stabilisation mechanisms and the degree to which SOC is vulnerable to decomposition. Samples were collected under three different land uses: arable, grassland and deciduous woodland on a silty-clay loam soil and analysed for TOC, pH, C/N ratio and texture down the first one metre of the soil profile. Soil organic matter (SOM) physical fractionation and the extent of fresh mineral surfaces were also analysed to elucidate SOM stabilisation processes.</p><p>Results showed that soil texture was similar among land uses and tended to become more fine down the soil profile, but pH did not significantly change with soil depth. Total C, total N and C/N ratio decreased down the soil profile and were affected by land use in the order woodland > grassland > arable. SOM fractionation revealed that the free particulate organic matter (fPOM) fraction was significantly greater in both the topsoil and subsoil under woodland than under grassland or arable. The mineral associated OC (MinOC) fraction was proportionally greater in the subsoil compared to topsoil under all land uses: arable > grassland > woodland. Clay, Fe and Mn availability play a significant role (R<sup>2</sup>=0.87) in organic carbon storage in the top 1 m of the soil profile.</p><p>It is evidently clear from the findings that land use change has a significant effect on the dynamics of the SOC pool at depth, related to litter inputs to the system.</p>

scholarly journals Higher Long-Term Soil Moisture Increases Organic Carbon Accrual Through Microbial Conversion of Organic Inputs

2021 ◽  
Author(s):  
Itamar Shabtai ◽  
Srabani Das ◽  
Thiago Inagaki ◽  
Behrooz Azimzadeh ◽  
Carmen Martínez ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Moisture ◽  
Chemical Composition ◽  
Organic Carbon ◽  
Fold Increase ◽  
Sodium Dithionite ◽  
Sodium Pyrophosphate ◽  
Microbial Conversion ◽  
High Moisture

High long-term soil moisture may either stimulate or inhibit soil organic carbon (SOC) losses through changes to mineral and chemical composition, and resultant organo-mineral interactions. Yet, the trade-off between mineralization and accrual of SOC under long-term variation in unsaturated soil moisture remains an uncertainty. In this study, we tested the underexplored relationships between long-term soil moisture and organo-mineral chemical composition, and its implications for SOC persistence. The results provide new insights into SOC accrual mechanisms under different long-term moisture levels commonly observed in well-drained soils. Differences in long-term mean volumetric water content ranging from 0.4 - 0.63 (v/v) on fallow plots in an experimental field in New York, USA, were positively correlated with SOC contents (R2 = 0.228; P = 0.019, n = 20), mineral-associated organic matter (MAOM) (R2 = 0.442; P = 0.001; n = 20) and occluded particulate organic matter (oPOM) contents (R2 = 0.178; P = 0.033; n = 20). Higher long-term soil moisture decreased the relative content of sodium pyrophosphate extractable Fe (R2 = 0.33; P < 0.005; n = 20), increased that of sodium dithionite extractable Fe (R2 = 0.443; P < 0.001; n = 20), and increased the overall importance of non-crystalline Al pools (extracted with sodium pyrophosphate and hydroxylamine extractable) for SOC retention. Higher long-term soil moisture supported up to a four-fold increase in microbial biomass (per unit SOC), and lower C:N ratios in MAOM fractions of high-moisture soils (from C:N 9.5 to 9, R2 = 0.267, P = 0.011, n =20). This was reflected by a 15% and 10% greater proportion of oxidized carboxylic-C to aromatic-C and O-alkyl C, respectively, as measured with 13C-NMR, and a more pronounced FTIR signature of N-containing proteinaceous compounds in high-moisture MAOM fractions, reflective of microbial metabolites. SOC accrual increased with increasing soil moisture (P = 0.019), exchangeable Ca2+ (P = 0.013), and pyrophosphate-extractable Al content (P = 0.0001) and Al/Fe ratio (P = 0.017). Taken together, our results show that high long-term soil moisture resulted in SOC accrual by enhancing microbial conversion of plant inputs to metabolites that interact with reactive minerals.

scholarly journals Higher Long-Term Soil Moisture Increases Organic Carbon Accrual Through Microbial Conversion of Organic Inputs

2021 ◽  
Author(s):  
Itamar Shabtai ◽  
Srabani Das ◽  
Thiago Inagaki ◽  
Behrooz Azimzadeh ◽  
Carmen Martínez ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Moisture ◽  
Chemical Composition ◽  
Organic Carbon ◽  
Fold Increase ◽  
Sodium Dithionite ◽  
Sodium Pyrophosphate ◽  
Microbial Conversion ◽  
High Moisture

High long-term soil moisture may either stimulate or inhibit soil organic carbon (SOC) losses through changes to mineral and chemical composition, and resultant organo-mineral interactions. Yet, the trade-off between mineralization and accrual of SOC under long-term variation in unsaturated soil moisture remains an uncertainty. In this study, we tested the underexplored relationships between long-term soil moisture and organo-mineral chemical composition, and its implications for SOC persistence. The results provide new insights into SOC accrual mechanisms under different long-term moisture levels commonly observed in well-drained soils. Differences in long-term mean volumetric water content ranging from 0.4 - 0.63 (v/v) on fallow plots in an experimental field in New York, USA, were positively correlated with SOC contents (R2 = 0.228; P = 0.019, n = 20), mineral-associated organic matter (MAOM) (R2 = 0.442; P = 0.001; n = 20) and occluded particulate organic matter (oPOM) contents (R2 = 0.178; P = 0.033; n = 20). Higher long-term soil moisture decreased the relative content of sodium pyrophosphate extractable Fe (R2 = 0.33; P < 0.005; n = 20), increased that of sodium dithionite extractable Fe (R2 = 0.443; P < 0.001; n = 20), and increased the overall importance of non-crystalline Al pools (extracted with sodium pyrophosphate and hydroxylamine extractable) for SOC retention. Higher long-term soil moisture supported up to a four-fold increase in microbial biomass (per unit SOC), and lower C:N ratios in MAOM fractions of high-moisture soils (from C:N 9.5 to 9, R2 = 0.267, P = 0.011, n =20). This was reflected by a 15% and 10% greater proportion of oxidized carboxylic-C to aromatic-C and O-alkyl C, respectively, as measured with 13C-NMR, and a more pronounced FTIR signature of N-containing proteinaceous compounds in high-moisture MAOM fractions, reflective of microbial metabolites. SOC accrual increased with increasing soil moisture (P = 0.019), exchangeable Ca2+ (P = 0.013), and pyrophosphate-extractable Al content (P = 0.0001) and Al/Fe ratio (P = 0.017). Taken together, our results show that high long-term soil moisture resulted in SOC accrual by enhancing microbial conversion of plant inputs to metabolites that interact with reactive minerals.

scholarly journals From fibrous plant residues to mineral-associated organic carbon – the fate of organic matter in Arctic permafrost soils

2020 ◽  
Vol 17 (13) ◽  
pp. 3367-3383
Author(s):  
Isabel Prater ◽  
Sebastian Zubrzycki ◽  
Franz Buegger ◽  
Lena C. Zoor-Füllgraff ◽  
Gerrit Angst ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
Organic Carbon ◽  
The Arctic ◽  
Plant Residues ◽  
N Losses ◽  
Organic C ◽  
Arctic Soils ◽  
C Cycle ◽  
C Stock

Abstract. Permafrost-affected soils of the Arctic account for 70 % or 727 Pg of the soil organic carbon (C) stored in the northern circumpolar permafrost region and therefore play a major role in the global C cycle. Most studies on the budgeting of C storage and the quality of soil organic matter (OM; SOM) in the northern circumpolar region focus on bulk soils. Thus, although there is a plethora of assumptions regarding differences in terms of C turnover or stability, little knowledge is available on the mechanisms stabilizing organic C in Arctic soils besides impaired decomposition due to low temperatures. To gain such knowledge, we investigated soils from Samoylov Island in the Lena River delta with respect to the composition and distribution of organic C among differently stabilized SOM fractions. The soils were fractionated according to density and particle size to obtain differently stabilized SOM fractions differing in chemical composition and thus bioavailability. To better understand the chemical alterations from plant-derived organic particles in these soils rich in fibrous plant residues to mineral-associated SOM, we analyzed the elemental, isotopic and chemical composition of particulate OM (POM) and clay-sized mineral-associated OM (MAOM). We demonstrate that the SOM fractions that contribute with about 17 kg C m−3 for more than 60 % of the C stock are highly bioavailable and that most of this labile C can be assumed to be prone to mineralization under warming conditions. Thus, the amount of relatively stable, small occluded POM and clay-sized MAOM that currently accounts with about 10 kg C m−3 for about 40 % of the C stock will most probably be crucial for the quantity of C protected from mineralization in these Arctic soils in a warmer future. Using δ15N as a proxy for nitrogen (N) balances indicated an important role of N inputs by biological N fixation, while gaseous N losses appeared less important. However, this could change, as with about 0.4 kg N m−3 one third of the N is present in bioavailable SOM fractions, which could lead to increases in mineral N cycling and associated N losses under global warming. Our results highlight the vulnerability of SOM in Arctic permafrost-affected soils under rising temperatures, potentially leading to unparalleled greenhouse gas emissions from these soils.

Soil organic carbon pools and stocks in different land uses of a temperate Himalayan region

2020 ◽  
Vol 68 (2) ◽  
pp. 162-169
Author(s):  
Shakeel Mir ◽  
J.A. Wani ◽  
J.A. Sofi ◽  
M.H. Chesti ◽  
A.H. Mir ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Himalayan Region ◽  
Carbon Pools ◽  
Land Uses ◽  
Soil Organic Carbon Pools

scholarly journals Effect of Land Use on Organic Carbon Storage Potential of Soils with Contrasting Native Organic Matter Content

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Sabina Yeasmin ◽  
Eshara Jahan ◽  
Md. Ashik Molla ◽  
A. K. M. Mominul Islam ◽  
Md. Parvez Anwar ◽  
...  
Keyword(s):  
Land Use ◽  
Organic Matter ◽  
Organic Carbon ◽  
Carbon Storage ◽  
Organic Matter Content ◽  
Fallow Land ◽  
Land Uses ◽  
Storage Potential ◽  
The Impact ◽  
Native Organic Matter

This study aimed to determine the impact of land use on organic carbon (OC) pools of soils with contrasting native organic matter (OM) content. Surface (0–15 cm) soils of four land uses (cropland, orchard, grassland, and fallow) were collected from four agroecological zones (AEZs) of Bangladesh with different OM content (AEZ-7: very low, −3: low, −9: medium, and −5: high). Bulk soils were physically fractionated into particulate and mineral associated OM (POM and MOM: >53 and <53 µm, respectively). Both bulk and fractionated soils were analyzed for OC and nitrogen (N). Among the land uses, undisturbed soils (grassland and fallow land) had significantly higher total OC (0.44–1.79%) than disturbed soils (orchard and cropland) (0.39–1.67%) in all AEZs. The distribution of OC and N in POM and MOM fractions was significantly different among land uses and also varied with native OM content. In all AEZs, cropland soils showed the lowest POM-C content (0.40–1.41%), whereas the orchard soils showed the highest values (0.71–1.91%). The MOM-C was highest (0.81–1.91%) in fallow land and lowest (0.53–1.51%) in orchard, and cropland had a moderate amount (0.70–1.61%). In croplands, distribution of a considerable amount of OC in the MOM pool was noticeable. These findings reveal that total OC in soils can be decreased with cultivation but does not inevitably indicate the loss of OC storage in the stable pool. Carbon storage potential of soils with both high- and low-native OM contents can be increased via proper land use and managements.

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