SOM Composition Research Articles

Soil management effects on soil organic matter properties and carbon sequestration (SOMPACS)

SOMPACS is a project recommended by EJP SOIL for funding under the 1st External Call "Towards Healthy, Resilient and Sustainable Agricultural Soils". The goal of this project is to assess management practices that enrich organic matter pools that are resilient to rapid microbial decomposition. The project started in 2022 as a consortium of 12 research institutions from Poland, Germany, Ireland, Lithuania, UK, Italy and USA for a period of three years. Soil and vegetation samples from eight long-term experiments that differ in soil management practices (i.e., conventional vs. no-tillage; mineral vs. organic fertilization; with and without catch crop; and arable land vs. undisturbed grassland) are investigated. Study sites include: 22- and 54-year long experiments in Lithuania; 26-year long experiment in Italy; 30- and 40-year long experiments in Ireland; 30- and 46- and 100-year long experiments in Poland; and 178-year long Broadbalk experiment in Great Britain. Additional experimentation includes assessing the impact of root growth promoting amendments (commercially available humic substances, biochar and biogas digestate) on stable organic matter pools. In parallel with soil sampling, plant productivity are measured in all field experiments. This investigation is couples fields studies with small-scale experimental plots and laboratory incubations under controlled conditions. In addition to assessing basic soil properties, the following state-of-the-art analyses are conducted: SOM composition and stability by Py-GC-MS; fractionation of aggregate size classes and C pools of increasing physicochemical protection; isotopic analysis of δ13C and δ15N performed on different SOM pools; microbiological properties (community-level physiological profiling, selected functional genes involved in C and N cycles, microbiome and mycobiome analyses by next-generation sequencing, genetic diversity using terminal restriction fragment length polymorphism); enzymatic activity; soil water retention and soil water repellency; mineral composition of clay fraction; (8) soil structure stability. SOM composition and stability by Py-GC-MS; fractionation of aggregate size classes and C pools of increasing physicochemical protection; isotopic analysis of δ13C and δ15N performed on different SOM pools; microbiological properties (community-level physiological profiling, selected functional genes involved in C and N cycles, microbiome and mycobiome analyses by next-generation sequencing, genetic diversity using terminal restriction fragment length polymorphism); enzymatic activity; soil water retention and soil water repellency; mineral composition of clay fraction; (8) soil structure stability. The most resistant SOM pool (humin) are isolated by different methods (isolation vs. extraction) and examined for chemical composition and structure, using spectrometric and spectroscopic techniques (mass spectrometry, NMR, FTIR, EPR, UV-Vis-NIR, fluorescence). The carbon stocks in the soil profile will be evaluated and the carbon extractable in cold water will be determined to assess the potential carbon leaching and microbial availability. Additionally, in-field soil carbon dioxide (CO2) fluxes from selected experiments is monitored. Thus far, soil samples (0-100 cm depth) were collected and the humin fraction from surface A horizon was isolated for spectroscopic studies. Crop yield and vegetation productivity was also assessed. The research was financed by NCBR (EJPSOIL/I/78/SOMPACS/2022).

Plant footprint decreases the functional diversity of molecules in topsoil organic matter after millions of years of ecosystem development

AbstractAimTheory suggests that the diversity of molecules in soil organic matter (SOM functional diversity) provides key insights on multiple ecosystem services. We aimed to investigate how and why SOM functional diversity and composition change as topsoils develop, and its implications for key soil functions (e.g., from nutrient pool to water regulation).LocationWe reported data on 16 soil chronosequences globally distributed in nine countries from six continents.Time Period2016–2017.Major Taxa StudiedSoil microbes (bacteria and fungi) and vascular plants.MethodsSOM functional diversity and composition without mineral interference were measured using diffuse reflectance mid‐infrared Fourier transform spectroscopy (DRIFT). We aimed to characterize the main environmental factors related to SOM functional diversity and composition. Also, we calculated the links among SOM functional diversity and key soil functions.ResultsWe found that SOM functional diversity declines after millions of years of soil formation (pedogenesis). We further showed that increases in plant cover and productivity led to a higher ratio of reduced (e.g., alkanes) over oxidized carbon forms (i.e., C: O‐functional groups ratio), which was positively correlated to SOM functional diversity as soils age. Our findings indicated that the plant footprint (i.e., the accumulation of plant‐derived material promoting the C: O‐functional group ratio) would explain the reduction of SOM functional diversity as ecosystems develop. Moreover, the dissimilarity in SOM composition consistently increased with soil age, with the soil development stage emerging as the main predictor of SOM dissimilarity across contrasting biomes.Main ConclusionsOur global survey contextualized the natural history of SOM functional diversity and composition during long‐term soil development. Together, we showed how plant footprint drives the losses of SOM functional diversity with increasing age, which might provide a novel mechanism to explain typically reported losses in ecosystem functions during ecosystem retrogression.

What makes soil landscape robust? Landscape sensitivity towards land use changes in a Swiss southern Alpine valley

Landscape sensitivity is a concept referring to the likelihood that changes in land use may affect in an irreversible way physical and chemical soil properties of the concerned landscape. The objective of this study is to quantitatively assess the sensitivity of the southern Alpine soil landscape regarding land use change-induced perturbations. Alpine soil landscapes can be considered as particularly sensitive to land use changes because their effects tend to be enhanced by frequent extreme climatic and topographic conditions as well as intense geomorphologic activity. In detail, the following soil key properties for soil vulnerability were analysed: (i) soil texture, (ii) bulk density, (iii) soil organic carbon (SOC), (iv) saturated hydraulic conductivity (Ksat), (v) aggregate stability and (vi) soil water repellency (SWR). The study area is characterized by a steep, east-west oriented valley, strongly anthropized in the last centuries followed by a progressive abandonment. This area is particularly suitable due to constant lithological conditions, extreme topographic and climatic conditions as well as historic land use changes. The analysis of land use change effects on soil properties were performed through a linear mixed model approach due to the nested structure of the data. Our results show a generally high stability of the assessed soils in terms of aggregate stability and noteworthy thick soils. The former is remarkable, since aggregate stability, which is commonly used for detecting land use-induced changes in soil erosion susceptibility, was always comparably high irrespective of land use. The stability of the soils is mainly related to a high amount of soil organic matter favouring the formation of stable soil aggregates, decreasing soil erodibility and hence, reducing soil loss by erosion. However, the most sensitive soil property to land use change was SWR that is partly influenced by the amount of soil organic carbon and probably by the quality and composition of SOM.

Soil organic matter accumulation before, during, and after the last glacial maximum in Byers Peninsula, Maritime Antarctica

Organic matter is incorporated into soil by biological activity, and its preservation depends on composition and organic-mineral interactions. Frost activity, dry and cold climate, and glacial retreat-advance dynamics complexify soil organic matter storage in Antarctica. Byers Peninsula is the largest ice-free area in Antarctica and hosts a high diversity of vegetable and animal species. We hypothesize that (i) the SOM in the Byers Peninsula may reveal a distinct composition due to the antiquity of the ice-free areas not entirely obliterated by the advancing glaciers during the LGM; and (ii) the advancing ice caps at Byers allowed the accumulation of organic carbon at sheltered points of the Peninsula. Thus, the objectives of this work were: i) to characterize physically and chemically selected soils at Byers Peninsula, with emphasis on organic C and N stocks in different soil types, and ii) SOM dating of representative soil profiles. Thirteen soil profiles were dug, described, and classified. The plant species present at each site were identified. Chemical and physical attributes were determined. The C and N contents, δ13C and δ15N ratio isotopes were determined in the SOM physical size-fractionated particles. The C and N stocks were calculated for each SOM fraction. The deepest horizon of six soil profiles were dated by the 14C method.. Soils from Byers Peninsula showed a diverse and varied biochemical nature of SOM, resulting in varying content of C and N. The δ13C weighted mean of the SOM reflects the dominant vegetation type present in each sampling location, except for pre-Holocene soils and soils influenced by ornithogenesis. The highest organic C and N pools were recorded at subsurface horizons and attributed to the organo-mineral association fraction in upper platforms. For all soil groups, there was a significant overlap of δ13C and enrichment of δ15N in all fractions of SOM, requiring the combination of these two signatures to identify possible sources of contribution to SOM in this environment. The oldest soils, subjected to early-mid Holocene uplift, revealed an endolithic signature of pre-LGM age, the first recorded in Maritime Antarctica to this day. This first pre-LGM SOC record can indicate the initial modern colonization of Maritime Antarctica and suggests that ice caps advance during LGM was limited. Soils formed during and after the LGM in low platforms have a lacustrine signature indicating an influence of snowmelt, ice thawing, and permafrost degradation in selecting hygrophilous species. Soils formed in raised beaches have the lowest organic C and N stocks, and the isotopic composition of SOM indicates ancient ornithogenic influence.

Humus status of chernozem soils formed under deep hydrogen release and different humidification conditions

Purpose of the study: to reveal changes in some humus characteristics in chernozems under the influence of of two factors, specifically, humidification and the flow of endogenous hydrogen. Place and time of the study. Soil sampling and hydromenty were carried out on the territory of the Gryazinsky district of the Lipetsk region (Krivoborgsko-Saltykovsky trough, the territory with leached chernozems) and on the territory of the Oktyabrsky district of the Voronezh region (Khopersky deep fault, the territory with ordinary chernozems) in June 2017. Methods. The molecular hydrogen content was measured directly in the field with a portable hydrogen gas analyzer VG-3B. The total soil organic carbon (SOM) content was determined by the Tyurin method, and pH was measured potentiometrically. To assess the SOM composition, an alkaline pyrophosphate extraction was used. The luminance values of soil samples were determined using the CIELAB international chromaticity system and the LRV system on the Nix Color Sensor spectrocolorimeter. Results. The study showed that under the influence of hydrogen flow in different humidification regions, the effect of these two factors was different. Tthe establishment of the reductive regime, signs of podzolization and gleing in the morphological profile, acidification of the soil bulk and brightening of the upper humus horizon were found to be common features between the soils of these regions. However, the effect of such active reducing agent as hydrogen on the SOM and qualitative composition in these regions varied greatly. In the drier region with ordinary chernozems, SOM accumulated in hydrogen relief depressions (from 2.4 to 5.4%), and due to their sharp predominance (three times, sometimes four times) in SOM composition and predominance in the soil profiles, fulvic acids determined a sharp increase in soil acidity. The leached chernozems, on the contrary, manifested a significant SOM loss (from 3.9 to 2.2%), with humic acids predominating in SOM composition. This effect was most likely associated with the removal of more mobile SOM components outside the soil profile in the more humic climate of the Lipetsk region.

Hydrodynamic‐Driven Changes in the Source and Composition of Sedimentary Organic Matter via Grain Size Distribution in Shallow Lakes

AbstractSediment organic matter (SOM) differs in composition and function in different size fractions in relation to material and energy flows. The hydrodynamic effects on a lake's autochthonous (terrestrial plants) and allochthonous (microalgae, aquatic plants, and bacteria) inputs and transformation, and the components of SOM are still far from clear. To elucidate the SOM composition as driven by the hydrodynamic conditions associated with sedimentary grain size, we performed an ecosystem‐level investigation in the shallow lake Izunuma, Japan, measuring source‐specific fatty acids and the current velocity. High organic matter concentrations occurred in the finer fractions. Bacteria were dominant in the <32 μm fraction, microalgae were mainly present in the <32 and 63–125 μm fractions, aquatic plants appeared to be evenly distributed in all size fractions, and terrestrial plants mainly comprised the >125 μm fraction. Although the linear correlation between current velocity and sedimentary total organic carbon (TOC) was not statistically significant, the relationship between current velocity frequency and sedimentary TOC was significant. The highest Pearson coefficient occurred at a current velocity of 6 cm/s in sand. The relationship between allochthonous inputs and current velocity frequency was similar to that of TOC. Autochthonous organics had the greatest coefficient with two peaks at 4.5 and 8 cm/s. The threshold for sand resuspension varied with organic sources, while this phenomenon was absent in cohesive mud. Hydrodynamic forces affected the grain size of sediments and drove the gradient distribution of the SOM sources, which should be considered when managing freshwater lakes in light of future climate change.

Spatially-distributed microbial enzyme activities at intact, coated macropore surfaces in Luvisol Bt-horizons

Soil macropores serve as preferential pathways for water and solute transport as well as for root growth. They are often coated with organic material and known as "hotspots" of nutrient and C turnover. Differences in the SOM composition between macropores and soil matrix as well as between macropore types (biopores, cracks, pinhole fillings) imply potential differences in the microbial community composition and enzymatic activities. The objective of this work was to detect and assess the spatial distribution of enzyme activities related to C turnover, xylanase (XYL) and phenol oxidase (POX), and the composition of microbial communities in structural components of Luvisol Bt-horizons, developed from loess and glacial till. We applied conventional enzyme assays and phospholipid fatty acids (PLFA) analysis to study materials separated from different types of macropores and soil components as well as bulk soil samples. The spatial distribution of enzyme activities on surfaces of large soil core slices (20 cm in diameter) was quantified by soil zymography. Higher XYL activities were detected in separated burrow wall materials, clay-organic coatings, and pinhole fillings from both sites, as compared to the respective soil matrix or bulk soil samples. The XYL activities correlated with bacteria-specific PLFAs. POX activities were solely found increased for earthworm burrow walls from the loess-derived Bt-horizon, but not for burrows from till samples. Zymograms revealed particularly increased XYL activities at rooted earthworm burrows, emphasising evidence for hotspots of enzyme activity and C turnover. The zymography of POX was hampered by methodological restrictions.

Boreal tree species affect soil organic matter composition and saprotrophic mineralization rates

AimsTo investigate how different tree species affect the composition of SOM and its mineralization in boreal forest ecosystems.MethodsWe used pyrolysis GC–MS for molecular-level characterization of the SOM formed under five common boreal tree species at a replicated field experiment ~50years after plantation. We incubated soil samples at 4, 9, 14 and 19 °C and measured inherent CO2 production and substrate-induced respiration. We then evaluated if the saprotrophic microbial activity and its temperature sensitivity was controlled by the SOM composition.ResultsThe molecular composition of the SOM emerged as key factor influencing SOM properties in plots with different tree species. Most of the variance in the SOM content was explained by the organo-chemical composition of the SOM. More importantly, the fraction of the microbial community able to utilize the native SOM was largely controlled by the SOM organo-chemical composition. Temperature sensitivity of CO2 production (Q10) was not explained by SOM composition. However, the microbial access to different SOM pools varied with temperature.ConclusionsThese results bridge the gap between the paradigms of short-term litter and long-term SOM decomposition showing that, on an intermediate timescale (~50 years), boreal tree species affect SOM molecular composition and saprotrophic mineralization rates.

Water‐soluble phenolic metabolites in lichens and their potential role in soil organic matter formation at the pre‐vascular stage

AbstractSoil organic matter (SOM) is the largest reservoir of organic carbon in the biosphere. However, little is known about the processes of its formation at the pre‐vascular stage. Lichens are among the pioneer colonizers on mineral substrates and are possible early land flora. This study is the first report on the identification and quantification of water‐soluble phenolic compounds (PCs), potential precursors of humic substances, in epigeyic lichens from two systematic groups. Results show (Folin–Denis assay) that cyanobiont‐containing lichens (order Peltigerales) possess three to five times more total soluble PCs than Lecanoralean lichens (Cladonia, Cetraria spp.) and mosses. Soluble PCs in lichens occur in the conjugated form. Alkali‐hydrolysable compounds (esters) predominate over acid‐hydrolysable compounds (glycosides). Phenolic complexes with N‐containing compounds or reducing sugars, or both, have been identified by thin layer chromatography (TLC). Benzoic acid derivatives were most common among PCs, detected in lichens by reversed‐phase high‐pressure liquid chromatography (RP‐HPLC). Phenolic acids occur in the order (μg 100 g−1): p‐hydroxybenzoic acid (327–1,007) > syringic acid (87–361) > salycilic acid (135–210) > vanillic acid (12–19) (Peltigeralean lichens); salicylic acid (53–102) > p‐hydroxybenzoic acid (45–54) > caffeic acid (29) > syringic acid (18) > vanillic acid (9–13) (Lecanoralean lichens). Protocatechuic, caffeic and p‐coumaric acids were rare; ferulic acid was not detected. Syringyl and vanillyl aldehydes and ketones occur in much larger amounts than acids. Methoxy‐substituted and ortho‐substituted phenols, detected in lichens, are known for their high reactivity in soils under lignified vegetation, suggesting their important roles in SOM formation under a cryptogam cover.Highlights Phenolic composition of SOM and humification processes at pre‐vascular stage are largely overlooked Soluble phenolic acids, aldehydes and ketones are quantified in lichens for the first time Lichens are depleted in phenylpropanoids and enriched in syringyl structures and monophenols Lichen‐derived phenolic compounds are potential precursors of humic substances under cryptogam cover

Irrigation with sediment-laden river water affects the soil texture and composition of organic matter fractions in arid and semi-arid areas of Northwest China

Soil organic carbon (SOC) is the largest reservoir of organic carbon in the terrestrial ecosystem, and is an effective mean of enhancing crop production in the irrigated area of the arid and semi-arid regions. Understanding long-term changes in composition of SOM under irrigation from sediment-laden Yellow River water is essential to manage sustainability issues in the agro-ecosystem. A total of 45 soils, including 39 of irrigated fields differing in irrigation history and 6 of non-cultivated and non-irrigated natural fields as the control, were sampled at 0–20 cm depth. The soil was analyzed for total SOC content, partitioning of light (LFOM) and heavy (HFOM) fraction organic matter based on NaI solution density of 1.7 g m3 and for particle size distribution. Compared to the non-irrigated and non-cultivated control soil, the LFOM and HFOM in irrigated soils increased with the duration of irrigation though SOM existed dominantly as the heavy fraction. The soils irrigated for <50 years have overall lesser LFOM and HFOM and more sand compared to those with >50 years irrigation. Further, a positive relationship existed between the fine particle and the SOM or its fractions (negative relation with coarse particle) suggesting either SOM accumulated as fine particles or the fine mineral particles better preserved SOM. In addition, field soil moisture at the time of sampling during October 2009 correlated with HFOM (p < 0.001) and LFOM (p < 0.01). The study suggested that the long-term irrigation with water diverted from Yellow River increased fine particle, SOC and the light and heavy fraction in the Ningxia Irrigation Zone.

Human activity formed deep, dark topsoils around the Baltic Sea

Previous findings showed that the humus-rich topsoils designated as Chernozems around the Baltic Sea were influenced by the addition of pyrogenic organic matter linked with human activity. For a deeper insight into the human activities, we investigated the isotopic signatures of sulphur (δ34S) and the 14C age from nine soil profiles in order to clarify which kind of organic matter was added to the soils and to estimate the beginning of the Chernozem formation. The study area was expanded by two additional Baltic Chernozem profiles on the island of Fehmarn in which we also analyzed the portions of black carbon (BC) with the benzene polycarboxylic acids (BPCA) method and the SOM composition with the Pyrolysis-field ionization mass spectrometry (Py-FIMS). The compound classes from Py-FIMS and the BC portions were similar to all other Baltic Chernozems and Chernozems from European loess areas and indicated an input of combustion residues to the soils. The δ34S isotope signature of the SOM in the Axh-horizons (Median: δ34S=11.5‰) at the island of Poel and Sjaelland indicated an input of seaweed (δ34S=20‰) or other marine biomass. The AMS14C ages from the humin fraction, i.e. the oldest fraction of SOM, of the Axh-horizons and the settlement history implied that the formation of the Baltic Chernozems started in a time period between the Nordic Bronze Age (3800 to 2800BP) to the Roman Iron Age (2700 to 2000BP). In summary, the results provided a strong evidence for an input of combustion residues and marine biomass by anthropogenic activities and we conclude that the formation of the Baltic Chernozems reflects an anthropo-pedogenesis. Therefore, we propose to classify these soils as Anthrosols.

Laboratory Assessment of Forest Soil Respiration Affected by Wildfires under Various Environments of Russia

Pyrogenic carbon emission rates were estimated in the soils of three natural zones in Russia: forest-tundra, south-taiga, and forest-steppe. Postfire soils were found to be characterized by essential losses of soil C due to the combustion fire effect. Soils lost 3 or 5 parts of initial carbon content and showed an essential decrease in the C/N ratio during the fire effect. The pH values increased due to soil enrichment by ash during the fire events. CO2 emission rates were highest in natural soil samples, because the amount of organic matter affected by mineralization in those soils was higher than in natural ones. Simultaneously, the total values of mineralized carbon were higher in postfire soils because the SOM quality and composition were altered due to the fire effect. The only exception was in forest-tundra soils, where a high portion of dissolved organic compounds was released during the surface fire. The quality of initial SOM and intensity of the wildfire play the most important roles in the fate of SOM in postfire environments. Further study of CO2 emissions is needed to better characterize postfire SOM dynamics and develop an approach to model this process.

Fossil redox-conditions influence organic matter composition in loess paleosols

The soil memory recorded in paleosols of loess-paleosol sequences is an important contributor to our understanding of past climatic conditions. Molecular proxies based on the organic matter preserved in paleosols form an essential part of this record, but the long-term preservation of SOM is poorly understood, especially for sediment traps and slope profiles. This paper addresses the composition of organic material from the Early Weichselian A-horizons of the Rocourt paleosol, a major paleostratigraphic marker for the Eemian and Early Weichselian in Western Europe. NaOH-extractable organic matter from an exceptionally thick Rocourt profile in the Kesselt Quarry (Belgian Loess Belt) was analyzed by pyrolysis-Gas Chromatography/Mass Spectrometry (pyrolysis-GC/MS) and the results evaluated against paleopedological data. The molecular composition of the organic matter at Kesselt was compared with reference samples from two nearby quarries (including the type locality at Veldwezelt-Hezerwater), and to a sample from the contemporary Nussloch sequence in Germany. The SOM composition found at the four sites indicated a large content of microbial matter and was dominated by carbohydrates and N compounds, many of which were not reported before from SOM pyrolysates. Differences in the molecular composition between samples, both within profiles and between sites, coincided with differences in landscape position (slope-shoulder-plateau) and fossil redox conditions (surface gleys). Samples form drier and more upland situations contained more burnt material, while samples from slope profiles and surface gleys contained even more microbial material, in particular chitin. Results therefore suggest that the admixture of microbial SOM is considerable in loess-paleosols and that differences in edaphic conditions (in particular slope position and soil moisture) and occurrence of wildfires are important for the long-term preservation of SOM. These should therefore be considered when interpreting biogeochemical proxies.

Major Sources of Organic Matter in a Complex Coral Reef Lagoon: Identification from Isotopic Signatures (δ13C and δ15N).

A wide investigation was conducted into the main organic matter (OM) sources supporting coral reef trophic networks in the lagoon of New Caledonia. Sampling included different reef locations (fringing, intermediate and barrier reef), different associated ecosystems (mangroves and seagrass beds) and rivers. In total, 30 taxa of macrophytes, plus pools of particulate and sedimentary OM (POM and SOM) were sampled. Isotopic signatures (C and N) of each OM sources was characterized and the composition of OM pools assessed. In addition, spatial and seasonal variations of reef OM sources were examined. Mangroves isotopic signatures were the most C-depleted (-30.17 ± 0.41 ‰) and seagrass signatures were the most C-enriched (-4.36 ± 0.72 ‰). Trichodesmium spp. had the most N-depleted signatures (-0.14 ± 0.03 ‰) whereas mangroves had the most N-enriched signatures (6.47 ± 0.41 ‰). The composition of POM and SOM varied along a coast-to-barrier reef gradient. River POM and marine POM contributed equally to coastal POM, whereas marine POM represented 90% of the POM on barrier reefs, compared to 10% river POM. The relative importance of river POM, marine POM and mangroves to the SOM pool decreased from fringing to barrier reefs. Conversely, the relative importance of seagrass, Trichodesmium spp. and macroalgae increased along this gradient. Overall, spatial fluctuations in POM and SOM were much greater than in primary producers. Seasonal fluctuations were low for all OM sources. Our results demonstrated that a large variety of OM sources sustain coral reefs, varying in their origin, composition and role and suggest that δ13C was a more useful fingerprint than δ15N in this endeavour. This study also suggested substantial OM exchanges and trophic connections between coral reefs and surrounding ecosystems. Finally, the importance of accounting for environmental characteristics at small temporal and spatial scales before drawing general patterns is highlighted.

Soil chemical properties and organic matter composition of a subtropical Cambisol after charcoal fine residues incorporation

Brazil is the world’s greatest charcoal producer with an annual production of 10 million tons. However, about 15 % is lost as charcoal fines, which can be used as soil fertilizer and source of soil stable carbon (C). In this study we, investigated the impact of charcoal fines application on soil chemical properties and organic matter (SOM) stability and composition. Four doses (0, control, 10, 20 and 40 Mg ha−1) of charcoal fines were incorporated to the soil at 10 cm. Soil samples were collected at four soil depths (0–5, 5–10, 10–20, and 20–30 cm) 20 months after charcoal incorporation. Soil chemical properties were determined, and SOM composition was evaluated by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM-EDX) and carbon stable isotopic analysis. Soil chemical properties were affected mainly in the upper depth (0–5 cm) and only at the highest dose (40 Mg ha−1), which also increased the total C content in 37.7 % compared to the control. Probably, the observed effects solely on the surface are due the concentration of charcoal on the upper depth, despite its incorporation. The dose of 40 Mg ha−1 also increased the total C content at 10–20 cm depth compared to the control. Such result was assigned to the leaching of some finest charcoal particles. The SEM-EDX and SOM δ13C signature confirmed the presence of charcoal at both 0–5 and 10–20 cm soil depths. FTIR and TGA indicated an increase in SOM aromaticity and thermostability until 20 cm depth after charcoal incorporation. No effects were observed at the deepest soil depth (20–30 cm), suggesting that charcoal was not leached to this depth within 20 months. The application of charcoal fines ameliorated the soil chemical properties. In general, the charcoal increased the SOM aromaticity and thermostability and changed the δ13C signature at 0–5 and 10–20 cm. Charcoal leaching from the 0–10 to the 10–20 cm depth was observed, but further downward transport was not evidenced by our data. Charcoal fine residues show a potential to be used as an effective soil fertilizer, as well as a stable C source into the soil.

Organic matter properties in soils afforested with Pinus radiata

Afforestation causes important alterations in SOM content and composition that affect the soil functions and C balance. The aim of this study was to identify the mechanisms that determine the changes in SOM composition following afforestation of grasslands. The study included 4 chronosequences and 5 paired plots comprising pastures and land afforested with Pinus radiata. The SOM was characterized by 13C CP-MAS NMR spectroscopy and differential scanning calorimetry. During the first 10–20 year after afforestation, the changes in SOM content varied from slight gains to large losses (>40 %). The analyses revealed that even SOM compounds considered resistant to decomposition were degraded during this time. The SOM gains, observed 20 year after stand establishment, were favoured by the higher recalcitrance of pine litter and possibly by soil acidification. The concentrations of most SOM compounds, particularly the stable compounds, were higher at the end of the rotation. The low degree of protection, along with the favourable climatic conditions, may also explain the rapid decomposition of SOM, including resistant compounds, in these soils. DSC analysis complemented the information about SOM composition provided by other techniques. The accumulation of stable SOM compounds at the end of the rotation suggests a longer soil C turnover in these afforested soils, which may alleviate the gradual loss of SOC in intensively managed forest soils.

Palynofacies and paleoecology from Abu El Gharadig – 4 well, Northern Western Desert, Egypt

Abd El Hakam A. Baioumi and Medhat M. M. Mandur Egyptian Petroleum Research Institute (EGYPT) Abdelhakam.bayomi@yahoo.com DOI: 10.7813/2075-4124.2013/5-2/A.3 ABSTRACT Kharita and Baharyia Formations Northern Western Desert, Egypt are characterized by presence of maximum flooding surface and supported by presence of glauconite, underlain by transgressive system tract and overlain prograditional parasequence sets. Moreover, upper part of Kharita and Bahariya formations represent start of agraditional phase. Composition of dispersed sedimentary organic matter SOM shows presence of three main groups.These include amorphous organic matter group, palynomorph group. The cluster analysis of sedimentary organic matter SOM reveals presence of two palynofacies groups AB palynomorph group is present in waxing quantity of cluster C. From previous data results include to environment of deposition is ranged between low to moderate energy fluviomarine to shallow marine environment. Key words: palynofacies, paleoecology, Northern Western Desert 1. INTRODUCTION This study deals with palynofacies of 4 core samples representing Kharita (Middle – Late Albian) and Bahariya formations (Early Cenomanian) from AG well, located in northern part of Western Desert. (long. 28o 30' 15 E and lat. 29˚ 46' 04 N) Fig. 1 The palynofacies recovered from Albian – Cenomanian clastic sediments of Kharita and Bahariya formations are studied to identify associated paleoenvironment. Abu Gharadig Basin is an elongated graben, trending E – W bounded to north and south, respectively by Qattara ridge and Sitra platform [1] and [2] Stated that the source of gases present in Bahariya formation is believed to have been derived from deep deposits of basin As Cretaceous system is considerd as main targets in exploration for petroleum in Egypt, [3-8]. Fig. 1. Location map of studied borehole AG.4

Pinus afforestation in South Brazilian highlands: soil chemical attributes and organic matter composition

In the last three decades, exotic tree species are being introduced in the natural pastures of the highlands located at the northeastern part of Rio Grande do Sul State (RS), Brazil. This alteration of land use may impart drastic changes in the soil attributes. In this context, this work aimed to evaluate the impact of Pinus taeda afforestation on soil chemical attributes and organic matter (SOM) composition in Leptosols from Campos de Cima da Serra, RS. Soil samples under eight year old (Pi8) and 30 year old (Pi30) Pinus plantations and under native pasture (NP) were studied. Contents of exchangeable cations and of micronutrients and soil pH were determined. The SOM composition was investigated by means of elemental analyses and FTIR spectroscopy. The soil under pasture had a higher content of nutrients and of SOM in comparison to Pinus soils, reflecting the higher input and decomposition rate of the below ground added residue in the grassland environment. The SOM in pasture soils showed a higher content of carbohydrate and of structures derived from microbial metabolism. Besides the depletion of nutrients and of SOM, Pinus afforestation affected the SOM quality: following afforestation, the proportion of chemically recalcitrant structures and of carboxylic groups increased, whereas N-containing groups decreased.

Organic Matter in Clay Density Fractions from Sandy Cropland Soils with Differing Land‐Use History

Land‐use history is often overlooked when assessing soil fertility of intensive cropland production systems. The unusually high organic carbon (OC) content of many sandy cropland soils in Northwestern Europe is unexpected given their general low clay content (3–8%) and organic matter (OM) input typical of cropland, but appears to be related to historical heathland land‐use. Clay fraction OM composition was compared between two groups of sandy cropland soils with (HC) or without (CC) a history of heathland/forest land‐use. Light (1.6–2.2 g cm−3) and heavy (&gt;2.2 g cm−3) clay fractions in HC soils were nearly twice as rich in OC (on average 199 g kg−1) compared with those of CC soils (on average 109 g kg−1). The hypothesized preferential presence of stable heathland derived OM in light soil fractions, was not supported by our data. Pyrolysis‐field ionization mass spectrometry of the clay fractions revealed a more decomposed character of OM in the CC soils and lasting long‐term influence of land‐use history on SOM composition. This could be concluded from higher proportions of lipids and sterols, a lower thermostability in the HC compared with the CC soils, and enrichment of alkylaromatics and heterocyclic N‐containing compounds in the latter. The density fractionation methodology separated organic‐mineral particles with similar OM loadings but lower proportions of sterols and medium to long‐chained lipids in the heavy compared with the light clay fraction. Given the very high clay OC loadings (6–16 mg C m−2) and low binding capacity of the quartz/kaolinite/mica dominated clays, we hypothesize that OM–OM interactions are involved as an OM stabilization mechanism. However, contrary to our hypothesis high clay OC loading (and hence thick OM layering) were found in all sandy croplands regardless of land‐use history or density fraction.

Airborne contaminants in the refractory organic carbon fraction of arable soils in highly industrialized areas

Airborne carbonaceous particles produced by industrial activity have been recorded in soils in proximity to contamination sources that produce coal dust, coke and other residues from fossil fuel combustion. The present study assesses the contribution of airborne contaminants to the refractory organic carbon pool of three soils (a sandy Albic Luvisol, sandy Orthic Luvisol and a loamy Haplic Chernozem) in C-depleted and conventionally managed plots from European long-term experiments located in industrialized regions. The C-depleted plots (unmanured plots and bare fallow) are depleted in labile C and thus relatively enriched in refractory C as compared with the conventionally managed plots. Bulk soils and particle-size fraction were analyzed for soil organic carbon (SOC) structure by cross-polarization magic-angle spinning (CPMAS) 13C nuclear magnetic resonance (NMR) spectroscopy. Coarse-intermediate separates were subjected to a morphological characterization of organic matter (OM) composition by coal petrography. The C-depleted plots show unusually high proportions of aromatic C in nearly all separates, most pronounced in coarse-intermediate fractions. Coal petrographic analysis indicates that high aromaticity in separates 2000–20 μm can be explained by the presence of air-borne contaminants that are identified as coal, coke and combustion residues from fossil fuels. For the two sandy sites, aromatic C in the fine separates (<6 μm) is dominated by protonated aryl C as revealed by dipolar dephasing (DD) NMR experiments. For the loamy soil, aromatic C was comparatively high and about half of the aryl signal was attributable to non-protonated/C-substituted carbons. These results indicate a contribution of airborne contaminants to the refractory C pool for all investigated sites. For the two sandy soils, this contribution appears to be limited to coarse-intermediate separates; in the loamy soil, a contamination is also present in fine separates. From the OC balance of the C-depleted plots, it was estimated that the contribution from contaminants to the refractory C pool is still smaller than that from native OM, which is found mainly within fine particle-size separates. The presence of refractory contaminants will strongly affect the estimation of the long-term turnover of OC at such long-term experiments. A careful examination of the SOM composition and the SOM fractions at such sites is necessary to avoid biased results on SOM turnover.