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Los incendios forestales son un factor de perturbación importante en muchos ecosistemas terrestres, especialmente en las zonas europeas de clima Mediterráneo. Esto se debe a la confluencia de condiciones climáticas, ecológicas y socio-económicas específicas. El fuego produce cambios importantes en la materia orgánica del suelo (MOS) tanto a nivel cualitativo como cuantitativo, que afectan, a su vez, a propiedades físicas, químicas y biológicas relevantes del suelo. Estos cambios afectan también a un gran número de factores y procesos bióticos y abióticos relacionados entre sí. El principal objetivo de esta Tesis Doctoral es el de profundizar en el conocimiento del impacto de los incendios forestales sobre la MOS en relación con los cambios en la repelencia al agua del suelo, empleando para ello técnicas avanzadas de análisis molecular. Debido al elevado número de variables que pueden influir en la repelencia al agua del suelo y la alteración química de la materia orgánica tras el fuego, para este estudio se eligieron los suelos arenosos del Parque Nacional de Doñana, suelos bien conocidos y poco complejos. En todo caso, para conocer el efecto del fuego, se ha seguido el esquema clásico de comparación de suelos quemados con suelos no afectados (control), de idénticas características geomorfológicas y climáticas. La repelencia al agua es una de las principales propiedades edáficas afectadas por los incendios forestales. Esta propiedad física reduce la afinidad del suelo por el agua, lo que conlleva importantes consecuencias hidrológicas, geomorfológicas y ecológicas en los ecosistemas terrestres. Los cambios inducidos por el fuego sobre esta propiedad pueden deberse a numerosos factores, aunque se admite que la principal variable implicada es la alteración que produce en la MOS, y en particular en su fracción más lábil (fracción lipídica) que tiene un marcado carácter hidrofóbico. Debido a sus implicaciones medioambientales, actualmente existen innumerables trabajos sobre los efectos del fuego en la MOS y la repelencia al agua, que se revisan en el capítulo 1. Sin embargo, el estado actual del conocimiento muestra algunas lagunas y aspectos insuficientemente estudiados, bien debido a la complejidad inherente al sistema suelo o bien por la falta de técnicas analíticas adecuadas. Numerosos trabajos científicos indican que tanto el tipo de vegetación, como la composición química de la MOS influyen marcadamente sobre la repelencia al agua en el suelo. Estos trabajos se han centrado principalmente en el estudio de suelos completos tanto en superficie como a diferentes profundidades. Sin embargo, la información existente sobre la influencia de la materia orgánica y la vegetación en el grado de hidrofobicidad de diferentes fracciones físicas del suelo es limitado. Este aspecto se estudia en detalle en el capítulo 3. En concreto se estudia la relación entre suelos bajo diferentes cubiertas vegetales, dominadas por alcornoques (Quercus suber), helecho águila (Pteridium aquilinum), pino piñonero (Pinus pinea) y jaguarzo (Halimium halimifolium), la cantidad y calidad de la materia orgánica, y la repelencia al agua en cuatro fracciones de tamaño de partículas (1-2, 0.25-1, 0.05-0.25 y 24, y el ratio alcanos de cadena corta/larga, C

BACKGROUND: Environmental, economic and safety challenges motivate shift towards safer materials for food packaging. New bioactive packaging techniques, i.e. addition of essential plant oils (EOs), are gaining attention by creating barriers to protect products from spoilage. Analytical pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) was used to fingerprint a bioactive polylactic acid (PLA) with polybutylene succinate (PBS) (950 g kg-1:50 g kg-1) film extruded with variable quantities (0, 20, 50 and 100 g kg-1) of Origanum vulgare EO. RESULTS: Main PLA:PBS pyrolysis products were lactide enantiomers and monomer units from the major PLA fraction and succinic acid anhydride from the PBS fraction. Oregano EO pyrolysis released cymene, terpinene and thymol/carvacrol peaks as diagnostic peaks for EO. In fact, linear correlation coefficients better than 0.950R2 value (P < 0.001) were found between the chromatographic area of the diagnostic peaks and the amount of oregano EO in the bioplastic. CONCLUSION: The pyrolytic behaviour of a bio-based active package polymer including EO is studied in detail. Identified diagnostic compounds provide a tool to monitor the quantity of EO incorporated into the PLA:PBS polymeric matrix. Analytical pyrolysis is proposed as a rapid technique for the identification and quantification of additives within bio-based plastic matrices. Ministerio de Economía y Competitividad GL2012-38655-C04-01, AGL2012-38357-C02-01 Junta de Andalucía AGR-7252

Fire alters soil organic matter inducing quantitative and qualitative changes that presumably will affect post-fire soil microbial recolonisation. Several studies have evidenced marked soil organic carbon reduction after moderate and high intensity fire, which limit the total recovery of microbial biomass during years. In order to evaluate the role of soil organic matter alteration in short-term microbial colonization process, we perform a preliminary experiment where unaltered soil from Sierra Nevada Natural Park was heated at 300 ºC during 20 minutes in a muffle furnace (H300) to simulate a medium-high intensity fire. After heating, soil samples were inoculated with unaltered fresh soil, rewetted at 55-65% of water holding capacity and incubated during 3 weeks. At the same time, unheated soil samples were incubated under the same conditions as control (UH). In addition, trying to partially alleviate soil organic matter fire-induced alterations effects on microbial colonization, we include an organic amendment treatment (M+). So, part of heated and unheated samples were amended with a mix of ground alfalfa:straw (1:1) and soil microbial abundance and activity were monitored together with soil organic matter changes. Heating process reduces total organic carbon content. After one week of incubation carbon content in heated samples was lower than the control one, in both, amended and un-amended samples. Microbial biomass and respiration were negatively affected by heating. Ground mulching addition increase microbial biomass and respiration but was not enough to reach control values during the whole study. Nevertheless, viable and cultivable fungi and bacteria showed different pattern. After two weeks of incubation both, fungi and bacteria were higher in heated samples. Ground mulching addition appears to stimulate fungal response in both, heated and unheated samples. Preliminary results of this experiment evidence the transcendence of soil organic matter fire-induced changes on microbial colonization process and the importance to determine several microbial parameters to obtain a more faithful conclusion about microbial response. The organic amendment appears to alleviate partially heated-induced damage, highlighting the positive stimulation on fungal abundance in both, heated and unheated samples. Ministerio de Economía y Competitividad CGL2013-47862-C2-1- R Ministerio de Economía y Competitividad CGL2012-38655-C04-01

Depending on soil and fire characteristics, soil water repellency (SWR) may be induced, enhanced or destroyed by burning. The spatial pattern of SWR may be extremely heterogeneous as a consequence of the temperature peaks, the variation of fire temperature, the distribution of fuel, or the amount and type of ashes. In this research, we have studied the effect of stone cover and position on the intensity and spatial distribution of fire-induced SWR after low-, moderate- and high-severity fire. Generally, SWR increased with fire severity, but stones did induce some differences and increased the heterogeneity of the spatial distribution of fire-induced SWR. In low-stone-cover areas, SWR from soil surfaces below stones increased respect to non-covered soil surfaces. In areas under high stone cover, SWR increased from non-covered soil surfaces to soil surfaces below stones after low-severity fire. In moderate- and high-severity burnt soils under high stone cover, SWR was more severe than in non-covered soil surface, but no significant differences were observed. Ministerio de Economía y Competitividad CGL2010-21670-C02-01

Water repellency is a property of many fire-affected soils that contributes to delayed wetting rates and shows many hydrological and geomorphological consequences. Fire-induced soil water repellency (SWR) may be modulated by pre-fire soil and vegetation properties. Many studies have been carried out to investigate the relationship between SWR and these properties. But, to our knowledge, no studies have considered the effect of surface stones in the spatial distribution of fire-induced SWR. In this research, we study the occurrence and spatial and vertical distribution of SWR and its consequences on soil structure after experimental burning in a previously wettable soil under different stone covers (0, 15, 30, 45 and 60%). In our experiment, burning induced critical or subcritical SWR in the upper millimetres of previously wettable soil. Fire-induced SWR did not vary with stone cover, but critical SWR was reached in inter-stone soil areas. At stone-covered soil areas, SWR was increased, but WDPTs remained mostly below the 5 s threshold Ministerio de Economía y Competitividad CGL2010- 21670-C02-01

Crude oils can be described compositionally by a number of methods. SARA analysis divides crude oil fractions (saturated hydrocarbons, aromatic hydrocarbons, resins, asphaltenes) according to their polarisability and polarity using a family of related methods. Problems appear because several of the analytical methods in use do not produce approximately similar results. In this work we tried to make a correlation of two SARA analysis methods: gravity-driven column chromatographic separation (LC) and thin layer chromatography combined with flame ionisation detector (TLC-FID, Iatroscan). In a correlation study we have used different standard crude oils: North Sea Oil-1, ASTM oil #CO1207 USA (July 2012) and the Pannonian (Croatian) oils: Privlaka-13, Hrastilnica-3, Đeletovci-1 Zapad oil, as samples. Samples were analysed repeatedly over a period of several months by both SARA analysis methods. All of the mentioned oils are mostly paraffinic-aromatic types of oil. Different solvents to dissolve maltenes were used for each method and results for LC method are expressed in mass percentages while results for TLC-FID (Iatroscan) method percentages are calculated directly from the raw peak areas. Results that are given in the table show the range of correlation coefficients for saturated hydrocarbons to be from 1, 15-1, 49, aromatic hydrocarbons 1, 23-1, 95, resins 0, 32-0, 41 and asphaltenes 0, 55-0, 84. NSO-1 is a deasphaltened oil from the Oseborg field, Norway. However, using both of the techniques, the presence of asphaltenes in the NSO-1 oil was determined. Analysis of the composition of crude oils can be endlessly complexed, therefor, many reasons are possible to explain such oscillations in the results. The use of different solvents can be one of the factors ; variability of the FID response in Iatroscan method (which can also be due to differences in ionisation efficiency resulting from slight variations of the concentration of material in the adsorbent phase) ; the amount of sample taken for the analysis, overloading in a very small spot at the origin of the rod and many other reasons. Despite the oscillations in the results, the coefficient range for each crude oil fraction does show some correlation between the used methods.