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Poster presentado en lal EGU General Assembly 2015, held 12-17 April, 2015 in Vienna, Austria. id.12736, The replacement of native beech forests (Fagus sylvatica) by Scots pine (Pinus sylvestris) afforestation may exert changes in soil properties, particularly in soil organic matter (SOM) [1]. It is known that the products generated by Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) pyrolysis of organic matter are related to their origin [2 and references therein]. Therefore this technique can be used to investigate said changes. In this work, Py-GC/MS is used to study changes in SOM quality surrogated to the effect of the centennial replacement of beech by Scots pine. The soils studied were two acid soil profiles developed on quartzites under a humid climate at an altitude of 1400-1500 masl from Moncayo (Iberian range, NE-Spain). For each soil profile three organic layers (litter: OL, fragmented litter OF and humified litter OH) and the mineral soil horizons (Ah, E, Bhs and C) were sampled. After 100 years since the pine afforestation, differences in the relative abundance of lipids released by pyrolysis were observed in the O-layers ranging from 3.82-7.20% in pine soils and 0.98-1.25% in beech soils. No differences were observed in mineral horizons with depth except for the C horizons where beech lipid content was much higher (21.25%) than in that under pine (1.07%). Both pine and beech soils show similar nitrogen compounds relative contents along the soil profile, increasing from OL to Ah (3.49-9.11% and 2.75-11.73% in beech and pine respectively) with a conspicuous reduction in the E horizon. It is remarkable the absence of nitrogen compounds in beech Bhs and C horizons. The relative content of aromatic compounds in O-layers show opposite trends for beech and pine; an enrichment in aromatic compounds is observed in beech OL layer (12.39%) decreasing to 4.11% in OH layer in contrast, whereas for pine O-layers the aromatic compounds relative abundance was higher in the OH (5.83%) than in the OL layer (2.8%). Mineral Ah and E horizons show similar values in both beech (18.30-10.09%) and pine (15.81-10.01%) soils; nevertheless the relative abundance of aromatic compounds content is higher in beech mineral horizons Bhs (41.96%) and C (30.91%) than in those under pine (11.43% and 13.04% for Bhs and C respectively). Polycyclic aromatic hydrocarbons (PAHs) were only observed in the mineral soil horizons showing similar relative abundances ranging from 0.61-6.63% in beech and 0.96-3.05% in pine soils. The highest PAHs relative abundance was found in the Bhs horizon under beech. This may indicate the occurrence of fire events in the area and its translocation and accumulation by leaching from top soil in the spodic horizon. Differences in the relative abundances of lignin derived pyrolysis products (Methoxyphenols) were mainly observed in the O-layers whereas the relative abundances were similar for the mineral horizons that ranged from 1.49-4.31% in beech and 1.42-4.67% in pine. Lignin relative abundance is much higher in OH beech layer (31.88%) than in pine OH layer (14.99%) whereas similar relative contents were found in OL and OF layers ranging from 26.21-27-12% and 20.22-25.92% in beech and pine respectively. In the soil developed under beech the polysaccharide derived moieties show a relative content increase along the profile from a 9.86% in OL layer to a 29.86% in E horizon followed by a remarkable decrease in the Bhs (4.86%) and C (11.22%). Besides, the polysaccharide relative abundance in the soil under pine show a similar trend ranging from 12-23% to 30.65% but the decrease in Bhs and C horizons was found less marked (26.83% and 24.12% respectively)., This study is part of the results of the FUEGOSOL (CGL2013-43440-R) and GEOFIRE Projects (CGL2012-38655-C04-01) funded by the Spanish Ministry for Economy and Competitiveness. N.T Jiménez-Morillo is funded by a FPI research grant (BES-2013-062573).

EGU General Assembly 2015, held 12-17 April, 2015 in Vienna, Austria. id.1200, The replacement of native beech forests (Fagus sylvatica) by Scots pine (Pinus sylvestris) afforestation may exert changes in soil properties, particularly in soil organic matter (SOM) (Carceller and Vallejo, 1996). Stable isotopic signatures of light elements (d13C, d15N) in soils and plants are valuable proxies for the identification of biogeochemical processes and their rates in the pedosphere (Andreeva et al., 2013 and refs therein). In this work the C and N stable isotopic analysis is used as a proxy to detect changes in SOM surrogated to the effect of centennial replacement of beech by the Scots pinewood. Two acid soil profiles, developed on quartzites under a humid climate at an altitude of 1400-1500 masl, have been sampled in Moncayo (Iberian range, NE-Spain). For each soil profile three O-layers (litter: OL, fragmented litter OF and humified litter OH) and mineral soil horizons (Ah, E, Bhs and C) were sampled. Content and bulk isotopic signature of light elements (C and N) were analysed in a Flash 2000 elemental micro-analyser coupled via a ConFlo IV interface to a Delta V Advantage isotope ratio mass spectrometer (IRMS) (Thermo Scientific, Bremen, Germany). Isotopic ratios are reported as parts per thousand deviations from appropriate standards. The standard deviations of d13C and d15N were typically less than 0.05 per thousand, 0.2 per thousand, respectively. After 100 years since the pine afforestation, no differences on C content were observed in the O-layers, ranging from 30-47% in pine soils and 37-47 % in beech soils. Similarly, no differences on N content were observed in the O-layers, ranging from 1.24-1.86 % in pine soils and 1.70-1.71 % in beech soils. C and N contents decrease progressively in depth with the exception of E-horizons where the lowest C and N content values were found. C/N ratio is higher in pine soil (20.7-38.1) than in beech O soil horizons (21.8-27.5), showing similar behavior with soil depth. Pine biomass was slightly enriched in 13C as compared to that from beech (OL enrichment factor= 1.24 0.13 per thousand). Along the soil profile the C isotopic signature (d13C) reflects the main vegetation signature being higher in pine than beech in the organic soil horizons (OL, OF and OH) down to the first mineral Ah horizon. At deeper horizons d13C value tends to equal that of the original beech soil indicating a limited influence of the afforested specie with depth even 100 years after afforestation. A consistent enrichment in d15N with depth was observed in the two profiles. This N enrichments have been related with progressive N losses being particularly pronounced in forest soils (Szpak, 2014 and refs therein). This phenomenon can be also related to migrations of N forms in a more evolved organic matter. In this view N losses in organic layers under beech seem to be less pronounced that under the alien pine., Andreeva BD, Zech M, Glaser B, Erbajeva MA, Chimitdorgieva, Ermakova OD, Zech, W. (2013). Stable isotope (δ13C, δ15N, δ18O) record of soils in Buryatia, southern Siberia: Implications for biogeochemical and paleoclimatic interpretations. Quaternary International 290-291 (2013) 82-94 pp. Carceller F, Vallejo VR (1996). Influencia de la vegetación en los procesos de podsolización en los suelos de la Sierra del Moncayo (Zaragoza). Geogaceta 1127-1130. Szpak P (2014). Complexities of nitrogen isotope biogeochemistry in plant-soil systems: implications for the study of ancient agricultural and animal management practices. Front. Plant Sci. 5: 288 1-19 pp., This study is part of the results of the FUEGOSOL (CGL2013-43440-R) and GEOFIRE Projects (CGL2012-38655-C04-01) funded by the Spanish Ministry for Economy and Competitiveness. N.T Jiménez-Morillo is funded by a FPI research grant (BES-2013-062573).

Poster presentado en las IV Jornadas del IUCA- 11 de noviembre (2015) Área Territorio P-54, Referencias [1] Amelung et al. Adv. Agron. 100, 155-250 (2008) [2] González-Pérez et al. Org. Geochem. 53, 119-130 (2012) [3] Balesdent, J. y Mariotti, A. Soil Biol. Biochem. 19, 25-30 (1987) [4] Makarov, M.I. Eurasian Soil Sci. 42, 1335-1347 (2009) [5] De la Rosa et al. Geoderma 191, 24-30 (2012) [6] Szpak, P. Front. Plant Sci. 5 (288), 1-19 (2014) [7] Assis et al. Sci. Agric. 68 (2), 230-236 (2011), La sustitución de bosques naturales de haya (Fagus sylvatica) por repoblaciones de pino silvestre (Pinus sylvestris) puede inducir cambios en las propiedades edáficas, especialmente en la composición y dinámica de la materia orgánica del suelo (MOS). Técnicas como la espectrometría de masas de relaciones isotópicas (IRMS) [1] o la pirólisis con cromatografía de gases y espectrometría de masas (Py-GC/MS) [2] permiten una mejor caracterización de la génesis y dinámica de la MOS. La firma isotópica del C (δ13C) puede utilizarse como trazador orgánico ya que es característica de cada patrón fotosintético [3] mientras que la relación isotópica del N (δ15N) aporta información sobre los ciclos del N [4]. Mediante pirólisis analítica (Py-GC/MS) se obtiene una firma molecular de la MOS relacionada con su origen [5]. El objetivo del presente estudio consiste en la utilización de técnicas de IRMS y Py-GC/MS para la identificación de cambios cualitativos en la MOS derivados de una reforestación centenaria. Para ello, se muestrearon dos perfiles edáficos (en hayedo y en pinar) desarrollados sobre areniscas cuarcíticas a una altitud de entre 1400-1500 msnm en la vertiente NE del Parque Natural del Moncayo. Para cada perfil, se muestrearon los horizontes orgánicos (hojarasca inalterada: OL; hojarasca fragmentada: OF; hojarasca humificada: OH) y minerales (Ah, E, Bhs y BC). La firma isotópica (δ13C y δ15N) se determinó en un micro-analizador elemental Flash 2000 acoplado mediante una interfaz Conflo IV a un espectrómetro de masas de relaciones isotópicas Delta V Advantage (Thermo Scientific, Bremen, Alemania). La pirólisis con cromatografía de gases y espectrometría de masas (Py-GC/MS) se realizó mediante un pirolizador de doble inyección (Frontier Laboratories, modelo 2020i) acoplado a un equipo de GC/MS Agilent 6890N. Los valores de δ13C reflejaron la firma isotópica de la vegetación dominante, poniendo de manifiesto la profundidad a la que se ven limitados los aportes de MOS en el pinar (horizonte E, 30-60 cm) al asemejarse sus valores a los del perfil desarrollado bajo hayedo. La firma isotópica de N (δ15N) fue significativamente más pesada en el horizonte OH de pinar respecto del hayedo indicando un mayor grado de mineralización del N. A lo largo de los perfiles, se produce un enriquecimiento en 15N en profundidad, característico de la degradación de la MOS [6]. Los pirogramas totales obtenidos mediante Py-GC/MS mostraron la variabilidad química de la MOS derivada del tipo de vegetación dominante así como de las diferentes condiciones ecológicas en cada tipo de bosque. La abundancia de alcanos impares de cadena larga en el perfil de hayedo respecto de pinar es indicativa de un mayor grado de conservación y estabilidad de la MOS [7]. Las series de n-alcanos también indicaron la aparición de posibles biomarcadores de haya en el horizonte E de pinar reforzando los resultados de δ13C obtenidos.

Fires largely affect soil organic carbon (SOC), resulting both in loss of organic matter and the genesis of pyromorphic forms that are generally considered to be highly resistant to degradation. Calcium is known to contribute to SOC stabilisation, so SOC is more protected and fire effects might be less pronounced for soils developed from Ca-bearing materials (e.g., limestone, gypsum) than in other soils. In this work, we investigated the effect of fire on SOC stability in soils developed from calcareous and gypseous bedrocks. Twelve monoliths (15 x 25 x 5 cm) were collected from the top of soils with calcareous mollic (Rendzic Phaeozem, PHrz) or gypseous ochric (Haplic Gypsisol, GYha) horizons in a semiarid pinewood forest in Northeast Spain. In a laboratory designed experiment six blocks were heated from the surface until 250 °C was reached at 1 cm depth, and other six monoliths were preserved as control samples. The O layer and first and second cm from Ah horizon were scrapped from the surface of the monoliths and analysed separately. Total SOC content was obtained by dry combustion. To assess the content and mean residence time (MRTs) of labile and stable SOC pools, the samples were incubated during 100 days at 25 ºC in a Respicond IV apparatus. Respiration data were acquired continuously and fitted to a double-exponential decay model. The results are analysed in relation to the thermal treatment, soil type and depth using ANOVA for repeated measures. Thermal treatment had contrasting effects on the GYha and PHrz. At the GYha, burning decreased the contents and MRTs of both labile and stable SOC, but the effects were larger on the stable SOC, pointing to a conversion of stable SOC into forms more prone to degradation. For the PHrz, burning decreased the labile SOC contents while increased its MRT, but did not affect the amount of stable SOC, which indeed tended to increase, suggesting the formation of stable SOC due to fire at expenses of the more labile forms., Poster presentado en el 5th International Conference of Fire Effects on Soil Properties (FESP5) University College Dublin 14th-17th July (2015) http://www.ucd.ie/ecomodel/fesp5/program.html

10 páginas, 3 figuras, 4 tablas, 71 referencias.-- Special Issue: Advances Towards an Integrated Assessment of Fire Effects on Soils, Vegetation and Geomorphological Processes, Wildfires represent one of the main factors of land degradation in Mediterranean environments having negative effects to several ecosystem services. In this work, the fire-induced changes associated with depth (O horizon and Ah at 0–1, 1–2 and 2–3 cm depths) were studied in a gypseous soil under Aleppo pine forest. Topsoil monoliths were burned in an outdoor combustion tunnel simulating a fire of moderate intensity. In the O horizon, burning caused an immediate and significant decrease in water repellency (WR), total organic carbon (TOC) and pyrolyzed carbon (PyC) and an increase in total inorganic carbon. The Ah horizon was also significantly affected by fire, but mainly in its first shallower centimetre and with a different direction according to soil properties: TOC, gypsum, WR and PyC decreased, whereas soil aggregate stability and pH increased. Soil burning not only involved the loss of the pre-fire organic matter content of the O horizon and the upper centimetre of the Ah horizon but also decreased their relative abundance of markers of resins, lignin and polysaccharides. Moreover, the soil burning exerted the cracking of alkylic long-chain molecular series, some of them until the 2 cm Ah depth. The reduction of organic lipophilic molecules in the upper soil centimetre may be related to the fire-induced decreases in WR. Moderate burning of the studied gypseous ochric horizon does not modify any of the properties studied at depths greater than 2 cm., This study was supported by the Government of Aragón (Spain) and ‘La Caixa’ (GA-LC-055/2011) and the Spanish "Ministerio de Economía y Competitividad" through project GEOFIRE (ref. CGL2012-38655-C04-01).

3 pages, 1 figure, 8 references.-- Comunicación oral presentada en Session 1. Pyrogenic C: Distribution and stability, en European Science Foundation-Exploratory Workshop, celebrado del 5-7 de noviembre 2013, en Sevilla, España., Wildfire is an important disturbance factor in many ecosystems, especially in the Mediterranean Basin (Keeley et al., 2012). Forest fires exert changes in soil organic matter (SOM) quality and quantity (González‐Pérez et al., 2004) that in turn affect relevant and closely related characteristics like soil runoff and erosion response, due to changes on factors like wettability and aggregation (Certini et al., 2011; Mataix‐Solera et al., 2011). The effects of heat in SOM are highly variable and dependent of many interrelated factors (Badía et al., 2011).

[EN]: Changes produced by fire on soils depends on several factors (vegetation, soil type, temperature, etc.). Here we study the influence of fire on a gypsiferous forest soil located northwest of the city of Zaragoza. Six blocks of undisturbed soil were collected and burned under laboratory conditions reaching 272.9 ± 21.7 oC at 1cm depth. The fire caused significant differences (p, Este trabajo forma parte del Proyecto de Investigación en materia de medio ambiente y sostenibilidad financiado por DGA-La Caixa. Convocatoria 2011, Ref. GA-LC-055/2011.

Póster P37 presentado en las 13 Jornadas de Análisis Instrumental, celebradas del 14-16 de noviembre 2011, en Barcelona, España.-- cmartin@irnase.csic.es, Analytical pyrolisis (Py-GC/MS) is a fast and reproducible technique widely used in the structural characterization of organic matrices. Usual analytical methods for the study of polycyclic aliphatic hydrocarbons (PAHs) involve more or less complex and time-consuming sample preparation and extraction steeps, often with the use of high quantities of organic solvents. In order to illustrate the potential of the technique for a rapid qualitative assessment of PAHs, Py-GC/MS is used here giving results of PAHs assemblages directly detected in a number of extremely complex organic matrices. Homogenised samples (1-5 mg) are placed in a double-shot pyrolyzer (Frontier Laboratories, model 2020i) attached to an Agilent 6890N GC-MS. The initial temperature was 100°C that was increased at 20°C min-1 to a final pyrolysis temperature of 500°C for 1 min. The GC instrument was equipped with a DB5MS (J&W Scientific; 30 m × 250 µm × 0.25 µm film thickness) column; oven temperature programme was: 50°C (1 min) to 100°C at 30°C min-1, then to 300°C at 20°C min-1 (held 10 min). The carrier gas was He at a controlled flow of 1 ml min-1. The detector was an Agilent 5973 mass selective detector and mass spectra were acquired with 70 eV ionizing energy. Compound assignment was achieved via extracting ion chromatograms (XIC) for selected ions, low resolution mass spectra and comparison with published and stored (NIST and Wiley libraries).

13 páginas.- 10 figuras. - 1 tabla.- referencias.- Supplementary data to this article can be found online athttps://doi.org/10.1016/j.scitotenv.2020.139121, 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., This study is part of the results of a microproject funded by the “Instituto de Estudios Altoaragoneses-Diputación de Huesca (Call 2018). Lucía Buendía was supported by a novel research contract, funded by the Institute for Research into Environmental Sciences (IUCA) of the University of Zaragoza. This work has been partially financed by the Regional Government of Aragón (Geoforest research group S51_17R) co-financed with FEDER 2014-2020 “Construyendo Europa desde Aragón”. The authors would also like to thank Federico Fillat for his help in the field and for their constructive comments and suggestions, which led to a substantial improvement of the paper.