Plant Neighbour Identity Matters to Belowground Interactions under Controlled Conditions

Background: Root competition is an almost ubiquitous feature of plant communities with profound effects on their structure and composition. Far beyond the traditional view that plants interact mainly through resource depletion (exploitation competition), roots are known to be able to interact with their environment using a large variety of mechanisms that may inhibit or enhance access of other roots to the resource or affect plant growth (contest interactions). However, an extensive analysis on how these contest root interactions may affect species interaction abilities is almost lacking. Methodology/Principal Findings: In a common garden experiment with ten perennial plant species we forced pairs of plants of the same or different species to overlap their roots and analyzed how belowground contest interactions affected plant performance, biomass allocation patterns, and competitive abilities under abundant resource supply. Our results showed that net interaction outcome ranged from negative to positive, affecting total plant mass and allocation patterns. A species could be a strong competitor against one species, weaker against another one, and even facilitator to a third species. This leads to sets of species where competitive hierarchies may be clear but also to groups where such rankings are not, suggesting that intransitive root interactions may be crucial for species coexistence. Conclusions/Significance: The outcome of belowground contest interactions is strongly dependent on neighbours

The paradox of forbs in grasslands and the legacy of the mammoth steppe

The grassland biome supports an enormous diversity of life and includes ecosystems used extensively by humans. Although graminoids lend grasslands their characteristic appearance, forbs are largely responsible for their taxonomic, phylogenetic, and functional diversity. In terms of abundance, however, forbs often play a subordinate role relative to graminoids. Yet this may be a relatively recent phenomenon; evidence is mounting that forbs comprised a major part of the richness of, and were abundant in, the extensive and highly productive grasslands of the Pleistocene, the so-called “mammoth steppe”. As a legacy of their past prevalence under intensive grazing by megafaunal herbivores, we hypothesize that forbs were, and still are, dependent on niche construction by large mammalian herbivores. We suggest that the high species richness of forbs in grasslands globally merits greater research and conservation attention, and management actions tailored to sustain their abundance and diversity

The shift from plant-plant facilitation to competition under severe water deficit is spatially explicit

The stress-gradient hypothesis predicts a higher frequency of facilitative interactions as resource limitation increases. Under severe resource limitation, it has been suggested that facilitation may revert to competition, and identifying the presence as well as determining the magnitude of this shift is important for predicting the effect of climate change on biodiversity and plant community dynamics. In this study, we perform a meta-analysis to compare temporal differences of species diversity and productivity under a nurse plant (Retama sphaerocarpa) with varying annual rainfall quantity to test the effect of water limitation on facilitation. Furthermore, we assess spatial differences in the herbaceous community under nurse plants in situ during a year with below-average rainfall. We found evidence that severe rainfall deficit reduced species diversity and plant productivity under nurse plants relative to open areas. Our results indicate that the switch from facilitation to competition in response to rainfall quantity is nonlinear. The magnitude of this switch depended on the aspect around the nurse plant. Hotter south aspects under nurse plants resulted in negative effects on beneficiary species, while the north aspect still showed facilitation. Combined, these results emphasize the importance of spatial heterogeneity under nurse plants for mediating species loss under reduced precipitation, as predicted by future climate change scenarios. However, the decreased water availability expected under climate change will likely reduce overall facilitation and limit the role of nurse plants as refugia, amplifying biodiversity loss

Tracking the Longitudinal Stability of Medical Students’ Perceptions Using the AAMC Graduation Questionnaire and Serial Evaluation Surveys

Reports on a study that examined the longitudinal stability of student perceptions of their medical education over time, as measured by the AAMC Graduation Questionnaire survey and other satisfaction surveys. Presented at the AAMC (Association of American Colleges) Annual Meeting, RIME (Research in Medical Education) Program, November 2004

Análisis aerodinámico computacional en CFD y modelado completo en CATIA V5 R19 del avión caza Heinkel He 162 Volksjager

Este trabajo es una continuación del Trabajo Fin de Grado, Recuperación del Patrimonio Histórico. Modelado en CATIA V5 R19 del avión caza Heinkel He 162 Volksjäger. En este caso, el alcance del trabajo va más allá del modelado del mismo. El objetivo es, tras haber completado los estudios ingenieriles superiores, aportar el matiz diferenciador entre la titulación de grado y el máster, aplicando los conocimientos adquiridos a partir de las futuras líneas de mejora que se establecieron en su momento cuando se completó el TFG previamente mencionado. El proyecto consta de dos grandes bloques de trabajo claramente diferenciados. En primer lugar, se completará el modelado del Heinkel He 162 Volksjäger con la creación de partes como el Cockpit o las escotillas, y se harán simulaciones de mecanismos completos. Por otro lado, se hará un estudio aerodinámico de la aeronave en Flow Simulation, un paquete de Soliworks, para obtener características de actuación de la aeronave como el techo de vuelo a la velocidad máxima operativa, características aerodinámicas en el techo de vuelo y la polar parabólica del avión.This project is a continuation of the Bachelor’s Thesis, Recuperación del Patrimonio Histórico. Modelado en CATIA V5 R19 del avión caza Heinkel He 162 Volksjäger. In this case, the scope of the project does not only include the modelling of the fighter. The main purpose is, after having completed the highest engineering studies, to demonstrate the difference that studying the master, makes over just completing the degree, to apply the acquired knowledge starting from the improvement lines stablished at the end of the mentioned Bachelor’s thesis. The project consists of two clearly differenced parts. On the one hand, the modelling of the Heinkel He 162 Volksjäger will be completed by creating new parts such as the Cockpit or the landing gear hatches. In addition, simulations of full mechanisms will be done too. On the other hand, an aerodynamic study will be done using Flow Simulation, a working package from Solidworks. Its main objective is to obtain performance characteristics such as the service ceiling at maximum operating speed, aerodynamic specifications at the mentioned service ceiling and the aircraft drag polar.Universidad de Sevilla. Máster en Ingeniería Aeronáutic

Recuperación del patrimonio histórico. modelado en CATIA V5 R19 del avión caza Heinkel He 162 Volksjäger

Este trabajo forma parte de una recopilación de patrimonio histórico aeronáutico, en la que anteriormente se ha conseguido obtener planos, imágenes y documentos de aeronaves clásicas como el Ansaldo SVA 5, el avión caza español Saeta o el Spitfire Mk IX, caza británico de la Segunda Guerra Mundial. En este caso, el avión que se va a documentar y modelar es el caza Heinkel He 162 más conocido como Salamander. Se trata de uno de los primeros cazas de la Segunda Guerra Mundial que estaba impulsado por un motor a reacción a diferencia de los anteriores que empleaban un sistema de hélices. El Heinkel He 162 es exactamente el tercer avión a reacción, precedido por el Me 262 y el Me 163 y el más rápido de esta primera generación de aviones. El documento se dividirá en varios apartados, cada uno de los cuales abarcará el modelado y ensamblaje de cada una de las partes del caza en cuestión. El modelado se realizará a través del software Catia V.5. R19 empleando las conocimientos básicos aprendidos en la asignatura “Diseño y Fabricación Asistidos por Ordenador” impartida en el Grado, además de ampliar dichos conocimientos empleando nuevos módulos desconocidos para mí, como son el módulo de superficie Generative Shape Design o el Wireframe and Surface Design, el modelo de estilo libre Free Style, el de inserción de imágenes Sketch Tracer y el de simulación de mecanismos DMU Kinematics.This work is part of a compilation of aeronautical historical heritage, in which previously it has been possible to obtain plans, images and documents of classic aircraft such as the Ansaldo SVA 5, the Spanish fighter plane Saeta or the Spitfire Mk IX, British fighter of the Second World War. In this case, the aircraft to be documented and modeled is the Heinkel He 162 fighter better known as Salamander. It is one of the first fighters of the Second World War that was powered by a jet engine unlike the previous ones that used a propeller system. The Heinkel He 162 is exactly the third jet aircraft, preceded by the Me 262 and the Me 163 and the fastest of this first generation of aircraft. The document will be divided into several sections, each of which will cover the modeling and assembly of each of the parts of the fighter in question. The modeling will be done through the Catia V.5 software. R19 using the basic knowledge learned in the subject textit "Computer Aided Design and Manufacturing" learnt during the degree, in addition to expanding that knowledge using new modules unknown to me, such us the surface module Generative Shape Design or the Wireframe and Surface Design, the free style module Free Style, the inserting images module Sketch Tracer and the simulation of mechanisms module DMU Kinematics.Universidad de Sevilla. Grado en Ingeniería Aeroespacia