David Badía-Villas

Abstract: La Sociedad Española de Ciencia del Suelo (SECS) celebra periódicamente encuentros científicos (Reuniones) en determinadas localidades para, a través de salidas de campo, conocer los suelos de la zona. Con motivo de la celebración de estas reuniones, las personas implicadas en la organización acostumbran a recoger dicho conocimiento en un libro o memoria de excursiones. El libro se suele distribuir durante la celebración de la Reunión pero fuera de la misma es muy difícil acceder a ella a pesar del indudable interés que tiene para diferentes colectivos. Por esta razón, el Instituto de Estudios Altoaragoneses ha sido receptivo al publicar la información de la 27Reunión SECS, que tiene a Huesca como sede, en un Cuaderno Altoaragonés de Trabajo. De esta forma se garantiza la supervivencia de la misma más allá de la Reunión. Esta edición tiene lugar veinte años después de que el propio Instituto de Estudios Altoaragoneses, a través de su Colección de Estudios Altaroagoneses, editara la monografía de los suelos de Fraga; se da también la circunstancia que han transcurrido treinta años de la única reunión de suelos celebrada en Aragón (Zaragoza, 1979). A diferencia de esa pasada edición, que se centró en el valle del Ebro, dándole especial protagonismo a los suelos afectados por sales, en la presente reunión científica se ha optado por darle más énfasis a los suelos del piedemonte, Hoyas y Somontanos, y del propio Pirineo. Pero no nos olvidamos del sur, de forma que este trabajo recoge un transecto Norte-Sur que nos conducirá desde las más altas cumbres pirenaicas a las áridas estepas. A lo largo de estos dos ambientes extremos se incluyen los últimos glaciares ibéricos, pasando por bosques atlánticos y mediterráneos, sierras calizas, profundos cañones, depresiones intrapirenaicas, suaves piedemontes cultivados con olivos, almendros y viñedos, valles fluviales orlados por terrazas en graderío, sierras culminadas por iglesias románicas y castillos estratégicos, planícies semiáridas salpicadas de espartales y romerales, secanos y regadíos, lagunas temporales, endorreicas y saladas. Una amplia riqueza de ambientes y ecosistemas que se engloban en la denominada Magia de Huesca. Evidentemente esta diversidad paisajística del Alto Aragón tiene su expresión en los suelos, todavía insuficientemente estudiados en detalle. Con el fin de contribuir al conocimiento edafológico de esta región, se ofrece este trabajo. Este libro se ha estructurado en los siguientes apartados: la primera parte revisa el clima, litología, geomorfología y organismos vivos en el Alto Aragón, indicando el papel que tienen como factores formadores de suelos. Seguidamente se expone a través de qué procesos actúan los citados factores para dar lugar a los suelos. Los tipos de suelos, su denominación, se revisan en el siguiente capítulo siguiendo la clasificación de la Unión Internacional de las Ciencias del Suelo (IUSS), y la taxonomía norteamericana (STS). Finalmente se proponen cuatro rutas por los cuatro puntos cardinales del Alto Aragón, en concreto por las comarcas de la Hoya de Huesca, Sobrarbe, Somontano de Barbastro y Bajo Cinca. En estas rutas se describe con detalle el itinerario, los factores de formación de los suelos y se anexan varios perfiles representativos de la zona con detallada información de las propiedades físicas y químicas de los mismos.

Abstract: El Aiguabarreig es la unidad fluvial más extensa y probablemente de mayor interés biológico de la Península Ibérica, situada a caballo entre Aragón y Catalunya. En el Aiguabarreig confluyen, junto al área estrictamente fluvial, ambientes esteparios y mediterráneos que dan cabida a multitud de especies florísticas y faunísticas en un heterogéneo relieve. El interés naturalista de esta zona tiene su reflejo en la multitud de figuras de protección existentes a lo largo de los municipios de Torrente de Cinca, Mequinenza, Massalcoreig, La Granja d�Escarp, Seròs y Almatret. Así aparecen Espacios de Interés Natural (EIN), Lugares de Interés Comunitario (LICs) y Zonas de Especial Protección para las Aves (ZEPAs). Dado el extraordinario interés biogeográfico del Aiguabarreig, este trabajo aborda el estudio de sus paisajes y sus suelos, así como su distribución en el espacio. Disponer de una cartografía de los paisajes y sus suelos, sus propiedades, sus aptitudes y sensibilidad frente a los cambios de uso, puede servir para una correcta gestión del territorio. Esto tiene especial interés en el Aiguabarreig, donde existe una gran competencia por diferentes usos (agrícola, ganadero, turístico, industrial) y donde la ordenación del territorio debe abordarse desde diversas administraciones. Además se trata de una zona donde el hombre ha incidido en el medio natural desde tiempos inmemoriales atraído por el agua de los flumen Cinga, Sícoris e Hiberus. Y es que en el Aiguabarreig confluyen estos tres grandes ríos, Cinca, Segre y Ebro, que permiten aportar el verde vital al también hermoso gris de sus alrededores. El objetivo de este trabajo consiste en caracterizar y cartografiar los paisajes y los suelos del Aiguabarreig. El libro se estructura en cuatro grandes apartados. En su primera parte se describen el clima, la litología, el relieve, la vegetación y la fauna del Aiguabarreig. En este apartado, donde el lector encontrará recombinación más que creación, se recoge de forma sintética pero magníficamente ilustrada cuáles son los extraordinarios valores naturales de la zona. En un segundo apartado, el libro se centra ya en los suelos, esa porción del ecosistema que es fundamental para la vida aunque pase desapercibida para la mayoría de observadores; se indica cómo se forman los suelos, que propiedades tienen y qué nombre reciben además de ver como se distribuyen en la geografía del Aiguabarreig. En la tercera parte se aborda la interacción que establecen cada uno de los elementos del medio natural para configurar las unidades de paisaje del Aiguabarreig actual. En un cuarto apartado se recogen las principales tipologías de suelos de la zona, de forma individualizada; así se describen, con detalle, una veintena de los suelos estudiados. Se da buena cuenta de las propiedades morfológicas, físicas y químicas de cada perfil edáfico y los horizontes que lo constituyen. Con la bibliografía y los anexos metodológicos finaliza esta obra. Aun tratándose de un libro técnico, los autores han huido de la sobriedad de un trabajo de investigación incluyendo numerosos esquemas, tablas y fotografías que facilitan la comprensión de la información escrita. Además los excelentes mapas que acompañan el texto aportan al lector una rápida visión de la distribución espacial de los diferentes componentes del medio natural del Aiguabarreig.

Abstract: Soil organic carbon and nutrient content are analysed at topsoil cm-scale in a Rendzic Phaeozem from an Aleppo pine forest in semiarid Central Ebro Basin (NE-Spain). Soil depth affected by a severe wildfire is studied immediately after burning and a year later, trying to differentiate the heat shock and the ash/charcoal deposition effects. One week after the wildfire, soil organic carbon content (SOC) on burned topsoil decreases significantly at 0�1 cm soil depth. Wildfire degrades polysaccharides and proteins and eliminates, or at least reduces, biogenic compound markers, derived from lignin and lipids, but only above 2 cm soil depth. A characteristic cracking in the alkane series, as well as the presence of pyrogenic polycyclic aromatic hydrocarbons are also observed in the burned 1st cm topsoil. Below 2 cm the fire has little or no effect in soil organic matter molecular assemblage. Calcium, magnesium, potassium, ammonium, nitrate and phosphorous increased significantly a week after the fire, in the first cm soil depth. These modifications detected immediately after the fire (SOC decrease and nutrient increase) are related to the heat released during the severe wildfire. One year after the wildfire, SOC in the 1st cm of burned topsoil regain the same level to that observed in unburned sites, which could be a consequence of burned residues and black ash incorporation and even new inputs on soil surface derived from the reblooming processes, which starts after the fire. With the exception of nitrates whose concentration is higher in burned plots than the control ones within 0�3 cm of soil depth studied, nutrient concentration relatively decreased one year after the wildfire. Despite this decrease, fire effect (memory) still remains at the 1st cm topsoil, with many nutrients having comparatively high concentration in the burned soils under semiarid climate.

Abstract: Pedofeatures can be repositories of information about soil forming factors such as climate. The aim of this work is to provide a model of interpretation of a polygenetic soil in the Monegros desert (Ebro Basin, NE-Spain) and its relationship to environmental changes during the Quaternary. To achieve this goal, the physical, chemical, mineralogical and especially the micromorphic pedofeatures of this profile were studied. Carbonate accumulations extend into all of the horizons of the profile. The paleosol has a thick petrocalcic horizon at the top, with a massive-laminar structure comprising layers of micrite and sparite that sometimes form pendants. Towards its base, the petrocalcic horizon contains a spaced framework of orthic micrite nodules packed between relatively pure micritic laminar bands. Below the petrocalcic horizon, coatings and infillings of microcrystalline calcite occur in old channels, and soft concretions (some of them geodic) indicate an in situ accumulation process (Bkc, calcic horizon). Another calcic horizon with orthic nodules of calcite, impregnative and diffuse (Ckc), is present at the bottom part of the profile. Between the two nodular calcic horizons, two recarbonated argic horizons are found (Btkc and Btk) with coarse orthic nodules of dense micrite superimposed on textural pedofeatures. These textural micromorphic pedofeatures are: (1) interbedded microlaminated clay pockets not associated with current or past pores and (2) microlaminated clay and silt (dusty clay) present as weakly oriented coatings on channel walls. Reduction pedofeatures are associated with textural ones: (1) coatings of manganese oxides around pore channels and cracks, and (2) nodules of manganese and iron oxides within the peds. The presence of calcic horizons alternating with argic horizons, all positioned below the petrocalcic horizon, confirm fluctuations in paleohydrological conditions in the Pleistocene. Its presence indicates that the oldest soil corresponds to a Calcic Luvisol-like pedotype, which is overlain by an Haplic Calcisol-like pedotype and this, in turn, by a Petric Calcisol-like pedotype. This superposition of profiles indicates, within the mentioned climatic changes, a tendency towards increasing dryness during the Pleistocene in the semiarid Ebro Valley

Abstract: Soil water repellency has been studied for different soil types and plant covers, but uncertainty exists regarding the representativeness of water repellency measured on unaltered soil surfaces compared to sieved samples. Two different methods are used to characterize water repellency, which provide a certain degree of different information: the persistence of soil water repellency, measured by the water drop penetration time (WDPT) test; and the intensity of soil water repellency, measured by the ethanol percentage (EP) test. The main objectives of this research were to analyze the relationships between soil water repellency measured on undisturbed soil blocks and 2-mm hand sieved samples, and to compare the results between both methods (WDPT and EP tests). Water repellency was measured on the surface and at soil depths of 2 cm and 5 cm for three fine textured soil types (Rendzic Phaeozem, Hypercalcic Calcisol, and Eutric Cambisol) developed below different plant covers (mossy pine forest, evergreen oak forest, and meadow, respectively). At the class level, WDPT and EP tests offered similar results for unaltered and sieved samples. The EP test tends to slightly overestimate values on sieved samples, whereas the WDPT test tends to slightly underestimate measurements on sieved samples. Based on the good relationship between the two types of soil samples used (unaltered and sieved), conversion formulas for both tests have been obtained: a linear regression for EP test (R2=0.862; p<0.001) and a logarithmic model for WDPT test (R2=0.913; p<0.001). Differences in the wettability has been observed between soil depths and soil types: Rendzic Phaeozem under pinewood is very strongly hydrophobic and consistently severely water repellent at any soil depth; Hypercalcic Calcisol under oakwood has the same behavior on the surface, but water repellency decreases progressively with depth; finally, Eutric Cambisol under meadows is hydrophilic and mainly wettable for all depths.

Abstract: Mediterranean ecosystems have been severely affected by fires in the last decades. Due to social and economical changes, wildfires have caused hydrological and geomorphologic changes to be more pronounced, resulting in enhanced soil erosion. Soil heating caused by fires affects soil aggregate stability, water infiltration and may generate hydrophobicity. In order to understand how wildfire affects the soil hydrological behavior in general, and infiltration and runoff processes in particular, it is advantageous to use a rainfall simulator. Over the burnt areas wood-chips mulching was applied in order to reduce the rain splash, and to measure the erosion reduction. The study was carried out on gypseous and calcareous soils in northeast Spain, affected by wildfire in 2009. Results showed that gypseous soils have higher runoff rates and sediment production compared to calcareous soils. The application of wood-chips reduced in all cases runoff and sediment yield and the effect of fire on water repellency was apparent especially on calcareous soils.

Abstract: We investigate the effects of bedrock and slope position on soil diversity in a semiarid, wooded, mountainous environment, and we use these results to examine differences between the current diagnostic criteria of the Soil Taxonomy System (STS) and World Reference Base (WRB) classification systems. To achieve these objectives, we characterize a total of ten pedons occurring across representative catenas on limestone and gypsum bedrocks. Differing parent material causes the most variation among diagnostic horizons of the soils. In soils overlying limestone catena, a mollic horizon can be consistently defined according to STS criteria. But according to WRB criteria, a mollic definition can receive different interpretations due to differing color values associated with high lime content and its bleaching action, as well as the introduction of the concept �finely divided lime�. In soil classification, it is proposed to consider the concept �equivalent calcium carbonate�. Under these assumptions, soils in limestone catena are classified as Lithic Haploxerolls/Rendzic-Epileptic Phaeozems at the top, which transition into Pachic Haploxerolls/Rendzic Phaeozem at the mid-slope. The foot slope of the limestone catena also includes occasional Pachic Calcixerolls/Calcic Chernozems, through the presence of calcic horizons. Topography causes variations in soil depth and water retention, which tend to increase from the top of the hillslope to its base, and for this reason, the estimated soil moisture regime changes from aridic, at the top, to xeric along both catenas. This feature strongly influences soil classification, especially in gypsum catena because the soil moisture regime is used at first taxonomic level in STS. The STS soil classification is therefore tentative, given uncertainties concerning the exact soil climate regime. The soils of uppermost areas of gypsum catena are classified as Leptic Torriorthent/Haplic Leptosol (gypsiric) according to the STS and WRB while soils from the middle and lower slope, with prominent pedogenic gypsum accumulations, are classified as Gypsic Haploxerept by STS. These soils would correspond to different units (Hypergypsic, Haplic or Salic Gypsisols) according to the WRB, a level of specificity contributed to in part by mineralogical class in the STS. Similarly to the equivalent calcium carbonate, the term �equivalent gypsum� should be used. At the base of gypsum catena, a salic horizon is defined according to the WRB but not according to the STS due to differences in its definition, which should be standardized. This study shows that the current versions of the STS and WRB include certain inconsistencies that require clarification and standardization in order to serve as a foundation for a universal classification system and to improve the systems themselves.

Abstract: The crop residues buried in semiarid soils as a carbon sink are evaluated. Both C-CO2 evolved and C sequestered from agricultural soils amended with barley straw were measured seasonally over 2 farming seasons in a semiarid environment (NE Spain). Six experimental soils with low organic matter content and contrasted properties were selected. The CO2 efflux, as a result of soil microbial activity, showed a significant seasonal variation according to changes in both soil moisture and temperature being the spring and early summer when respiration rates get higher. On annual average, more organic, calcareous soils, evolved higher carbon dioxide efflux (up to 53 mg CO2/kg and day) than soils with high levels of gypsum or more soluble salts (up to 25 mg CO2/kg and day), which have a lower percentage of organic carbon. Straw residue incorporation increases these CO2 emissions significantly for each soil type. Although CO2 emissions are significantly and negatively correlated with the C storage, straw addition increases soil organic C content, at the end of the period of study. Calcareous soils stored up to 550 kg C/ha and year, gypseous soils up to 1135 kg C/ha and year and saline soils up to 1450 kg C/ha and year. According to the amount of stored C in the different soil types, the isohumic coefficient of barley straw ranges from 0.087 to 0.259 (kg of humus formed from 1 kg of dry straw).

Abstract: After a wildfire the soil is covered by ash. Ash properties depend on vegetation type, amount of fuel and fire intensity. The ash layer controls the post-fire soil hydrologic response, but little is known about the effect of ash thickness and ash type on infiltration, which is relevant for post-fire runoff and soil losses and for ecosystems rehabilitation and restoration. This paper analyses the role of i) ash type (black or white), ii) thickness (5, 15 and 30 mm-thick) and iii) temporal variation (0, 15 and 40 days) under three simulated rain events (55 mm for 1 h) on soil surface hydrology. The rainfall was simulated on 0.25 m2 plots, and time to ponding, runoff and runoff discharge were measured. The infiltration rates, the initial infiltration rate (f0), the steady-state infiltration rate (fc), and the infiltration decay factor (k), were calculated and the Horton infiltration equation applied. The results show that soils covered with white ash doubled the runoff rates of soils covered with black ash. In general, runoff decreases as the ash thickness increases and the runoff decreases with the number of rainfall events after the fire in plots coveredwithwhite ash. Ponding time and k are positively correlated by the ash thickness and f0 and fc are correlated by the rainfall events (in three runs). Ash type and ash depth are key factors on the soil hydrology after a wildfire.

Abstract: The Central Ebro Valley, one of the most arid regions of Europe, has one of the longest histories of continuous and sustainable irrigation within Europe. Despite this sustainable outcome, the further expansion of irrigation into areas that have less favorable soil conditions produces unfavorable results and environmental problems. A representative soil toposequence of currently rainfed agricultural land, located very close to El Basal protected area, has been characterized in order to get information on the soils and to assess their capacity to be irrigated. The studied toposequence comprises three different landforms, a structural platform, a depression, and a step which links them; in these landforms soil profiles were described, analyzed, and classified using standard methodologies. <br /><br />The soil properties and their stages of pedogenic evolution are closely related to their topographic position. Petric Calcisols on the structural platform and Leptic Regosols on the step, both with very shallow rooting depth, give way to a series of salt-affected soils in the depression, such as Hypersalic Solonchak or Salic Solonetz. These severely salt-affected soils, which are included in irrigation plans, have the severe potential to limit agricultural management and plant production; moreover, their proximity to the protected area of El Basal, which includes a saline wetland, is inadvisable due to the probable changes in water and nutrient cycles. For these reasons, a buffer zone around the protected area is proposed. Moreover, the soil toposequence shows a great pedodiversity that should be considered as adding value to the recognized biodiversity of El Basal area.

Abstract: A macro- and micromorphologic study was done on the soils from a stepped sequence of seven dated fluvial terraces in the lower Segre river valley (Lleida, northeast Spain) under a present-day semiarid Mediterranean climate. The soils have evolved from the Holocene through the early Pleistocene, providing an excellent morphostratigraphic framework for evaluating time-dependent factors influencing soil formation in a dry and calcareous environment. Throughout the chronosequence, some properties are regularly age-related specially carbonatation in subsurface horizons. The carbonates occur mainly as micrite, and although microsparite and sparite also appear in the oldest soils, they are replaced by fine-grained calcite by dissolution-reprecipitation processes (micritization process), which is active at present. Some pedological paleofeatures as the presence of sparite and recarbonated argillans in oldest terrace can be interpreted as the reflex of climatic changes during the Quaternary. In spite of this climate variability. the soils display progressive and systematic patterns of carbonate accumulation: on the lowest terraces. the soils do not yet have secondary carbonates but in the beginning Late Pleistocene calcic horizons, with carbonate pendents, are developed; these pendents increase its thickness with age although pendent growth rates decreases from Late Pleistocene to Middle Pleistocene. In the middle of the Late Pleistocene, calcic horizons evolved to petrocalcic horizons, which increase its thickness in the Middle and specially in Early Pleistocene. The presence of calcic and petrocalcic horizons is the primary basis for soil classification. This criterion is applicable not only to the soils of the lower Segre river basin, but also to many soils throughout the semiarid Mediterranean region. (C) 2008 Elsevier B.V. All rights reserved.

Abstract: Livestock behaviour in the Pyrenees includes free grazing and a long resting period that provoke the accumulation of dung and urine in some places, so-called camping areas. The aims of this study were (i) to analyse any change in flora composition, and in the nutritional and chemical plant content of a livestock camping area (ii) to relate the botanical and plant composition with the soil chemical properties. In a linear transect, five sampling zones were established, from the centre of the camping area to the surrounding Nardus stricta-dominant pasture. The above ground plant biomass and the topsoil were sampled in each zone with 6 replicates per zone. Plant species were classified and weighed to calculate: above ground biomass, nutritional and chemical content, and the Shannon diversity and evenness indices. Additionally, soils were sampled in two periods, at the beginning and at the end of the grazing period. Soil available nutrients (nitrate, ammonium, phosphorus, potassium, calcium, magnesium), total nitrogen, organic carbon and pH were related with these plant measures. Plant chemical content (protein, lignin and hemicellulose) was related to the proportion of grasses, legumes and other plants. Both plant and soil nutrients increased linearly towards the centre of the camping area. However, the relationship between plant species richness, diversity and evenness relative to its position along the studied transect was bell-shaped. From the outskirts to the centre of the camping area, plants with a low nutrient demand were progressively replaced by species with a medium and high nutrients demand and by pioneers. The strong soil nutrient concentration into the centre of the camping area reduced plant diversity, at a small spatial scale. However, at a large spatial scale, the camping area introduced patches with new species in the poor Nardus stricta-dominant pasture. To ensure positive effects of camping areas on plant diversity, and to manage more effectively the nutrients returned to the soil, a reduction in the stocking rate should be pursued.

Abstract: A set of experiments with a rainfall simulator was performed in the field to evaluate the efficiency of parallel contour seeding as a post-fire restoration strategy in the arid central Ebro Valley (NE Spain). Rainfall simulations were conducted in spring, after seeded plant development, on calcareous and gypsiferous soils, with the same experimental design (two-soil treatments-seeded and nonseeded-per two soil types and per nine replicates). The parallel contour seeding treatment increases soil cover and soil surface roughness, which significantly ameliorates the hydrological and erosional response of both calcareous and gypsiferous burned soils. Seeding decreased soil loss, both in calcareous (23- fold) and gypsiferous soils (4- fold). In addition, it decreased the sediment concentration of runoff for calcareous (6- fold) and gypsiferous soils (2- fold) and the runoff coefficient for calcareous (3.5- fold) and gypsiferous soils (1.5- fold). On the other hand, seeding increased the steady state infiltration rate (3- fold), as well as surface soil moisture (1.2- fold) and wetting front depth (2- fold), with a similar order of magnitude for both soils. Time to runoff and runoff quality (electrical conductivity [EC] and pH) were not affected by seeding. Gypsiferous soils had a higher soil loss, runoff coefficient, and EC flow and a lower time to runoff, steady state infiltration rate, and wetting front depth than calcareous soils. Some of these differences were directly related to differences in soil gypsum and carbonate content (i. e., EC and pH of water runoff) and others are related to the proportion of surface soil protection, an indirect effect of soil characteristics. The results suggest that parallel contour seeding is an effective restoration measure with a short-term response that allows conservation of water and soil on recently burned arid lands, especially in situations of high erosion risk as occurs with soils with low plant cover.

Abstract: A study on the effects of fire and torrential rainfall on the soil erosion and hydrology of Pinus halepensis L. forest of the semi-arid Central Ebro Valley (NE-Spain) were carried out. A portable sprinkler-based rainfall simulator was used with two levels of rainfall energy (12,6Jm(-2)mm(-1) and 24,7 J m(-2)mm(-1)) and similar intensity (85 +/- 18 mm h(-1)). Rainfall simulations were conduced immediately after artificial burn of litter cover on nine different micro-plots and compared with paired unburned areas (2-soil status x 2 rainfall energies x 9 plots or replicates). In each rainfall simulation, the soil loss, soil infiltration (calculated by Horton model, wetting front, runoff coefficient, and runoff quality (EC and pH) were measured Fire increased significantly the sediment loss: 18.5 times with fine rainfall and 33.6 with coarse rainfall Sediment losses were as solutes dissolved in overland flow, mainly in unburned plots, and as particles in suspension, mainly in burned plots. Fire increased runoff quantity (about 1. 6 times) and decreased quality (by increasing significantly both EC and pH). These results indicate that when litter cover was burned, first rainfalls duplicate runoff and increase 20-30 times soil erosion in relation to unburned plots, especially with high rainfall energy. Soil infiltration decreased significantly in burned plots, with the highest rainfall energy. Because there is a high post-fire degradation risk, a restoration strategy for a short-term response should be designed on steep slopes with erodible soils, especially in and Mediterranean areas where torrential rainfall and wildfire are highly probable and their occurrence will increase with climate change.

Abstract: Livestock management may be an important variable controlling the distribution of soil chemistry in grazed summer pastures. Flocks congregate in some areas, produce spatial segregation of excretion. The study goal was to quantify the temporal variation (at the beginning and end of a summer grazing period) and the spatial variation in soil chemical properties in long-term livestock camping areas. In six linear transects, five topsoil sample points were obtained at 1, 20, 40, 60, and 80 meters from the centre of the camping areas to the surrounding Nardus stricta-dominant pasture that has been grazed for centuries. Soil available nutrients, total nitrogen (N), and organic carbon (C) increased linearly from 60 in towards the centre of the camping area as a result of stock concentration. Available N (nitrate, ammonium), phosphorus, potassium, and calcium were at least three times greater at the centre compared to surroundings. At, the end of the grazing period, cations (potassium, ammonium, magnesium) and organic C and N increased significantly at the centre in contrast with the mobile anions (nitrates and phosphates) easily lost or absorbed by plants. Long-term livestock grazing with permanent camping areas resulted in significant lateral and temporal increases of available nutrients in higher quantities than ecosystem can recycle. A reduction in stocking rate by paddock or rotation among different camping areas would aid in managing soil nutrients more effectively.

Abstract: In landscape reconstruction in an opencast coal mine, a gradient of slopes can be obtained. The slope gradient can affect different processes, such as plant growth, especially in semi-arid conditions. On the other hand, to favor the heterogeneity of habitats and ensure long-term restoration, late successional woody species have been planted but with heterogeneous results. In this study, the effect of a slope gradient (from 11.4 to 15.5 degrees) on the growth and survival of five Mediterranean woody species 10 years after the reconstruction of mining banks was evaluated. Slope gradient reduced height growth significantly from 10 cm degree(-1) (lentish) to 25 cm degree(-1) (pine) in 10-year- old woody species. This gradient also reduced basal diameter growth from 0.22 mm degree(-1) (juniper) to 0.58 mm degree(-1) (pine). Survival and slope were not significantly correlated. Growth and survival of the 10-year- old woody species were equal to or higher than those of the same species in other afforestations in semi-arid conditions. This outcome demonstrates the adequacy of species and applied techniques of restoration that allow a long-term reliability of reclaimed mine slopes.

Abstract: odic and alkali soils are characterized by the occurrence of excess sodium (Na) to levels that can adversely affect soil structure and disturb the availability of nutrients for plant growth. Structural problems in these soils are created by certain physical processes (slaking, swelling and dispersion of clay minerals) and speci�c conditions (surface crusting and hardsetting), which affect water and air movement, seedling emergence, root penetration, runoff and erosion, as well as tillage and sowing operations. Such changes ultimately impact choice of crops, and crop growth and yield, which are also affected by osmotic and ion-speci�c effects in these soils. Of the salt-affected soils worldwide, about 60% are sodic and alkali soils, warranting attention for ef�cient, inexpensive and environmentally feasible amelioration. Sodic and alkali soil amelioration primarily involves increasing calcium (Ca2+) on the cation exchange complex at the expense of Na+. The replaced Na+ is removed from the root zone through in�ltrating water resulting from excessive irriga- tion(s). Several approaches aiming at amelioration of these soils have been used, which include application of water, crop, chemical amendment, electric current and tillage as amelioration tools. In addition, management of plant nutrient elements in these soils has been addressed as a crucial factor in improving crop productivity and soil fertility. While the principles and technologies aiming at the amelioration of sodic and alkali soils are fairly well understood, their adoption in poor and developing countries is very slow because the majority of the affected lands are in the possession of resource-poor communities or form part of the common property resources of the villages. This paper reviews various amelioration and nutrient management approaches as well as con- straints to large-scale adoption of the amelioration approaches. This information will assist researchers and farm advisers in choosing appropriate management practices to achieve maximum bene�ts from these soils while considering the participation of the farmers in the planning and setting of the amelioration programmes.

Abstract: Mature leaves of two minority grapevine varieties of the Somontano de Barbastro have been characterized by ampelometry. Fifteen basic foliar characteristics (Primer descriptor priority list) and seven additional characteristics derived from relationships among the first 15 have been quantified. From these data, a theoretical leaf has been reconstructed graphically. The leaves of the two studied varieties have a common structure: five-lobbing leaves with a palm venation pattern. Climate significantly influenced characteristics relating to leaf lobes, sinuses or major veins. Leaves of the �Parraleta� variety showed relatively little change in characteristics such as angles between major veins. Stronger variations were observed in leaves of the �Moristel� variety.

Abstract: Six different microsatellite loci (VVS2, VVMD5, VVMD7, ssrVrZAG47, ssrVrZAG62, and ssrVrZAG79) have been used in order to characterize 12 presumed accessions of Spanish 'Parraleta' cultivar and two of 'Graciano' cultivar. No differences were detected among the accessions of 'Parraleta'. Its allelic profile indicates a probable synonymy with other minor cultivars such as 'Ribote', 'Bomogastro' and 'Salceño Negro'. The two accessions of 'Graciano' analyzed differed in the six microsatellite loci. 'Graciano 17-15' was coincident to the 'Rojal' cultivar in all the analyzed alleles as well as in the ampelographic description. 'Parraleta' and 'Graciano 15-5' are thought to be closely related because they share 58% of the alleles for the loci analyzed

Abstract: The effect of heating and ash deposition on microbiological properties was studied in two arid soils in an incubation experiment, simulating the effects of bushfire. Top soil (0-15 cm) was heated to 150degreesC, 250degreesC and 500degreesC for 30 minutes; unheated soil was taken as a control (25degreesC). Samples of the soil heated to 250degreesC were mixed with black ash (1%, w/w) for analysis of their effect on microbial population and activity. Soils were incubated for nine months and their basal respiration was assessed three times a month. Normalized and specific respiration, biomass-C, bacteria, and fungi numbers were analyzed one month after heating and in the final month of incubation to assess short-term and long-term effects of fire on soil microbiology. At the start of the incubation period and for intermediate heating treatments (150degreesC and 250degreesC), basal and specific soil respiration and biomass-C were enhanced in calcareous soil but depleted in gypsiferous soil. At the highest temperature (500degreesC), these biological properties, as well as specific respiration and colony forming units, were significantly reduced in both soil types and for each period of sampling. At the end of the incubation period, all biological properties maintained the differences between treatments but with lower values than at the beginning of the incubation. Black ash addition increased basal respiration in both soils but did not affect other biological properties. These results demonstrate the existence of both labile and permanent effects of soil burning and a differential response on C dynamics as a function of soil properties.

Abstract: Fire passage is accompanied by a heat wave and ash deposition affecting the upper soil layer. Changes in soil properties are directly related to heat intensity, the amounts of ashes deposited, and soil type. We subjected two soils (gypsiferous soil and calcareous soil) to artificial heating and ash incorporation and compared changes in select chemical and physical properties. The two soils studied were selected to provide a wide range of characteristics in soils of the semiarid Ebro Valley (NE Spain). Samples of both soils were heated for 30 minutes in a muffle furnace at temperatures of 25degrees, 150degrees, 250degrees and 500degreesC. Ashes were added only on soil samples heated at 250degreesC in a quantity related to plant biomass growing on each soil (twice the amount in calcareous soil than in gypsiferous soil). Increasing heat intensity increased organic matter combustion as well as nutrient availability. Heating soil to 250degreesC caused a decrease in pH and an increase in electrolytic conductivity (ECe) and soluble Ca. Heating soil to 500degreesC caused an increase in pH and a decrease in ECe and soluble Ca. Total N content decreased at temperatures greater than 250degreesC, with about one-third being volatilized. Changes in chemical properties were similar for both soils although quantitative differences between soils were found. Cation exchange capacity (CEC) was reduced for gypsiferous soil heated to 500degreesC and to 250degreesC for calcareous soil. Heating increased sand-sized particles by fusion of clay, greatest in soil heated to 500degreesC. Soil aggregate stability (SAS) of both soils was reduced by heating to 250degreesC with greater reductions at 500degreesC, likely due to a reduction in organic matter and clay size particle content. A negative correlation was observed among SAS and soil erodibility (K-USLE). Bulk density and particle density increased in both soils when heated to 500degreesC. Water availability increased when soils were heated to 500degreesC likely due to texture and structural modifications. Addition of the ashes increased organic matter content, C/N ratio, and pH in both soils and increased nutrient availability. These responses were greater in calcareous, than in gypsiferous soil. Physical soil properties were not significantly modified by ash addition.

Abstract: The impact of straw incorporation (6 Mg ha(-1) year(-1)) into agricultural soils compared with straw removal on organic matter mineralization and salinity was studied. The mineralization coefficient (CO2-C evolved/organic C ratio) was obtained to evaluate organic matter mineralization. Soil salinity was measured as means of electrolytic conductivity of saturation paste extract. Both parameters were measured seasonally during two years in two salt-affected soils of the semiarid Central Ebro Valley (northeast Spain), a saline soil and a saline-sodic soil. The electrolytic conductivity (ranging from 2.5 dS m(-1) to 24.3 dS m(-1)) and the mineralization coefficient (ranging from 5.9 10(-4) day(-1) to 37.9 10(-4) day(-1)) varied widely during seasonal samplings of both soils. The lowest electrolytic conductivity values, coincided with the highest mineralization coefficient values. Straw mulching and burying decreased significantly the average seasonal electrolytic conductivity of both soils: 2.5 times in the saline soil and 1.9 times in the saline-sodic soil. The EC reduction only increased significantly (P < 0.05) the mineralization coefficient on saline soil (1.6 times). Straw amendment, followed by rainy periods, allowed the soluble salts leaching but did not modify significantly sodium content. A logarithmic regression fit was found between mineralization coefficient and electrolytic conductivity (r(2) = 0.41), considering both soils. Infiltration, water aggregate stability, and qCO(2) were improved with the straw amendment, but only in saline soil. Soil differences showed the existence of a double effect: an osmotic and a specific ion effect.

Abstract: The nitrification capacity of agricultural soils has received little attention in semi-arid Mediterranean environments in spite of the importance of the NO3- in the ecosystem. In this study, a laboratory experiment was carried out to evaluate potential nitrification in six agricultural soils from semiarid Central Ebro Valley (northeastern Spain). Triplicate topsoil samples (0-15 cm) were collected seasonally over a 2-year period. The nitrification capacity was evaluated by fresh soil incubation at 25 degrees C and field capacity with a NH4+-N source. Verhulst's equation was used to express the accumulation of NO3--N with time. The potential nitrification rate (K-max) was derived from the equation and used to quantitatively characterize the nitrification process. The K-max(,) obtained by fitting a sigmoidal curve, allowed us to distinguish the K-max, nitrification capacity of each semiarid agricultural soil. The varied between K-max seasons which indicate that time-variable soil properties (such as salinity and climate) influenced the nitrification rate even in an incubation experiment. On an annual average, K-max, for saline or highly gypsiferous soils ranged from 8.5 to 9.4 mg NO3--N kg(-1) d(-1). For the rest of the soils K-max ranged from 36.3 to 43.7 mg NO3--N kg(-1) d(-1). Potential nitrification rate was negatively correlated (P < 0.01) with soil salinity and positively correlated with total organic C, microbial activity, and microbial biomass. Highly gypsiferous soil showed a low K-max (8.9 mg NO3--N kg(-1) soil d(-1)) with the lowest NO3--N content in field samplings (7 kg NO3--N ha(-1) as an annual average). This fact demonstrated certain inhibition of the nitrification that can be attributed to unbalanced properties in the highly gypsiferous soil.

Abstract: The effectiveness of seeding introduced species, with or without straw mulching, was tested as a measure of post-fire erosion control in gypsiferous (Xeric Haplogypsid) and calcareous soils (Xeric Torriorthent) in Central Ebro Valley (NE-Spain). Paired control, seeding, and combined seeding and mulching plots were established in four replicated plots for each soil tested. Seeding rate was 30 g m(-2) and straw mulch was applied at 100 g m(-2) in each plot. Plant projective cover (total and specific), plant biomass, bare soil cover and sediment yield were determined over a 2-year period. During the first year of sampling, species introduced by seeding increased plant cover (about 30%) without significant differences observed between soils. Plant cover was similar in seeding-only and seeding-mulching treatments, although the latter treatment significantly enhanced plant weight. During the second year these differences disappeared because species introduced by seeding practically did not survive. So, the introduced herbs did not interfere with native plants. Bare soil cover remained significantly lower in treated plots than on the control plots for both soils during both years of sampling. In the second year, the reduction of bare soil was attributed to both the straw mulch and litter from the seeding species. Soil protection was significantly higher in calcareous soils than in gypsiferous soils which is related to their physical and chemical properties. Cumulative sediment yield decreased significantly over time with both treatments on both soils. Soil losses from control plots were three times higher than seeding plots and 3.3 times higher than from seeding and mulching plots in gypsiferous soils. Soil losses from control plots were two times higher than from seeding plots and 2.7 times higher than the combined seeding and mulching plots in the calcareous soils. Cumulative soil loss was higher from the gypsiferous soils than from the calcareous soils due to the lower plant cover.

Abstract: Se estudia la dinámica de la vegetación en tres áreas del dominio de la maquia de coscoja y escambrón (Rhamno-Quercetum cocciferae), en el NE de España, a lo largo del primer año después de un incendio. Se compara una zona de maquia madura (Maquia) con otra dos en las que, cuarenta años antes del incendio, se produjeron sendas actuaciones antrópicas: la reforestación con Pinus halepensis (Pinar) y el cultivo, con posterior abandono (Erial). La riqueza florística a lo largo del año es más elevada en el Erial que en la Maquia y el Pinar debido a la presencia de diversos terófitos que colonizan el suelo tras el incendio. Brachypodium ramosum es la especie dominante en la Maquia y el Pinar al final del período de estudio, y también en el Erial, tras finalizar su ciclo vital los terófitos que habían sido más abundante hasta ese momento (destacando por su número Euphorbia exigua). La diversidad muestra una tendencia similar a la riqueza florística, con un máximo en primavera. Por el contrario, la densidad es más baja en el Erial que en las otras dos áreas. La relación entre la densidad de especies rebrotadoras y germinadoras es elevada en la Maquia, intermedia en el Pinar y baja ene el Erial. La presencia de especies rebrotadoras se considera un carácter intrínseco de la Maquia y su desaparición va ligada a actividades antrópicas como el laboreo, tal y como sucede ene Erial. En tan corto plazo, no existe una convergencia hacia una composición florística común a las tres áreas estudiadas tras el incendio. La similitud entre las áreas Maquia y Pinar pone en evidencia que la reforestación apenas modificó la composición florística original.

Abstract: The influence of the lithology and climate on soil genesis of the eastern Pyrenees (Spain) was studied. Ten soil profiles were analyzed and classified along two altitudinal transects, from 700 to 1,600 meters of elevation. Plant communities ranged with elevation, and consistently with art increase of precipitation and a decrease of temperature, from oak forest to beech Sorest. One transect was made on siliceous parent material (schists, limolites) and the other on calcareous material (marls, limestones). Pedogenic carbonate content, absent in the siliceous transect, decreased with the increase of elevation. The pH, cation exchange capacity, and clay content were higher in the calcareous transect than in the siliceous transect. The exchangeable complex was always saturated in the calcareous toposequence but, in the siliceous sequence, deer-eased with the increase of elevation. An increase of organic matter content and C/N ratio were observed with elevation, especially in the siliceous transect. The humus type was lime mull along the entire calcareous toposequence, while different transition types of humus between mull and moder were described in the siliceous toposequence. A decrease of exchangeable cations with depth, especially in the siliceous transect, was observed. The main genetic features in the soils studied were melanization and decarbonatation-recarbonatation processes in the calcareous transect and desaturation processes in the siliceous transect. Soils were classified as Mollisols and Inceptisols in the calcareous toposequence and as Inceptisols in rite siliceous toposequence.

Abstract:

Abstract: Evolution of microbial activity in semiarid agricultural soils was studied measuring the basal (CO2 evolved) and specific microbial respiration (qCO(2)). The effects of straw residue management (buried or removed), irrigation (dry or irrigation farming), and chemical composition of the soils (calcareous, gypsiferous, or saline) were analyzed. Seasonal samplings were carried out over a 2-year period. Both irrigation management and harvest residue management, as well as soil chemical composition, influence basal respiration significantly. Straw burying and water addition increased soil respiration in every sampling. On annual average, calcareous soils, with low levels of gypsum and salts and higher percentage of organic carbon, evolved the highest rates of carbon dioxide. Basal and specific microbial respiration were positively and significantly correlated. The release of carbon dioxide per unit of microbial biomass (qCO,) was considerable in the experimental soils, especially with buried straw, although basal respiration was low. High levels of qCO(2) were related to severe climatic conditions and management disturbances (ploughing action, fluctuation of organic carbon content), stressing factors that rejuvenate microbial population.

Abstract: This chapter review the research of last two decades of the authors on soil erosion and conservation measures in semiarid ecosystems affected by wildfires in the Ebro Basin (northeastern Spain)

Abstract: La estabilidad de agregados es una propiedad física relacionada con su resistencia a la ruptura cuando son sometidos a una determinada energía. Es una propiedad clave en el control y la gestión del agua en el suelo, influyendo en la infiltración, la escorrentía superficial y por tanto en la erosión. Esto la convierte en un parámetro de sumo interés para su análisis tras un incendio forestal. La estabilidad de agregados está altamente influenciada por la química y la biología del suelo y por tanto ha sido considerada por muchos investigadores como una propiedad informativa de la salud del suelo. Existen muchos métodos para estudiar la agregación del suelo y la estabilidad de los agregados, aportando todos ellos unos resultados cuyos valores siempre son relativos a la energía aplicada en cada procedimiento, y por tanto no siempre comparables. En este capítulo se realiza una revisión y se describen los principales métodos empleados para su estudio, y se destacan sus ventajas e inconvenientes cuando se emplean para el estudio de suelos quemados. Se resumen también los patrones más frecuentes de agregación encontrados en suelos quemados en diversos estudios realizados por diferentes grupos de investigación españoles, así como las interpretaciones de los resultados que se han encontrado. El principal objetivo de este capítulo es servir de referencia para futuros investigadores que continúen con esta línea de investigación. En el encontraran las bases metodológicas para el estudio de la agregación del suelo, así como apuntes para la interpretación de sus resultados. La información aquí recogida podrá ayudar en la elección del método o los métodos más adecuados a los objetivos concretos y particularidades de los suelos objeto de un futuro estudio.

Abstract: En este capítulo se recogen los resultados de experiencias desarrolladas en los últimos años en zonas quemadas del valle medio del Ebro. Se analiza la sucesión vegetal post-incendio en el dominio del coscojar con pino carrasco; se estudia la evolución de la erosionabilidad de diferentes suelos quemados, así como el impacto del fuego (efecto calor y efecto incorporación de cenizas) en suelos yesosos y margosos. Finalmente se ofrecen los resultados de algunas prácticas de rehabilitación postincendio como son la siembra de herbáceas y la plantación de especies arbustivas y arbóreas.

Abstract: Montes de Zuera has been catalogued within Natura Network because are composed of a dense and divers forest of Aleppo pine, very unusual in the context of the semiarid Ebro Valley. Because the lack of soil information in this area, a toposequence of forest soils developed on limestones and marls of Aragonian (middle-upper Miocene) has been studied. The morphological, physical and chemical properties of five soil profiles were determined along a hillslope using official methods. Soils were classified using the Soil Taxonomy System (STS) and the World Reference Base (WRB). The soils have a fine texture, mainly clay-loam in surface horizons and silty-clay-loam in subsurface horizons. The water holding capacity of soil profile increases gradually from the upper part to the base of the hillslope. Soils have a high percentage of organic matter at surface, which decreases gradually with depth. Soil organic matter is significantly and positively correlated with soil aggregate stability and water holding capacity, at various tensions. The calcium carbonate content is higher than 40% in all the surface horizons, and increases with depth. Dense forest cover facilitates the accumulation of organic matter at surface and, in spite of high carbonate content, a mollic horizon can be defined in the different profiles studied. These mollic epipedons are thiner in the upper part than in the base of the hillslope. Secondary accumulation morphologies, specifically pseudomycelia, were only found in profiles at the base of the hillslope. With these properties, the soils mainly belong to Haploxerolls group (Rendzic Phaeozem by WRB) with differences at subgroup level (STS) related to its position along the slope: mollic on a lithic contact in the headslope (Lithic Haploxeroll), a mollic horizon of variable thickness in the rectilinear slope (Pachic or Entic Haploxeroll), with secondary carbonates in the footslope (Pachic Calcixeroll) or fluventic properties in the contact with bottom valley (Fluventic Haploxeroll).

Abstract: En la cuenca media del río Alcanadre, la secuencia de terrazas aluviales escalonadas ofrecen un excelente marco morfo-estratigráfico con el que evaluar la evolución del suelo desde el Holoceno al Pleistoceno Inferior. Los diferentes depósitos fluviales están formados por gravas y cantos, fundamentalmente calizos, con matriz limo-arenosa provenientes de las Sierras Exteriores (Pre-Pirineo). Las terrazas del río Alcanadre se han correlacionado espacialmente con las del río Cinca, previamente datadas por luminescencia ópticamente estimulada y análisis paleomagnético, para obtener una edad aproximada. Se ha observado como los suelos desarrollados sobre las terrazas inferiores, holocenas, mantienen sus originales propiedades flúvicas. Los desarrollados sobre las terrazas intermedias, del Pleistoceno superior, presentan una incipiente acumulación de carbonatos secundarios, en forma de cemento geopetal (horizonte cálcico). En superficies del Pleistoceno Medio se observan acumulaciones masivas, cementadas (horizonte petrocálcico), a poca profundidad y de grosor moderado. En superficies más viejas, del Pleistoceno Inferior, el horizonte petrocálcico incrementa su espesor. De esta forma el suelo inicial, Fluvisol háplico (calcárico), evoluciona primero a Calcisol háplico y posteriormente a Calcisol pétrico. En resumen, los suelos presentan una progresiva acumulación de carbonato cálcico secundario (carbonatación) a lo largo del tiempo, lo que repercute directamente en su manejo y su clasificación. Este criterio es aplicable a otras terrazas de ríos próximos bajo clima semiárido.

Abstract: iARASOL, programa interactivo para el estudio y clasificación de suelos de Aragón

Abstract: EDAFOS, an interactive program for knowledge of the soil. University of Zaragoza, Spain. (English and Spanish versions)