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4 páginas.-- 2 figuras.-- 8 referencias.-- Póster presentado en el VIII Congreso Ibérico de las Ciencias del Suelo. VIII Congresso Ibérico de Ciências do Solo. DONOSTIA-SAN SEBASTIÁN. 20 - 22 junio 2018..-- El documento completo se encuentra para su descarga en http://www.cics2018.com/libro-de-abstracts/, [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 (, [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., Trabajo parcialmente financiado por los proyectos INTERCARBON (CGL2016-78937-R) y COSEPROM (CGL2013-43845-P). Reconocimiento a D. Monis y A. Carmona por su inestimable ayuda duran-te la pirólisis analítica.

Póster presentado en el EGU General Assembly 2017, 23–28 April 2017, Vienna, Austria, INTRODUCTION The Swan Coastal plain of Western Australia is dominated by fire-prone banksia woodland (Burrows and McCaw, 1990). In these areas, prescription burning is often used to reduce the risk of wildfires, by reducing available fuels (Boer et al., 2009). Little research has been conducted on the effects of prescription burning on Banksia woodlands, and, in particular, information on the impacts on soil properties and soil water repellency (SWR) is carce. Here, we have studied the impact of fire on SWR in a Banksia woodland and monitored its evolution in the medium-term. It is expected that results are useful for management and restoration of fire-affected Banksia woodlands. METHODS An experimental fire was conducted on May 7th 2015 in Kings Park, Perth, Western Australia. The fire affected an area of 6 ha of mixed Banksia/Allocasuarina woodland under moderate fire intensity. At the time of ignition, the wind speed below the canopy was 1.2 km/h. During the prescribed burning, air temperatures were on average 20 ± 1◦C and relative humidity ranged between 45 and 55% (measured using a Kestrel portable weather station). Fuel moisture averaged 11.8% (measured using Wiltronics moisture meter) and soil moisture at 1 cm deep ranged from 0.1% to 8.6% (measured with a PR2 soil profile probe attached to a HH2 data logger). Temperatures greater than 120 ◦C were measured 1 cm below the soil surface using iButton temperature sensors. SWR was measured under lab conditions in oven-dry samples (48 h, 105 ◦C) with the water drop penetration time (WDPT) test. Soil microbial activity was determined with the 1-day CO2 test that is based on the measurement of the CO2 burst produced after moistening dry soil (Muñoz-Rojas et al., 2016)., PRELIMINARY RESULTS AND DISCUSSION SWR was severe in the control (mean WDPT = 2608 s) and pre-burned areas (2722 s). One week after the prescribed fire, persistence of soil water repellency remained stable in the burned area (2402 s). In contrast, extreme SWR was observed in the burned area (3750 s). This may be explained by a reduction of water repellency by burning (Zavala et al., 2009; Jordán et al., 2014), as environmental conditions led to an increase in control areas. Although prescribed burning usually do not produce high severity fires, evidences of high severity were found, due to prolonged smouldering caused by subsurface Banksia root clusters. In some cases, this led to release of iron oxides, observed as red spots in the surface. Fire in Mediterranean and semi-arid environments has a significant effect on microbial biomass and the composition of soil microbial communities during the post-fire period, when soil nutrients become available (Bárcenas-Moreno et al., 2011; Muñoz-Rojas et al., 2016). In our study, microbial activity increased sharply in the burned area and most likely contributed to a decrease of organic hydrophobic substances in the first centimetres of the soil profile. Bárcenas-Moreno et al. (2011) observed that bacterial activity increases immediately after fire, while fungi decreased and recovered slowly. These processes may contribute to explain differences in SWR following fire, since this soil property may be influenced by fungal activity (Lozano et al., 2013)., This research has been partly funded by the University of Western Australia through the project "Soil water repellence in biodiverse semiarid environments: new insights and implications for ecological restoration" (UWA Research Collaboration Awards, Ref. ENV.2013.6.2-4) and the Spanish Ministry for Economy and Competitiveness through the research projects GEOFIRE (Ref. CGL2012-38655-C04-01) and POSTFIRE (Ref. CGL2013-47862-C2-1-R).

Póster presentado en el EGU General Assembly 2017, 23–28 April 2017, Vienna, Austria, 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, This study is part of the results of the GEOFIRE and POSTFIRE Projects (CGL2012-38655-C04-01 and CGL2013-47862-C2-1-R respectively) funded by the Spanish Ministry for Economy and Competitiveness. N.T Jiménez-Morillo is funded by a FPI research grant (BES-2013-062573).

Póster presentado en el EGU General Assembly 2017, 23–28 April 2017, Vienna, Austria, 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 aims to study SWR and its impact on water economy in relation with soil functioning and plant strategies for water uptake in pristine BW. Results are expected to shed light on the origin and implications of SWR in the area and provide useful information for improving ongoing restoration plans. Materials and methods The study was conducted in natural BW of WA. Soil samples were collected at different soil depths (0-1, 1-10, 20-30 and 40-50 cm). Rationale for sampling depths was based on the different severities of SWR at each layer under field conditions. Soil water repellency was assessed under laboratory conditions in oven-dry samples (48 h, 105 ºC) and the chemical organic assemblage of bulked soil subsamples from each layer was analysed by direct analytical pyrolysis (Py-GC/MS)., 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 has been funded by the University of Western Australia (Research Collaboration Award 2015: ‘Soil water repellence in biodiverse semi arid environments: new insights and implications for ecological restoration’) and the Spanish Ministry of Economy and Competitiveness (research projects GEOFIRE, CGL2012-38655-C04-01, and POSTFIRE, CGL 2013-47862-C2-1-R.

Póster presentado en el EGU General Assembly 2017, 23–28 April 2017, Vienna, Austria, 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 and electrical conductivity (EC) were determined in deionised water (1:2.5 and 1:5 w/v, respectively). The structural characterization of soil organic matter (SOM) was analysed by direct analytical pyrolysis (Py-GC/MS) performed at 500 ◦C (González-Vila et al., 2009). Only chromatogram peaks with an area higher than 0.2 % were identified and used to obtain the relative abundance of main chemical families in each vegetation cover., 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., This research has been funded by the University of Western Australia (Research Collaboration Award 2015: ‘Soil water repellence in biodiverse semi arid environments: new insights and implications for ecological restoration’) and the Spanish Ministry of Economy and Competitiveness (research projects GEOFIRE, CGL2012-38655-C04-01, and POSTFIRE, CGL 2013-47862-C2-1-R.

Póster presentado en la XXXII Reunión Nacional de Suelos (RENS2019) 10-13 de septiembre de 2019 en Sevilla, Los incendios forestales son un factor de perturbación en muchos ecosistemas terrestres incluidas las zonas mediterráneas. El fuego produce cambios cualitativo y cuantitativo en la materia orgánica del suelo (MOS) que afectan a sus propiedades físicas, químicas y biológicas. En este trabajo empleamos la espectroscopía de masas de relaciones isotópicas (IRMS), para estudiar la composición isotópica de carbono (C) e hidrógeno (H) de biomasa y de MOS en diferentes fracciones físicas del suelo, con el fin de evaluar las alteraciones producidas por el fuego en la estructura de la MO, así como posibles aportes de biomasa al suelo tras el incendio. Se analizaron muestras del suelo completo (arenosol), así como de 3 fracciones de tamaño arena (gruesa, media y fina) y de biomasa de la vegetación predominante alcornoque (Quercus suber) procedentes del Parque Nacional de Doñana. Para los análisis se utilizó un micro-analizador elemental Flash HT 2000 acoplado mediante una interfaz Conflo IV a un espectrómetro de masas de relaciones isotópicas de flujo continuo Delta V Advantage (Thermo Scientific, Bremen, Alemania). Los resultados de la composición isotópica de C confirman la existencia de dos compartimentos de MOS con diferentes grados de evolución. La fracción gruesa contienen MO poco evolucionada, empobrecida en 13C y con valores de δ13C similares a la biomasa foliar, mientras que las fracciones finas mostraron una MO más evolucionada, probablemente sometida a una mayor actividad microbiana y enriquecida en 13C. El fuego no produjo cambios significativos en dicha tendencia, aunque sí se observó un aumento del contenido de 13C en todas las fracciones afectadas. Esto puede atribuirse a una eliminación selectiva de compuestos isotópicamente ligeros (menor contenido de 13C) o a la incorporación de material parcialmente quemado. Con respecto a la composición isotópica de H, se observó que la fracción gruesa mantiene valores bajos de δ2H, similar al de la biomasa foliar, mientras que la fracción media-fina muestra un valor δ2H más enriquecido y que puede relacionarse con procesos de evaporación que produce un enriquecimiento en deuterio en el agua. Estos resultados revelan también la existencia de dos compartimentos diferentes relacionados con el agua del suelo y dependientes del tamaño de partículas., Proyecto INTERCARBON (CGL2016-78937-R) cofinanciado con fondos de cohesión EU-FEDER. N.T. Jiménez-Morillo agradece su contrato FPI (BES-2013-062573). Desiré Monis por su asistencia técnica.

Póster presentado en el EGU General Assembly 2015, 12-17 April 2015, Vienna, Austria, 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., This study is part of the results of the GEOFIRE Project (CGL2012-38655-C04-01) (BES-2013-062573), funded by the Spanish Ministry for Economy and Competitiveness. Dr. J.M. de la Rosa is the recipient of a fellowship from the JAE-Doc subprogram financed by the CSIC and the European Social Fund.

Soil water repellency (SWR), is a property of complex origin attributed to the accumulation and traslocation of hydrophobic compounds, mainly lipids [1, 2]. However, the extraction of soil lipids does not always suppress SWR and unextractable macromolecular fractions may also be responsible for SWR [3]. This may be the case with soils after wildfires, which alter SWR in different grades [4]. Burnt (B) and unburnt (UB) sandy soils under Quercus suber forest (Doñana National Park, Spain) were studied. SWR of bulk and of six size fractions were assessed by-droppenetration- time test (WDPT). The molecular composition of soil organic matter (SOM) was studied by analytical pyrolysis (Py-GC/MS). Partial least squares regression (PLS) was used to check whether SWR may be forecasted by total abundances of pyrolysis compounds and several indices were calculated to illustrate the extent to which individual compounds could be used as proxies for SWR, viz: a) factor loadings of PLS models, b) Pearson¿s R-squared coefficients, and c) subtraction of average values of samples with extreme WR values. The indices were represented as density surfaces in van Krevelen diagrams [5]. The PLS models for whole samples showed that SWR depends on SOM composition and that this can be predicted from pyrochromatographic data. Nonetheless, the significance of PLS models highly improved (P, Projects INTERCARBON (CGL2016-78937-R) and COSEPROM (CGL2013-43845-P). NTJM is funded by FPI grant (BES-2013-062573). D. Monis and A. Carmona for technical assistance.

Low soil-water affinity and soil water repellence (SWR, hydrophobicity) prevents water from wetting or infiltrating soils in burnt and unburnt ecosystems, causing changes on their hydrology, geomorphology, geochemistry, and biochemistry. A wildfire may destroy, develop or enhance SWR in previously wettable or water-repellent soils (e.g., Doerr et al., 2009; Jordán et al., 2013 and references therein). Hydrophobicity is at least in part attributed to a lipid-like cover, rich in fatty acids (FAs). Recently, we have shown that FAs had a major role in the water repellency observed in sandy soils in Doñana National Park (DNP, SW-Spain) under trees (Quercus suber, Pinus pinea) and shrubs (Pteridium aquilinum, Halimium halimifolium) vegetation (Jiménez-Morillo et al., 2016). To get further insight into how fire affect the distribution of soil lipids and their role in SWR, a study was performed on different size fractions of a DNP sandy soil under Quercus suber cover. Two soil samples were taken, one in a burnt site and another in an adjacent unburnt (control) one, both having the same physiographic characteristics. SWR was determined using water-drop-penetration-time test in the, The authors thanks the Spanish Ministry of Economy and Competitiveness (MINECO) through the INTERCARBON project (CGL2016-78937-R)

Soil water repellency (SWR) is caused by hydrophobic organic substances released by plant residues, roots or soil microorganisms that inhibit or delay rainwater infiltration. Banksia woodlands (BW) are iconic ecosystems of semi-arid environments of Western Australia (WA) comprised by an overstorey dominated by Proteaceae, e.g. Banksia menziesii and Banksia attenuata, in combination with other species, such as Eucalyptus spp. Although located in poor dune soils, BW provide numerous ecosystem services and sustain a high biodiversity. A characteristic feature of BW is their dimorphic root architecture, formed by a proteoid (cluster) system that radiate from the parent root and spreads to form thick mats below the soil surface. These clusters secrete large amounts of organic acids and phenolics to increase the uptake of P and other minerals that can be related to SWR. In contrast, the parent root penetrates soil deeply, reaching the water table. This study, conducted in natural BW of WA, aimed to assess SWR and its impact on water economy in relation with soil functioning and plant strategies for water uptake in pristine BW. Soil samples were collected at different depths (0-1, 1-10, 20-30 and 40- 50 cm) based on the different SWR severities found in each layer under field conditions. SWR was assessed under laboratory conditions in oven-dry samples (48 h, 105 ºC) and the chemical organic assemblage of bulked soil subsamples from each layer was analysed by direct analytical pyrolysis (Py-GC/MS). SWR 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 well aggregated soil layer where the 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. Among other soil organic compounds, well resolved 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%). 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.

4 figuras.- 3 referencias.- Póster presentado en el 21st. International Symposium on Analytical and Applied. Pyrolysis, 9-12 May 2016, Nancy, France, Burned soils restoration/rehabilitation techniques include tillage, tree logging, reforestation with native or non-native species, and other management. In some cases, restoration may cause additional impacts on soils, producing more severe damages than those caused directly by fire. Triggered soil erosion processes, loss of soil fertility and alterations in the hydrological cycle are among these negative impacts. Analytical pyrolysis (Py-GC/MS) together with graphic interpretation tools like van Krevelen¿s diagram [1] may be used to shed light on alterations caused by burning and restoration plans to soil organic matter (SOM). The objective of this research is to study fire impacts on SOM in a sandy soil under pine (Pinus pinea) forest affected by a severe fire in August 2012 in Doñana National Park (SW Spain). mm) collected from burned adjacent areas before (B) and after restoration practices (BR) (logging and extraction of burned trees). An adjacent unburned (UB) area was used as a control. Bulk soil samples and its fractions were studied by Py-GC/MS and the results were interpreted taking advantage of a van Krevelen diagram using the H/C and O/C atomic ratios calculated from the chemical formulas of compounds as inferred from their mass spectra. The percentage of main compound families obtained by analytical pyrolysis, including alkane/alkene pairs, unspecific aromatic compounds (UAC), peptides, methoxyphenols, fatty acids, carbohydrate-derived, N-compounds and polycyclic aromatic hydrocarbons (PAH), show conspicuous differences among bulk samples from the B, BR and UB control areas. Compared to the UB site, the samples from the B site showed lower proportions of lignin methoxyphenols and increased ones of UAC and PAH. It could be hypothesized that fire produced defunctionalization of methoxyphenols, increasing the proportion of soil recalcitrant compounds. In all cases, the coarse fraction showed a high content of carbohydrate-derived compounds and methoxyphenols followed by fatty acids that could be explained by litter inputs after the fire [2]. While the coarse fraction from BR soil showed the highest proportion of methoxyphenols, the UB coarse fraction showed the major proportions of alkyl compounds. On the other hand, although the SOM composition from fine fractions varied largely from one area to another, SOM was found generally more altered than in the coarse fractions. In fact, SOM from the UB fine fraction shows a high proportion of alyl compounds and comparatively lower of carbohydrate- and lignin-derived compounds. In contrast, SOM from B fine fraction did not show a high contribution of alkyl compounds, which may be due to a thermal cracking of alkane/alkene chains [3]. In addition, a high contribution of UAC and PAH was observed in this B fine fraction. Finally, the fine fraction of BR samples showed a high contribution from labile compounds, possibly due to topsoil mixing caused by tilling during rehab actions. The van Krevelen diagram applied to pyrolysis compounds differentiates among chemical processes caused by fire and rehab practices. Among the main processes identified are condensation (oxidation and hydration), demethylation (oxidation and dehydrogenation) and oxidation-reduction. Figure: van Krevelen diagram based in the chemical formula of the Pyrolysis compounds as inferred from their mass spectra. Atomic ratios are mean values of detected compounds [1] DW. van Krevelen. Fuel 29, 269-284, 1950. [2] NT. Jiménez-Morillo et al. Land Degrad Develop. 2014. DOI: 10.1002/ldr.2314 [3] JA. González-Pérez et al. Org Geochem. 39: 940-944. 2008. DOI: 10.1016/j.orggeochem.2008.03.014., Projects GEOFIRE (CGL2012-38655-C04-01) and POSTFIRE (CGL2013-47862-C2-1-R). The Spanish Ministry for Economy and Competitiveness and CSIC for their support. N.T Jiménez-Morillo is funded by a FPI research grant (BES-2013-062573)

Fire is considered one of the main disturbing factors of ecosystems at global scale. Among other impacts, fire causes include physical and chemical changes on soil organic matter (SOM) (González-Pérez et al., 2004). One of the main consequences of burning is the formation of highly refractory material with a high degree of aromatization, black carbon (BC) (Hedges et al., 2000). The chemical composition of BC and the intensity of fire impacts on SOM depend strongly on fire conditions (De la Rosa et al., 2008). Therefore, the knowledge of the intensity and duration of temperature peaks is key to understand these processes (Davis, 1959). Nevertheless, in situ-determination is difficult. Burning experiments under laboratory conditions and traditional analytical techniques have provided hardly interpretable and contradictory results on temperature and time of heating. The main objective of this research is to study the relations between temperature and fire resilience with the chemical composition of fire-affected organic matter, through the combination of two new analytical techniques: [i] solid-state 13C-NMR spectroscopy and [ii] carbon isotope ratio mass spectrometry. To achieve this, litter samples were collected below the canopy of oaks (Quercus suber) in the Doñana National Park (SW Spain). Litter was air dried and heated at 250, 300 and 350 oC in a muffle furnace during different periods of time (5 and 15 minutes). Unburned air-dried litter samples were used as control. After heating, litter samples were analyzed using 13C-NMR spectroscopy and ¿13C ratio mass spectrometry. 13C-NMR analyses showed that increasing temperature and time of heating contributed to a decreased content of both O-Alkyl C compounds (60-110 ppm, carbohydrates) and lignin-derived compounds (45-60 ppm) and increased content of aromatic compounds (110-160 ppm). Litter samples heated at 350 oC during 15 minutes showed the highest aromaticity (65%). The progressive increase of aromaticity may be related to the degradation of thermolabile compounds, like polysaccharides, becoming highly aromatic compounds (Almendros et al., 2003; Baldock & Smernik, 2002). On the other hand, lignin defunctionalization may also be occurring, which also contributes to the formation of aromatic compounds (Knicker, 2007). ¿13C values showed no significant differences among treatments below 300 oC and 15 minutes of heating compared to the control. Above these thresholds, the carbon isotope composition showed a progressive depletion, reaching a value of -31.8 ¿ at 300 oC and 15 minutes of heating (5.4 ¿ lower than control). The temperature-induced 13C-depletion may be explained by a removal of compounds rich in heavy isotopes, such as those derived from carbohydrates, by condensation in compounds with a high degree of aromatization (Bird & Ascough, 2012) or both processes. After 13C-NMR and ¿13C experiments, the highest aromatization was observed in samples heated at 300 oC during 15 minutes. Both techniques showed that ¿13C composition changes only when the proportion of aromatic compounds exceeds the proportion of O-Alkyl C. These results suggest that, in the case of fires with medium-high temperatures and duration, the combined utilization of these techniques may be a powerful tool to approach temperature peaks and time of heating., his research is a result of the GEOFIRE (CGL2012-38655-C04-01) and POSTFire (CGL2013-47862-C2-1-R) projects, funded by the Spanish Ministry of Economy and Competitiveness.

Póster presentado en la XVI Reunión Científica de la Sociedad Española de Cromatografía y Técnicas Afines (SECyTA2016) P‐ENV‐27, Low soil‐water affinity and soil water repellency (SWR, hydrophobicity) prevents water from wetting or infiltrating soils in burnt and unburnt ecosystems, triggering hydrological, geomorphological, geochemical, and biochemical changes. Fire may destroy, develop or even enhance SWR in previously wettable or water‐repellent soils. SWR is partially due to a lipid like cover, rich in fatty acids (FAs). Here we report the first results of a study on the effect of fire on the distribution of soil lipids and their role in the SWR. Two samples of sandy soil under Quercus suber canopy at the Doñana National Park (SW‐Spain) were taken. One come from a burnt site and the other from an adjacent unburnt (control) one, with the same physiographic characteristics. SWR was determined using water‐drop‐penetration‐time test in the 24 Fas and branched C>24 FAs, and negatively correlated with the even/odd FAs ratio. The 1 biosynthetic origin of these lipids and their transformation pathways during a fire will be discussed with the results of the ongoing measurements of the δ13CFA values.

Different fungal and bacterial response after fire is one of the first evidences that were reported in the literature. Divergent heat-resistance, different competitive capacities or even variable sensitivity grade to toxics substances have been proposed as the key factors determining these changes. In the last years, original soil pH and pH fire-induced changes have started to gain importance in the fungal and bacterial behaviour after fire, in both, wildfire and laboratory heating researches (Bárcenas-Moreno et al., 2011; Bárcenas-Moreno et al., 2016a; Bárcenas-Moreno et al., in press). Fungal proliferation is associated to low original pH (pH < 7, or acid conditions), owing to fungi appears to be more competitive than bacteria at this pH, although fungi can proliferate without problem at pH above 7. Therefore, bacteria proliferation after fire is related to pH fire-induced increment associate to ash deposition. Bárcenas-Moreno et al. (2011) found evidences of fungal facilitation to bacterial recovery when pre- and post-fire soil pH is below 7. One possible explanation suggested is related to fungal enzymatic capacities, which could allow fungi to be more competitive against fire-induced organic toxics compound, being releasedby partial combustion of organic matter. Fungal detoxification of soil in the first post-fire moment could facilitate subsequent bacterial colonization. In addition, we should take into account that vegetation plays an important role determining microbial community composition and function, since, plant species composition conditions organic matter quantity and quality (Bárcenas-Moreno et al., 2014). Thus, the establishment of fungal community associated to different plant community and soil pH, could allow us predict the potential response of microbial community after fire conditioned by pH fire-induced changes. In this preliminary study to deepen the fungal role in soil ecology after fire, we isolate soil fungi from, different forest unaltered areas with different pH and original vegetation, and fungal abundance. Diversity and enzymatic capacity to degrade Polycyclic Aromatic Hydrocarbons (PAHs) of viable and cultivable fungi were analysed. In addition, in one of the forest areas selected, we include an area that was burnt 6 years before and compare with the unburnt one. Soil samples were collected under the influence of pine, holm oak, kermes oak, cork oak, rockrose and high mountain shrubs from different geographical areas in the South of Spain. Soil samples collected under cork oak showed the highest viable and cultivable fungal abundance of all samples studied, while soil from high mountain shrubs displayed the lowest one. Nevertheless the number of different fungi isolated was more variable. The average percentage of fungi with laccase activity among all isolates was around 20%, with the highest percentage found under high mountain shrubs and the lowest one under pine on basic conditions (pH < 7) where no isolate was found with this activity. The results obtained in this preliminary study can help us to design new project in order to determine the potential role of fungi in different forest environment susceptible to suffer a wildfire in the future.

Poster presentado en lal EGU General Assembly 2015, held 12-17 April, 2015 in Vienna, Austria. id.2248, Wildfires may cause significant changes in soil physical and chemical properties. In addition, soil organic matter (SOM) content and chemical properties are usually affected by fire. Fire impacts may negatively affect soil health and quality, and induce or enhance runoff generation and, thereby, soil erosion risk and cause damages to the habitat of species. This fact is especially dramatic in Mediterranean ecosystems, where forest fires are a frequent phenomenon and restoration strategies are a key issue. The goals of this study are to determine: i) the immediate effects of fire on soil properties, including changes occurred in the quantity and quality of SOM and ii) the effect of post-fire actions on soil properties. In August 2012, a wildfire affected a forest area of approx. 90 ha in Montellano (Seville, SW Spain; longitude 37.00 º, latitude -5.56 º). This area is dominated by pines (Pinus pinaster and Pinus halepensis), and eucalypts (Eucaliptus globulus) with a Mediterranean climate. Dominant soil types are Rendzic Leptosols and Calcaric Haplic Regosols. It is a poorly limestone-developed soil (usually swallower than 25 cm). Four soil subsamples were collected 1 month and 25 months after fire within an area of approximately 200 m2. Subsamples were mixed together, homogenized, air-dried, crushed and sieved (2 mm). One control sample was collected in an adjacent area. The litter layer was removed by hand and studied separately. Branches, stems, bushes and plant residues on the fire-affected area were removed 16 months after the fire using heavy machinery as part of the post-fire management. The present research focuses on the study of the elemental composition (C, H and N) and physical properties (pH, water holding capacity, electrical conductivity) of bulk soil samples, and on the spectroscopic analysis (FT-IR, 13C NMR) and analytical pyrolysis data obtained from bulk the oils and from the humic acid fraction. immediate effects of fire, including the charring of vegetation and litter, as the input of charred residues may contribute to increase the total amount of soil organic matter. The post-fire removal of vegetation probably contributed to an additional loss of soil material due to an increase of the erosion risk. In addition, preliminary results point out that the burnt soil is not being recovered to the pre-fire conditions at a molecular level neither in the elemental composition. Results of this study will constitute a valuable tool for stake holders and decision makers to avoid additional alterations caused by post fire management of fire affected forests.

Poster presentado en EGU General Assembly 2014, held 27 April - 2 May, 2014 in Vienna, Austria, Soil is the largest carbon reservoir of terrestrial ecosystems, this reservoir is not inert, but it is constantly in a dynamic phase of accumulation an depletion. After the addition, in the soil, of organic residues of different origin and nature, two processes can occur in charge of SOM (Soil Organic Matter) during the pedogenesis: mineralization and humification. The accumulation of SOM in soil is controlled by the balance between carbon inputs and losses through mineralization and/or leaching. In particular the humification process leads to the formation of organic compounds (in some cases even complex organo-mineral) chemically stable able to distribute itself in the soil second rules of site-specific pedogenesis. The transport process along the profile can take very different forms which may extend in the formation of Bh horizons of accumulation in depth also strongly cemented (so-called ortstein). The transport process along the profile occurs for the occurrence of certain conditions such as deposition of high amounts of organic residues on the top of the profile, high porosity of the soil for the presence of coarse solid fractions (coarse sands or skeleton) that determinate a strong infiltrating capacity of the circulating waters, extreme temperatures can slow or stop the process of mineralization and/or humification in one intermediate step of the degradation process releasing organic metabolites with high or medium solubility and high loads of percolating water related to intense rainfall. The nature of the forest cover influence the quantity and quality of the organic materials deposited with marked differences between coniferous and deciduous especially in relation to resistance to degradation and production of intermediate metabolites. Two soils from Campania region located in Monte Santa Croce (Caserta, Italy) with andic properties, different forest cover (pine and chestnut) and that meets the requirements of the place and pedological formation suitable for the formation and accumulation of SOM in depth (Bh horizon) were studied. The content of the different soil C fractions was assessed for each soil profile and included: total extractable C, (TEC), total organic C (TOC), total extractable lipds (TEL), humified C (humic and fulvic acids, HA & FA) and non humic C (NHC), lignin C, cellulose C. Also were calculated parameters of humification, humification degree (DH), humification rate (HR), total level of humification (HU) and humification index (HI). The results are discussed in terms of how soil use and vegetation influences the identified C pools, and the humification indexes.

Presentación de la Comunicación oral presentada presentado en el EGU General Assembly 2014, 27 April- 2 mayo (2014), Vienna, Austria, 1. INTRODUCTION Climate change is predicted to have a large impact on semi arid areas which are often degraded and vulnerable to environmental changes (Muñoz-Rojas et al., 2012a; 2012b; 2013). However, these areas might play a key role in mitigation of climate change effects through sequestration of carbon in soils (United Nations, 2011). At the same time, increasing organic carbon in these environments could be beneficial for soil erosion control, soil fertility and, ultimately, food production (Lal, 2004). Several approaches have been carried out to evaluate climate change impacts on soil organic carbon (SOC) stocks, but soil carbon models are amongst the most effective tools to assess C stocks, dynamics and distribution and to predict trends under climate change scenarios (Jones et al., 2005 ). CarboSOIL is an empirical model based on regression techniques and developed to predict SOC contents at standard soil depths of 0 to 25, 25 to 50 and 50-75 cm (Muñoz-Rojas et al., 2013). CarboSOIL model has been designed as a GIS-integrated tool and is a new component of the agroecological decision support system for land evaluation MicroLEIS DSS (De la Rosa et al., 2004). 2. GENERAL METHODS In this research, CarboSOIL was applied in El-Fayoum depression, a semi arid region located in northern Egypt with a large potential for agriculture (Abd-Elmabod et al, 2012). The model was applied in a total of six soil-units classified according the USDA Soil Taxonomy system within the orders Entisols and Aridisols under different climate climate change scenarios. Global climate models based on the Organisation for Economic Co-operation and Development (Agrawala at al., 2004) and the Intergovernmental Panel on Climate Change (IPCC, 2007) were applied to predict short-, medium- and long-term trends (2030, 2050 and 2100) of SOC dynamics and sequestration at different soil depths (0-25, 25-50 and 50-75) and land use types (irrigated areas, olive groves, wheat, cotton and other annual crops, and fruit trees and berries). 3. RESULTS AND CONCLUSIONS According to results, considerable decreases of SOC stocks are expected in the 25-50 cm soil section under all considered land use types and all projected scenarios, in particular in Vertic Torrifluvents and Typic Torrifluvents under wheat, cotton and other annual crops. Oppositely, SOC stocks tend to increase in the deeper soil section (50-75 cm), mostly in Typic Haplocalcids under permanently irrigated areas and olive groves in the 2100 scenario. In the upper layer (0-25 cm), slight increases have been predicted under all considered land use types. The methodology used in this research could be applied to other semi arid areas with available soil, land use and climate data. Moreover, the information developed in this study might support decision-making for land use planning, agricultural management and climate adaptation strategies in semi arid regions.