Riparian woodland encroachment following flow regulation: a comparative study of Boreal and Mediterranean streams

Water development accompanying mankind development has turned rivers into endangered ecosystems. Improving the understanding of ecological responses to river management actions is a key issue for assuring sustainable water management. However, few studies have been published where ecological metrics have been quantified in response to various degrees of flow alteration. In this work, changes in natural distribution of trees and shrubs within the riparian corridor (as indicator of the ecological status of the fluvial ecosystem) were quantified at multiple sites along a flow alteration gradient (as indicator of impact) along two regulated river reaches, one Boreal and the other Mediterranean, each downstream of a dam. Based on the obtained relationships we evaluated differences in response trends related to local physico-climatic factors of the two biomes and regarding to differing life-forms. Woody vegetation establishment patterns represented objective indicators of ecological responses to flow alteration. We found different responses between life-forms. Both trees and shrubs migrated downwards to the channel after dam closure, but shrubs were most impacted under higher degrees of flow alteration in terms of lateral movement. In addition, our results show clear longitudinal recovery trends of natural patterns of tree and shrub distribution corresponding to a decrease in intensity of hydrologic alteration in the Boreal river. However, vegetation encroachment persisted along the entire Mediterranean study reach. This may result from a relatively low gradient of decrease of hydrologic alteration with distance from the dam, coupled with other overlapping pressures and the mediating effect of physico-climatic characteristics on vegetation responses.

Evolución de las características en micrófonos electret

A la hora del estudio de los fenómenos acústicos, es necesario el conocimiento de las características técnicas de los elementos utilizados. Un parte importante de ello son los micrófonos, sus características son esenciales para la obtención y comparación de los datos. Intentando describirlas, este trabajo quiere presentar un estudio detallado de una de las características que influyen en ellos, la característica de vida, especializándose en un tipo de micrófonos, los electret. La metodología seguida para el estudio de estos micrófonos se basa en la recopilación de información tras ensayos a diferentes temperaturas con el fin de caracterizarlos según las distintas distribuciones de vida existentes. En cuanto a los contenidos, se comienza explicando una base histórica de estos, origen, características generales y su evolución a lo largo de los años. Seguidamente se especifica una base teórica sobre distintas características que los afectan, antecedentes, y una explicación de las distintas distribuciones y formas del cálculo de vida. Posteriormente comienza la explicación del material utilizado, así como todas las características, para poder explicar la realización del estudio. Para ello: - Se han realizado tres ensayos a diferentes temperaturas, 140º, 125º y 110º dentro de una cámara térmica - Cada ensayo ha constado de diez micrófonos - El número de horas dentro de la cámara térmica ha variado dependiendo de la temperatura a la que se sometían los micrófonos en cada ensayo. - Tras cada hora se ha realizado una medida de cada uno de los micrófonos del nivel de presión sonora a la entrada, con el fin de ir comparándolos tras cada tiempo dentro de la cámara térmica. - Finalmente se ha realizado un estudio de fiabilidad con el que se ha obtenido el tiempo de vida. ABSTRACT. When the study of acoustic phenomena, the knowledge of technical characteristics for the different elements used is needed. An important part of this are the microphones, their characteristics are essential for obtaining and comparing data. Trying to describe it, this paper wants to present a detailed analysis of one of the characteristics that influence them, the characteristic of life, focusing in one type of microphones, the electret. The methodology for the study of these microphones is based on gathering information after some test at different temperatures in order to characterize them with different existing distributions of life. As for the contents, begins with a historical basis of them, origin, general characteristics and their evolution through the years. Afterward a theoretical background on different characteristics that affect them, history and an explanation of different distributions for calculating life forms. Then it begins with the explanation of the material used, as well as the features, in order to explain the study. For that: - There were three test at different temperatures, 140º, 125º and 110º in a thermal camera - Each test has consisted in ten microphones - The number of hours inside the thermal camera has varied depending on the subjected test which the microphones were - After each hour, it has been made a measurement of each microphone of their sound level pressure, in order to compare them after every hour inside the thermal camera - Finally, it has been made a reliability study to obtain their lifetime