Reviews and syntheses: Soil responses to manipulated precipitation changes – an assessment of meta-analyses

In the face of ongoing and projected climatic changes, precipitation manipulation experiments (PMEs) have produced a wealth of data about the effects of precipitation changes on soils. In response, researchers have undertaken a number of synthetic efforts. Several meta-analyses have been conducted, each revealing new aspects of soil responses to precipitation changes. Here, we conducted a comparative analysis of the findings of 16 meta-analyses focused on the effects of precipitation changes on 42 soil response variables, covering a wide range of soil processes. We examine responses of individual variables as well as more integrative responses of carbon and nitrogen cycles. We find strong agreement among meta-analyses that belowground carbon and nitrogen cycling accelerate under increased precipitation and slow under decreased precipitation, while bacterial and fungal communities are relatively resistant to decreased precipitation. Much attention has been paid to fluxes and pools in carbon, nitrogen, and phosphorus cycles, such as gas emissions, soil carbon, soil phosphorus, extractable nitrogen ions, and biomass. The rates of processes underlying these variables (e.g., mineralization, fixation, and (de)nitrification) are less frequently covered in meta-analytic studies, with the major exception of respiration rates. Shifting scientific attention to these less broadly evaluated processes would deepen the current understanding of the effects of precipitation changes on soil and provide new insights. By jointly evaluating meta-analyses focused on a wide range of variables, we provide here a holistic view of soil responses to changes in precipitation

Online simulations for conceptual understanding of thermoelectric devices

Computer simulations have been extensively used with educational purposes. However, the successful implementation in order to improve learning has been a matter of debate in research in education. The purpose of this case study is to analyze how a set of computer simulations can improve student understanding of thermoelectric devices. The study was developed in a learning context characterized by the advanced degree of difficulty of the topics treated, the high academic level of education of the students, and the online nature of the learning environment. As part of the course, students were provided with instructional materials that guided the simulation practice; a homework assignment and an instructional assessment were the strategies used for this purpose. Learning gains, instructional support effect, and students\u27 perceptions about the course were investigated. Students significantly improved their conceptual understanding of thermoelectric devices. Yet, the overall performance was considered as moderate. Neither the homework assignment nor the instructional assessment had an effect on the learning gains of the students. Student perceptions about the simulations were positive. This satisfaction was not associated with the student performance on the learning tasks. These results support the agreement that computer simulations have positive effects on student learning gains. The controversy of the instructional support findings can be explained by the difference on the learning context in which this study was developed when compared to the existing research on this field. Further research is recommended on how to enhance the user experience with the simulation through the use of different strategies for inquiry-based learning. Particularly, more studies for higher education and online learning are encouraged

Climate, Land Cover Change and the Seasonality of Photosynthetic Activity and Evapotranspiration in Tropical Ecosystems

Tropical ecosystems play a key role in regulating the global climate and the carbon cycle thanks to the large amounts of water and carbon exchanged with the atmosphere. These biogeochemical fluxes are largely the result of high photosynthetic rates. Photosynthetic activity is highly dependent on climate and vegetation, and therefore can be easily modified along with changes in those two factors. A better understanding of what drives or alters photosynthetic activity in the tropics will lead to more accurate predictions of climate and subsequent effects on ecosystems. The seasonal pattern of photosynthetic activity is one of the main uncertainties that we still have about tropical ecosystems. However, this seasonality of tropical vegetation and its relationship to climate change and land cover is key to understanding how these ecosystems could be affected and have an effect on climate In this dissertation, I present three projects to improve our understanding about tropical ecosystems and how their photosynthetic activity is affected by climate and land cover change. The lack of field-based data has been one of the main limiting factors in our study of tropical ecosystems. Therefore, in these projects I extensively use remote sensing-derived data to analyze large scale and long term patterns. In the first study, I looked at the seasonal relationship between photosynthetic activity and climate, and how model simulations represent it. Vegetation in most of the tropics is either positively correlated with both water and light, or positively correlated with one of them and negatively with the other. Ecosystem models largely underestimate positive correlations with light and overestimate positive correlations with water. In the second study, I focus on the effect of land cover change in photosynthetic activity and transpiration in a highly deforested region in the Amazon. I find that land cover change decreases tropical forests photosynthetic activity and transpiration during the dry season. Also, land cover change increases the range of photosynthetic activity and transpiration in forests and shrublands. These effects are intensified with increasing land cover change. In the last project, I quantify the amount of change in evapotranspiration due to land cover change in the entire Amazon basin. Our remote sensingderived estimates are well aligned with model predictions published in the past three decades. These results increase our confidence in climate models representation of evapotranspiration in the Amazon. Findings from this dissertation highlight (1) the importance of the close relationship between climate and photosynthetic activity and (2) how land cover change is altering that relationship. We hope our results can build on our knowledge about tropical ecosystems and how they could change in the future. We also expect our analysis to be used for model benchmarking and tropical ecosystem monitorin

Conectores y contrastividad: el caso de pues

Expondr\ue9 en este art\uedculo algunas consideraciones de orden contrastivo sobre el uso del conector pues. Dos aspectos ligados a la observaci\uf3n de este marcador resaltan particularmente: la alta frecuencia tanto en textos orales como escritos y de manera casi parad\uf3jica, las dificultades de emplearlo por parte de los aprendices de espa\uf1ol como lengua extranjera . Antes de iniciar el an\ue1lisis descriptivo de los diferentes casos de pues, intentar\ue9 enmarcar te\uf3ricamente el estudio de los conectores o marcadores del discurso, as\ued como del tipo de perspectiva contrastiva que se pretende aplicar. Sucesivamente aplicar\ue9 uno de los modelos tomados en consideraci\uf3n para analizar en detalle el conector mencionado, utilizando una serie de ejemplos sacados de corpora del espa\uf1ol, sea orales que escritos, as\ued como de textos escritos y transcritos

Competencias socioling\ufc\uedsticas en el laboratorio de lenguas

En este art\uedculo se hacen algunas propuestas para desarrollar en el laboratorio de lenguas las competencias socioling\ufc\uedsticas, componente que suele ser descuidado en el aula de espa\uf1ol LE, mediante el an\ue1lisis de muestras de lengua v\ue1lidas y bien dise\uf1adas

Presentaci\uf3n del curso online "Tres por tres" : muestras de materiales

Se presentan muestras de los materiales did\ue1cticos del curso on line "Tres por tres" para analizar el doble reto que supuso su elecci\uf3n. Por una parte no proponer simples transcripciones de lo que cualquier libro de texto brinda y en segundo lugar ofrecer muestras de lengua y actividades significativas en una perspectiva contrastiva, tanto desde un punto de vista ling\ufc\uedstico como intercultural