El eucalipto y los suelos bajo clima mediterráneo

El presente trabajo hace un recorrido sobre los efectos negativos que se atribuyen a las plantaciones forestales de eucalipto sobre los suelos. Se tratan en su mayor parte de creencias sin fundamento científico que han enraizado en la opinión pública, como reacción a la rápida extensión de estas plantaciones por el suroeste de la Península Ibérica, durante los años 1950 a 1980. Se revisan brevemente los principales efectos de la actividad humana descritos para los suelos y, sobre esta base, se observan los resultados obtenidos por otros autores y por el equipo investigador al que pertenece el autor. La selvicultura y explotación del eucalipto no produce incrementos en la erosión hídrica, con respecto a otras cubiertas forestales mediterráneas, siempre que las operaciones de preparación del terreno se realicen de forma correcta, en función de la pendiente y con respeto de las cubiertas naturales en las líneas de flujo principales. El eucalipto no provoca incrementos apreciables en la acidez de los suelos; puede producir ligeras extracciones netas de algunos minerales como Ca y Mg en suelos muy deficitarios, que deberán ser compensadas con una ligera fertilización artificial. El eucalipto no erradica en absoluto la actividad biológica del suelo; estas plantaciones presentan sotobosques de composición variable según múltiples factores y una elevada riqueza y actividad microbiana. Las plantaciones de eucalipto satisfacen en general los criterios y principios de los sistemas de certificación de la gestión forestal sostenible en lo relativo a la conservación de los suelos, siempre que se tenga en cuenta que se trata de sistemas intervenidos, relativamente intensivos y con un objetivo principal productor de madera, por lo que no pueden equipararse a los bosques naturales.____________________________________This paper deals with the negative effects attributed to the Eucalyptus plantations on soils. The quick expansion of these plantations in the southwest of the Iberian Peninsula, during the years 1950 to 1980, produced a strong reaction of conservationist groups and biased public opinion against this tree. We make a brief review on the main threats to the soil caused by human activity, and, on this basis, we revise the existing contributions regarding soil impact by eucalyptuses, as long as the results of the author’s research team. Eucalyptus forests and its logging produce no increases in erosion, with respect to other Mediterranean forest cover, provided the correct execution of the soil conservation practices (terraces, contour lines, etc., depending on the steepness), as well as the maintenance of the natural cover at the main flow lines. Eucalypts do not cause significant increases in acidity of the soil; it may cause slight net withdrawals of some minerals such as Ca and Mg in highly deficient soils, which must be offset by a slight artificial fertilization. Eucalypts do not disrupt the biological activity in the soil; the understories of these plantations may have varying composition in species, depending on multiple factors; they also have a high microbial activity. The Eucalyptus plantations generally meet the criteria and principles of the certification schemes for sustainable forest management regarding soil conservation; we must take into account that they are artificial systems, oriented to wood yield, thus they are not comparable to natural forests

El eucalipto y los suelos bajo clima mediterráneo

Las "Jornadas sobre el Eucalipto" fueron celebradas con motivo del X Aniversario del CIDE

The USLE soil erodibility nomograph revisited

The nomograph by Wischmeier et al. (1971) for calculating the K-factor in the USLE was extremely useful when there was low access to calculators. However, the generalised calculation of this factor requires the development of analytic procedures. This paper presents a detailed analysis of the nomograph and its underlying equation, which is applicable only when the silt plus very find sand fraction does not exceed 70%. We also examined the quality of fit on the nomograph of the adaptations to the equation that have been proposed, as a means of dealing with those areas where the original equation is not applicable. All models are shown to have areas where the fit is deficient or even unacceptable. Besides, the family of curves on the nomograph for the various values taken by the organic matter are not coincident with the mathematical function from which they presumably derive. The study also identifies those areas of the textural triangle in which the soils originally used in developing the USLE are located, with a view to according a lower predictive value to the contrasting areas in which calculations of the K-factor will necessarily be extrapolations. Finally, a new equation for calculating the K-factor is presented, which accurately reproduces the different sections of the nomograph, and allows the poorly functioning graph to be dispensed with. The paper ends with a link to a tool in R for simplifying the procedure for calculating the K-factor, taking into account varying situations of data availability.Funding for Open Access charges: Universidad de Huelv

Estimating textural fractions of the USDA using those of the International System: A quantile approach

Este artículo forma parte de una trilogía centrada en la revisión de los principales problemas que tiene uno de los factores más importantes de la Ecuación Universal de Pérdidas de Suelo (USLE), en concreto el Factor K de erosionabilidad del suelo. Se plantea un enfoque para solucionar la falta de correspondencias directas entre clasificaciones texturales de suelos.In soil science, the two most frequently used classification systems for the soil particle size distribution are the schemes by the United States Department of Agriculture (USDA) and the so-called International System (IS), whose difference is the upper particle size limit of the silt fraction, namely, 0.02 mm for the IS and 0.05 mm for the USDA system. The existence of these and other systems creates a disparity that hinders and prevents the use and exchange of soil information worldwide. To solve this problem, it is necessary to devise methodologies for the conversion of textural fractions between the different classification systems. This work focuses on the estimation of the USDA silt fraction from the basic textural fractions (sand, silt and clay) in the IS. Five models are currently available for that purpose: the log-linear interpolation method, the Minasny-McBratney-Bristow regression formula, the Shirazi-Boersma-Johnson interpolation method, the Minasny-McBratney regression formula, and the Padarian-Minasny-McBratney regression formula. The accuracy of some of these methods has already been assessed, but in this work we develop a new methodology, based on a local quantile regression, which improves and enriches this evaluation, providing both the regions of the textural triangle where the predictions of the models are acceptable, and the regions where each model is most appropriate. The data used were taken from the publicly available National Cooperative Soil Survey Soil Characterization Database, from which more than 270,000 soil horizon samples were selected for having valid texture data. The analysis carried out concludes that the Padarian-Minasny-McBratney regression formula is the best model of those evaluated. In addition, the tool developed for the evaluation of the models becomes a new model that provides point estimates of the USDA silt fraction from the basic textural fractions in the IS, with further improvement, compared to the 5 models evaluated, as it also provides a prediction interval for those estimates.Funding for open access charge: Universidad de Huelva / CBU

Aprendizaje Colaborativo en Profesionales de Nuevas Tecnologías

En los cursos de Nuevas Tecnologías de la Información y las Comunicaciones orientados a alumnos con estudios universitarios, se debe considerar en el aprendizaje métodos que permitan formar al alumno utilizando grupos de trabajo y donde las prácticas desempeñadas sean casos reales. Muchos de estos alumnos van a formar parte, o están formando parte, de grupos de trabajo en empresas, grupos de investigación, etc. El método que se propone, pretende desarrollar el currículum de los alumnos desde un entorno colaborativo práctico donde cada alumno es una pieza importante del trabajo a realizar y donde el resultado final depende de todos. Para ello se realizan prácticas colaborativas, con escaso contenido teórico, donde se combinan factores de descubrimiento, análisis y consulta entre compañeros. Posteriormente se realiza una clase magistral y participativa, por parte del profesor, del contenido teórico correspondiente a dichas prácticas.Jiménez Herranz, JM.; Lloret, J.; Esteve Domingo, M.; Díaz Santos, JR. (2004). Aprendizaje Colaborativo en Profesionales de Nuevas Tecnologías. The International Institute of Informatics and Systemics (IIIS). http://hdl.handle.net/10251/671

Estimation of water retention capacity in soil: corrections to the CRA pedotransfer formula

El parámetro de capacidad de retención de agua en el suelo (CRA) es un modelo de base física ampliamente utilizado por técnicos forestales e investigadores en ecología forestal del territorio español, como uno de los factores estimadores de las disponibilidades de agua para las plantas y, por ende, de la calidad de estación. Dentro del proyecto Caracterización de suelos forestales de la provincia de Huelva se han apreciado una serie de anomalías en cuanto a los valores obtenidos para el parámetro CRA, especialmente en lo referente a la influencia de la pendiente sobre el modelo para su cálculo, así como en la determinación del agua disponible para la vegetación, en relación a la reserva total. Este trabajo plantea una sencilla modificación del modelo que permite obtener valores de capacidad de retención de agua más acordes con la calidad de la estación, en los terrenos forestales de fuerte pendiente, y también extiende el modelo al cálculo de la máxima reserva de agua disponible en el suelo. La bondad de estos parámetros se contrasta mediante el análisis de correlaciones frente a un índice de calidad de estación, con resultados satisfactorios.In Spain, a physical model to estimate the soil water capacity, which is called the CRA parameter, was implemented by Gandullo (1985). This parameter is broadly used in forest management and forest ecology research in relationship with site index and soil quality variables. While running a soil mapping project in the southwest of Spain some problems related to the CRA model were detected, mainly related to the influence of slope on total soil water capacity, as well as the estimation of available water capacity. A simple correction of the model is proposed in this paper, as well as a complementary parameter for available water capacity. The quality of those new parameters is tested by means of correlation analysis against Site Index variable

Human Immunodeficiency Virus/Hepatitis C Virus Coinfection in Spain: Prevalence and Patient Characteristics

Background: The purpose of this study was to assess the prevalence of anti-hepatitis C virus (HCV) antibodies (Abs) and active HCV infection in human immunodeficiency virus (HIV)-infected (HIV+) patients in Spain in 2015. This was a cross-sectional study. Methods: The study was performed in 41 centers in 2015. Sample size was estimated for an accuracy of 2%, the number of patients from each hospital was determined by proportional allocation, and patients were selected using simple random sampling. Results: The reference population was 35 791 patients, and the sample size was 1867 patients. Hepatitis C virus serostatus was known in 1843 patients (98.7%). Hepatitis C virus-Abs were detected in 695 patients (37.7%), in whom the main route of HIV acquisition was injection drug use (75.4%). Of these 695 patients, 402 had HCV RNA, 170 had had a sustained viral response (SVR) after anti-HCV therapy, and 102 cleared HCV spontaneously. Hepatitis C virus-ribonucleic acid results were unknown in 21 cases. Genotype distribution (known in 367 patients) was 1a in 143 patients (39.0%), 4 in 90 (24.5%) patients, 1b in 69 (18.8%) patients, 3 in 57 (15.5%) patients, 2 in 5 (1.4%) patients, and mixed in 3 (0.8%) patients. Liver cirrhosis was present in 93 patients (23.1%) with active HCV infection and in 39 (22.9%) patients with SVR after anti-HCV therapy. Conclusions: The prevalence of HCV-Abs and active HCV infection in HIV+ patients in Spain is 37.7% and 22.1%, respectively; these figures are significantly lower than those recorded in 2002 and 2009. The predominant genotypes in patients with active HCV infection were 1a and 4. A high percentage of patients had cirrhosis. Cirrhosis is also common in patients with SVR after anti-HCV therapy.This study was supported by grant GLD14-00279 from the GILEAD Fellowship Programme (Spain). J. B. is an investigator from the Programa de Intensificación de la Actividad Investigadora en el Sistema Nacional de Salud (I3SNS) (Ref. no. INT15/00079).S

Los fondos americanos de la Biblioteca Histórica de la Universidad Complutense de Madrid: Guía de recursos

La Biblioteca Histórica de la Universidad Complutense de Madrid guarda entre sus fondos más de un millar de libros antiguos sobre América o impresos en América, lo que la convierte en uno de los conjuntos más importantes de España sobre tema americano. Esta guía de recursos reúne manuscritos e impresos producidos en el continente americano, así como los que tratan sobre América. Dadas sus especiales características, se ha dedicado un capítulo a Estados Unidos y Canadá

Exploring APOE genotype effects on Alzheimer's disease risk and amyloid β burden in individuals with subjective cognitive decline: The FundacioACE Healthy Brain Initiative (FACEHBI) study baseline results

Introduction: Subjective cognitive decline (SCD) has been proposed as a potential preclinical stage of Alzheimer's disease (AD). Nevertheless, the genetic and biomarker profiles of SCD individuals remain mostly unexplored. Methods: We evaluated apolipoprotein E (APOE) ε4's effect in the risk of presenting SCD, using the Fundacio ACE Healthy Brain Initiative (FACEHBI) SCD cohort and Spanish controls, and performed a meta-analysis addressing the same question. We assessed the relationship between APOE dosage and brain amyloid burden in the FACEHBI SCD and Alzheimer's Disease Neuroimaging Initiative cohorts. Results: Analysis of the FACEHBI cohort and the meta-analysis demonstrated SCD individuals presented higher allelic frequencies of APOE ε4 with respect to controls. APOE dosage explained 9% (FACEHBI cohort) and 11% (FACEHBI and Alzheimer's Disease Neuroimaging Initiative cohorts) of the variance of cerebral amyloid levels. Discussion: The FACEHBI sample presents APOE ε4 enrichment, suggesting that a pool of AD patients is nested in our sample. Cerebral amyloid levels are partially explained by the APOE allele dosage, suggesting that other genetic or epigenetic factors are involved in this AD endophenotype

The genomic history of the Iberian Peninsula over the past 8000 years

We assembled genome-wide data from 271 ancient Iberians, of whom 176 are from the largely unsampled period after 2000 BCE, thereby providing a high-resolution time transect of the Iberian Peninsula.We document high genetic substructure between northwestern and southeastern hunter-gatherers before the spread of farming.We reveal sporadic contacts between Iberia and North Africa by ~2500 BCE and, by ~2000 BCE, the replacement of 40% of Iberia's ancestry and nearly 100% of its Y-chromosomes by people with Steppe ancestry.We show that, in the Iron Age, Steppe ancestry had spread not only into Indo-European-speaking regions but also into non-Indo-European-speaking ones, and we reveal that present-day Basques are best described as a typical Iron Age population without the admixture events that later affected the rest of Iberia. Additionally, we document how, beginning at least in the Roman period, the ancestry of the peninsula was transformed by gene flow from North Africa and the eastern Mediterranean