Distribution, sources, and decomposition of soil organic matter along a salinity gradient in estuarine wetlands characterized by C:N ratio, δ 13 C‐δ 15 N, and lignin biomarker

2020 ◽  
Vol 27 (2) ◽  
pp. 417-434
Author(s):  
Shaopan Xia ◽  
Zhaoliang Song ◽  
Qiang Li ◽  
Laodong Guo ◽  
Changxun Yu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Salinity Gradient ◽  
C:N Ratio ◽  
Estuarine Wetlands

scholarly journals An Approach to Incorporate Rhizosphere Priming Effect into Soil Organic Matter Models

2021 ◽  
Author(s):  
Oleg Chertov ◽  
Yakov Kuzyakov ◽  
Irina Priputina ◽  
Pavel Frolov ◽  
Vladimir Shanin ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Priming Effect ◽  
C:N Ratio ◽  
Target Function ◽  
Terrestrial Ecosystems ◽  
Model Verification ◽  
Mineral N ◽  
Soil System ◽  
Plant Soil

Abstract Purpose. This study is aimed to develop a model of priming effect (accelerated mineralisation of soil organic matter (SOM)) induced by root exudate input into nitrogen (N) limited rhizosphere soil as a typical case for most terrestrial ecosystems. This ecologically important process in the functioning of the “plant-soil” system was parameterized for temperate and boreal forests.Methods. A model of priming effect has been developed based on the concept of N mining to making up for the N scarcity in exudates by accelerating SOM mineralisation. Lacking N for microbial growth is mined from the SOM mineralisation considering C:N ratio of soil. The model has a built-in food web module, which calculates soil fauna feeding on microorganisms, the release of by-products of faunal metabolism and mineral N used for root uptake.Results. The model verification demonstrated the similar order of the priming effect as in the published experiments. Testing at the pedon level revealed a high sensitivity of the model to N content in root exudates. Testing of the model at the ecosystem level revealed that CO2 emission from the priming can reach 25–30% of CO2 emission from the whole Ah horizon of forest soil. The same intensities were simulated for the fauna-derived N released within the rhizosphere.Conclusion. The new model reflects important ecological consequences of the main target function of priming effects within the “plant – soil – microorganisms – fauna” system – the microbial acceleration of C and N cycling in the rhizosphere and detritusphere to mobilise mineral N for plants.

scholarly journals Fungal Community, Not Substrate Quality, Drives Soil Microbial Function in Northeastern U.S. Temperate Forests

2020 ◽  
Vol 3 ◽  
Author(s):  
Amelia A. Fitch ◽  
Ashley K. Lang ◽  
Emily D. Whalen ◽  
Kevin Geyer ◽  
Caitlin Hicks Pries
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Community Composition ◽  
Fungal Community ◽  
Enzyme Production ◽  
C:N Ratio ◽  
Am Fungi ◽  
Fungal Community Composition ◽  
Substrate Quality ◽  
Soil Microbial

Mycorrhizal fungi can affect soil organic matter cycling through several mechanisms including priming, nutrient competition, and direct enzyme production. Differences in nutrient foraging strategies between ectomycorrhizal (EcM) and arbuscular mycorrhizal (AM) fungi produce divergent belowground dynamics: where EcM can take up organic nitrogen and directly break down soil organic matter (SOM) by producing enzymes, AM fungi are limited to scavenging mineral N. EcM-associated tree species also have leaf litter with relatively higher ratios of carbon to nitrogen (C:N), and belowground saprotrophic communities more dominated by fungi. Consequently, free-living microbes in EcM-dominated soils should experience nitrogen limitation, with subsequent increases in enzyme production and decreased carbon use efficiency (CUE). However, the relative importance of the effects of substrate quality and fungal community composition on enzyme production and CUE are unclear. To assess this distinction, we sampled the organic horizon and 10 cm of the mineral horizon in northern temperate forest soils along a gradient of EcM dominance. We characterized fungal community composition by measuring EcM relative abundances from extracted fungal DNA and the fungal to bacterial (F:B) ratios from phospholipid fatty acid (PLFA) analysis. We assessed soil substrate quality as the soil C:N ratio. Soil microbial functions were measured as potential activities of five hydrolytic and two oxidative enzymes, and microbial CUE. We found that the fungal community, represented by either the F:B ratio, EcM relative abundance, or both, affected CUE and six measured enzyme activities, while the C:N ratio affected only oxidative and chitin-targeting extracellular enzyme activities. Our results highlight the use of EcM relative dominance as a predictor of soil microbial community composition and function independent of substrate quality.

scholarly journals Organic-Matter Activity of Some Typical Soils of Puerto Rico

1969 ◽  
Vol 39 (2) ◽  
pp. 65-76
Author(s):  
Fernando Abruña-Rodríguez ◽  
José Vicente-Chandler
Keyword(s):  
Organic Matter ◽  
Puerto Rico ◽  
Soil Organic Matter ◽  
Close Association ◽  
C:N Ratio ◽  
Organic Matter Content ◽  
Exchange Capacity ◽  
Matter Content ◽  
Soil Samples ◽  
Considerable Portion

The exchange capacity of the organic matter in typical soils of Puerto Rico was evaluated from: (1) The variation in the exchange capacity of soil samples following destruction of the organic matter, (2) titration curves of extracted organic matter, (3) and the correlations between exchange capacity and organic-matter content of soil samples. The first method was the most practical and gave fairly accurate results. The second method gave results which were in all cases too high. The third method, though probably the most accurate, is impractical. Results obtained with the first and third methods were similar. The exchange capacity of the organic matter varied rather widely, but was generally between 100 and 150 m.e. per 100 gm. On the average it accounted for about 25 percent of the total exchange capacity of the soils studied. The organic matter removed by flotation had the highest exchange capacity and the more readily oxidizable portions generally appeared to be the most active. This suggests the importance of conserving the more readily lost portions of the soil organic matter. A considerable portion of the soil organic matter was extremely resistant to oxidation, had a narrow C:N ratio, and apparently little exchange capacity. This suggests a close association between the organic matter and the inorganic soil colloids. The marked resistance to oxidation of a considerable portion of the organic matter may partly explain the high contents found even in continuously cultivated soils in Puerto Rico.

scholarly journals SOIL ORGANIC MATTER FRACTIONS IN PRESERVED AND DISTURBED WETLANDS OF THE CERRADO BIOME

2015 ◽  
Vol 39 (1) ◽  
pp. 222-231 ◽  
Author(s):  
Ricardo Fernandes de Sousa ◽  
Eliana Paula Fernandes Brasil ◽  
Cícero Célio de Figueiredo ◽  
Wilson Mozena Leandro
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Analysis ◽  
C:N Ratio ◽  
Soil Surface ◽  
Fulvic Acids ◽  
Shallow Water Table ◽  
Cerrado Biome ◽  
Total Soil ◽  
Organic Matter Fractions

Veredas are humid tropical ecosystems, generally associated to hydromorphic soils and a shallow water table. The soils of these ecosystems are affected by the use of the areas around these veredas. The objective of this study was to determine soil organic matter (SOM) fractions in veredas adjacent to preserved (native savanna) and disturbed environments (agricultural areas and pastures) in the Cerrado biome. Soil samples were collected from the 0-10 and 10-20 cm layers along reference lines drawn along the relief following the upper, middle and lower positions of one of the slopes, in the direction of the draining line of the vereda. The soil analysis determined: total soil OC, total nitrogen and C:N ratio; C and N contents and C:N ratio in particulate and mineral-associated fractions (of SOM); fulvic acids, humic acids and humin fractions and ratio between humic and fulvic acids. The agricultural use around the veredas induced changes in the SOM fractions, more pronounced in the lower part of the slope. In the soil surface of this part, the OC levels in the humic substances and the particulate fraction of SOM, as well as total soil OC were reduced in the vereda next to crop fields.

scholarly journals Obtaining more benefits from crop residues as soil amendments by application as chemically heterogeneous mixtures

SOIL ◽  
2020 ◽  
Vol 6 (2) ◽  
pp. 467-481
Author(s):  
Marijke Struijk ◽  
Andrew P. Whitmore ◽  
Simon R. Mortimer ◽  
Tom Sizmur
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Properties ◽  
Nutrient Availability ◽  
Soil Structure ◽  
Crop Residues ◽  
Soil Amendments ◽  
C:N Ratio ◽  
Mineral N ◽  
Available N

Abstract. Crop residues are valuable soil amendments in terms of the carbon and other nutrients they contain, but the incorporation of residues does not always translate into increases in nutrient availability, soil organic matter (SOM), soil structure, and overall soil fertility. Studies have demonstrated accelerated decomposition rates of chemically heterogeneous litter mixtures, compared to the decomposition of individual litters, in forest and grassland systems. Mixing high C:N ratio with low C:N ratio amendments may result in greater carbon use efficiency (CUE) and nonadditive benefits in soil properties. We hypothesised that nonadditive benefits would accrue from mixtures of low-quality (straw or woodchips) and high-quality (vegetable waste compost) residues applied before lettuce planting in a full factorial field experiment. Properties indicative of soil structure and nutrient cycling were used to assess the benefits from residue mixtures, including soil respiration, aggregate stability, bulk density, SOM, available N, potentially mineralisable N, available P, K, and Mg, and crop yield. Soil organic matter and mineral N levels were significantly and nonadditively greater in the straw–compost mixture compared to individual residues, which mitigated the N immobilisation occurring with straw-only applications. The addition of compost significantly increased available N, K, and Mg levels. Together, these observations suggest that greater nutrient availability improved the ability of decomposer organisms to degrade straw in the straw–compost mixture. We demonstrate that mixtures of crop residues can influence soil properties nonadditively. Thus, greater benefits may be achieved by removing, mixing, and reapplying crop residues than by simply returning them to the soils in situ.

scholarly journals Altered litter inputs modify carbon and nitrogen storage in soil organic matter in a lowland tropical forest

2020 ◽  
Author(s):  
Emma J. Sayer ◽  
Catherine Baxendale ◽  
Ali J. Birkett ◽  
Laëtitia M. Bréchet ◽  
Biancolini Castro ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Tropical Forest ◽  
Tropical Forests ◽  
C:N Ratio ◽  
N Availability ◽  
Litter Addition ◽  
Lowland Tropical Forest ◽  
Litter Removal ◽  
Som Storage

AbstractSoil organic matter (SOM) in tropical forests is an important store of carbon (C) and nutrients. Although SOM storage could be affected by global changes via altered plant productivity, we know relatively little about SOM stabilisation and turnover in tropical forests compared to temperate systems. Here, we investigated changes in soil C and N within particle size fractions representing particulate organic matter (POM) and mineral-associated organic matter (MAOM) after 13 years of experimental litter removal (L−) and litter addition (L+) treatments in a  lowland tropical forest. We hypothesized that reduced nitrogen (N) availability in L− plots would result in N-mining of MAOM, whereas long-term litter addition would increase POM, without altering the C:N ratio of SOM fractions. Overall, SOM-N declined more than SOM-C with litter removal, providing evidence of N-mining in the L− plots, which increased the soil C:N ratio. However, contrary to expectations, the C:N ratio increased most in the largest POM fraction, whereas the C:N ratio of MAOM remained unchanged. We did not observe the expected increases in POM with litter addition, which we attribute to rapid turnover of unprotected SOM. Measurements of ion exchange rates to assess changes in N availability and soil chemistry revealed that litter removal increased the mobility of ammonium-N and aluminium, whereas litter addition increased the mobility of nitrate-N and iron, which could indicate SOM priming in both treatments. Our study suggests that altered litter inputs affect multiple processes contributing to SOM storage and we propose potential mechanisms to inform future work.

Changes of carbon-isotope ratios in soil organic matter relative to parent vegetation and site specificity

2020 ◽  
Vol 48 (4) ◽  
pp. 2085-2094
Author(s):  
Silviu L. BADEA ◽  
Roxana E. IONETE ◽  
Diana COSTINEL ◽  
Constantin NECHITA ◽  
Mihai BOTU ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Isotopic Composition ◽  
Carbon Isotope ◽  
Isotope Composition ◽  
C:N Ratio ◽  
Site Specificity ◽  
Natural Environments ◽  
High Concentration ◽  
Industrial Sites

Investigating the correlation between biodiversity and ecosystem function in natural environments using carbon-isotope composition (δ13C) allows distinguishing the nutrient cycling pattern and anthropogenic effects incorporation in plants and soil processes. The mechanisms behind the isotopic composition of soil organic matter (SOM) and parent vegetation in relation to the context of site-specificity was approached in this work. Formation of SOM can be affected by the presence of a high concentration of heavy metals in soils. Still, no systematic studies were performed in most of the industrial sites to support this hypothesis.  In order to explore this incomplete understood influence, investigation of carbon isotope signatures (d13C) variations in soil organic matter were performed in two industrial areas from Romania (Copșa Mică industrial platform and Baia Sprie mining zone). The current study, also, investigated the C:N ratio variation, as well as the influence of N speciation regarding d13C values of SOM. The decrease in C:N ratio indicated an increasing effect of the microbial products on SOM matter at increasing depth, for both regions, while an increase of the denitrification processes with depth was found for both areas. For the most appropriate depth (20-40 cm), the soil from Baia Sprie region was more enriched in 13C comparing with the soil from Copsa Mica region, and this higher isotope fractionation of SOM might be due to a higher carbon content, respectively a higher nitrogen content of Baia Sprie soil. It was concluded that the SOM of the surface soil in the two investigated regions has an 13C isotopic composition similar to the plant remains from which it was formed, offering an integrated value of plant material, time and the local origin and providing useful markers of tree isotopic composition.

The fate of biologically fixed nitrogen in legume-based dryland farming systems: a review

2001 ◽  
Vol 41 (3) ◽  
pp. 361 ◽  
Author(s):  
I. R. P. Fillery
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
C:N Ratio ◽  
Farming Systems ◽  
Climatic Conditions ◽  
Plant Residues ◽  
N Loss ◽  
Mineral N ◽  
Tropical Regions ◽  
Intensively Managed

Considerable progress has been made with the quantification of inputs and losses of nitrogen (N) for a number of legume-based dryland rotations, enabling the fate of legume-derived N to be determined with greater accuracy than previously. Analyses of nitrate (NO3–) in soil profiles to a depth of at least 0.6 m, during and after legume phases, together with measurements of net N mineralisation are providing a much clearer insight of the capacity of legume phases to supply inorganic N. Advances in procedures used to determine drainage have improved estimates of NO3– leaching for a range of soils and rainfall conditions. The loss of N from urine patches and rates of ammonia volatilisation from grazed fields are fairly well characterised. In contrast, the amounts of N lost from legume-based rotations through denitrification are largely unknown. The ingestion of 60–70% of the legume N by animals in intensively managed pastures highlights the pivotal roles grazing animals can play in the transformations of N in pastures. Most of the ingested N is excreted, with the proportion returned in urine dependent on the N content of feed consumed. The tendency of sheep and cattle to defecate close to camping areas when set-stocked can cause large transfers of N within pasture paddocks. Transfer of N from pastures to laneways and to milking sheds (about 55 kg N/ha.year), and export of N in milk (80 kg N/ha.year), are major loss processes in intensively managed dairy pastures. Export of N in meat and wool are insignificant in respect to N2 fixation in improved pastures. Gaseous losses, specifically ammonia (NH3) volatilisation, can account for between 30 to 50% of urine voided to dead pasture or dry soil in summer and autumn. Lower proportions of urine N (10–25% of N applied) are lost after application to green pasture, with gaseous losses further reduced where rainfall occurs soon after urination. Although these losses of N are significant in the context of urine patches, micrometeorological techniques that measure NH3 volatilisation over an area of several hectares of grazed green pasture indicate that NH3 losses chiefly fall in the range 1–7% of urine N excreted. Annual rates of leaching of the order 15–35 kg NO3– N/ha have often been obtained under grazed legume pastures for a range of soil and climatic conditions. Uptake of NO3– by non-leguminous species in mixed pastures appears to be the main reason for the smaller quantities of leached NO3– than might be anticipated from the high rates of N addition in urine patches. The maintenance of low NO3– concentrations in field soils, together with low temperatures during periods of excess soil water, also appear to restrict denitrification in soil under mixed pasture swards, even though measurements undertaken in controlled soil environments suggest that denitrification could potentially account for up to 25–30% of urine N. The magnitude and timing of N release from legume residues remaining after grazing, and subsequent immobilisation of mineralised N, is affected by the efficiency of C use by the decomposer population, the demand for N, the chemical nature of the plant residues, and a range of soil factors. Green residues decompose rapidly with up to 40% of residue mineralised within 12 months. A slower rate of decomposition occurs in mature residues that possess a wider C:N ratio, and greater lignin:N ratio and/or polyphenol:N ratios. Where legume phases are followed by a crop phase, 10–20% of previously green legume residue N is typically used by the first succeeding crop, while less than 10% of N in mature pasture residue is normally in the first following crop. Loss of mineralised residue N from soil, by either NO3– leaching or denitrification, are small in Mediterranean-type climates, but can be large in wet temperate or tropical regions. Nevertheless, the soil organic matter pool is the main sink for N in legume residues. Mineralisation of soil organic matter after legume phases can result in the accumulation of 70–150 kg N/ha, chiefly as NO3–, in many soils during either winter or summer fallows. Between 40 and 100 kg NO3– N can be leached from the rooting zone of the first succeeding crop in soils that possess large hydraulic conductivities, highlighting that the greatest risk of N loss from legume-based rotations exists at the onset of subsequent cropping phases when the crop demand for mineral N is low. Few studies have evaluated the loss of legume- or soil-derived NO3– by denitrification in crops that follow legumes, making it difficult to assess the importance of this N loss process. Australian cereal crops can use as little as 21–36% of available soil-derived mineral N after legume phases on sandy soils with low water holding capacity, and up to 45–50% in the case of finer-textured red or red brown earths. Better synchronisation of N supply from legume phases with subsequent demand for mineral N would further enhance the efficiency of recovery of legume N. The review outlines ways in which this might be achieved, and it also discusses options that could be used to reduce N loss in grazed pastures.

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