Foliar photochemical processes and carbon metabolism under favourable and adverse winter conditions in a Mediterranean mixed forest, Catalonia (Spain)

Evergreen trees in the Mediterranean region must cope with a wide range of environmental stresses from summer drought to winter cold. The mildness of Mediterranean winters can periodically lead to favourable environmental conditions above the threshold for a positive carbon balance, benefitting evergreen woody species more than deciduous ones. The comparatively lower solar energy input in winter decreases the foliar light saturation point. This leads to a higher susceptibility to photoinhibitory stress especially when chilly (< 12 C) or freezing temperatures (< 0 C) coincide with clear skies and relatively high solar irradiances. Nonetheless, the advantage of evergreen species that are able to photosynthesize all year round where a significant fraction can be attributed to winter months, compensates for the lower carbon uptake during spring and summer in comparison to deciduous species. We investigated the ecophysiological behaviour of three co-occurring mature evergreen tree species (Quercus ilex L., Pinus halepensis Mill., and Arbutus unedo L.). Therefore, we collected twigs from the field during a period of mild winter conditions and after a sudden cold period. After both periods, the state of the photosynthetic machinery was tested in the laboratory by estimating the foliar photosynthetic potential with CO2 response curves in parallel with chlorophyll fluorescence measurements. The studied evergreen tree species benefited strongly from mild winter conditions by exhibiting extraordinarily high photosynthetic potentials. A sudden period of frost, however, negatively affected the photosynthetic apparatus, leading to significant decreases in key physiological parameters such as the maximum carboxylation velocity (Vc,max), the maximum photosynthetic electron transport rate (Jmax), and the optimal fluorometric quantum yield of photosystem II (Fv/Fm). The responses of Vc,max and Jmax were highly species specific, with Q. ilex exhibiting the highest and P. halepensis the lowest reductions. In contrast, the optimal fluorometric quantum yield of photosystem II (Fv/Fm) was significantly lower in A. unedo after the cold period. The leaf position played an important role in Q. ilex showing a stronger winter effect on sunlit leaves in comparison to shaded leaves. Our results generally agreed with the previous classifications of photoinhibition-tolerant (P. halepensis) and photoinhibitionavoiding (Q. ilex) species on the basis of their susceptibility to dynamic photoinhibition, whereas A. unedo was the least tolerant to photoinhibition, which was chronic in this species. Q. ilex and P. halepensis seem to follow contrasting photoprotective strategies. However, they seemed equally successful under the prevailing conditions exhibiting an adaptive advantage over A. unedo. These results show that our understanding of the dynamics of interspecific competition in Mediterranean ecosystems requires consideration of the physiological behaviour during winter which may have important implications for long-term carbon budgets and growth trends

A dimensão geopolítica do fracassado projeto da Superliga Europeia de Futebol: um ensaio sobre economia, política e esporte no século XXI

The main objective of this research is to analyse and understand the reasons behind why the European Football Super League project, promoted by twelve teams from the Premier League (EPL), LaLiga and Serie A, from April 2021, has failed. In this sense, after reviewing the underlying precedents of such a phenomenon, and focusing the study from an interdisciplinary field such as geopolitics of football, the authors question whether, apart from the popular clamour against a semi-closed competition, it has been the combination of geopolitical interests of the various actors which has not let the project succeed.El objetivo principal de esta investigación es analizar y entender las causas por las cuales el proyecto de la Superliga europea de fútbol, impulsada por doce equipos de la Premier League (EPL), LaLiga y la Serie A, de abril de 2021, fracasó. En este sentido, después de repasar los antecedentes del fenómeno, y focalizar el estudio en un campo interdisciplinar como es la geopolítica del fútbol, los autores se cuestionan si al margen del clamor popular en contra de una competición semi-cerrada, ha sido la combinación de intereses geopolíticos de los varios actores lo que no ha dejado avanzar el proyecto.O principal objetivo desta pesquisa é analisar e compreender as causas do fracasso do projeto da Superliga europeia de futebol, promovida por doze equipes da Premier League (EPL), LaLiga e Série A em abril de 2021. Nesse sentido, após revisar os antecedentes do fenômeno, e focando o estudo em um campo interdisciplinar como a geopolítica do futebol, os autores questionam se, além do clamor popular contra uma competição semifechada, foi a combinação dos interesses geopolíticos dos diversos atores que impediu o projeto de avançar

Foliar photochemical processes and carbon metabolism under favourable and adverse winter conditions in a Mediterranean mixed forest, Catalonia (Spain)

Evergreen trees in the Mediterranean region must cope with a wide range of environmental stresses from summer drought to winter cold. The mildness of Mediterranean winters can periodically lead to favourable environmental conditions above the threshold for a positive carbon balance, benefitting evergreen woody species more than deciduous ones. The comparatively lower solar energy input in winter decreases the foliar light saturation point. This leads to a higher susceptibility to photoinhibitory stress especially when chilly (< 12 °C) or freezing temperatures (< 0 °C) coincide with clear skies and relatively high solar irradiances. Nonetheless, the advantage of evergreen species that are able to photosynthesize all year round where a significant fraction can be attributed to winter months, compensates for the lower carbon uptake during spring and summer in comparison to deciduous species. We investigated the ecophysiological behaviour of three co-occurring mature evergreen tree species (Quercus ilex L., Pinus halepensis Mill., and Arbutus unedo L.). Therefore, we collected twigs from the field during a period of mild winter conditions and after a sudden cold period. After both periods, the state of the photosynthetic machinery was tested in the laboratory by estimating the foliar photosynthetic potential with CO² response curves in parallel with chlorophyll fluorescence measurements. The studied evergreen tree species benefited strongly from mild winter conditions by exhibiting extraordinarily high photosynthetic potentials. A sudden period of frost, however, negatively affected the photosynthetic apparatus, leading to significant decreases in key physiological parameters such as the maximum carboxylation velocity (V_(c,max)), the maximum photosynthetic electron transport rate (J(max)), and the optimal fluorometric quantum yield of photosystem II (F_v/F_m). The responses of V_(c,max) and J(max) were highly species specific, with Q. ilex exhibiting the highest and P. halepensis the lowest reductions. In contrast, the optimal fluorometric quantum yield of photosystem II (F_v/_Fm) was significantly lower in A. unedo after the cold period. The leaf position played an important role in Q. ilex showing a stronger winter effect on sunlit leaves in comparison to shaded leaves. Our results generally agreed with the previous classifications of photoinhibition-tolerant (P. halepensis) and photoinhibition-avoiding (Q. ilex) species on the basis of their susceptibility to dynamic photoinhibition, whereas A. unedo was the least tolerant to photoinhibition, which was chronic in this species. Q. ilex and P. halepensis seem to follow contrasting photoprotective strategies. However, they seemed equally successful under the prevailing conditions exhibiting an adaptive advantage over A. unedo. These results show that our understanding of the dynamics of interspecific competition in Mediterranean ecosystems requires consideration of the physiological behaviour during winter which may have important implications for long-term carbon budgets and growth trends

Improved understanding of drought controls on seasonal variation in Mediterranean forest canopy CO2 and water fluxes through combined in situ measurements and ecosystem modelling

Water stress is a defining characteristic of Mediterranean ecosystems, and is likely to become more severe in the coming decades. Simulation models are key tools for making predictions, but our current understanding of how soil moisture controls ecosystem functioning is not sufficient to adequately constrain parameterisations. Canopy-scale flux data from four forest ecosystems with Mediterranean-type climates were used in order to analyse the physiological controls on carbon and water flues through the year. Significant non-stomatal limitations on photosynthesis were detected, along with lesser changes in the conductance-assimilation relationship. New model parameterisations were derived and implemented in two contrasting modelling approaches. The effectiveness of two models, one a dynamic global vegetation model ('ORCHIDEE'), and the other a forest growth model particularly developed for Mediterranean simulations ('GOTILWA+'), was assessed and modelled canopy responses to seasonal changes in soil moisture were analysed in comparison with in situ flux measurements. In contrast to commonly held assumptions, we find that changing the ratio of conductance to assimilation under natural, seasonally-developing, soil moisture stress is not sufficient to reproduce forest canopy CO2 and water fluxes. However, accurate predictions of both CO2 and water fluxes under all soil moisture levels encountered in the field are obtained if photosynthetic capacity is assumed to vary with soil moisture. This new parameterisation has important consequences for simulated responses of carbon and water fluxes to seasonal soil moisture stress, and should greatly improve our ability to anticipate future impacts of climate changes on the functioning of ecosystems in Mediterranean-type climates

Tecnologías Digitales para Transformar la Sociedad. (Vol. 3.)

El presente libro titulado, “Tecnologías Digitales para la Transformación Social (vol.3)”, es el resultado de un conjunto de reflexiones llevadas a cabo durante el desarrollo de la asignatura de “Usos, posibilidades y límites de las tecnologías de la información y la comunicación”, del grado de Educación Social, de la Universidad de Barcelona. La asignatura tiene como objetivo reforzar el carácter crítico del estudiantado en relación a uso de las tecnologías digitales, pero a la vez proveerle de competencias digitales que posibiliten un uso comprensivo y eficaz de estas. Con este fin, desde el comienzo del curso, instamos al estudiantado a elegir y analizar algún caso o fenómeno concreto, de especial interés para ellos, en el que se apreciara con claridad la incidencia que las tecnologías digitales han tenido en su desarrollo. El resultado ha sido la redacción de doce artículos, que abordan temáticas tan variadas como la convivencia escolar, los procesos de enseñanza y aprendizaje, las relaciones de género, el feminismo, la brecha digital, la inmigración irregular, terrorismo, inclusión digital en contextos escolares, movimientos sociales, entre otras temáticas relevantes, que, como hemos dicho, han estado fuertemente condicionadas por la incidencia de las tecnologías digitales y el internet. Junto a estos doce artículos, se han incluido en el libro, además, otros tres trabajos que abordan temáticas similares, y que a la vez sirven de marco de profundización teórica y conceptual del libro. Dos de ellos fueron realizados por el profesorado de la asignatura, un uno por un colectivo conformado por educadores sociales del País Vasco. Finalmente mencionar que este libro se trata de la tercera edición de una colección que ya incluye el primer volumen editado por Rivera-Vargas y Lindín (2018) y el segundo editado por Lindín, Rivera-Vargas y Pitarque (2019). Esperamos continuar realizando este libro año tras año, toda vez que consideramos importante dar visibilidad a las iniciativas y reflexiones que nuestro estudiantado realiza durante el desarrollo de las clases, y que, en la mayoría de los casos no cuenta con la visibilidad que merece

Does soil moisture overrule temperature dependence of soil respiration in Mediterranean riparian forests?

Soil respiration (SR) is a major component of ecosystems' carbon cycles and represents the second largest CO2 flux in the terrestrial biosphere. Soil temperature is considered to be the primary abiotic control on SR, whereas soil moisture is the secondary control factor. However, soil moisture can become the dominant control on SR in very wet or dry conditions. Determining the trigger that makes soil moisture as the primary control factor of SR will provide a deeper understanding on how SR changes under the projected future increase in droughts. Specific objectives of this study were (1) to investigate the seasonal variations and the relationship between SR and both soil temperature and moisture in a Mediterranean riparian forest along a groundwater level gradient; (2) to determine soil moisture thresholds at which SR is controlled by soil moisture rather than by temperature; (3) to compare SR responses under different tree species present in a Mediterranean riparian forest (Alnus glutinosa, Populus nigra and Fraxinus excelsior). Results showed that the heterotrophic soil respiration rate, groundwater level and 30 cm integral soil moisture (SM30) decreased significantly from the riverside moving uphill and showed a pronounced seasonality. SR rates showed significant differences between tree species, with higher SR for P. nigra and lower SR for A. glutinosa. The lower threshold of soil moisture was 20 and 17% for heterotrophic and total SR, respectively. Daily mean SR rate was positively correlated with soil temperature when soil moisture exceeded the threshold, with Q10 values ranging from 1.19 to 2.14; nevertheless, SR became decoupled from soil temperature when soil moisture dropped below these thresholds

Micro light plates for low-power photoactivated (gas) sensors

We report a miniaturized device integrating a photoactive material with a highly efficient Light Emitting Diode light source. This so-called micro light plate configuration allows for maximizing the irradiance impinging on the photoactive material, with a minimum power consumption, excellent uniformity, and accurate control of the illumination. We demonstrate these advantages with an example application: photoactivated gas sensors with a power consumption as low as 30 μW (this is 1000 times lower than the best figures reported to date). The letter also presents a quantitative model and a set of design rules to implement it in further integrated applications

Mitigating the stress of drought on soil respiration by selective thinning: contrasting effects of drought on soil respiration of two oak species in a Mediterranean forest

Drought has been shown to reduce soil respiration (SR) in previous studies. Meanwhile, studies of the effect of forest management on SR yielded contrasting results. However, little is known about the combined effect of drought and forest management on SR. To investigate if the drought stress on SR can be mitigated by thinning, we implemented plots of selective thinning and 15% reduced rainfall in a mixed forest consisting of the evergreen Quercus ilex and deciduous Quercus cerrioides; we measured SR seasonally from 2004 to 2007. Our results showed a clear soil moisture threshold of 9%; above this value, SR was strongly dependent on soil temperature, with Q10 of 3.0-3.8. Below this threshold, the relationship between SR and soil temperature weakened. We observed contrasting responses of SR of target oak species to drought and thinning. Reduced rainfall had a strong negative impact on SR of Q. cerrioides, whereas the effect on SR for Q. ilex was marginal or even positive. Meanwhile, selective thinning increased SR of Q. cerrioides, but reduced that of Q. ilex. Overall, our results showed that the negative effect of drought on SR can be offset through selective thinning, but the effect is attenuated with time