Cerdanyola del Valles

Barcelona, Spain

Cerdanyola del Valles

Barcelona, Spain
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Ojeda G.,National University of Colombia | Patricio J.,University of Coimbra | Mattana S.,Cerdanyola del Valles | Sobral A.J.F.N.,University of Coimbra
Journal of Soils and Sediments | Year: 2016

Purpose: Biochar is a carbon-rich product, able to enhance soil fertility and mitigate CO2 emissions. While biochar effects on agriculture are becoming known, its impact elsewhere, e.g., on estuarine ecosystems, has yet to be assessed. The main aim of the present study was to determine the effect of biochar on sediment–water retention, CO2 emissions from sedimentary organic carbon decomposition, sediment pH and electrical conductivity, in aerobic conditions similar to those observed at low tide. Materials and methods: Sediments from the Mondego Estuary (Portugal) were mixed with pine gasification biochar at different doses (5, 10, 14 %) and immersed in water with different salinity values (15, 25, 30) for 96 h. The influence of biochar on water retention, the residence time of water and CO2 emissions between −0.75 and −1.5 MPa, total organic carbon, pH and electrical conductivity (EC) were determined. Carbon chemical composition and polycyclic aromatic hydrocarbon (PAH) concentrations were determined in sediments and biochar. Differences between biochar treatments after immersion in different water salinities were analysed using the Kruskal–Wallis test. Results and discussion: Results showed that biochar was able to (a) increase sediment–water content in terms of quantity and residence time, (b) decrease CO2 emissions, but only with a specific soil–water content and at the highest biochar dose, (c) increase sediment pH at all biochar doses and (d) increase sediment EC at the highest biochar dose. In contrast, the percentage of carbon mineralised was not modified. Biochar carbon was rich in PAHs and less decomposable than sedimentary carbon. The increments observed in sediment pH and EC were unable to change sediment alkaline or saline status according to standard classifications. Conclusions: Our results suggest that the remarkable water adsorption capacity of biochar–sediment mixtures may be considered the main factor in regulating CO2 emission rates from sediments, together with high PAH concentrations, which probably restrain the organic matter decomposition process. © 2016 Springer-Verlag Berlin Heidelberg

Barba J.,Cerdanyola del Valles | Lloret F.,Cerdanyola del Valles | Yuste J.C.,CSIC - National Museum of Natural Sciences
Plant and Soil | Year: 2015

Aims: Drought-induced forest die-off and subsequent species replacement may modify environmental conditions and eventually affect litter decomposition. We aimed to disentangle the effects of tree species and die-off state on litter decomposition in a mixed forest where Pinus sylvestris populations experiencing severe drought-induced die-off are being replaced by Quercus ilex. Methods: Litter bags with leaves and fine roots from both species were placed under canopies representing three habitats of the die-off and replacement process (healthy and dead P. sylvestris and healthy Q. ilex). Mass was assessed over 3 years. Results: Species-specific chemistry of litter (C:N ratio) had a direct effect on mass loss, but also indirect effects, attributed to the decomposer microbial community associated with a given habitat-species. In their respective original habitats, oak leaves decomposed 44 % faster than pine needles, whereas oak roots decomposed 46 % slower than pine roots. Conclusions: Forest die-off and species replacement affected litter decomposition. This effect can have great implications in forest functioning, particularly if drought-induced die-off worsens in the next decades, according with the trend observed in the studied system. © 2015 Springer International Publishing Switzerland

Llusia J.,Cerdanyola del Valles | Llusia J.,Global Ecology Unit CREAF CSIC UAB | Roahtyn S.,Weizmann Institute of Science | Yakir D.,Weizmann Institute of Science | And 6 more authors.
Trees - Structure and Function | Year: 2015

Key message: Warmer summer conditions result in increased terpene emissions except under severe drought, in which case they strongly decrease.Abstract: Water stress results in a reduction of the metabolism of plants and in a reorganization of their use of resources geared to survival. In the Mediterranean region, periods of drought accompanied by high temperatures and high irradiance occur in summer. Plants have developed various mechanisms to survive in these conditions by resisting, tolerating or preventing stress. We used three typical Mediterranean tree species in Israel, Pinus halepensis L., Quercus calliprinos and Quercus ithaburensis Webb, as models for studying some of these adaptive mechanisms. We measured their photosynthetic rates (A), stomatal conductance (gs), and terpene emission rates during spring and summer in a geophysical gradient from extremely dry to mesic from Yatir (south, arid) to Birya (north, moist) with intermediate conditions in Solelim. A and gs of P. halepensis were threefold higher in Birya than in Yatir where they remained very low both seasons. Quercus species presented 2–3-fold higher A and gs but with much more variability between seasons, especially for Q. ithaburensis with A and gs that decreased 10–30-fold from spring to summer. Terpene emission rates for pine were not different regionally in spring but they were 5–8-fold higher in Birya than in Yatir in summer (P < 0.05). Higher emissions were also observed in Solelim for the drought resistant Q. ithaburensis (P < 0.001) but not for Q. calliprinos. α-Pinene followed by limonene and 3-carene were the dominant terpenes. Warmer summer conditions result in increased Terpene emission rates except under severe drought, in which case they strongly decrease. © 2015 Springer-Verlag Berlin Heidelberg

Bagaria G.,Cerdanyola del Valles | Bagaria G.,University of Barcelona | Helm A.,University of Tartu | Roda F.,Cerdanyola del Valles | And 3 more authors.
Oecologia | Year: 2015

Changes in species richness along the ecological succession gradient may be strongly determined by coexisting extinction debts of species from the original habitats and colonization credits of those from the replacing habitats. The magnitude of these processes and their causes remain largely unknown. We explored the extinction debt and colonization credit for grassland and forest specialist plants, respectively, and the local and landscape factors associated to the richness of these species groups in a 50-year process of forest encroachment into semi-natural Mediterranean grasslands. A set of sampling plots of persistent grasslands and forests and their transitional habitat (wooded grasslands) was selected within fixed-area sites distributed across the landscape. Our results confirm the extinction debt and suggest colonization credit (according to observed trends and model predictions) in wooded grasslands when compared to persistent forests, despite wooded grasslands and persistent forests having similar tree cover. Grassland connectivity and solar radiation had opposing effects on the richness of both grassland and forest specialists, and it is possible that the availability of seed sources from old forests may have accelerate the payment of colonization credit in the wooded grasslands. These results suggest that extinction debt and colonization credit have driven species turnover during the 50 years of forest encroachment, but at different rates, and that local and landscape factors have opposing effects on these two phenomena. They also highlight the importance of documenting biodiversity time lags following habitat change when they are still in progress in order to timely and adequately manage habitats of high conservation value such as the grasslands studied here. © 2015 Springer-Verlag Berlin Heidelberg

Clotet M.,Cerdanyola del Valles | Basnou C.,Cerdanyola del Valles | Bagaria G.,Cerdanyola del Valles | Pino J.,Cerdanyola del Valles | Pino J.,University of Barcelona
Biological Invasions | Year: 2016

Habitat invasion by alien plants is strongly modulated by environmental and landscape factors. However, the effect of landscape history remains largely unknown, despite the fact that it could play an important role in many stages of invasion processes, even long after land-use changes have occurred determining invasion debts. We analysed the effects of past landscape and recent changes therein, together with habitat type and current context (i.e. climate, topography and landscape), on three components of the invasion process at habitat scale: alien species presence (i.e. at least one alien species occurring), richness (number of species found) and abundance (mean species cover). We selected 531 plots in nine habitat types in Barcelona province (7725 km2) and recorded alien (neophyte) species cover. We performed Generalized Linear Models on these invasion components using the generated data and a set of predictors of habitat, context and landscape factors obtained from plot sampling and digital cartography. The results show that invasion components are affected by diverse habitat and context factors and, in some cases, by landscape history. Alien species presence is influenced by habitat type and the current environmental context, and by the number of habitat changes in the adjacent landscape; on the other hand, species richness is only associated with the current context and species abundance is only influenced by historical cropland cover. The association between alien species presence and abundance and past and recent landscape changes suggests the existence of accumulated invasion debts at habitat scale that might be relevant to habitat management. © 2016 Springer International Publishing Switzerland

Diaz-de-Quijano M.,Global Ecology Unit CREAF CEAB UAB | Kefauver S.,Cerdanyola del Valles | Ogaya R.,Cerdanyola del Valles | Vollenweider P.,Swiss Federal Institute of forest | And 2 more authors.
European Journal of Forest Research | Year: 2016

Ozone concentrations in the Pyrenees have exceeded the thresholds for forest protection since 1994. We surveyed the severity of visible O3 injuries, crown defoliation, and tree mortality of Pinus uncinata, the dominant species in subalpine forests in this mountain range, along two altitudinal and O3 gradients in the central Catalan Pyrenees and analysed their relationships with the local environmental conditions. The severity of visible O3 injuries increased with increasing mean annual [O3] when summer water availability was high (summer precipitation/potential evapotranspiration above 0.96), whereas higher [O3] did not produce more visible injuries during drier conditions. Mean crown defoliation and tree mortality ranged between 20.4–66.4 and 0.6–29.6 %, respectively, depending on the site. Both were positively correlated with the accumulated O3 exposure during the last 5 years and with variables associated with soil–water availability, which favours greater O3 uptake by increasing stomatal conductance. The results indicate that O3 contributed to the crown defoliation and tree mortality, although further research is clearly warranted to determine the contributions of the multiple stress factors to crown defoliation and mortality in P. uncinata stands in the Catalan Pyrenees. © 2016 Springer-Verlag Berlin Heidelberg

Cotillas M.,Cerdanyola del Valles | Espelta J.M.,Cerdanyola del Valles | Sanchez-Costa E.,Cerdanyola del Valles | Sabate S.,Cerdanyola del Valles | Sabate S.,University of Barcelona
European Journal of Forest Research | Year: 2016

In the last decades, the global interest in the role of forests as carbon sinks has grown, and thus, studies aimed at estimating tree biomass have progressively increased. However, few surveys have focused on young coppices, although they are abundant worldwide in areas regenerating after disturbance (e.g. wildfire, clearcutting). In the Mediterranean Basin, young coppices are very frequent, and most of them are formed by evergreen and deciduous oaks (Quercus spp.). In this survey, we have studied the biomass allocation patterns of two oaks coexisting in coppices, the evergreen Quercus ilex and the deciduous Quercus cerrioides, comparing them in the light of their different leaf habit, which may influence their physiological performance in the context of climate change. We have also obtained allometric equations for each species and its components, which we have used to calculate the carbon stock in the sampled area, as an insight into the potential of young oak coppices to sequester carbon. The results indicate a higher biomass investment of Q. ilex in the stump and a higher leafiness and allocation to roots in Q. cerrioides. In the light of these differences, the evergreen Q. ilex could be defined as a “resource-saving” species in comparison with the more “resource-demanding” Q. cerrioides. The allometric equations were able to predict from 78 to 99 % of the variation in biomass using diameter as predictor variable for all the tree components aside of the stump. Overall carbon stock estimation in the young coppice of our study area was 43.2 Mg ha−1, of which 62 % is stored belowground. These results highlight the importance of biomass allocation in the belowground compartment in Mediterranean young oak coppices as a temporal carbon sink. Moreover, they provide evidence that these forests may store a relevant amount of carbon, often ignored in forest inventories. © 2016 Springer-Verlag Berlin Heidelberg

Anderegg W.R.L.,University of Utah | Martinez-Vilalta J.,Cerdanyola del Valles | Martinez-Vilalta J.,University of Barcelona | Cailleret M.,ETH Zurich | And 12 more authors.
Ecosystems | Year: 2016

Drought- and heat-driven tree mortality, along with associated insect outbreaks, have been observed globally in recent decades and are expected to increase in future climates. Despite its potential to profoundly alter ecosystem carbon and water cycles, how tree mortality scales up to ecosystem functions and fluxes is uncertain. We describe a framework for this scaling where the effects of mortality are a function of the mortality attributes, such as spatial clustering and functional role of the trees killed, and ecosystem properties, such as productivity and diversity. We draw upon remote-sensing data and ecosystem flux data to illustrate this framework and place climate-driven tree mortality in the context of other major disturbances. We find that emerging evidence suggests that climate-driven tree mortality impacts may be relatively small and recovery times are remarkably fast (~4 years for net ecosystem production). We review the key processes in ecosystem models necessary to simulate the effects of mortality on ecosystem fluxes and highlight key research gaps in modeling. Overall, our results highlight the key axes of variation needed for better monitoring and modeling of the impacts of tree mortality and provide a foundation for including climate-driven tree mortality in a disturbance framework. © 2016 Springer Science+Business Media New York

Barba J.,Cerdanyola del Valles | Curiel Yuste J.,CSIC - National Museum of Natural Sciences | Poyatos R.,Cerdanyola del Valles | Janssens I.A.,University of Antwerp | Lloret F.,Cerdanyola del Valles
Oecologia | Year: 2016

How forests cope with drought-induced perturbations and how the dependence of soil respiration on environmental and biological drivers is affected in a warming and drying context are becoming key questions. The aims of this study were to determine whether drought-induced die-off and forest succession were reflected in soil respiration and its components and to determine the influence of climate on the soil respiration components. We used the mesh exclusion method to study seasonal variations in soil respiration (RS) and its components: heterotrophic (RH) and autotrophic (RA) [further split into fine root (RR) and mycorrhizal respiration (RM)] in a mixed Mediterranean forest where Scots pine (Pinus sylvestris L.) is undergoing a drought-induced die-off and is being replaced by holm oak (Quercus ilex L.). Drought-induced pine die-off was not reflected in RS nor in its components, which denotes a high functional resilience of the plant and soil system to pine die-off. However, the succession from Scots pine to holm oak resulted in a reduction of RH and thus in an important decrease of total respiration (RS was 36 % lower in holm oaks than in non-defoliated pines). Furthermore, RS and all its components were strongly regulated by soil water content-and-temperature interaction. Since Scots pine die-off and Quercus species colonization seems to be widely occurring at the driest limit of the Scots pine distribution, the functional resilience of the soil system over die-off and the decrease of RS from Scots pine to holm oak could have direct consequences for the C balance of these ecosystems. © 2016 Springer-Verlag Berlin Heidelberg

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