Suchergebnisse

14 páginas,6 figuras, 4 tablas. ; A 6-yr experiment in drought manipulation was conducted in a Quercus ilex L. Mediterranean forest to simulate the drought conditions projected for the coming decades. We investigated the eff ects of those drought conditions on soil urease, protease, and β-glucosidase activities and the changes in C and N stocks in soil, leaves, and leaf litter. Elimination of runoff and rainfall resulted in lower soil water content than in control soils in autumn, winter, and spring (27, 61, and 53%, respectively). In soils subjected to runoff plus partial rainfall elimination, urease activities were reduced by 25% in autumn, winter, and spring; soil protease activities by 33% in winter and spring; and β-glucosidase by 25 to 30% in summer and spring. Drought reduced the C/N ratio of the leaf litter of the dominant species, Q. ilex, by 11%, indicating a decrease in N remobilization before leaf fall. We therefore did not observe an increase in the C/N concentration ratio in litter and soil as we had expected. Drought decreased N availability in spring, the growing season, by reducing soil NO3 − concentration. Th e reduction in enzyme activities in the droughtaff ected soils was mainly due to the prolonged decrease in water availability and, to a lesser extent, to current soil water availability, mainly in summer, and to changes in the nutritional quality of the enzyme substrate. Th e observed drop in soil enzyme activity can contribute to a decrease in the amount of N liberated and consequently to a decline in the plant N capture, which was observed in some community species such as Arbutus unedo L. ; Th is research was supported by the European project NEU NITROEUROPE (GOCE017841), by the Spanish Government Grants CGL2006-04025/BOS and Consolider-Ingenio Montes CSD2008- 00040, and by the Catalan Government Grant SGR 2009-1458. ; Peer reviewed

6 páginas, 2 figuras. ; Global warming leads to shifts in vegetation types in given temperate environments. The fastest species movement is due to the globalized supply and use of exotic plants in gardening and urban landscaping. These standard practices circumvent dispersal limitations and biological and environmental stresses; they have three major global impacts: (i) the enhancement of biological invasions, (ii) the elevation of volatile organic compound emissions and the resulting increase in photochemical smog formation, and (iii) the enhancement of CO2 fixation and water use by gardened plants. These global effects, none of which are currently considered in globalchange scenarios, are increasingly amplified with further warming and urbanization. We urge for quantitative assessment of the global effects of gardening and urban landscaping. ; We acknowledge financial support by the Estonian Ministry of Education and Science (grant SF1090065s07), the Estonian Academy of Sciences, the Spanish Ministry of Education and Science (grants CGL2004–01402/BOS and CGL-2006–04025/BOS), the European Commission RTN 'ISONET' contract MC-RTN-CT-2003–504720, the European Science Foundation 'VOCBAS' program, the Fundació Abertis (2007 grant) and the Catalan government (grant SGR2005–00312). ; Peer reviewed

4 páginas, 2 figuras. ; Ultrasonic acoustic emissions were measured in Quercus ilex trees of a Mediterranean forest in Catalonia (NE Spain) each season from summer of 2004 to autumn of 2005. Acoustic emissions were maximum during hot and dry summer periods. Acoustic emissions started below 17% soil moisture, 0.85 RWC, and 2.5 MPa leaf water potential. They were negatively correlated with soil moisture and leaf water potential. The relationship between acoustic emissions and leaf water potential was the strongest, indicating that xylem tension is the most important factor inducing both cavitation (acoustic emissions) and a decrease in leaf water potential. Future increase of xylem cavitation derived from climate change may result in growth and survival limitations for this species in the drier southern limits of its current distribution. ; This research was financially supported by MEC REN2003-04871 and CGL 2004-01402/BOS grants from the Spanish Government, a Fundacio´n BBVA 2004 grant, a Catalan Government SGR2005-00312 grant, and the European project ALARM (Contract 506675, EU sixth framework programme). ; Peer reviewed

9 páginas. 7 figuras ; A holm oak forest was exposed to an experimental drought during 5 years to elucidate the growth responses of the dominant species Quercus ilex, Arbutus unedo and Phillyrea latifolia. Soil water availability was partially reduced, about 15% as predicted for this area for the next decades by GCM and ecophysiological models, by plastic strips intercepting rainfall and by ditch exclusion of water runoff. The stem diameter increment was highly correlated with annual rainfall in all species, and drought treatment strongly reduced the diameter increment of Q. ilex (41%) and specially of A. unedo (63%), the species showing higher growth rates. Stem mortality rates were highly correlated with previous stem density, but drought treatment increased mortality rates in all species. Q. ilex showed the highest mortality rates (9% and 18% in control and drought plots, respectively), and P. latifolia experienced the lowest mortality rates (1% and 3% in control and drought plots, respectively). Drought strongly reduced the increment of live aboveground biomass during these 5 years (83%). A. unedo and Q. ilex experienced a high reduction in biomass increment by drought, whereas P. latifolia biomass increment was insensitive to drought. The different sensitivity to drought of the dominant species of the holm oak forest may be very important determining their future development and distribution in a drier environment as expected in Mediterranean areas for the next decades. These drier conditions could thus have strong effects on structure (species composition) and functioning (carbon uptake and biomass accumulation) of these Mediterranean forests. ; This research was financially supported by MEC projects CLI97-0344, REN2003-04871, and CGL 2004-01402/BOS from the Spanish Government, and by the European project ALARM (Contract 506675, EU sixth framework programme). ; Peer reviewed

6 páginas, 4 figuras, 1 tabla. ; The Digital Climatic Atlas and the Ecological and the Forestry Inventory of Catalonia (NE Spain) were analysed to study the climate effect on leaf mass per area (LMA) and leaf area index (LAI) on Quercus ilex L., one of the most widely spread tree species in the Mediterranean region. 195 sites in this region of 31,895 km2 were considered. The relationship between climatic variables (total annual rainfall, mean annual temperature, mean minimum winter temperatures, and mean annual solar radiation) and LMA and LAI were analysed by simple and multiple regressions. LMA was higher in the drier sites and specially in the colder sites. There was also a significant correlation between solar radiation and LMA. On the contrary, LAI values, which were negatively correlated with LMA values, were lower in drier and colder sites, and were not significantly affected by solar radiation. The results highlight that high LMA values do not seem to be a specific protection to dry conditions but to a wide range of environmental stress factors, including low temperatures. ; This research was financially supported by MEC projects REN2003- 04871, and CGL2004-01402/BOS from the Spanish Government, by the European project ALARM (Contract 506675, EU sixth framework programme) and by a Fundacio´n BBVA 2004 and a SGR2005-00312 AGAUR-Generalitat de Catalunya grants. ; Peer reviewed

7 páginas, 3 figuras, 1 tabla ; A holm oak forest was exposed to an experimental drought (reduction of 15 per cent soil moisture as predicted for this area for the next decades by General Circulation Models and ecophysiological models) during 7 years to elucidate the reproductive responses of the dominant species Quercus ilex L., Arbutus unedo L. and Phillyrea latifolia L. Soil moisture was partially reduced by plastic strips intercepting rainfall and by ditch exclusion of water runoff. During the period studied, meteorological conditions and soil moisture were continuously monitored, together with fl ower and fruit production in the three dominant species. In Q. ilex and A. unedo, fl ower and specially fruit production were strongly correlated with annual rainfall, but not in P. latifolia. The experimental drought reduced fl ower and fruit production in Q. ilex by 30 per cent and 45 per cent, respectively. Reductions in fl ower and fruit production were not signifi cant in A. unedo and were not observed in P. latifolia. A decrease in production of reproductive structures and the different response of the species studied to a decrease in water availability could induce important changes in the competitive ability of the different species and in the long term in the community species composition and future distribution of these Mediterranean species. ; This research was fi nancially supported by CGL 2004-01402/BOS and GCL 2006-04025/BOS grants from the Spanish Government, a Fundación Banco Bilbao Vizcaya 2004 grant, a Catalan Government SGR2005-00312 grant and the European project Assesing Large scale Risks for biodiversity with tested Methods (contract 506675, European Union sixth framework programme). ; Peer reviewed

Forest ecosystems in the Mediterranean Basin are mostly situated in the north of the Basin (mesic). In the most southern and dry areas, the forest can only exist where topography and/or altitude favor a sufficient availability of water to sustain forest biomass. We have conducted a thorough review of recent literature (2000-2021) that clearly indicates large direct and indirect impacts of increasing drought conditions on the forests of the Mediterranean Basin, their changes in surface and distribution areas, and the main impacts they have suffered. We have focused on the main trends that emerge from the current literature and have highlighted the main threatens and management solution for the maintenance of these forests. The results clearly indicate large direct and indirect impacts of increasing drought conditions on the forests of the Mediterranean Basin. These increasing drought conditions together with over-exploitation, pest expansion, fire and soil degradation, are synergistically driving to forest regression and dieback in several areas of this Mediterranean Basin. These environmental changes have triggered responses in tree morphology, physiology, growth, reproduction, and mortality. We identified at least seven causes of the changes in the last three decades that have led to the current situation and that can provide clues for projecting the future of these forests: (i) The direct effect of increased aridity due to more frequent and prolonged droughts, which has driven Mediterranean forest communities to the limit of their capacity to respond to drought and escape to wetter sites, (ii) the indirect effects of drought, mainly by the spread of pests and fires, (iii) the direct and indirect effects of anthropogenic activity associated with general environmental degradation, including soil degradation and the impacts of fire, species invasion and pollution, (iv) human pressure and intense management of water resources, (v) agricultural land abandonment in the northern Mediterranean Basin without adequate management of new forests, (vi) very high pressure on forested areas of northern Africa coupled with the demographic enhancement, the expansion of crops and higher livestock pressure, and the more intense and overexploitation of water resources uses on the remaining forested areas, and (vii) scarcity and inequality of human management and policies, depending on the national and/or regional governments and agencies, being unable to counteract the previous changes. We identified appropriate measures of management intervention, using the most adequate techniques and processes to counteract these impacts and thus to conserve the health, service capacity, and biodiversity of Mediterranean forests. Future policies should, moreover, promote research to improve our knowledge of the mechanisms of, and the effects on, nutrient and carbon plant-soil status concurrent with the impacts of aridity and leaching due to the effects of current changes. Finally, we acknowledge the difficulty to obtain an accurate quantification of the impacts of increasing aridity rise that warrants an urgent investment in more focused research to further develop future tools in order to counteract the negative effects of climate change on Mediterranean forests.

5 p. -- Postprint del artículo publicado en Trends in Plant Science. Versión revisada y corregida (difiere de la versión publicada en pequeños retoques en la redacción realizados por la revista) -- ; Here, we propose a new term, 'ethnobotanical convergence', to refer to the similar uses for plants included in the same node of a phylogeny. This phylogenetic approach, together with the 'omics' revolution, shows how combining modern technologies with traditional ethnobotanical knowledge could be used to identify potential new applications of plants. ; T.G. and J.V. were supported by the Catalan Government project 2014SGR514 and the Spanish Government projects CSO2014-59704-P and CGL2013-49097-C2-2-P. J. P. was supported by the European Research Council Synergy grant SyG-2013-610028 IMBALANCE-P, the Spanish Government project CGL2013-48074-P, and the Catalan Government project 2014SGR274. ; Peer reviewed

7 páginas, 2 figuras. ; Physical CO2 diffusion from sub-stomatal cavities to the chloroplasts where photosynthesis takes place is an important limitation of photosynthesis largely neglected in research related to global climate change. This limitation is particularly important in leaves with robust structures such as evergreen sclerophylls. In these leaves, photosynthesis is less sensitive to changes in stomatal openness, which is considered to be the primary limitation of photosynthesis. In this review we state that, because of large limitations in internal diffusion in C3 plants, photosynthesis and the intrinsic efficiency of the use of plant water responds more strongly to elevated levels of CO2 in leaves with more robust structures. This provides an additional explanation for the current apparent expansion of evergreen sclerophylls in many Earth ecosystems, and adds a new perspective to research of the biological effects of increasing atmospheric CO2. ; This study was supported by the Estonian Ministry of Science and Education (grant number SF1090065s07), a collaborative project between the Estonian Academy of Sciences and the Spanish CSIC, the Spanish Government (CGL2006-04025/BOS, CGL2010-17172/BOS and Consolider-Ingenio Montes CSD2008-00040), the CSIC grant PIF08- 006-3 and the Catalan Government grant SGR 2009-458. Research by JF was financed by the Spanish Ministry of Education and Research (Project BFU2008-1072-E/BFI). ; Peer reviewed

6 páginas, 4 figuras. ; Current climate projections predict drier and warmer conditions in the Mediterranean basin over the next century. While advanced spring growth due to warming has been described in the literature, few data are available on the effects of drought on phenology. Hence, the phenology and growth of two Mediterranean shrubs, Erica multiflora and Globularia alypum, was studied in a rainfall exclusion field experiment to simulate spring drought in a natural shrubland. We estimated the onset of growth in spring by monitoring the appearance of new stems, and the end of growth in summer by following the elongation of stems. Drought treatment caused earlier onset of the spring growing season in E. multiflora, whereas no advance was observed in G. alypum. However, growth cessation was not affected in E. multiflora. Drought reduced the growth of both shrubs, as reflected in less stem elongation. The results show that a drier climate might affect not only growth but also spring phenology of some Mediterranean species. We suggest that a reduction in the cooling effect of transpiration may have analogous effects to warming and might advance the start of growth in E. multiflora, a species whose phenology has been described as warming-sensitive. The lengthening of the growing season resulting from advanced growth did not imply higher productivity, as growth was restricted by drought. ; This work was supported by the European Union [project NITROEUROPE IP grant number GOCE017841], the Spanish Government [grant number CGL2006-04025 ⁄BOS], the project Consolider-Ingenio Montes [grant number CSD2008- 00040] and the Catalan Government [grant number SGR2009-458]. ; Peer reviewed

5 páginas, 2 figuras. ; During the Cretaceous and early Tertiary, when the climate was warm and the atmospheric CO2 concentration ([CO2]) was at least double that of the present-day, polar forests populated high latitude landmasses. We investigated the density and length of stomata and other epidermal cells of two deciduous and three evergreen "living fossil" tree species representative of these ancient forests. These tree species were grown in a simulated Cretaceous high latitude environment at either ambient (400 ppmv) or elevated (800 ppmv) [CO2] during four years. After 4 years growing at elevated [CO2], the leaf stomatal density and index (percentage of leaf epidermal cells that are stomata) of these plants were similar to those of their counterparts growing at ambient [CO2]. While the CO2 enrichment only modified the stomatal pore length in two of the five studied species, it increased significantly the overall length of the epidermal cells of all the species, reducing their density. These results revealed that leaf epidermal cells of these "living fossil" species were more sensitive than stomata to an experimental doubling of atmospheric CO2 concentration. ; and David J. Beerling for allowing us to participate in the experiment. This study was supported by a European Union Marie Curie postdoctoral fellowship to L.L. (contract N EVK2eCTe2002e50022), by the Spanish Government CGL2006-4025/BOS, CGL2007-64583/BOS and Consolider-Ingenio MONTES CSD2008-00040 projects, the Catalan government SGR2009-458 project, and the Spanish National Research Council CSIC-PIF08-006-3 project. ; Peer reviewed

12 páginas, 3 figuras, 1 tabla. ; The goals of this study are: (1) to determine whether increasing atmospheric CO2 concentrations and changing climate increased intrinsic water use efficiency (iWUE, as detected by changes in D 13 C) over the last four decades; and if it did increase iWUE, whether it led to increased tree growth (as measured by tree-ring growth); (2) to assess whether CO2 responses are biome dependent due to different environmental conditions, including availability of nutrients and water; and (3) to discuss how the findings of this study can better inform assumptions of CO2 fertilization and climate change effects in biospheric and climate models. ; This research was supported by Spanish Government CGL2006- 04025/BOS and Consolider-Ingenio Montes CSD2008-00040 grants, and a Catalan Government SGR2009-458 grant. The work is a contribution to the research agenda of the Global Carbon Project of the Earth System Science Partnership. J.G.C. acknowledges the support of the Australian Climate Change Science Program. ; Peer reviewed

4 páginas, 1 figura. ; The research conducted by the authors is supported by the Spanish Government projects CGL2006-04025 ⁄BOS, CGC2010-17172 and Consolider Ingenio Montes (CSD2008-00040), by the European project NEU NITROEUROPE (GOCE017841), and by the Catalan Government project SGR 2009-458. ; Peer reviewed

35 páginas, 4 tablas, 1 figura. ; Ecometabolomics, which aims to analyze the metabolome, the total number of metabolites and its shifts in response to environmental changes, is gaining importance in ecological studies because of the increasing use of new technical advances, such as modern HNMR spectrometers and GC-MS coupled to bioinformatic advances. We review here the state of the art and the perspectives of ecometabolomics. The studies available demonstrate ecometabolomic techniques have great sensitivity in detecting the phenotypic mechanisms and key molecules underlying organism responses to abiotic environmental changes to biotic interactions. But such studies are still scarce, and in most cases they are limited to the direct effects of a single abiotic factor or of biotic interactions between two trophic levels under controlled conditions. Several exciting challenges remain to be achieved through the use of ecometabolomics in field conditions, involving more than two trophic levels, or combining the effects of abiotic gradients with intra- and inter-specific relationships. The coupling of ecometabolomic studies with genomics, transcriptomics, ecosystem stoichiometry, community biology and biogeochemistry may provide a further step forward in many areas of ecological sciences, including stress responses, species lifestyle, life history variation, population structure, trophic interaction, nutrient cycling, ecological niche and global change ; This research was supported by the Spanish Government project CGL2006-04025/BOS, CGC2010-17172 and Consolider-Ingenio Montes (CSD2008-00040), by the Catalan Government project SGR 2009-458, and by the European project NEU NITROEUROPE GOCE017841. ; Peer reviewed

11 páginas,4 tablas, 9 figuras, 1 apéndice (http://dx.doi.org/10.1016/j.foreco.2011.08.019) ; Although some studies have observed significant correlations between latitude and climate gradients and tree leaf nutrientconcentration and stoichiometry, others have not. This study examined the nutrientconcentrations of tree leaves in 3530 plots of the Catalonian Forest Inventory. Catalonia is a Mediterranean region located in NE Iberian Peninsula. It has a long land-use history and includes the large industrial-urban area of Barcelona but still contains a large forest area (42%). In the forests of Catalonia, leaf nutrientconcentration increased and leaf C:nutrient ratios decreased from south to north, which paralleled the increase in MAP (mean annual precipitation) and the decrease in MAT (mean annual temperature), which was expected in a Mediterranean climate where the availability of water is the most limiting factor for plant nutrient uptake. In addition, the availability of water, which influences productivity, was associated with low leaf N:P content ratios, which is consistent with the Growth Rate Hypothesis. At a regional scale, the results support the Soil-Age Hypothesis because the youngest soils in the Pyrenees had the lowest leaf N:P ratios. Furthermore, the type of forest (evergreen, deciduous, or coniferous) explained some of the variation in leaf nutrientconcentrations and stoichiometry. Nutrientconcentrations were highest in deciduous trees and lowest in coniferous trees. Leaf nutrientconcentrations and stoichiometry were mainly correlated with climate, but other factors such as the chemical properties of soil and rock, phylogenetics, and different ecological histories and anthropogenic factors such as pollution, had an effect. ; This research was supported by the European Project NEU NITROEUROPE (GOCE017841), by Spanish Government Projects CGL2006-04025/BOS, CGL2010-17172/BOS and Consolider-Ingenio Montes CSD2008-00040, and by Catalan Government Project SGR 2009-458. ; Peer reviewed