Antonio López-Pintor

Los ríos temporales (RTs) son ecosistemas fluviales en los que los efectos de las perturbaciones antrópicas se mezclan con los de la propia perturbación natural que impone la temporalidad del flujo. A pesar de los avances en el conocimiento de los RTs, todavía persisten muchas lagunas de conocimiento que limitan el desarrollo de metodologías adecuadas para la evaluación de su estado ecológico. En esta revisión identificamos los retos actuales para la correcta evaluación del estado ecológico de los RTs y analizamos las oportunidades existentes para hacerles frente. Estos retos se centran en: la diferenciación entre RTs naturales o hidrológicamente impactados, la diferenciación entre perturbaciones naturales y antrópicas, el desarrollo de índices biológicos para pozas desconectadas y cauces secos, la adaptación de los índices hidrogeomorfológicos, y la aplicación de la teoría de metacomunidades en RTs. Las oportunidades están relacionadas con: el uso de nuevas herramientas moleculares, la existencia de índices alternativos a los tradicionales, la disponibilidad de datos para poder hacer modelización, y la implicación social en la evaluación del estado hidrológico y ecológico. La revisión se centra mayoritariamente en el conocimiento científico y de gestión acumulado desde la implementación de la DMA en España, pero recoge experiencias en otros RTs del mundo para guiar acciones de conservación y gestión en estos ecosistemas únicos y altamente amenazados por el cambio global.

Traditional agricultural systems and their spatial context constitute socio-ecological landscapes for their long co-evolutionary history. However, these systems not only generate positive but also negative agri-environmental externalities, such as soil erosion, diffuse pollution and potential wild biodiversity degradation. In this paper, we present a methodological approach for developing and testing indicators to estimate the effects of these externalities, especially designed to be used to help guide land-use policy changes. Our results show that the indicators proposed can recognize the different environmental situations posed by the three selected study areas, in terms of potential erosion and diffuse pollution, as well as in the actual agri-environmental externalities assessment. As expected, they also respond to the changes in land use and management introduced by two scenarios, ecological and productive. Although the erosion and diffuse pollution indicators showed a linear response, the diversity indicator showed a non-linear response, which highlights the importance of the spatial structure of landscape in agri-environmental assessment. In fact, several ecological processes can be affected by landscape spatial structure, potentially giving unexpected results both in terms of indicators and of real impact of agri-environmental externalities. Therefore, some landscape structure assessment should accompany that of externalities when considering land-use policy objectives.

Summary: Canopies are complex multilayered structures comprising individual plant crowns exposing a multifaceted surface area to sunlight. Foliage arrangement and properties are the main mediators of canopy functions. The leaves act as light traps whose exposure to sunlight varies with time of the day, date and latitude in a trade‐off between photosynthetic light harvesting and excessive or photoinhibitory light avoidance. To date, ecological research based upon leaf sampling has been limited by the available technology, with which data acquisition becomes labour intensive and time‐consuming, given the overwhelming number of leaves involved. In the present study, our goal involved developing a tool capable of measuring a sufficient number of leaves to enable analysis of leaf populations, tree crowns and canopies. We specifically tested whether a cell phone working as a 3D pointer could yield reliable, repeatable and valid leaf angle measurements with a simple gesture. We evaluated the accuracy of this method under controlled conditions, using a 3D digitizer, and we compared performance in the field with the methods commonly used. We presented an equation to estimate the potential proportion of the leaf exposed to direct sunlight (SAL) at any given time and compared the results with those obtained by means of a graphical method. We found a strong and highly significant correlation between the graphical methods and the equation presented. The calibration process showed a strong correlation between the results derived from the two methods with a mean relative difference below 10%. The mean relative difference in calculation of instantaneous exposure was below 5%. Our device performed equally well in diverse locations, in which we characterized over 700 leaves in a single day. The new method, involving the use of a cell phone, is much more effective than the traditional methods or digitizers when the goal is to scale up from leaf position to performance of leaf populations, tree crowns or canopies. Our methodology constitutes an affordable and valuable tool within which to frame a wide range of ecological hypotheses and to support canopy modelling approaches.