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Here, a degraded soil, located in a semi-arid Mediterranean region, was characterized 17 years after organic amendment with sludge or compost (differing in their stabilization degree) for restoration purposes. To do this, (i) soil physicochemical properties and plant cover, (ii) soil organic matter (SOM) content and composition, (iii) soil basal respiration and enzymatic activities, and (iv) abundance, taxonomic composition, and functionality (shotgun metagenomics) of microbial communities were studied. Increased SOM and nutrient contents were found in soil from amended plots with respect to the control, with no differences between amendment types. This is explained by the lasting effects of organic amendments and the higher plant cover. Thermal and pyrolytic analyses showed that the restoration process enriched soil mainly with SOM of intermediate recalcitrance and of high chemical diversity. SOM composition did not differ between amendment types. Increased microbial abundances and activities were found in the amended plots, without differences between compost and sludge. Shotgun metagenomics showed that microbial communities changed in taxonomic and functional terms between amended and unamended plots, but these differences were rather limited. The taxonomic differences between treatments were mainly driven by increasing abundances of Actinobacteria and decreasing abundances of Proteobacteria in soil from amended plots. Soil microbial communities in amended plots showed some functional adaptation to the increased nutrient contents and predominant nutrients forms. This, together with the higher microbial abundances detected, explained the conspicuous soil enzymatic activities reported in amended plots. The effectiveness of the studied soil restoration process was confirmed here from an integrative perspective.

Tidal marshes store large amounts of organic carbon in their soils. Field data quantifying soil organic carbon (SOC) stocks provide an important resource for researchers, natural resource managers, and policy-makers working towards the protection, restoration, and valuation of these ecosystems. We collated a global dataset of tidal marsh soil organic carbon (MarSOC) from 99 studies that includes location, soil depth, site name, dry bulk density, SOC, and/or soil organic matter (SOM). The MarSOC dataset includes 17,454 data points from 2,329 unique locations, and 29 countries. We generated a general transfer function for the conversion of SOM to SOC. Using this data we estimated a median (± median absolute deviation) value of 79.2 ± 38.1 Mg SOC ha−1 in the top 30 cm and 231 ± 134 Mg SOC ha−1 in the top 1 m of tidal marsh soils globally. This data can serve as a basis for future work, and may contribute to incorporation of tidal marsh ecosystems into climate change mitigation and adaptation strategies and policies.

Removing lampenflora, phototrophic organisms developing on rock surfaces in tourist cavities due to the artificial lighting, is a challenge for sustainable and appropriate long-term management of caves. Photosynthetic-based biofilms usually cause rock biodeterioration and an ecological imbalance in cave ecosystems. In this work, a detailed investigation of the effects of the 3 most commonly used lampenflora cleaning operations (NaClO, H2O2 and UVC) was carried out in Pertosa-Auletta Cave (Italy). The application of NaClO showed good disinfection capability over extended periods of time without causing any appreciable rock deterioration. The H2O2 treatment showed to be corrosive for the rock surfaces covered with vermiculation deposits. The chemical alteration of organic and inorganic compounds by H2O2 did not remove biomass, favoring biofilm recovery after three months of treatment. Both NaClO and H2O2 treatments were effective at removing photoautotrophs, although the bacterial phyla Proteobacteria and Bacteroidetes as well as Apicomplexa and Cercozoa among the Eukaryotes, were found to be resistant to these treatments. The UVC treatments did not show any noticeable effect on the biofilms.

Soils represent an essential natural, practically non-renewable resource that provides many critical ecosystem services necessary for life. Furthermore, soils play a critical role in maintaining the balance of the carbon cycle, acting as the largest terrestrial carbon pool which made them crucial in mitigating climate change. Understanding the complexity and dynamics of soils is, therefore, apart from preserving and managing this valuable natural resource, critical for the benefit of current and future generations. However, the changing climate and increasing intensity of agricultural production pose significant threats to the sustainability and role of soils, mainly by contributing to a depletion in soil organic matter (SOM) and altering its dynamics. Indeed, Mediterranean soils face these threats in a more severe way due to their geographic location, particular climate and inherent low content of SOM. It is critical to shedding light on this respect by combining different analytical procedures and providing complementary and valuable information on processes that regulate the accumulation, decomposition, and transformation of SOM. The main objective of this thesis was to investigate and deepen our knowledge about the two main threads affecting carbon dynamics in Mediterranean soils i.e., climate change and intensive agricultural practices. For this, advanced analytical techniques appropriate for the study of complex matrices such are soils were tested and combined to study SOM in two distinct and representative Mediterranean soils, in terms of extension and ecosystem relevance: Mediterranean savannahs, commonly known as “dehesas” (Section I) and agricultural soils (Section II).

Slash-and-burn of Amazon Forest (AF) for pasture establishment has increased the occurrence of AF wildfires. Recent studies emphasize soil organic matter (SOM) molecular composition as a principal driver of post-fire forest regrowth and restoration of AF anti-wildfire ambience. Nevertheless, SOM chemical shifts caused by AF fires and post-fire vegetation are rarely investigated at a molecular level. We employed pyrolysis–gas chromatography–mass spectrometry to reveal molecular changes in SOM (0–10, 40–50 cm depth) of a slash-burn-and-20-month-regrowth AF (BAF) and a 23-year Brachiaria pasture post-AF fire (BRA) site compared to native AF (NAF). In BAF (0–10 cm), increased abundance of unspecific aromatic compounds (UACs), polycyclic aromatic hydrocarbons (PAHs) and lipids (Lip) coupled with a depletion of polysaccharides (Pol) revealed strong lingering effects of fire on SOM. This occurs despite fresh litter deposition on soil, suggesting SOM minimal recovery and toxicity to microorganisms. Accumulation of recalcitrant compounds and slow decomposition of fresh forest material may explain the higher carbon content in BAF (0–5 cm). In BRA, SOM was dominated by Brachiaria contributions. At 40–50 cm, alkyl and hydroaromatic compounds accumulated in BRA, whereas UACs accumulated in BAF. UACs and PAH compounds were abundant in NAF, possibly air-transported from BAF.

Today’s agriculture has the challenge of ensuring food supply for a growing population while human activity has already deteriorated about 40% of the world’s soils, reducing productive capacity and increasing reliance on mineral fertilizers. In this context, valorizing and recycling mineral and agricultural waste for use as substrates or soil supplements enhance a sustainable economy, as well as the development of activities focused on finishing the soil nutrients’ cycle. Looking for an effective solution to the massive waste generation and to enhance the agronomic qualities of soils, this study investigates the agronomic impact of contrasting inorganic and organic materials such as green compost (GC), wood biochar (WB), rice husk ash (RA), and volcanic ash (VA) as amendments to an alkaline Luvisol under controlled conditions. In this sense, barley seeds were planted and grown in a greenhouse under controlled conditions for 60 days on a soil amended with the aforementioned materials. The amendments demonstrated appropriate attributes for improving soil agronomic properties, enhancing the soil’s nutritional content with no effect on barley germination. The WB showed high aromaticity and abundance of refractory organic C. Both ash-rich amendments showed high P and K contents, which are important elements for plant development. The GC has high water retention capacity and an adequate C and N balance. Although the application of the amendments had no effect on barley yields, the plants from the ash-amended pots showed an increase of Photosystem II efficiency, indicative of a better physiological status. In terms of toxicological safety, the abundance of trace elements in soils and plants was investigated. All soils met the maximum allowable limits for these persistent pollutants. Nevertheless, longer-term tests on plants are required to determine the risk of Pb accumulation, particularly in soils amended with GC and compost-ash mixtures. The simultaneous combination of

Mediterranean savannahs (dehesas) are agro-sylvo-pastoral systems with a marked seasonality, with severe summer drought and favourable rainy spring and autumn. These conditions are forecasted to become more extreme due to the ongoing global climate change. Under such conditions, it is key to understand soil organic matter (SOM) dynamics at a molecular level. Here, analytical pyrolysis (Py-GC/MS) combined with chemometric statistical approaches was used for the molecular characterization of SOM in a five-years field manipulative experiment of single and combined rainfall exclusion (drought) and increased temperature (warming). The results indicate that SOM molecular composition in dehesas is mainly determined by the effect of the tree canopy. After only five years of the climatic experiment, the differences caused by the warming, drought and the combination of warming+drought forced climate scenarios became statistically significant with respect to the untreated controls, notably in the open pasture habitat. The climatic treatments mimicking foreseen climate changes affected mainly the lignocellulose dynamics, but also other SOM compounds (alkanes, fatty acids, isoprenoids and nitrogen compounds) pointing to accelerated humification processes and SOM degradation when soils are under warmer and dryer conditions. Therefore, it is expected that, in the short term, the foreseen climate change scenarios will exert changes in the Mediterranean savannah SOM molecular structure and in its dynamic.

Organic carbon (OC) association with soil minerals stabilizes OC on timescales reflecting the strength of mineral–C interactions. We applied ramped thermal oxidation to subsoil B horizons with different mineral–C associations to separate OC according to increasing temperature of oxidation, i.e. thermal activation energy. Generally, OC released at lower temperatures was richer in bioavailable forms like polysaccharides, while OC released at higher temperatures was more aromatic. Organic carbon associated with pedogenic oxides was released at lower temperatures and had a narrow range of 14C content. By contrast, N-rich compounds were released at higher temperatures from samples with 2 : 1 clays and short-range ordered (SRO) amorphous minerals. Temperatures of release overlapped for SRO minerals and crystalline oxides, although the mean age of OC released was older for the SRO. In soils with more mixed mineralogy, the added presence of older OC released at temperatures greater than 450°C from clays resulted in a broader distribution of OC ages within the sample, especially for soils rich in 2 : 1 layer expandable clays such as smectite. While pedogenic setting affects mineral stability and absolute OC age, mineralogy controls the structure of OC age distribution within a sample, which may provide insight into model structures and OC dynamics under changing conditions.

Fire-induced alterations to soil pH and organic matter play an important role in the post-fire microbial response. However, the magnitude of which each parameter affects this response is still unclear. The main objective of this work was to determine the magnitude in which soil pH and organic matter fire-induced alterations condition the response of viable and cultivable micro-organisms using laboratory heating, mimicking a range of fire intensities. Four heating treatments were applied to unaltered forest soil: unheated, 300, 450, and 500 degrees C. In order to isolate the effect of nutrient or pH heating-induced changes, different culture media were prepared using soil:water extracts from the different heated soils, nutrient, and pH amendments. Each medium was inoculated with different dilutions of a microbial suspension from the same original, unaltered soil, and microbial abundance was estimated. Concurrently, freeze-dry aliquots from each soil:water extract were analyzed by pyrolysis-gas chromatography/mass spectrometry. The microbial abundance in media prepared with heated soil was lower than that in media prepared with unheated soil. Nutrient addition and pH compensation appear to promote microbial proliferation in unaltered and low-intensity heated treatments, but not in those heated at the highest temperatures. Soil organic matter characterization showed a reduction in the number of organic compounds in soil-heated treatments and a marked increase in aromatic compounds, which could be related to the observed low microbial proliferation.

La repelencia al agua del suelo (RAS) se atribuye a la acumulación de compuestos hidrofóbicos (lípidos), pero su extracción no siempre elimina la RAS, lo que sugiere que componentes macromoleculares no extraíbles también pueden estar relacionados con una RAS. Se han estudiado suelos quemados (B) y control (UB) del Parque Nacional de Doñana (Huelva, España) bajo dos tipos de vegetación (alcornoque y brezo) y fracciones de suelo: gruesa (1–2 mm) y fina (<0.05 mm). La composición molecular de la materia orgánica del suelo (MOS) se analizó mediante espectrometría de masas de ultra-alta resolución. Además, se empleó la regresión por mínimos cuadrados parciales (PLS) para explorar la relación entre la RAS y la MOS definida por la abundancia de los 1221 compuestos orgánicos comunes. También se utilizaron índices para obtener gráficas que faciliten la identificación de biomarcadores de la RAS. En los suelos quemados, la RAS estaba significativamente relacionada (P<0.05) con compuestos aromáticos y condensados, mientras que, en los suelos control, la MOS incluía compuestos aromáticos y ligninas. En las fracciones finas, la RAS estuvo relacionada principalmente con lípidos, pero, no se encontró correlación en las fracciones gruesas. Los resultados permiten concluir que la hidrofobicidad depende de varias famílias de compuestos orgánicos. La combinación de la FT-ICR/MS con herramientas estadísticas ha facilitado la obtención de nuevos biomarcadores de RAS.

Las sabanas mediterráneas (dehesas) son sistemas agrosilvopastoriles típicos, caracterizados por la presencia dispersa de robles (Quercus spp.) y especies arbustivas. Estos ecosistemas están sometidos a una marcada estacionalidad, propia del clima mediterráneo, lo que se refleja en la dinámica microbiana del suelo. La interacción de los factores que más afectan la dinámica microbiana (clima, vegetación y suelo), es clave para comprender los ciclos biogeoquímicos que, a su vez se espera que se reflejen en la estructura de la materia orgánica (MOS). Para evaluar el efecto del cambio climático, utilizamos pirólisis analítica (Py-GC/MS) para la caracterización molecular de la MOS en un experimento de imitación en campo (2017-2021). Entre los 117 compuestos biogénicos encontrados, las distribuciones y contenidos de ác. grasos y n-alcanos fueron más sensibles a los tratamientos climáticos. Además, se observa una degradación preferencial de compuestos derivados de holocelulosa y acumulación de compuestos derivados de la lignina, que se encuentra poco evolucionada, lo que apunta a condiciones desfavorables para la su degradación. Los resultados sugieren que la composición molecular de la MOS y la aplicación de Py-GC/MS aporta información sobre los cambios ambientales del suelo y que tienen valor como biomarcadores para el seguimiento del cambio climático en suelos mediterráneos.

Soil water repellency (SWR) is a physical property due to a complex interaction of factors (e.g., fire, soil organic matter, soil texture) that reduces the soil water infiltration capacity. Traditionally, SWR is attributed to the accumulation and redistribution of hydrophobic compounds within soil profile. To obtain further insight into chemical compounds, which could be associated with SWR, a study was done on coarse (1–2 mm) and fine (< 0.05 mm) granulometric fractions of burned and unburned sandy soils under two Mediterranean vegetation biomes from Doñana National Park (Spain). The water drop penetration time (WDPT) test was used to assess the SWR. The molecular composition of extracted humic substances from the soil organic matter (SOM) was determined by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS). Partial least squares (PLS) regressions showed that the SWR can be predicted (P = 0.006) solely based on the abundances of approximately 1200 common compounds determined by FT-ICR/MS. This model confirmed the significant correlation between a specific SOM molecular composition and the SWR. The comparative analysis revealed that the SWR in the burned samples was significantly (P < 0.05) related to the abundance of aromatic and condensed compounds, while in the unburned samples there was a significant influence of aromatic hydrocarbons and lignin compounds. In the fine fraction, lipid compounds were significantly associated with the SWR. Contrastingly, the coarse fraction did not show any correlation. Alternatively, soils with a high SWR were significantly related to the presence of lipids and lignin. This analysis showed that combining FT-ICR/MS molecular characterizations with statistical treatments is a powerful approach for exploratory analysis suggesting that the structural features associated with SWR in the studied soils are different depending on the types of vegetation or the soil physical fractions with different particle size.

This study aims to evaluate the effects of technosols made with different organic amendments to restore degraded soils in a semiarid limestone quarry. The effects on soil quality, functionality and organic matter dynamics of the technosols amended with waste of gardening, greenhouse horticultural, stabilized sewage sludge and two mixtures of sludge with both vegetable composts were assessed. Several physical and chemical properties, humus fractions, soil respiration and molecular composition was performed after 6 and 18 months. Un-amended soils, and nearby natural undegraded soils served as reference. Amended technosols increased water retention capacity, electrical conductivity, total organic carbon and nitrogen, respect to not amended and natural soils. Humus fraction composition was not altered over time. Un-amended soils, very poor in organic matter, did not show any pyrolyzable compounds or labile soil organic matter by thermogravimetry. In contrast, the pyrochromatograms of natural soils showed lignocellulosic materials, polypeptides and a noticeable presence of alkylic compounds. In technosols with both types vegetable compost, the organic matter structure was more complex, showing compounds from lignin-derived and long-chain alkyl, polysaccharides, chlorophyll isoprenoids and nitrogen. In sludge technosol, a set of sterols was outstanding. The mixtures showed a molecular fingerprint of materials derived from the decomposition of the organic amendments that formed them. These signs of the contribution of different organic matter forms derived from the amendments were also reported by the series exothermic peaks found in the calorimetry. This short-term study indicates a clear effect of the amendments on the recovery of soil organic matter and presumably of its functionality. After the amendments application, microbial activity and soil respiration rates increased rapidly but ceased 18 months later. The molecular composition of the organic matter of the soils

Analytical pyrolysis is a tool widely used for investigating the nature of macromolecules. This technique has been applied with success for solving the chemical structure of geo- and biopolymers. However, with complex macromolecules, such as fungal melanins, analytical pyrolysis presents some drawbacks due to the fact that they rarely can be obtained in a pure grade and contains a mixture of polysaccharides, chitin, proteins, nucleic acids, and lipids, among other materials. Analytical pyrolysis permits the characterization of the compounds co-extracted or linked to the melanin. Nevertheless, our data revealed that under the conditions usually employed in the pyrolysis of melanins, the technique presented serious limitations due to the complex structure and diversity of components that suffer extensive thermal degradation through secondary reactions with the production of considerable number of artifacts. To the light of pyrolysis data, the melanin of Ochroconis spp. is not based on 3,4-dihydroxyphenylalanine (DOPA) or 1,8-dihydroxynaphthalene (DHN), and it is suggested that it could be a type of pyomelanin, based on the polymerization of homogentisic acid and other phenolic compounds.

High severity wildfires cause a drastic alteration of soil carbon cycling – both oxidising and thermally altering soil organic matter (SOM) - and usually are followed by strong runoff and erosion events. To restore wildfire-degraded soils, SOM needs to be rebuilt while soil erosion is prevented. Post-fire straw mulching has been shown to mitigate soil erosion by providing a protective cover against rainsplash. However, SOM takes many decades or centuries to rebuilt naturally. Biochar, co-applied with straw to the soil surface can replace the SOM of the O-horizon, while the stabilised soil – by straw mulching – may gain in SOM naturally and by downward movement of biochar. We conducted a field study to test if straw-only and straw-biochar co-application could restore soils degraded by wildfire in one high burn severity (HBS) and one moderate burn severity (MBS) study area in southern Portugal and Spain, respectively, by monitoring erosion and SOM for the most intense rainfall period of the first post-fire year. Burned sites were characterized for soil and sediment physical properties, TOC content, SOM quality by thermogravimetry (DTG) and nuclear magnetic resonance (NMR 13C) spectroscopy. Straw-biochar mulching significantly reduced soil erosion by 76% and 65% in the HBS and MBS sites, respectively, in both cases similar to the erosion reduction by straw-only mulching. DTG and NMR 13C indicated that a relatively small proportion of the biochar eroded, i.e. 0.7%, indicating that co-application of straw with biochar may help restore the SOC lost in the wildfire in the medium term. The amount of SOM eroded was lower with straw-biochar mulching than in the untreated plots for both study areas. Straw-biochar mulching mitigate erosion of wildfire-degraded soils under extreme rainfall, while a relatively small proportion of the biochar is lost by erosion. Future studies need to monitor medium term effects.

Cylindrospermopsin (CYN) and Microcystin-LR (MC-LR) are biotoxins produced by cyanobacteria species that, due to climate change and water eutrophication, proliferate together with an increase of the associated cyanotoxins. Both toxins are usually found in the aquatic environment and filter feeding organisms such as mussels are particularly exposed which may be the cause of metabolic alterations. In this work, pyrolysis gas chromatography mass spectrometry (Py-GC/MS) is used to evaluate compositional changes in mussel (M. galloprovincialis) after exposure for 14 days to cyanotoxins of Chrysosporum ovalisporum (CYN), Microcystis aeruginosa (MC-LR) and to a combination of both toxins. The pyrolysis of mussel flesh produced complex chromatograms, with up to 100 different compounds, but very similar between treatments. Major groups found were N compounds (pyridine, N-alkyl molecules) (18.2 % ± 1.5) and peptide/protein derived compounds that include alkyl indols and diketopiperazines (DKPs) (17.7 % ± 2.4), series of medium chain length (C14-C22) saturated, mono and polyunsaturated fatty acids (45.1 % ± 5.0), steroids (7.5 % ± 0.6) and aromatics with undetermined origin (8.9 % ± 1.1). A chemometric treatment of the chromatographic data allowed the discrimination between the different mussel populations exposed to cyanotoxins. The results are discussed in terms of the probable effects exerted by the biotoxins in mussel composition and the possible metabolic pathways affected.

This work studies carbon (C) and hydrogen (H) isotope composition of plant biomass and soil organic matter (SOM) in an attempt to assess both, changes exerted by fire and possible inputs of charred materials to the soil after a wildfire. Isotope composition of bulk soil, soil particle size fractions and biomass of the dominant standing vegetation in the area (Quercus suber) from Donana National Park (SW-Spain) were studied by isotope ratio mass spectrometry (IRMS). SOM C isotope composition indicates the occurrence of two SOM pools with different degree of alteration. Coarse soil fractions (>0.5 mm) were found C-13 depleted with delta O-13 values close to those in leaf biomass, pointing to a predominance of poorly transformed SOM. Conversely, fine fractions (<0.1 mm) were found enriched in C-13 as corresponds to a more humified SOM. The fire produced no changes in this trend, although a consistent C-13 enrichment (c. 1 parts per thousand) was observed in all soil fractions with decreasing size. Concerning H isotopes, the coarse fractions (>0.5 mm) displayed significant lower delta H-2 values than the intermediate and fine ones (<0.5 mm), again similar to those in leaf biomass (c.-80 parts per thousand), whereas the fine fractions were found deuterium (H-2)-enriched with significant higher delta H-2 values (c. 50 parts per thousand), suggesting physical speciation of H depending on soil particle size. The fire produced a significant H-2 depletion (Delta H-2 c. -10 parts per thousand) in the finer fractions (<0.1 mm). The study of stable isotope analysis added new information and complements the results obtained by other proxies to better understand the effect of fire on SOM. (C)2020 Elsevier B.V. All rights reserved.

Sedimentary organic matter (OM) origin and molecular composition provide useful information to understand carbon cycling in coastal wetlands. Core sediments from threors’ Contributionse transects along Ria Formosa lagoon intertidal zone were analysed using analytical pyrolysis (Py-GC/MS) to determine composition, distribution and origin of sedimentary OM. The distribution of alkyl compounds (alkanes, alkanoic acids and alkan-2-ones), polycyclic aromatic hydrocarbons (PAHs), lignin-derived methoxyphenols, linear alkylbenzenes (LABs), steranes and hopanes indicated OM inputs to the intertidal environment from natural—autochthonous and allochthonous—as well as anthropogenic. Several n-alkane geochemical indices used to assess the distribution of main OM sources (terrestrial and marine) in the sediments indicate that algal and aquatic macrophyte derived OM inputs dominated over terrigenous plant sources. The lignin-derived methoxyphenol assemblage, dominated by vinylguaiacol and vinylsyringol derivatives in all sediments, points to large OM contribution from higher plants. The spatial distributions of PAHs (polyaromatic hydrocarbons) showed that most pollution sources were mixed sources including both pyrogenic and petrogenic. Low carbon preference indexes (CPI > 1) for n-alkanes, the presence of UCM (unresolved complex mixture) and the distribution of hopanes (C29–C36) and steranes (C27–C29) suggested localized petroleum-derived hydrocarbon inputs to the core sediments. Series of LABs were found in most sediment samples also pointing to domestic sewage anthropogenic contributions to the sediment OM. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

The two most widely extended mountain grasslands in Europe (Nardus-mat grasslands and chalk grasslands) are distributed forming complex patterns. In the Ordesa and Monte Perdido National Park (Central Pyrenees, NE-Spain), they grow as secondary pastures within the treeline ecotone at the subalpine belt. This work aims to show the influence of soil properties on the spatial distribution of these pastures, under a dynamic geomorphology. Soils are sampled under both grasslands, which grow on different cumulative levels: Nardus-mat grasslands in the upper level (L1) and chalk grasslands in the lower level (L2). Soils in L1 have a significantly higher acidity, lower soluble ions and exchangeable calcium content than those in L2, reflecting a more intense leaching process, consistent with a longer period of slope stability. Qualitative differences are detected in the soil organic matter of the soil, using carbon and nitrogen isotopes, lighter in L2 soils than in L1 soils, due to a higher proportion of legumes growing in L2 (chalk grasslands). Soils in L1 and L2 shared many physical properties, such as a fine and homogeneous texture in the whole profile (silty clay or silty clay loam), and high aggregate stability and porosity in the topsoil. In contrast, the soils in L2 are shallower than in L1, which reduces their water-holding capacity. The soil is classified as Orthoeutric Cambisol (Clayic, Humic) in L1 but its rejuvenation, by gully erosion, transforms it into an Hypereutric Leptosol (Loamic, Ochric) in L2 (Typic Haplocryept and Lithic Haplocryept, respectively by Soil Taxonomy system). Definitely, the distribution of both grasslands for the studied area is linked to two cumulative levels of different ages, which in turn is strongy related to different soil properties.

Soil organic matter (SOM) is a major component of the biogeochemical cycle contributing to soil general properties and conservation. The progressive depletion of the SOM in Mediterranean ecosystems results in an increased advance of desertification. The SOM not only plays a crucial role in soil resilience, but also represents a repository of environmental information on soil forming factors in particular climatic constraints. In this research, analytical pyrolysis (Py-GC/MS) is used to study SOM composition in 30 soils under contrasting bioclimatic scenarios as defined by the classical Emberger (Q) index. Partial least squares (PLS) regression using the major pyrolysis compounds as descriptors allowed to predict (P < 0.05) Q indexes, and provide molecular proxies of climatic variability effects on SOM composition. In addition, pyrolytic compound assemblages from soils developed under extreme climatic conditions were compared using a graphical approach based on surface density plots built from the major 193 pyrolysis compounds represented in the plane defined by their H/C and O/C atomic ratios. The differences between the proportions of the individual pyrolysis compounds in terms of the bioclimatic scenarios were also illustrated by a simulation of SOM molecular composition under extreme conditions of aridity or wetness. Although no cause-to-effect is inferred, the results show that SOM composition retains environmental information on the Q index. This is mainly related with the total abundances of methoxyphenols and alkylbenzene compounds, suggesting that the degree of transformation of SOM could be related with the variable accumulation of microbial and plant biomass controlled by climatic factors which is a potential field for future research. © 2020 Elsevier B.V.

The impact of wildfires and of restoration actions on soil organic matter (SOM) content and structure was studied in a soil under pine (Pinus pinea) from Doñana National Park (SW Spain). Samples were collected from burnt areas before (B) and after post-fire restoration (BR) and compared with an unburnt (UB) site. Analytical pyrolysis (Py-GC/MS) was used to investigate SOM molecular composition in whole soil samples and in coarse (CF) and fine (FF) fractions. The results were interpreted using a van Krevelen graphical-statistical method. Highest total organic carbon (TOC) was found in UB soil and no differences were found between B and BR soils. The CF had the highest TOC values and FF presented differences among the three scenarios. Respect to SOM structure, the B soil was depleted in lignin and enriched in unspecific aromatics and polycyclic aromatic hydrocarbons, and in all scenarios, CF SOM consisted mainly of lignocellulose derived compounds and fatty acids. In general, FF SOM was found more altered than CF. High contribution of unspecific aromatic compounds and polycyclic aromatic hydrocarbons was observed in B-FF whereas BR-FF samples comprised considerable proportions of compounds from labile biomass, possibly due to soil mixing during rehabilitation actions. The fire caused a defunctionalisation of lignin-derived phenolics and the formation of pyrogenic compounds. The van Krevelen diagram was found useful to—at first sight—differentiate between chemical processes caused by fire and of the rehabilitation actions. Fire exerted SOM demethoxylation, dealkylation and dehydration. Our results indicate that soil management actions after the fire lead to an increase in aromaticity corresponding to the accumulation of lignin and polycyclic aromatic compounds. This suggests additional inputs from charred lignocellulosic biomass, including black carbon, that was incorporated into the soil during rehabilitation practices. © 2020 Elsevier B.V.

The presence of the toxin cylindrospermopsin is increasingly frequent in samples from different ecosystems and it is a serious problem both at environmental level and for animal and human health. To be able to prevent CYN exposure risk, it is important to have suitable analytical methods, but also quick and economical ones. Analytical pyrolysis coupled to GC/MS (Py-GC/MS) represents an important alternative for the rapid detection, characterization or “fingerprinting” of different materials. However, it has been less studied with cyanotoxins up to date. The present work aims to investigate: 1) the suitability of Py-GC/MS for detection of CYN and its decomposition products in raw and cooked fish samples before consumption and 2) the influence of the different cooking methods on the presence of different CYN degradation products detected by Py-GC/MS. For first time, these results present that Py-GC/MS could be a rapid and economical alternative for the detection and monitoring of CYN and its degradation products (DP. m/z 290.1, 169.1 and 336.2) in raw or cooked fish. Moreover, the changes induced in CYN and DP by cooking could be amenable and detected by Py-GC/MS.

Siliceous speleothems frequently reported in volcanic caves have been traditionally interpreted as resulting from basalt weathering combined with the activity of microbial communities. A characteristic feature in lava tubes from Hawaii, Azores and Canary Islands is the occurrence of black jelly-like speleothems. Here we describe the formation process of siliceous black speleothems found in a lava tube from La Palma, Canary Islands, Spain, based on mineralogy, microscopy, light stable isotopes, analytical pyrolysis, NMR spectroscopy and chemometric analyses. The data indicate that the black speleothems are composed of a hydrated gel matrix of amorphous aluminum silicate materials containing charred vegetation and thermally degraded resins from pines or triterpenoids from Erica arborea, characteristic of the overlying laurel forest. This is the first observation of a connection between fire and speleothem chemistry from volcanic caves. We conclude that wildfires and organic matter from the surface area overlying caves may play an important role in the formation of speleothems found in La Palma and demonstrate that siliceous speleothems are potential archives for past fires.

Natural preservatives are used in food packages to improve the shelf life of perishable products. Carvacrol and thymol, the main components of oregano essential oil (OEO), are used in active packaging due to their antimicrobial and antioxidant properties. Here, the effect of a bioactive polylactic acid (PLA)/polybutylene succinate (PBS) package in the conservation of lettuce compounds with dietetic value is studied. Analytical pyrolysis (PyGC/MS) was used to detect changes in dietary components such are phytosterols (PHSTs) and polyunsaturated fatty acids (PUFAs) after 1, 4 and 8 days of packaged in PLA/PBS (95:5%) films containing different OEO concentrations (2-10%). Lettuce PUFAs and PHSTs content decreased when packed in films without OEO. However, when packed in films containing 5 and 10% OEO, these bioactive components were preserved during the estimated lettuce shelf life, for up to 8 days of storage.

The introduction of coniferous species in former deciduous forests may exert changes in soil organic matter, particularly in its molecular composition. In this work, pyrolysis-gas chromatography–mass spectrometry was used to study changes in SOM quality related to the centennial afforestation of Scots pine in an area formerly covered by European beech forest in the NE-flank of the Moncayo Natural Park (NE-Spain). For each soil profile three organic layers (fresh litter, fragmented litter and humified litter) and mineral soil horizons (Ah, E, Bhs and C) were studied. A total of 128 compounds were identified in the pyrograms, and composition differences were detected among the organic and mineral soil layers as well as between soils under beech and pine, for the main compound classes: nitrogen compounds, aromatics, lignin methoxyphenols, polycyclic aromatic hydrocarbons, lipids and polysaccharide-derived moieties. Such chemical differences were found to be derived from the biomass composition of the predominant vegetation type that was incorporated into the soil and from its progression into the soil profile. The analysis of the distribution of alkanes indicated higher SOM stabilization in the native beech forest soil. The signal of beech biomarkers (long chain n-alkanes C31-C33) found in the pine E horizon indicates the permanence of SOM derived from the natural forest ca. 100 years after the afforestation.

Environmental research about causes and effects of progressive soil desertification is attracting the attention of the scientific community. Factors that accelerate soil organic matter (SOM) mineralization may also induce structural changes in its molecular composition, but the specific impact of different climatic factors (annual precipitation, number of days with precipitations, temperature…) has not yet been the subject of systematic research. This study attempts to identify potential climatic molecular proxies in SOM, i.e., pyrolytic compounds correlated with specific climatic indices. A set of 16 Spanish soils under differing climatic conditions were selected. Molecular characterization of SOM was done by pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS) applied to whole soil samples. Up to 193 compounds were identified corresponding to alkanes, alkylbenzenes, N‐compounds, olefins, phenols and carbohydrate derivatives. Simple and multiple correlations between pyrolytic and climatic ariables showed that the concentration of several compounds was significantly correlated (P < 0.05) with particular climatic variables. In a second stage, using van Krevelen [1,2] diagrams, it was possible to display different patterns of pyrolytic compounds responsive to specific climatic characteristics. Finally, extrapolation functions were applied to simulate SOM molecular composition under future climatic scenarios, e.g., changes in temperature, evapotranspiration, rainfall, etc. This study demonstrates the potential of Py‐GC/MS in identifying specific molecules and compound families useful for predicting climate impact on SOM, as well as for monitoring soil quality in terms of the progress of desertification, References [1] D.W. van Krevelen, Fuel 29, 269–284 (1950). [2] G. Almendros, Z. Hernández, J. Sanz, S. Rodríguez‐Sánchez, M.A. Jiménez‐González, J.A. González‐Pérez, J. Chromatogr. A. 1533, 164–173 (2018).

In less than 50 years the area occupied by peat bogs in the Gulf of Cádiz (SW‐Spain) has been reduced by more than 90%. The peat bog studied here may well be considered as relict and one of the last and more Meridional still in existence in the Northern hemisphere. The vertical molecular composition of a 85 cm peat bog from Ribetehilo lagoon (Doñana National Park; SW‐Spain 37° 7'30.81"N; 6°37'50.19"O) is studied using analytical pyrolysis (Py‐GC/MS) and ultra‐high resolution mass spectrometry (ESI‐FT‐ICR/MS). The results obtained by the two techniques were similar, showing as shallow OC composition was dominated by fresh material from upper vegetation cover, while more transformed and humified material was accumulated in the bottom layers. This may be due to i) intense microbial activity combined with large fluctuations of the water table occurring during the year; and/or ii) anaerobic rocesses. In general, the lack of peat preservation in depth is probably a sign of bog degradation processes, probably linked with climate changes to which Mediterranean wetlands are particularly responsive.

Changes in climatic and environmental conditions can affect both, plant chemical and isotope composition. Therefore, biomass carbon isotope composition is frequently used to gain information about the environmental conditions at the time a plant was growing [1]. In this field, the majority of studies use isotope values obtained from bulk samples. However, these values are a weighed mean average of the different plant compounds. The Isotopic characterization of individual biogeochemical compounds represents a relevant analytical advance able to differentiate the isotopic composition of the main plant components i.e. polysaccharides, lignin, polypeptides, lipids and waxes, etc. Here, we investigate the link between molecular and isotope composition of bark from three Eucalyptus species (E. grandis, E. dunni and a hybrid E. grandis x E. dunni) using Py-CSIA. Bulk samples and lignin extracted were analysed by Py-CSIA; this technique, although not widely used, has been previously developed and applied, with different variants [2-7], to characterize plant products including lignin [8], sugars [9] and terpenes [10]. Our results support the idea that the pyrolysis compound specific isotope analysis (Py-CSIA) can provide valuable and accurate isotopic fingerprinting of biomass. Despite that wood/bark from different origins provide very similar pyrolysis pattern, isotopic composition of relevant specific compounds can make the difference giving additional valuable information., [1] Michenerand Lajtha (Eds). Stable Isotopes in Ecology and Environmental Science (2nd Ed.) Blackwell Publishing Ltd (2007) 566p. [2] Gonñi and Eglinton, J. High Resol. Chromat. 17 (1994), 476. [3] Pulchan et al., J. Anal. Appl. Pyrolysis 42 (1997), 135. [4] Gleixner and Schmidt. In Nitrogen-containing Macromolecules in the Bio- and Geosphere. Stankiewicz and van Berger (Eds), ACS Symposium Series 707 (1998), pp. 34–46. [5] Gleixner et al. Rapid Commun. Mass Spectrom. 13 (1999) 1278. [6] Schulten and Gleixner Water Res. 33 (1999) 2489. [7] Gleixner et al. Organic Geochemistry 33 (2002) 357. [8] Steinbeiss et al. J. Anal. Appl. Pyrolysis 75 (2006) 19. [9] González-Pérez et al. J. Sci. Food Agric. 96 (2016) 948. [10] Llana-Ruíz-Cabello et al. J. Chrom A 1525 (2017) 145.

The determination of heavy metals in soils and organic amendments, such as compost, manure, biofertilizer, and sludge, generally involves the digestion of samples with aqua regia, and the determination of those in the solution using various techniques. Portable X-ray fluorescence (PXRF) has many advantages in relation to traditional analytical techniques. However, PXRF determines the total elemental content and, until now, its use for the analysis of organic amendments has been limited. The objective of this work is the calibration of a PXRF instrument to determine the aqua regia-soluble elemental contents directly in solid samples of organic amendments. Our proposal will avoid the digestion step and the use of other laboratory techniques. Using a training set of samples, calibration functions were obtained that allow the determination of the aqua regia-soluble contents from the PXRF readings of total contents. The calibration functions (obtained by multiple linear regression) allowed the quantitative determination of the aqua regia-soluble contents of Fe, K, P, S, Zn, Cu, Pb, Sr, Cr, and Mn, as well as the organic matter content and a semi-quantitative assessment of Al, Ca, V, Ba, Ni, and As contents. The readings of Si, Fe, Al, Ca, K, or S were used as correction factors, indicating that the calibrations functions found are truly based on the chemical composition of the sample matrix. This study will allow a fast, cheap, and reliable field analysis of organic amendments and of other biomass-based materials

Wildfires are a global phenomenon occurring in tropical, temperate and boreal regions that affect 300-460 Mha every year (Randerson el al. 2012; Giglio el al. 2013) (Chapter 1). Temperate regions have been affected historically by wildfires (Pausas el al. 2008; Lasheras-Álvarez el al. 2013) and during the 20th century a drastic increase in the extent and severity of burnt areas has occurred. This has made wildfires one of the main threats for ecosystems, particularly those in Mediterranean areas. The obvious consequence of a wildfire is the partial or complete loss of the vegetation. However, wildfires may also cause changes in the physical, chemical and biological properties of soil (González-Pérez el al. 2004; Certini, 2005). The alteration of geomorphological and hydrological processes of the topsoil following a wildfire (de la Rosa el al. 2013a; Faria el al. 2015a) can boost erosion processes that, in turn, are often associated with quantitative and qualitative changes in soil organic matter (SOM) (Chapters 3, 4, 5, 6, 7, 8, 9, 10 and 11). In fact, desertification risk in connection with increased wildfire recurrence is very high in Mediterranean ecosystems (Shakesby, 2011) and the design and application of proper post-fire restoration strategies is paramount for reducing such risk. Restoration of both quality and quantity of SOM is important for soil rehabilitation after a wildfire. Nevertheless, many studies have focused only on the effects of fire in the total amount of SOM, with only scarce the attention paid to the SOM chemical composition and molecular structure, despite its relevance (Almendros el al. 1984a,b; González Pérez el al. 2004, 2008; Certini el al. 2011, de la Rosa el al. 2013a; Faria el al. 2015a,b; Aznar el al. 2016; Jiménez-González el al. 2016; Jiménez-Morillo el al. 2016a, 2017).

Biochar has been shown as a potential mean to enhance carbon sequestration in the soil. In Brazil, approximately 15% of the produced charcoal is discarded as charcoal fines, which are chemically similar to biochar. Therefore, we aimed to test charcoal fines as a strategy to increase soil carbon sequestration. Charcoal fines of hardwood Mimosa scabrella were incorporated into a Cambisol down to 10 cm (T1 = 0 and T4 = 40 Mg ha−1) in Southern Brazil. Soil samples were collected (0–30 cm) 20 months after charcoal amendment. Soil organic matter (SOM) acid extract, humic acid, fulvic acid, and humin fractions were separated. Solid-state 13C nuclear magnetic resonance (NMR) spectra from charcoal and SOM in T1 and T4 were obtained before and after 165 days of incubation under controlled conditions. Charcoal increased soil carbon as fulvic (10–20 cm) and humic acids (10–30 cm) and, especially, as humin (0–5 cm), which probably occurred due to the hydrophobic character of the charcoal. The 13C NMR spectra and mean residence times (MRT) measured from incubation essays indicated that the charred material decomposed relatively fast and MRT of T1 and T4 samples were similar. It follows that the charcoal fines underwent similar decomposition as SOM, despite the high charcoal dose applied to the soil and the high aryl C contribution (78%) to the total 13C intensity of the charcoal NMR spectra

Castañar cave (Cáceres, Spain) characteristically contains a series of Mg-Si phases forming fibres and films associated to aragonite, magnesite, huntite and spheroidal dolomite in moonmilk, which form coatings and crust speleothems. These Mg-Si phases consist of kerolite, sepiolite and its admixtures. Under scanning electron microscope kerolite appears as colloform, smooth masses or films. Sepiolite mostly occurs as isolated fibres 50 to 200 nm thick and up to 50 µm long and mats of interwoven fibres of several shapes, which often look like jelly, flexible-like films. Both minerals are highly hydrated and with low crystallinity. In order to evaluate a possible role of organic matter in the biogeochemical formation of these minerals, two samples of moonmilk and 4 controls were analyzed by analytical pyrolysis (Py-GC/MS). The pyrolizate of the samples consisted mainly of a) methoxyl-lacking benzenes, b) unsaturated and saturated hydrocarbons, c) polycyclic aromatic and d) hydroaromatic hydrocarbons. This chemical assemblage is not compatible with a recent biogenic origin of the organic matter in the moonmilk. This is suggested by the small proportions of fatty acids in addition to the lack of nitrogen- and carbohydrate-derived compounds. In fact, most of the aromatic compounds (e.g., phenols and catechols) which would be expected from plant or microbial biomass were in negligible proportions whereas methoxyphenols (typical lignin-derived compounds) were completely absent, suggesting no contribution from biomass of vascular plants. Conversely, the signature of alkyl compounds found in these samples (homologous series) is compatible with that in coals, kerogens or other forms of fossil organic matter. In particular, the whole pyrograms resembled the control shale from the host rock, which suggests that the organic matter was in fact inherited from the host rocks. Concerning the mineral phase, the low crystallinity and textures of kerolite and sepiolite indicate formatio

Mulching has amply proven its effectiveness to mitigate post-fire soil erosion but its impacts on soil organic matter (SOM) quality and quantity continue poorly studied. The present study addressed this knowledge gap for a eucalypt plantation in central Portugal that had been burnt and, immediately after the wildfire, mulched with 13.6 Mg ha−1 of eucalypt logging residues some five years before. This was done by performing a range of analytical techniques (elemental and isotope analyses, analytical pyrolysis and 13C NMR spectroscopy) not only on the bulk soil samples but also on their humic acids (HAs) and free organic matter (FOM) fractions. While mulching reduced soil and SOM losses with 91 and 93%, respectively, it also improved SOM quality of the topsoil, in particular in terms of HAs and FOM. At 0–4 cm depth, both HAs and FOM contents were roughly twice as high in the mulched plots as in the control plots. The effects of mulching on the molecular composition of HAs and FOM fractions, however, varied markedly. Analytical pyrolysis (Py-GC/MS) revealed that mulching had led to a noticeable accumulation of labile, aliphatic SOM constituents such as carbohydrate-derived and alkyl compounds (fatty acids and n-alkanes) but that it hardly affected the composition of HAs. Even so, solid-state 13C NMR spectroscopy showed that mulching had resulted in a relative increase in aryl C in the FOM fraction, suggesting an enhanced preservation of the pyrogenic OM. Overall, the combined use of a range of analytical techniques allowed to conclude that, five years after their application, the forest logging residues had led to a greater preservation of the fire-derived pyrogenic OM (mainly aromatic compounds) in the topsoil as well as to higher contents of SOM's most labile molecular constituents (mainly carbohydrates and n-alkyl compounds). The former reflected the reduced erosion rates, while the latter was probably due to a combination of reduced erosion rates with the additiona

We studied the fire record and its environmental consequences during the Holocene in the Central Ebro Basin. This region is very sensitive to environmental changes due to its semiarid conditions, lithological features and a continuous human presence during the past 6000 years. The study area is a 6 m buried sequence of polycyclic soils developed approximately 9500 years ago that is exceptionally well preserved and encompasses four sedimentary units. The content and size distribution of macroscopic charcoal fragments were determined throughout the soil sequence and the analysis of the composition of charcoal, litter and sediments via analytical pyrolysis (Py-GC/MS). The high amount of charcoal fragments recovered in most horizons highlights the fire frequencies since the beginning of the Neolithic, most of which were probably of anthropogenic origin. In some soil horizons where charcoal was not found, we detected a distribution pattern of lipid compounds that could be related to biomass burning. On the other hand, the low number of pyrolysates in the charcoal could be attributed to high-intensity fires. No clear pattern was found in the composition of pyrolysates related to the age of sediments or vegetation type. The most ancient soil (Unit 1) was the richest in charcoal content and contains a higher proportion of larger fragments (>4 mm), which is consistent with the burning of a relatively dense vegetation cover. This buried soil has been preserved in situ, probably due to the accumulation of sedimentary materials because of a high-intensity fire. In addition, the pyrogenic C in this soil has some plant markers that could indicate a low degree of transformation. In Units 2–4, both the amount of charcoals and the proportions of macrofragments >4 mm are lower than those in Unit 1, which coincides with a more open forest and the presence of shrubs and herbs. The preservation of this site is key to continuing with studies that contribute to a better assessment of the

In present days there is a growing concern about the progress of desertification in different areas of the world. The unsuitable management of the soils and the change of land use may increase the desertification risk. On the other hand, desertification is typically associated with the decrease of soil organic matter (SOM) levels with the consequent loss of fertility in the soil. Presumably, all these aspects are reflected in the molecular composition of SOM. Previous studies have evidenced that a correlation exists between the carbon sequestration efficiency and the relative abundance of specific SOM constituents, e.g., alkane homologous series [1] or lignin-derived methoxyphenols [2]. This study aims to identify molecular descriptors of the SOM composition, which are responsive for the impact of climate, quantified with bioclimatic indices defining a continuous gradient between wet and dry areas. A total of 33 soil samples were collected from different areas of Spain. The studied soils presented a large variability in their chemical and physical properties, and were developed under different geological substrate and vegetation type. The sampling was carried out in the topsoil (0–10 cm) where the SOM content is higher. In order to assess desertification levels we used the De Martonne aridity index. This index was calculated from the annual average rainfall and annual average temperature for each soil sampling point. The SOM was analyzed by pyrolysis - gas chromatography mass spectrometry (Py-GC/MS) of whole soil samples. A total of 193 pyrolysis compounds were identified, and used as predictor variables in Partial Least Squares (PLS) regression models forecasting the De Martonne aridity index. The results showed that a significant prediction of this index (R = 0.869) exclusively using the information provided by Py-GC/MS analysis of the corresponding soils is possible. A graphical-statistical method based in the classical van Krevelen diagram was used for displayin, [1] M.A. Jiménez-González, A.M. Álvarez, Z. Hernández, G. Almendros, Biology and Fertility of Soils 54 (2018) 617–629. [2] M.A. Jiménez-González, A.M. Álvarez, P. Carral, F.J. González-Vila, G. Almendros J. Chromatography A 1508 (2017) 130–137. [3] D.W. van Krevelen, Fuel 29 (1950) 269–284.

Plastic gradually fragments into smaller pieces forming microscopic fractions of less than 5 mm commonly known as microplastics. These microplastics have become one of the most persistent pollutants of the sea and beaches, due to their small size, their ubiquity and global distribution [1]. An estimated 80% of microplastics pollution comes from land, while about 18% of these marine debris is attributed to the fishing industry [2]. Moreover, previous studies reported up to 44% of raw pellets and values above 100g/l of sand in the coastal zones of the Canary Islands. The Canary Islands constitutes an area of accumulation of microplastics, being found this type of pollution even in beaches infrequently visited [3]. Microplastics represents a major threat to the environment due to the following reasons [4]: • Are typically hydrophobic with large surface areas and high adsorption capacity of POPs (Persistent Organic Pollutants) and PBTs (Persistent, Bioaccumulative and Toxic substances). • As they adsorb POPs, microplastics can result in a double-entry pollution vector: as a POPs vector and by the plastic itself. • High abundance and long residence time. • Absorption and ingestion by aquatic organisms and subsequent transfer to higher trophic evels. Given that microplastic is a relatively new environmental problem and their newly increased pollution levels, it is important to better understand their impact. The establishment of standardized analysis procedures for their chemical characterization is required among the scientific community. A total of 10 microplastic samples collected in the Canary Islands were optically characterized and analysed using pyrolysis-gas chromatography coupled to mass spectrometry (Py-GC/MS). The pyrolysis temperature was 400 ºC for 1 minute and the chromatographic conditions and compound assignment procedure are described elsewhere in [5]. The studied microplastics were mainly light polyolefins (polyethylene, PE and polypropylene, PP) but one, [1] Andrady, A.L. (2011). Microplastics in the marine environment. Mar. Pollut. Bull. 62: 1596―1605. [2] Rochman, C.M. (2018). Microplastics research—from sink to source. Science 360 (6384): 28―29. [3] Herrera, A., Asensio, M., Martínez, I., Santana, A., Packard, T., & Gómez, M. (2018). Microplastic and tar pollution on three Canary Islands beaches: an annual study. Mar. Pollut . Bull. 129: 494―502. [4] Anderson, J.C., Park, B.J., & Palace, V.P. (2016). Microplastics in aquatic environments: Implications for Canadian ecosystems. Environ. Pollut. 218: 269―280. [5] González-Pérez J.A., Jiménez-Morillo N.T., de La Rosa Arranz J.M., Almendros G., González-Vila F.J. (2015). Pyrolysis-gas chromatography-isotope ratio mass spectrometry of polyethylene. J. Chrom. A 1388: 236―243.

Purpose: Data management strategies of pyrolysis results and NMR acquisition modes were examined in humic acids (HAs) from control soils and fire-affected soils. The information supplied by dipolar dephasing (DD) 13C NMR spectroscopy and Curie-point pyrolysis were used to assess chemical structures hardly recognizable and measurable, or of unclear interpretation, when using 13C NMR under standard acquisition pulses (cross-polarization/magic angle spinning, CPMAS). Materials and methods: The HAs were isolated from two forest soils under Pinus halepensis and Pinus sylvestris in control and burned sites affected by medium or severe-intensity wildfires. For NMR analyses, during DD acquisition conditions, a 180° 13C pulse was inserted to minimize phase shifts. Curie-Point pyrolysis was carried out at 510 °C for 5 s, and the pyrolysis fragments were analyzed by GC/MS. The total abundances of the major pyrolysis products were compared by an update of the classical Van Krevelen’s graphical-statistical approach, i.e., as surface density values in the space defined by the compound-specific H/C and O/C atomic ratios. Results and discussion: The DD 13C NMR experiments displayed significant differences in the HA spectral profiles as regards to the standard CPMAS 13C NMR acquisition conditions, mainly in the chemical shift region of alkyl structures as well as for tannin- or carbohydrate-like O-alkyl structures. In fact, the comparison between DD and CPMAS solid-state NMR suggested shortening of alkyl chains and generation of carbohydrate-derived, unsaturated structures—viz. furans—which adds to the aromatic domain. Pyrolytic results showed fire-induced specific changes in HAs chemical structure and its molecular diversity. The changes were evident in the location and sizes of the different clusters of pyrolysis compounds defined by their atomic ratios. Conclusions: The DD 13C NMR provided specific information on the fate of aliphatic structures and the origin of unsaturated HA s

Mulching is an effective treatment of post-fire soil erosion. However, little is known concerning its effects on soil organic matter (SOM) composition and properties. This study evaluated the long-term effects of forest residue mulch on the molecular composition of humic acids from a burnt eucalypt plantation in central Portugal. Mulching treatment increased the abundance of organic carbon and humics acids extracted five years after the wildfire. The molecular composition of soil samples indicated that mulching may help the recovery of the most labile fractions of fire affected soils. In addition, the composition of the HA extracted from both mulched and untreated fire affected plots was very similar.

Straw and pig slurry Solid-State Anaerobic Digestion (SS-AD) was carried out in a pilot-scale apparatus using percolate recirculation technology. The digestion experiments were performed using 1, 2 and 4 recirculations per day; an additional experiment without percolate recirculation was used as control. The initial mixture and the digestates were analysed by means of chemical analyses and Pyrolysis–Gas Chromatography/Mass Spectrometry (Py–GC/MS), a direct analytical technique that allows investigating the changes in the organic matter (OM) composition of digestates and the effect of percolate recirculation frequency. Chemical analyses suggested a positive effect of percolate recirculation on OM degradation. The highest values of OM loss were found with 2 (26%) and 4 (31%) recirculation cycles per day, that also corresponded with the lowest values of the hydrophilic water extractable organic matter fraction (5.5 and 6.3% respectively). Py-GC/MS showed that the anaerobic digestion proceeded with progressive polysaccharide degradation (from c. 19% in the initial mixture to 10–8% with 2–4 recirculation cycles) and selective enrichment of lignin derived compounds (from c. 58% in the initial mixture to 67–69% with 2–4 recirculation cycles). In addition, a shift in the fatty acids distribution was observed with a decrease in the long/short chain ratio of fatty acid methyl esters. These results indicate that under our experimental conditions, percolate recirculation had a positive effect on the OM degradation. Also OM stabilization is observed with relative increases in recalcitrant lignin at the expense of the more liable polysaccharide fraction. This paper represents the first attempt to apply Py-GC/MS to evaluate the OM quality in digestates obtained by SS-AD of pig slurry and straw optimized by percolate recirculation.

[EN]: Easily Extractable Glomalin (EEG) is an operational term applied to an organic fraction of the soil supposed to contain mainly glomalin-related soil proteins (GRSP), a glycoprotein abundantly found in soils that is produced in the hyphae and spores of arbuscular mycorrhizal fungi (AMF). The EEG fraction is the most immunoreactive to glomus monoclonal antibody MAb32B11 and is related to relavant soil characteristics, such as its stability and resilience to degradation, formation of aggregates and stabilization of organic carbon. In this study we carried out a detailed molecular characterization >fingerprint> of the pyrolysis products of the GFE fraction extracted from a Mediterranean soil beneath different plant covers, affected and not affected by fire and at different times of the year. A total of 139 compounds were identified and grouped according to their probable biogenic origin. There is little variation between samples, indicating that the EEG is a structurally stable soil organic fraction, composed mainly of polysaccharides (42 ± 5%), non-specific aromatic compounds (24 ± 3%) and hydro-aromatics (12 ± 3%). The remaining 20% contains aromatic polycyclic hydrocarbons (8%), lipids (7% fatty acids and alkane/alkene pairs), lignin (5%) and protein/peptide derivatives (2%)., [ES]: Glomalina Fácilmente Extraible (GFE) es un término operacional aplicado a una fracción orgánica del suelo que se supone contiene principalmente proteínas del suelo relacionadas con glomalina (PSRG), una glicoproteina abundante en los suelos y producida en las hifas y esporas de hongos micorrícicos arbusculares (HMA). La fracción GFE es la más inmunoreactiva al anticuerpo monoclonal MAb32B11 de glomus y está relacionada con características relavantes de los suelos, como su estabilidad y resiliencia a la degradación, formación de agregados y estabilización de carbono orgánico. En este estudio realizamos una caracterización molecular detallada “fingerprint” de los productos de pirólisis de la fracción GFE extraidas de un suelo mediterráneo bajo diferentes cubiertas vegetales, afectado y no afectado por un incendio y en distintas épocas del año. Se identificaron un total de 139 compuestos que se agruparon dependiedo de su probable origen biogénico. Se observa escasa variación entre muestras, indicando que la GFE es una fracción estructuralmente estable, compuesta principalmente de polisacáridos (42 ± 5 %), compuestos aromáticos no específicos (24 ± 3 %) e hidroaromáticos (12 ± 3 %). El 20 % restante lo componen hidrocarburos policíclicos aromáticos (8 %), lípidos (7 % ácidos grasos y pares alcano/alqueno), lignina (5 %) y derivados de proteina/péptidos (2 %).

[EN]: Although combustion ashes from different types of biomass are frequently used as soil amendments, the CO2 sequestration associated with this practice has not been previously studied. The objective of this study is to quantify the C sequestration, in the form of carbonates, achieved in a synthetic calcareous soil treated with biomass ash (fly and bottom ashes) from a power generation plant that uses olive cake. It was estimated that, in the case of planted soil, CO2 fixation was 14.5 g per kg of fly ash or 16.5 g of CO2 per kg of bottom ash, and 19.7 g of CO2 per kg of bottom ash in bare soil without cultivation. This fixation of inorganic C plus the organic C (>black C>) contained in the ashes makes the reuse of ash as K fertilizer an environmentally sound practice, with a yearly C sequestration potential corresponding to 8% of the target of the >soil 4 per mille> initiative, launched at COP21., [ES]: A pesar de que las cenizas de combustión de diferentes tipos de biomasa son usadas con frecuencia como enmiendas para suelos, no se conoce el secuestro de CO2 asociado a esta práctica. El presente estudio tiene como objetivo cuantificar el secuestro de carbono, en forma de carbonato, que se produce en un suelo calcáreo sintético tratado con cenizas (volantes y de fondo) de biomasa procedentes de una planta de generación electrica a partir de orujillo de aceituna. Se estimó que la fijación en suelo, en el caso de un suelo cultivado, fue de 14.5 g de CO2 por kg de ceniza volante ó 16.5 g de CO2 por kg de ceniza de fondo, y de 19.7 g de CO2 por kg de ceniza de fondo sin cultivo de plantas. Esta fijación de C inorgánico más el C orgánico (“black C”) contenido en las cenizas hace que la reutilización de cenizas como fertilizante K pueda considerarse como una práctica ambientalmente ventajosa, con un potencial de secuestro anual de C correspondiente a un 8% del objetivo de la iniciativa > 4 por mil>, lanzada en la COP21.

Easily Extractable Glomalin (EEG) represents an organic fraction of the soil that contains mainly glomalin-related soil proteins (GRSP), a glycoprotein abundantly found in soils produced by arbuscular mycorrhizal fungi in the phylum Glomeromycota [1]. The EEG fraction is confirmed to have multiple ecological functions in soils, including the improvement of soil stability and resilience to degradation, facilitate aggregate formation and contribute to soil carbon storage [2]. Given its potential for soil C immobilization, a detailed molecular characterization "fingerprint" of pyrolysis products of EEG fraction extracted from a Mediterranean soil under different plant covers, affected and unaffected by forest fire and at different times is conducted. A total of 16 samples were extracted from soils in Gorga (NE Alicante, Spain). Further information about the sampling process and EEG extraction protocols are described elsewhere [3]. In short, samples were taken from the surface (to 2.5 cm depth; A horizon) under pine and shrub covers, immediately after a forest fire (July 2011), and at 4, 8 and 12 months after the fire. Surrounding soils with similar characteristics but unaffected by fire were taken as control. The EEG samples were analysed using pyrolysis-gas chromatography coupled to mass spectrometry (Py-GC/MS). Pyrolysis temperature was 400 ºC for 1 minute and detailed chromatographic conditions and compound assignment procedure were as described in [4]. A total of 139 compounds were identified and grouped according to their probable biogenic origin: polysaccharides (PS), lignin and polyphenols (LIG), proteins and polypeptides (PRO), non-specific aromatic compounds (ARO), hydro-aromatics (HAR), lipids (LIP), polycyclic aromatic hydrocarbons (PAH) and terpenes (TER). A remarkable high similarity was found between EEG samples from different plant covers, both affected and unaffected by forest fire and at different time over a year after the fire. This fact indicates th, [1] Janos, D.P., Garamszegi, S., Beltran, B. (2008). Glomalin extraction and measurement. Soil Biol. Biochem, 40: 728-739. [2] Wright, S.F., Upadhyaya, A. (1996). Extraction of an abundant and unusual protein from soil and comparison with hyphal protein of arbuscular mycorrhizal fungi. Soil Sci. 161: 575–586. [3] Lozano, E., Jiménez-Pinilla, P., Mataix-Solera, J., Arcenegui, V., Mataix-Beneyto, J. (2016). Sensitivity of glomalin-related soil protein to wildfires: Immediate and medium-term changes. Sci Total Environ. 572: 1238–1243. [4] González-Pérez, J.A., Almendros, G., de la Rosa, J.M., González-Vila, F.J. (2014). Appraisal of polycyclic aromatic hydrocarbons (PAHs) in environmental matrices by analytical pyrolysis (PyGC/MS). J. Anal. Appl. Pyrolisis 109: 1-8. [5] Lozano, E., Chrenková, K., Arcenegui, V., Jiménez-Pinilla, P., Mataix-Solera, J., Mataix-Beneyto, J. (2016). Glomalin-related soil protein response to heating temperature: a laboratory approach. Land Degrad. Dev. 27: 1432–1439. [6] Schindler, F., Mercer, E., Rice, J. (2007). Chemical characteristics of glomalin-related soil protein (GRSP) extracted from soils of varying organic matter content. Soil Biol. Biochem. 39: 320–329. [7] Zhang, J., Tang, X., Zhong, S., Yin, G., Gao, Y., He, X. (2017). Recalcitrant carbon components in glomalin-related soil protein facilitate soil organic carbon preservation in tropical forests. Sci. Rep. 7: 2391

[EN]: The combination of analytical pyrolysis (Py-GC-MS) and chemometric tools in obtaining molecular markers surrogated to soil water repellency of fire-affected forest soils is studied. Bulk (<2 mm) burnt and unburnt soil samples under Quercus suber cover (Doñana National Park) were collected, and up to 6 particle size fractions (1–2, 0.5–1, 0.25–0.5, 0.1–0.25, 0.05–0.1 and <0.05 mm) were isolated and analysed. It is observed that the levels of soil water repellency can be accurately predicted from the relative proportions of organic compounds released by pyrolysis. On the other hand, it was found that the pyrolysis compounds significantly related to water repellency were different depending on whether the soils had been affected by the fire, or not: In samples from unburnt areas, soil water repellency was associated mainly to the presence of lignin-derived compounds, carbo-hydrates, proteins and fatty acids. By contrast, in fire-affected forest soils, the high water repellency levels were associated with an organic matter consisting mainly of alkyl and aromatic structures, and less proportions of oxygen-containing compounds, [ES]: En este trabajo se evalúa la idoneidad de la combinación de técnicas de pirólisis analítica (Py-GC-MS) y herramientas quimio-métricas para obtener marcadores moleculares subrogados a la repelencia al agua en suelos afectados por un incendio forestal. Para ello, se estudiaron muestras de suelos completos (< 2 mm) en áreas forestales quemadas y no quemadas bajo Quercus suber (Parque Nacional de Doñana) así como 6 fracciones de distinto tamaño de partícula (1–2, 0.5–1, 0.25–0.5, 0.1–0.25, 0.05–0.1 y < 0.05 mm). Se observa que la repelencia al agua en los distintos suelos puede predecirse con precisión (P < 0.05) a partir de las abundancias de los compuestos orgánicos liberados por pirólisis. Por otro lado, pudo establecerse que los compuestos de pirólisis significativamente relacionados con la repelencia al agua eran diferentes en los suelos según hubieran sido afectados por el fuego o no. En las muestras tomadas en áreas no quemadas, la repelencia al agua estuvo principalmente asociada a la presencia de compuestos derivados de lignina, proteínas, carbohidratos y ácidos grasos. Por el contrario, en las muestras de suelo de las áreas quemadas, la repelencia al agua se correlacionó significativamente con la presencia de materia orgánica con predominio de estructuras alquílicas y aromáticas, y baja proporción de compuestos con grupos oxigenados.

Fire is one of the most important modulating factors of the environment and the forest inducing chemical and biological changes on the most reactive soil component, the soil organic matter (SOM). Assuming the complex composition of the SOM, we used an ultra-high resolution mass spectrometry analysis technique to assess the chemical composition and fire-induced alterations in soil particle size fractions (coarse and fine) from a sandy soil in a Mediterranean oak forest at Doñana National Park (Southwest Spain). Electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) showed that the coarse fraction of soils not affected by fires consisted mainly of polyphenolic compounds consistent with little-transformed SOM and fresh biomass, whereas the fine fraction was enriched in protein and lipid like homologues suggesting microbially reworked SOM. In fire-affected SOM, the coarse fraction contained a high proportion of aromatic compounds, consistent with inputs of charred litter or in situ chemical transformation of the SOM. Analysis of the fine fraction revealed two differentiated chemical families pointing to the existence of two carbon pools; a native microbial-derived moiety composed of lipids and polypeptide compounds, and a secondary, pyrogenic or thermally-altered moiety rich in aromatic compounds. This work represents the first application of ultra-high resolution mass spectrometry to study the chemical composition of SOM in different particle size fractions.

Post-fire rehabilitation actions and recovery attempts of burned soils include a range of management practices (tillage, tree logging, reforestation . . . ), in some cases producing an additional damage to that directly caused by fire. Among negative impacts derived from unappropriated rehab practices are the increase soil erosion, loss of soil fertility and alterations in the hydrological cycle. Analytical pyrolysis (Py-GC/MS) is an appropriate technique to study organic matter characteristics within complex matrices. Here this technique is used to study the alterations caused by burning and post-fire rehab plans to soil organic matter (SOM). Fire and post-fire rehab actions impact on SOM is studied in a sandy soil under pine (Pinus pinea) forest that was affected by a severe fire in August 2012 in Doñana National Park (SW Spain). Bulk samples as well as its sieved soil fractions (coarse, 1–2 mm, and fine, <0.05 mm) collected from an undisturbed burned area (B) and in an adjacent burned area after rehab practices (BR) (logging and extraction of burned trees) were studied. An additional adjacent unburned (UB) area was used as a control. Conspicuous differences among bulk samples from the B, BR and UB control areas were found in the relative proportions of the main molecular families obtained by analytical pyrolysis, including alkane/alkene pairs, unspecific aromatic compounds (UAC), peptides, methoxyphenols, fatty acids, carbohydrates, N-compounds and polycyclic aromatic hydrocarbons (PAH). The B site SOM showed lower proportion of lignin methoxyphenols and higher of UAC and PAH than the SOM from the UB site. This indicates that fire produced methoxyphenol de-functionalization, increasing the proportion of recalcitrant compounds. With respect to soil size fractions, in all cases, the coarse fraction showed a high content of carbohydrate-derived compounds and methoxyphenols followed by fatty acids, in line with inputs of new litter from stressed post-fire vegetation

Introduction Soil water repellency (SWR) has critical implications for restoration of vegetation in degraded areas as it is responsible of poor plant establishment and a high incidence of erosion processes. Different organic substances are capable of inducing SWR but polar molecules such as certain fatty acids, and waxes i.e. esters and salts of fatty acids, appear to be the main constituents of hydrophobic coatings on soil mineral particles (Doerr et al., 2005). Plant species most commonly associated with SWR are evergreen trees with a considerable amount of resins, waxes or aromatic oils such as eucalypts and pines. Most of these substances are abundant in ecosystems and are released to soil by plants as root exudates or decaying organic debris, and by soil fauna, fungi and other microorganisms, but a thorough knowledge of substances capable of inducing hydrophobicity in soils is still not complete (Jordan et al., 2013). Although SWR has been reported in most continents of the world for different soil types, climate conditions and land uses, there are still many research gaps in this area, particularly in semi-arid areas largely affected by this phenomenon. Materials and methods This research was conducted in three dominant ecosystems of Western Australia (WA), e.g. semi-arid grassland in the Pilbara region (North WA), Banksia woodland, and a coastal dune (both located in South WA). These environments have different climate characteristics and soil types but similar vegetation communities. Soil samples were collected under the canopy of a broad range of plant species that compose the dominant vegetation communities of these ecosystems, and SWR was measured under lab conditions in oven-dry samples (48 h, 105 ºC). Soil microbial activity was measured with the 1-day CO2 test, a cost-effective and rapid method to determine soil microbial respiration rate based on the measurement of the CO2 burst produced after moistening dry soil (Muñoz-Rojas et al., 2016). Soil pH an, Results Our results show that soil water repellence is strongly correlated to microbial activity, pH and electrical conductivity. After Py-GC/MS analysis, soil organic matter in the Banksia woodland and the coastal dune showed a high heterogeneity. In the Banksia woodland two different patterns were observed. Samples under Banksia spp. showed a SOM with clear signs of altereation (humified) that included a high contribution of stable families like unspecific aromatic compounds and alkane/alkene pairs whereas under Eucalyptus spp. showed a less altered SOM with a high relative contribution from lignocellulose (lignin and carbohydrates), together with a low relative content of recalcitrant families. However in the soil samples from coastal dunes a very similar SOM chemical composition was found in all cases. The dominant family was unspecific aromatic compounds (>30%), followed by alkane/alkene pairs and a high relative contribution from N bearing peptide compounds. This, together with a low relative amount of carbohydrate and lignin derived (methoxyphenols) compounds points to a SOM that undergoes great alteration processes, possible because of high turn-over rates. Very low contents of SOM were found in the Pilbara system, under Py-GC/MS detection levels, and therefore it was not possible to establish its chemical composition. A principal components analysis (PCA) axes based on the relative abundances of chemical families of compounds released after SOM pyrolysis (70.9 % of total variation explained in the two first axes) indicate that water repellence is closely related with fatty acids and the presence of short chain hydrocarbons.

Introduction Banksia woodlands (BW) are iconic ecosystems of Western Australia (WA) composed by an overstorey dominated by Proteaceae, e.g. Banksia menziesii and Banksia attenuata, in combination with other species, such as Eucalyptus spp., Verticordia spp. or Melaleuca spp. Although located in very poor dune soils, BW provide numerous ecosystem services and sustain a high biodiversity. In this area, annual rainfall is relatively high (about 800 mm) but permeability of the sandy substrate leads to a functionally arid ecosystem. Currently, BW are threatened by sand mining activities and urban expansion; therefore conservation and restoration of these woodlands are critical. Despite numerous efforts, the success of restoration plans is usually poor mostly due to the high sensitivity to drought stress and poor seedling survival rates (5-30%) (Benigno et al., 2014). A characteristic feature of BW is their root architecture, formed by a proteoid (cluster) system that spreads to form thick mats below the soil surface, favouring the uptake of nutrients (especially, P), and preventing soil erosion. Root exudates are related to numerous plant functions, as they facilitate penetration of roots in soil and enhance the extraction of scarce mineral nutrients and its further assimilation. Exudates may also interact directly with soil or indirectly through microbial mediated events being also related to soil water repellency (SWR; Lozano et al, 2014). Knowledge about the specific compounds able to induce SWR is limited (Doerr et al., 2000), but it is generally accepted that is caused by organic molecules coating the surface of soil mineral particles and aggregates (Jordán et al., 2013). Proteaceae release short-chained organic acids to enhance phosphate acquisition, which have been also reported to be related with SWR (Jiménez-Morillo et al., 2014). It is hypothesized that disruption of water dynamics in mature BW soils is underlying the failure of restoration plans. This research, Results and discussion Soil water repellency distributed discontinuously through the soil profile. The first thin layer (0-1 cm) composed of coarse sand and litter, located immediately above Banksia root clusters, showed wettable conditions. In contrast, the relatively well aggregated soil layer where the Banksia cluster root system is located (1-10 cm) was severely water-repellent. The 20-30 and 40-50 cm deep layers rendered wettable or subcritically water-repellent. After Py-GC/MS analysis, major compounds were identified and grouped according to their probable biogenic origin (lignin, polysaccharides, peptides, etc.). Among other soil organic compounds, well r esolved bimodal alkane/akene (C8-C31, maxima at C13 and C26) and fatty acids series (short-chained, C5-C9, and long-chained even-numbered C12-C18) were associated to the root cluster soil layer (1-10 cm). Also, a relatively high contribution of fire-derived polycyclic aromatic hydrocarbons (PAHs) was observed (7%), which is consistent with frequent fires occurring in BW. These results point to possible indirect links between organic substances released by roots and soil wettability involving soil microorganisms. Further discussion should shed light on possible ecological plant strategies and specific adaptations for water uptake in such arid ecosystems of WA.

This research deals with the assessment of organic matter structural differences in soil physical fractions before and after lipid extractions. Soil samples were collected in sandy soils, Arenosols (WRB 2006) from the Doñana National Park (SW Spain) under different vegetation cover: cork oak (Quercus suber, QS), eagle fern (Pteridium aquilinum, PA), pine (Pinus pinea, PP) and rockrose (Halimium halimifolium, HH). Two size fractions; coarse (C: 1-2 mm) and fine (F: 0.05-0.25 mm) were studied from each soil. . In addition, the two fractions from each soil were exhaustively Soxhlet extracted with a Dichlorometane-Methanol (3:1) mixture to obtain the lipid-free fractions (LF) from each size fraction (LFC and LFF). The composition of the organic matter at a molecular level in the different soil fractions was approached by analytical pyrolysis (Py-GC/MS) and FT-IR spectroscopy. These techniques are complementary and have been found suitable for the structural characterization of complex organic matrices (Moldoveanu, 1998; Piccolo and Stevenson, 1982); whereas Py-GC/MS provides detailed structural information of individual compounds present and a finger-printing of soil organic matter, FT-IR is informative about major functional groups present. The advantages of these techniques are well known: no need for pretreatment are fast to perform, highly reproducible and only small amount of samples are needed. Soil size fractions show contrasting differences in organic matter content (C 4-7 % and F > 40 %) and conspicuous differences were found in the pyrolysis products released by the fractions studied. The main families of pyrolysis compounds have well defined macromolecular precursors, such as lignin, polypeptides, polysaccharides and lipids (González-Vila et al., 2001)., The C fractions yield higher relative abundance of lignin and polysaccharide derived pyrolysis compounds. Regarding the differences in the soil organic matter as affected by the different vegetation covers, the C fraction from the PA soil presented a higher abundance of lignin derived pyrolysis products than the soils under the other vegetation. This is somehow unexpected since PA is a pteridophyte, not arboreal vegetation, i.e. low lignin content and, these lignin moieties probably remain in the soil from past vegetation or originate from surrounding woody arboreal vegetation. In contrast the F fractions released mainly lipids and aromatic compound of unspecific origin. Series of alkane/alkene pairs were present in all the pyrograms with varying abundance and composition. Lignin and polysaccharide derived pyrolysis compounds were scarce in the F fractions in all the cases, in fact, no sugar derived compounds were found in the HH sample. Regarding the composition of the LF soil fractions, the pyrolytic behavior of the LFC fractions was quite similar to the not extracted corresponding C soil fraction, showing a high proportion of lignin and sugar derived pyrolysis compounds. The LFF fractions also showed the same behavior as the C fraction, but with no lipid derived compounds which effectively indicates the occurrence of a selective and efficient removal of soil free lipids. Agreement was found between analytical pyrolysis results and FT-IR spectral features highlighting functional differences between fractions i.e. a decrease of OH- groups and an increase in aliphatics in the F fraction. With respect to the LF fractions, FT-IR spectra analysis was also consistent with the pyrolysis results with a slight increase in the lignin signals for LFF soil fractions under PA, PP and HH. For the soil under QS no differences were found between the LFF fractions and the whole organic matter in the F fraction, probably due to the high amount of organic matter in this fraction.