Evaluación de la pérdida de suelo en olivar a escala de microcuenca bajo distintos manejos de suelo

Los mecanismos de generación de escorrentía y pérdida de suelo han sido ampliamente estudiados en áreas semiáridas como Andalucía, aunque la mayoría de esfuerzos tanto en modelado como en medidas de campo han estado concentrados en escala de parcela, a pesar de sus limitaciones en la predicción hidrológica. Existen diversos estudios dedicados a la pérdida de suelo en olivar, todos ellos realizados sobre parcelas de un máximo de 200 m2 donde se analizan La incidencia del uso de olivar y/o el manejo del suelo correspondiente. Los resultados de estos estudios son diversos y, en algunos caso contradictorios, debido fundamentalmente a las distintas condiciones ambientales en las que se han realizado. Por consiguiente, parece adecuado ampliar la escala de estudio a unidades geomorfológicos no aisladas donde el número de fenómenos naturales que intervienen en la circulación de agua y sedimentos es mayor y más complejo que en las parcelas de ladera y donde los resultados responden mejor a las condiciones reales en las que tienen lugar. En este trabajo, se aborda el estudio de la erosión en dos microcuencas de aproximadamente 6 ha, sometidas a mínimo laboreo y a no laboreo con cubiertas. La primera parte, está dedicada a la análisis de su variabilidad intrínseca de las cuencas desde el punto de vista de la topografía y el suelo junto con las consideraciones derivadas del manejo. En ellas, se han localizado puntos donde lso procesos de erosión y depósito son evidentes para analizar las variables más influyentes en estos fenómenos, de manera que faciliten la interpretación de los valores de escorrentía y erosión. La segunda parte, está dedicada a la adquisición y análisis de datos que proporcionen información del balance hidrológico y las pérdidas de suelo a escala de microcuenca con los manejos correspondientes. Para ello, se ha diseñado e instalado una pequeña estación hidrológica en cada una de las cuencas de estudio de las cuales se han obtenido datos de precipitación, escorrentía y concentración de sedimentos en un ciclo de más de un año (2005-2006). Finalmente, en la última partes, se ha seleccionado un modelo de simulación de procesos hidrológicos y erosivos, AnnAGNPS (Annualized Agricultural Non Point Source), para su calibración y validación según los episodios registrados con el objeto de juzgar los resutlados del modelo así como su extrapolación a otros escenarios

Las reformas necesarias en el sistema de pensiones contributivas en España

The debate on the reform of the pension system in Spain is not very lively, in contrast with the international experience. The Spanish economic boom since the mis nineties, the slowdown in the number of pensioners due to the retirement of the cohorts born during the Civil War, and the outstanding immigration flows have contributed to a transitory strengh of Social Security accounts. The paper aims at extending and fostering this public debate. We present an evaluation of the contriburoty pension system in Spain until 2059, based on recent demographic projections. We propose a set of simple indicators to evaluate periodically the situation and perspectives of the Social Security system. And we elaborate on the main reforms that may balance the Social Security Accounts, already implemented in Europe

Computer Simulation of Packing of Particles with Size Distributions Produced by Fragmentation Processes

Fragmentation schemes inspired by theoretical results and conjectures of Kolmogorov are applied to produce particle size distributions of different natures, depending on fragmentation parameters. A two-dimensional computer simulation method of packing is applied to the resulting distributions and the void fraction is evaluated. The relationship between the void fraction and characteristic parameters of the fragmentation process is studied

A packing computational method relating fractal particle size distribution and void fraction in granular media

The study of granular systems is of great interest to many fields of science and technology. The packing of particles affects to the physical properties of the granular system. In particular, the crucial influence of particle size distribution (PSD) on the random packing structure increase the interest in relating both, either theoretically or by computational methods. A packing computational method is developed in order to estimate the void fraction corresponding to a fractal-like particle size distribution

Engineering education on geosciences in a changing world

Engineering aims to work with what knowledge is available to achieve society's goals (Coyle, Murphy, and Grimson 2007). The current environmental challenges and the characteristics of the labour market mean that the effectiveness of Engineering activities in Geosciences must be increased through the development of technical knowledge and the inclusion of suitable training aimed at solving real cases (European Commission 2010). Human capital – understood as the talents, skills and capabilities of higher education graduates – is perceived as an essential element for sustainable economic growth and development in the globalised economy (Sianesi and Van Reenan 2003). We need, therefore, to rethink our approaches to curriculum, instruction and assessment in science education, particularly because of the rapid growth of the scientific knowledge, tools/technologies and theories that have originated over the last 50 years (Duschl and Grandy 2013)

Opportunities of super high-density olive orchard to improve soil quality: Management guidelines for application of pruning residues

Applying pruning residues in the lanes of olive groves has become a popular practice because it is economical and accrues benefits for soil and water management. This study presents an analysis of the impact of different rates of pruning residue on soil properties, in particular related with soil quality. Over 4 annual campaigns, chopped pruning residues used as a mulch were analyzed in terms of composition, coverage and moisture content to evaluate their effects on the amount of soil organic carbon (−10 cm and −20 cm) and CO2 emissions, temperature and moisture. The experiment was carried out in a super-intensive olive orchard in Cordoba (SE, Spain) and used four amounts of fresh pruning residue: 7.5 t ha⁻1(T1), 15.0 t ha⁻1 (T2) and 30.0 t ha⁻1 (T3), with a control T0 = 0.0 t ha1.Mulch mean leaf fraction was 46.0 ± 17.5% (±SD) and initial water content, 24.8 ± 8.6%. The mulching benefits for soil moisture were observed in amounts of pruning residue >7.5 t ha⁻1, which are only produced in super-intensive olive groves or in orchards with high tree densities. The low impact of the treatments on soil moisture was explained by the dramatic annual variations in residue moisture contents, caused by the regimes of high temperatures and rainfall-evapotranspiration deficits inherent to the Mediterranean Basin climate. Thus, the mulching capacity only resulted efficient when the residues were still humid in spring. In addition, 15.0 t ha⁻1 of pruning residues was the threshold to provide significant increases in soil organic carbon at depths of 0–20 cm. Thus, accumulating pruning residue in lanes at rates of over 15 t ha⁻1 (T2 and T3) is more convenient than a uniform distribution with lower amounts, due to the low mineralization rates occurring during warm seasons and the larger inputs of OM increasing the annual balance of SOC

Entropy based parametrization of soils: Models and Tools

Particle-size distribution (PSD) is a fundamental soil physical property. The PSD is commonly reported in terms of the mass percentages of sand, silt and clay present

Computer simulation of random parckings for self-similar particle size distributions in soil and granular materials: porosity and pore size distribution

A 2D computer simulation method of random packings is applied to sets of particles generated by a self-similar uniparametric model for particle size distributions (PSDs) in granular media. The parameter p which controls the model is the proportion of mass of particles corresponding to the left half of the normalized size interval [0,1]. First the influence on the total porosity of the parameter p is analyzed and interpreted. It is shown that such parameter, and the fractal exponent of the associated power scaling, are efficient packing parameters, but this last one is not in the way predicted in a former published work addressing an analogous research in artificial granular materials. The total porosity reaches the minimum value for p = 0.6. Limited information on the pore size distribution is obtained from the packing simulations and by means of morphological analysis methods. Results show that the range of pore sizes increases for decreasing values of p showing also different shape in the volume pore size distribution. Further research including simulations with a greater number of particles and image resolution are required to obtain finer results on the hierarchical structure of pore space