scholarly journals Saltwater intrusion into tidal freshwater marshes alters the biogeochemical processing of organic carbon

2013 ◽  
Vol 10 (12) ◽  
pp. 8171-8183 ◽  
Author(s):  
S. C. Neubauer ◽  
R. B. Franklin ◽  
D. J. Berrier
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Saltwater Intrusion ◽  
Carbon Mineralization ◽  
Tidal Freshwater ◽  
Co2 Production ◽  
Soil Co2 ◽  
Short Term ◽  
Ch4 Production

Abstract. Environmental perturbations in wetlands affect the integrated plant-microbial-soil system, causing biogeochemical responses that can manifest at local to global scales. The objective of this study was to determine how saltwater intrusion affects carbon mineralization and greenhouse gas production in coastal wetlands. Working with tidal freshwater marsh soils that had experienced ~ 3.5 yr of in situ saltwater additions, we quantified changes in soil properties, measured extracellular enzyme activity associated with organic matter breakdown, and determined potential rates of anaerobic carbon dioxide (CO2) and methane (CH4) production. Soils from the field plots treated with brackish water had lower carbon content and higher C : N ratios than soils from freshwater plots, indicating that saltwater intrusion reduced carbon availability and increased organic matter recalcitrance. This was reflected in reduced activities of enzymes associated with the hydrolysis of cellulose and the oxidation of lignin, leading to reduced rates of soil CO2 and CH4 production. The effects of long-term saltwater additions contrasted with the effects of short-term exposure to brackish water during three-day laboratory incubations, which increased rates of CO2 production but lowered rates of CH4 production. Collectively, our data suggest that the long-term effect of saltwater intrusion on soil CO2 production is indirect, mediated through the effects of elevated salinity on the quantity and quality of autochthonous organic matter inputs to the soil. In contrast, salinity, organic matter content, and enzyme activities directly influence CH4 production. Our analyses demonstrate that saltwater intrusion into tidal freshwater marshes affects the entire process of carbon mineralization, from the availability of organic carbon through its terminal metabolism to CO2 and/or CH4, and illustrate that long-term shifts in biogeochemical functioning are not necessarily consistent with short-term disturbance-type responses.

scholarly journals Saltwater intrusion into tidal freshwater marshes alters the biogeochemical processing of organic carbon

2013 ◽  
Vol 10 (7) ◽  
pp. 10685-10720 ◽  
Author(s):  
S. C. Neubauer ◽  
R. B. Franklin ◽  
D. J. Berrier
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Saltwater Intrusion ◽  
Carbon Mineralization ◽  
Tidal Freshwater ◽  
Co2 Production ◽  
Soil Co2 ◽  
Short Term ◽  
Ch4 Production

Abstract. Environmental perturbations in wetlands affect the integrated plant-microbial-soil system, causing biogeochemical responses that can manifest at local to global scales. The objective of this study was to determine how saltwater intrusion affects carbon mineralization and greenhouse gas production in coastal wetlands. Working with tidal freshwater marsh soils that had experienced roughly 3.5 yr of in situ saltwater additions, we quantified changes in soil properties, measured extracellular enzyme activity associated with organic matter breakdown, and determined potential rates of anaerobic carbon dioxide (CO2) and methane (CH4) production. Soils from the field plots treated with brackish water had lower carbon content and higher C : N ratios than soils from freshwater plots, indicating that saltwater intrusion reduced carbon availability and increased organic matter recalcitrance. This was reflected in reduced activities of enzymes associated with the hydrolysis of cellulose and the oxidation of lignin, leading to reduced rates of soil CO2 and CH4 production. The effects of long-term saltwater additions contrasted with the effects of short-term exposure to brackish water during three-day laboratory incubations, which increased rates of CO2 production but lowered rates of CH4 production. Collectively, our data suggest that the long-term effect of saltwater intrusion on soil CO2 production is indirect, mediated through the effects of elevated salinity on the quantity and quality of autochthonous organic matter inputs to the soil. In contrast, salinity, organic matter content, and enzyme activities directly influence CH4 production. Our analyses demonstrate that saltwater intrusion into tidal freshwater marshes affects the entire process of carbon mineralization, from the availability of organic carbon through its terminal metabolism to CO2 and/or CH4, and illustrate that long-term shifts in biogeochemical functioning are not necessarily consistent with short-term disturbance-type responses.

Prediction of organic matter degradability in river sediments

2020 ◽  
Author(s):  
Julia Gebert ◽  
Florian Zander
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Spatial Variability ◽  
River Sediments ◽  
Redox Conditions ◽  
Time Dependent ◽  
Anaerobic Conditions ◽  
Short Term ◽  
Aerobic And Anaerobic

<p>Under anaerobic conditions, degradation of organic matter in river sediments leads to gas formation, with organic carbon being released mainly as CH<sub>4</sub> and CO<sub>2</sub>. Gas bubbles reduce sediment density, viscosity and shear strength, impede sonic depth finding and are suspected to affect the sediments’ rheological properties. Moreover, methane (CH<sub>4</sub>) is a potent greenhouse gas with a global warming potential (GWP<sub>100</sub>) of 28-36. Therefore, the climate impact may vary greatly depending on the way sediments are managed (for example, type and frequency of dredging and relocation in the water body or treatment on land). The objective of this paper is therefore to quantify the time-dependent stability, or inversely, the lability of sediment organic matter (SOM) as a basis for prediction of effects on sediment mechanical properties and on the release of greenhouse gases.</p><p>Within two years, over 200 samples of predominantly fine-grained sediment were collected from nine locations within a 30 km transect through the Port of Hamburg. All samples were, amongst other analyses, subjected to long-term (> 250 days) aerobic and anaerobic incubation for measurement of SOM degradation, yielding a comprehensive data set on the time-dependent change in degradation rates and the corresponding size of differently degradable SOM pools. SOM degradability exhibited a pronounced spatial variability with an approximately tenfold higher anaerobic and a roughly fivefold higher aerobic degradability of upstream SOM compared to downstream SOM. Lower δ<sup>13</sup>C values, higher DNA concentrations and a higher share of organic carbon in the light density fraction as well as elevated chlorophyll concentrations in the water phase support the hypothesis of increased biological sources of SOM at upstream locations and increased SOM degradability in shallow compared to deep layers (Zander et al., 2020).</p><p>First statistical and time series analyses indicate that</p><ul><li>Long-term SOM lability appears to be predictable from short-term measurements.</li> <li>The relationship between short-term and long-term SOM degradation is site-specific and also differs for layers of different age (depth). This supports the above-mentioned variability between sites regarding the size of differently degradable carbon pools, as well as for the depth profile at any one site.</li> <li>The relevance of the available electron acceptors (redox conditions) for SOM degradation, i.e. the ratio between carbon release under aerobic and anaerobic conditions, differs less by site but more so by layers of different age (depth). This is plausible as especially the top layers are exposed to more variability in redox conditions than the deeper layers that are always under reducing conditions.</li> </ul><p>Zander, F., Heimovaara, T., Gebert, J. (2020): Spatial variability of organic matter degradability in tidal Elbe sediments. Journal of Soils and Sediments, accepted for publication.</p>

scholarly journals Long-Term Nitrogen Addition Decreases Soil Carbon Mineralization in an N-Rich Primary Tropical Forest

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 734
Author(s):  
Xiankai Lu ◽  
Qinggong Mao ◽  
Zhuohang Wang ◽  
Taiki Mori ◽  
Jiangming Mo ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Organic Carbon ◽  
Tropical Forest ◽  
Soil Carbon ◽  
Tropical Forests ◽  
Carbon Mineralization ◽  
N Deposition ◽  
Soil Carbon Mineralization ◽  
N Additions

Anthropogenic elevated nitrogen (N) deposition has an accelerated terrestrial N cycle, shaping soil carbon dynamics and storage through altering soil organic carbon mineralization processes. However, it remains unclear how long-term high N deposition affects soil carbon mineralization in tropical forests. To address this question, we established a long-term N deposition experiment in an N-rich lowland tropical forest of Southern China with N additions such as NH4NO3 of 0 (Control), 50 (Low-N), 100 (Medium-N) and 150 (High-N) kg N ha−1 yr−1, and laboratory incubation experiment, used to explore the response of soil carbon mineralization to the N additions therein. The results showed that 15 years of N additions significantly decreased soil carbon mineralization rates. During the incubation period from the 14th day to 56th day, the average decreases in soil CO2 emission rates were 18%, 33% and 47% in the low-N, medium-N and high-N treatments, respectively, compared with the Control. These negative effects were primarily aroused by the reduced soil microbial biomass and modified microbial functions (e.g., a decrease in bacteria relative abundance), which could be attributed to N-addition-induced soil acidification and potential phosphorus limitation in this forest. We further found that N additions greatly increased soil-dissolved organic carbon (DOC), and there were significantly negative relationships between microbial biomass and soil DOC, indicating that microbial consumption on soil-soluble carbon pool may decrease. These results suggests that long-term N deposition can increase soil carbon stability and benefit carbon sequestration through decreased carbon mineralization in N-rich tropical forests. This study can help us understand how microbes control soil carbon cycling and carbon sink in the tropics under both elevated N deposition and carbon dioxide in the future.

scholarly journals Effects of Management and Hillside Position on Soil Organic Carbon Stratification in Mediterranean Centenary Olive Grove

Agronomy ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 650
Author(s):  
Jesús Aguilera-Huertas ◽  
Beatriz Lozano-García ◽  
Manuel González-Rosado ◽  
Luis Parras-Alcántara
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Quality ◽  
Management Practices ◽  
Soil Management ◽  
Olive Grove ◽  
No Tillage ◽  
Short Term ◽  
Degradation Degree

The short- and medium—long-term effects of management and hillside position on soil organic carbon (SOC) changes were studied in a centenary Mediterranean rainfed olive grove. One way to measure these changes is to analyze the soil quality, as it assesses soil degradation degree and attempts to identify management practices for sustainable soil use. In this context, the SOC stratification index (SR-COS) is one of the best indicators of soil quality to assess the degradation degree from SOC content without analyzing other soil properties. The SR-SOC was calculated in soil profiles (horizon-by-horizon) to identify the best soil management practices for sustainable use. The following time periods and soil management combinations were tested: (i) in the medium‒long-term (17 years) from conventional tillage (CT) to no-tillage (NT), (ii) in the short-term (2 years) from CT to no-tillage with cover crops (NT-CC), and (iii) the effect in the short-term (from CT to NT-CC) of different topographic positions along a hillside. The results indicate that the SR-SOC increased with depth for all management practices. The SR-SOC ranged from 1.21 to 1.73 in CT0, from 1.48 to 3.01 in CT1, from 1.15 to 2.48 in CT2, from 1.22 to 2.39 in NT-CC and from 0.98 to 4.16 in NT; therefore, the soil quality from the SR-SOC index was not directly linked to the increase or loss of SOC along the soil profile. This demonstrates the time-variability of SR-SOC and that NT improves soil quality in the long-term.

scholarly journals Short-Term Decomposition and Nutrient-Supplying Ability of Sewage Sludge Digestate, Digestate Compost, and Vermicompost on Acidic Sandy and Calcareous Loamy Soils

Agronomy ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 2249
Author(s):  
Nikolett Uzinger ◽  
Orsolya Szécsy ◽  
Nóra Szűcs-Vásárhelyi ◽  
István Padra ◽  
Dániel Benjámin Sándor ◽  
...  
Keyword(s):  
Organic Matter ◽  
Sewage Sludge ◽  
Organic Carbon ◽  
Carbon Content ◽  
Plant Biomass ◽  
Test Plant ◽  
Organic Carbon Content ◽  
Short Term ◽  
Mineral N ◽  
Average Residual

Organic waste and the compost and vermicompost derived from it may have different agronomic values, but little work is available on this aspect of sewage sludge. A 75-day pot experiment with perennial ryegrass (Lolium perenne) as the test plant aimed to investigate the fertiliser value and organic matter replenishment capacity of digested sewage sludge (DS) and the compost (COM) and vermicompost (VC) made from it, applied in 1% and 3% doses on acidic sand and calcareous loam. The NPK content and availability, changes in organic carbon content and plant biomass, and the efficiency of the amendments as nitrogen fertilisers were investigated. The final average residual carbon content for DS, COM, and VC was 35 ± 34, 85 ± 46, and 55 ± 46%, respectively. The organic carbon mineralisation rate depended on the soil type. The additives induced significant N mineralisation in both soils: the average increment in mineral N content was 1.7 times the total added N on acidic sand and 4.2 times it on calcareous loam for the 1% dose. The agronomic efficiency of COM and VC as fertilisers was lower than that of DS. In the short term, DS proved to be the best fertiliser, while COM was the best for organic matter replenishment.

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.

scholarly journals VARIABILIDADE ESPACIAL DO FLUXO DE CO2 DO SOLO EM POVOAMENTO DE EUCALIPTO

FLORESTA ◽  
2011 ◽  
Vol 41 (2) ◽  
Author(s):  
Alexandre Fonseca D’Andréa ◽  
Marx Leandro Naves Silva ◽  
Diego Antonio França de Freitas ◽  
Nilton Curi ◽  
Carlos Alberto Silva
Keyword(s):  
Organic Matter ◽  
Environmental Factors ◽  
Organic Carbon ◽  
Spatial Variability ◽  
Linear Correlation ◽  
Microbial Biomass Carbon ◽  
Co2 Flux ◽  
Water Evaporation ◽  
Soil Co2 ◽  
Soil Co2 Flux

A matéria orgânica do solo armazena a maior parte do carbono contido nos sistemas terrestres do planeta, sendo a maioria encontrada nos solos com floresta. O objetivo deste trabalho foi quantificar o fluxo de CO2 do solo e a sua variabilidade espacial em povoamento de Eucalyptus sp. Foram avaliados o fluxo de CO2 do solo, fatores ambientais (evaporação de água, temperatura e umidade do solo), atributos relacionados à fertilidade (pH, soma de bases e alumínio trocável), estrutura (densidade do solo e porosidade total) e matéria orgânica do solo (carbono orgânico total e carbono da biomassa microbiana). Análises de correlação linear simples indicaram que parte da variabilidade espacial do fluxo de CO2 do solo pode ser explicada pelo efeito conjunto do teor de carbono orgânico do solo, da biomassa da serapilheira e da presença de árvores no terreno, indicativas da participação de fatores bióticos no processo. No entanto, o fluxo de CO2 do solo é um fenômeno de natureza complexa, não sendo possível identificar um único atributo do solo ou do ambiente que, isoladamente, explique sua variação no espaço.Palavras-chave: Matéria orgânica; fatores ambientais; fertilidade; carbono; respiração do solo.AbstractSoil CO2 flux spatial variability on eucalyptus manmade forest.  The organic matter on soil retains most of carbon contained in the planet terrestrial systems, specially in forest soils. The aim of this work was to quantify soil CO2 flux and its spatial variability on Eucalyptus sp. manmade forest. In order to that, soil CO2 flux, environmental factors (water evaporation, soil temperature and moisture), fertility attributes (pH, bases sum and exchangeable aluminum), structure (bulk density and total porosity), and soil organic matter (total organic carbon and microbial biomass carbon) were evaluated. Simple linear correlation analyses indicated that part of the spatial variability of soil CO2 flux can be explained by the associated effect of soil organic carbon amount, litter biomass and presence of trees, indicatives of participation of biotic factors in the process. However, the soil CO2 flux is a complex phenomenon, been impossible to identify a single soil or environmental attribute, which, individually, could explain its spatial variability. Keywords: Organic matter; environmental factors; fertility; carbon; linear correlation. 

Nitrogen mineralisation in sugarcane soils in Queensland, Australia: I. evaluation of soil tests for predicting nitrogen mineralisation

Soil Research ◽  
2019 ◽  
Vol 57 (7) ◽  
pp. 738 ◽  
Author(s):  
D. E. Allen ◽  
P. M. Bloesch ◽  
T. G. Orton ◽  
B. L. Schroeder ◽  
D. M. Skocaj ◽  
...  
Keyword(s):  
Soil Properties ◽  
Mixed Effects ◽  
Mixed Effects Model ◽  
Co2 Production ◽  
Organic N ◽  
Model Parameters ◽  
Nitrogen Mineralisation ◽  
Short Term ◽  
Available N

We explored soil properties as indices of mineralisable nitrogen (N) in sugarcane soils and whether we could increase the accuracy of predicting N mineralisation during laboratory incubations. Utilising historical data in combination with samples collected during 2016, we: (i) measured mineralised N over the course of short-term (14 days) and long-term (301 days) laboratory incubations; (ii) compared models representing mineralisation; then (iii) related model parameters to measured soil properties. We found measures representing the labile organic N pool (Hydrolysable NaOH organic N; amino sugar Illinois soil N test) best related to short-term mineralised N (R2 of 0.50–0.57, P < 0.001), while measures of CO2 production (3, 7, 10 and 14 days) best related to longer-term mineralised N (R2 of 0.75–0.84, P < 0.001). Indices were brought together to model the active and slow pools of a two-pool mineralisation model in the statistical framework of a mixed-effects model. Of the models that relied on measurement of one soil property, cumulative CO2 production (7 days) performed the best when considering all soil types; in a cross-validation test, this model gave an external R2 of 0.77 for prediction of the 301-day mineralised N. Since the mixed-effects model accounts for the various sources of uncertainty, we suggest this approach as a framework for prediction of in-field available N, with further measurement of long-term mineralised N in other soils to strengthen predictive certainty of these soil indices.

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