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

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

12 páginas, 7 figuras.-- Metodología. ; [Background]: Drought is a common stressor in many regions of the world and current climatic global circulation models predict further increases in warming and drought in the coming decades in several of these regions, such as the Mediterranean basin. The changes in leaf water content, distribution and dynamics in plant tissues under different soil water availabilities are not well known. In order to fill this gap, in the present report we describe our study withholding the irrigation of the seedlings of Quercus ilex, the dominant tree species in the evergreen forests of many areas of the Mediterranean Basin. We have monitored the gradual changes in water content in the different leaf areas, in vivo and non-invasively, by 1H magnetic resonance imaging (MRI) using proton density weighted (ρw) images and spin-spin relaxation time (T2) maps. [Results]: ρw images showed that the distal leaf area lost water faster than the basal area and that after four weeks of similar losses, the water reduction was greater in leaf veins than in leaf parenchyma areas and also in distal than in basal leaf area. There was a similar tendency in all different areas and tissues, of increasing T2 values during the drought period. This indicates an increase in the dynamics of free water, suggesting a decrease of cell membranes permeability. [Conclusions]: The results indicate a non homogeneous leaf response to stress with a differentiated capacity to mobilize water between its different parts and tissues. This study shows that the MRI technique can be a useful tool to follow non-intrusively the in vivo water content changes in the different parts of the leaves during drought stress. It opens up new possibilities to better characterize the associated physiological changes and provides important information about the different responses of the different leaf areas what should be taken into account when conducting physiological and metabolic drought stress studies in different parts of the leaves during drought stress. ; This 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 the Catalan Government grant SGR 2009-1458. ; Peer reviewed

11 páginas, 6 tablas, 2 figuras. ; In an evergreen Mediterranean shrubland we conducted a 6-year field experiment simulating the warming and drought projected by general circulation models and ecophysiological models for the next decades: 20% reduction of soil moisture and 1 C of temperature increase. We tested whether warming and drought have effects on Ca, Fe, Mg, Mo, Na and S availability, concentrations and accumulation patterns in the three dominant plant species and in soil. Warming increased concentrations of Ca and Mo in leaves in Erica multiflora (42% and 65%, respectively) and in Dorycnium pentaphyllum (38% and 60%, respectively). Warming increased Mo accumulation in leaves and aboveground biomass in Globularia alypum (0.07 and 0.40 g ha 1 ) and in E. multiflora (0.12 and 0.4 g ha 1 ), and increased Fe accumulation in stem biomass of G. alypum (600 g ha 1 ), increasing the capacity to retain these nutrients in the ecosystem. The increase of Fe and Mo capture capacity under warming conditions was greater in G. alypum than in E. multiflora coinciding with its greater increases in photosynthetic capacity. Warming decreased soil total-Fe concentration by 24% and increased Mg accumulation in soil exchange complex by 19%. Drought increased Na leaf and stem concentrations (93% and 50%, respectively) and accumulation in leaf and aboveground biomass (780 and 800 g ha 1 , respectively) in G. alypum, allowing an increase of osmotic pressure which helps to prevent water losses and is related to its capacity to resist drought. Drought reduced S leaf and Mg leaf-litter concentrations of G. alypum and increased them in leaves of E. multiflora and also increased Mo and Na concentrations in leaves of D. pentaphyllum. Drought increased Fe soil solubility by 65%. The results indicate different effects of climate change on nutrient status in the ecosystem depending on whether the main change is warming or drought. The changes in concentration and biomass accumulation were different depending on the nutrient and the species, changing the stoichiometry among these nutrients and modifying the nutritional quality of plant tissues. ; This research was supported by Spanish Government projects CGL2004-01402/BOS, and CGL2006-0425/BOS, the Catalan Government project (SGR2005-00312), the European project ALARM (contract 506675) and NITROEUROPE (contract GOCE017841), and a Fundacio´n BBVA 2004 grant. ; Peer reviewed

AbstractThe COVID-19 pandemic has had a significant impact on global health, with millions of people affected by the disease. Recent studies have shown that environmental factors such as air quality, temperature, and humidity can impact the survival and transmission of the virus, leading to differences in the rate of spread and severity of the disease in different regions. In this global cross-sectional study, we analyzed the relationship between environmental factors and the transmission and survival of the virus in 167 cities distributed all over the world. We used a dataset containing daily COVID-19 data for 167 cities from 01/05/2020 to 01/01/2022, along with variables related to atmospheric and environmental conditions. We found an expected positive relationship between increases in atmospheric NO2 concentration and increases in the infective rate of COVID-19. We also found an unexpected negative relationship between PM10 and COVID-19 spread, which was stronger in unpolluted cities, and indicating a likely stronger and faster deactivation of the viruses by the absorption to the larger than to the smaller particles, to PM10 more than to PM2.5. Although a complete analysis would require taking into account the restrictions in the city and the immunization status of the population, and the variance of COVID-19 spread explained by PM10 was small, only up to approx. 2%, these results contribute to a better understanding of the impact of particles on the spread of COVID-19 and other respiratory viral diseases thus informing public health policies and interventions aimed at mitigating the impact of these pandemics.

19 páginas, 6 figuras, 2 tablas. ; Leaf elemental and secondary metabolite contents and morphological traits are important measures of time-dependent ecosystem changes. We aimed to test whether plants from older tropical forests have lower nutrient contents and different elemental stoichiometry than plants from younger ecosystems (''soil age'' hypothesis) and whether they had different contents of carbon based secondary compounds (CBSC) and morphological traits as a result of a longer evolution under tropical conditions. We conducted a phylogeny-independent study of the foliar chemical and structural traits in two sets of 86 species each measured in two different-aged tropical forests, a young soil forest in Hawaii and an old soil forest in Borneo. The leaf contents of nutrients and micronutrients tended to be higher in Hawaii than in Borneo but leaf N:P content ratio was not different. The ''soil age'' hypothesis was thus only partially supported by the results indicating that several other factors influence plant elemental content. Total phenolic content was twice larger in Hawaiian than in Bornean plant species. Terpene contents were not different in terpene-containing species but the percentage of species containing terpenes was much higher in Borneo (97%) than in Hawaii (34%) suggesting that the longer time of evolution in Borneo has allowed a more widespread development of very diverse defensive, allelopatic and information relationships of plants with specialist herbivores and other plants. Principal component analyses separated Hawaii and Borneo species on the basis of leaf elemental composition, total phenolics and terpene contents and leaf dry mass per area (LMA). The results collectively support the ''leaf economic spectrum'' and ''carbon excess'' paradigms because in both sets of species and also in the combined set of Borneo and Hawaiian species, there are negative relationships of N content with LMA and total phenolics. The results suggest thus that changes throughout time in N and P availability can be important but do not explain all the variability underlying the evolutionary changes in leaf chemistry and structure in these tropical forests. Other factors determining species biogeochemical niche such as K, Mg or S elemental stoichiometry, leaf economic traits and changes in plant defence and communication strategy are also likely to be involved. ; This research was supported by the Spanish Government projects CGL2006-04025/BOS, CGL2010- 17172, Consolider Ingenio Montes (CSD2008-00040), by the Catalan Government project SGR 2009-458 and by the Estonian Ministry of Education and Research (grant SF1090065s07) ; Peer reviewed

12 páginas, 4 tablas, 2 figuras. ; Aim Alien plant invasion is prominent in the Hawaiian Islands. There are many factors involved in invader success. To date, there is a general lack of information about one of them, which we aim to study here: the terpene emission capacity of both Hawaiian native and alien plants. Location Oahu (Hawaii). Methods We screened 35 alien and 35 native dominant plant species on Oahu Island for monoterpene emissions. The emission rates were measured from field-grown plants under standardized conditions of temperature and quantum flux density in the laboratory. Results The emission rates of total terpenes ranged from 0 µg g−1 h−1 to 55 µg g−1 h−1, and altogether 15 different terpenes were emitted in detectable amounts by the overall set of species. A phylogenetic signal was observed for total terpene emissions. Total terpene emission rates were higher in aliens than in native species (12.8 ± 2.0 vs. 7.6 ± 1.9 µg g−1 h−1, respectively). Main conclusions The greater terpene emission capacity may confer protection against multiple stresses and may partly account for the success of the invasive species, and may make invasive species more competitive in response to new global change-driven combined stresses. These results are consistent with aliens coming from very diverse ecosystems with generally higher biotic and abiotic stress pressures, and having higher nutrient concentrations. On the contrary, these results are not consistent with the 'excess carbon' hypotheses. These results indicate changes in vegetation terpene emissions brought about by alien plant invasions. ; This study was supported by the University of Hawai'i (G. P. Wilder research funds) and the grants from the Spanish Government (CGL2006-04025/BOS and Consolider-Ingenio Montes CSD 2008-00040), the Catalan Government (SGR 2009- 458), the Spanish National Research Council (CSIC-PIF08-006- 3), the Estonian Science Foundation (grant 7645), and the Estonian Ministry of Education and Science (SF1090065s07). ; Peer reviewed

17 páginas, 3 figuras, 4 tablas, 1 apéndice. ; Capacity for terpene production may confer advantage in protection against abiotic stresses such as heat and drought, and also against herbivore and pathogen attack. Plant invasive success has been intense in the Hawaiian islands, but little is known about terpene content in native and alien plant species on these islands. We conducted a screening of leaf terpene concentrations in 35 native and 38 alien dominant plant species on Oahu island. Ten (29%) of the 35 native species and 15 (39%) of the 38 alien species contained terpenes in the leaves. This is the first report of terpene content for the ten native species, and for 10 of the 15 alien species. A total of 156 different terpenes (54 monoterpenes and 102 sesquiterpenes) were detected. Terpene content had no phylogenetic significance among the studied species. Alien species contained significantly more terpenes in leaves (average ± SE=1965±367 μg g −1 ) than native species (830±227 μg g −1 ). Alien species showed significantly higher photosynthetic capacity, N content, and lower Leaf Mass Area (LMA) than native species, and showed higher total terpene leaf content per N and P leaf content. Alien species, thus, did not follow the expected pattern of "excess carbon" in comparison with native species. Instead, patterns were consistent with the "nutrient driven synthesis" hypothesis. Comparing alien and native species, the results also support the modified Evolution of Increased Competitive Ability (EICA) hypothesis that suggests that alien success may be favored by a defense system based on an increase in concentrations of less costly defenses (terpenes) against generalist herbivores. ; This research was supported by grants from the Spanish Government (CGL2006-04025/BOS and Consolider-Ingenio Montes CSD 2008-00040), the Catalan Government (SGR 2009-458), Estonian Science Foundation (grant 7645), and the Estonian Ministry of Education and Science (SF1090065s07) ; Peer reviewed

16 páginas, 3 tablas, 5 figuras. ; The capacity to produce carbon-based secondary compounds (CBSC), such as phenolics (including tannins) and terpenes as defensive compounds against herbivores or against neighboring competing plants can be involved in the competition between alien and native plant species. Since the Hawaiian Islands are especially vulnerable to invasions by alien species, we compared total phenolic (TP), total tannin (Tta), and total terpene (TT) leaf contents of alien and native plants on Oahu Island (Hawaii). We analyzed 35 native and 38 alien woody plant species randomly chosen among representative current Hawaiian flora. None of these CBSC exhibited phylogenetic fingerprinting. Alien species had similar leaf TP and leaf Tta contents, and 135% higher leaf TT contents compared with native species. Alien plants had 80% higher leaf TT:N leaf content ratio than native plants. The results suggest that apart from greater growth rate and greater nutrient use, alien success in Oahu also may be linked to greater contents of low cost chemical defenses, such as terpenes, as expected in faster-growing species in resource rich regions. The higher TT contents in aliens may counterbalance their lower investment in leaf structural defenses and their higher leaf nutritional quality. The higher TT provides higher effectiveness in deterring the generalist herbivores of the introduced range, where specialist herbivores are absent. In addition, higher TT contents may favor aliens conferring higher protection against abiotic and biotic stressors. The higher terpene accumulation was independent of the alien species origin, which indicates that being alien either selects for higher terpene contents post-invasion, or that species with high terpene contents are pre-adapted to invasiveness. Although less likely, an originally lower terpene accumulation in Hawaiian than in continental plants that avoids the increased attraction of specialist enemies associated to terpenes may not be discarded. ; This research was supported by the University of Hawaii (G. P. Wilder research funds), and grants from the Spanish Government (CGL2006- 04025/BOS, CGL2010-17172 and Consolider-Ingenio Montes CSD2008-00040), the Catalan Government (SGR 2009-458), the Estonian Ministry of Education and Science (grant SF1090065s07), the Spanish National Research council (CSIC-PIF08-006-3), and the Estonian Science Foundation (grant 7645). ; Peer reviewed

8 páginas, 2 tablas, 1 figura. ; Nuclear DNA amount has been assessed in a set of 6 Mediterranean plant species including subshrubs, shrubs and trees (Dorycnium pentaphyllum Scop., Erica multiflora L., Fumana ericoides (L.) Webb, Globularia alypum L., Pinus halepensis Mill and Rosmarinus officinalis L.). Genome size values have been assessed by flow cytometry from plants growing in their natural habitats, in plots with a particular experimental design to measure the effects of drought and warming and also with different phosphorus (P) concentration in soil. 2C values have been fairly constant in all the species studied under all conditions. These results, which provide first records of DNA content in all the studied species except for P. halepensis, suggest that moderate changes in climate such as a 0.73°C warming or a drought consisting of 19% decrease in soil moisture on an average of 7 years and the consequent changes in the soil availability of such an essential element as P (ranging from 80 to 160 g/g) do not affect genome size stability, at least not by producing rapid and significant variations. ; This work was subsidized by DGICYT (Spanish Government; projects CGL2004-04563-C02-02/BOS, CGL2004-01402/BOS, CGL2006-04025/BOS, CGL2007-64839-C02-01/BOS, CGL2007-64839-C02-02/BOS, including FEDER funding, and Consolider Ingenio Montes CSD2008-00040), by the European project NITROEUROPE (contract 017841), and by the Catalan government grant SGR2009-458. ; Peer reviewed

15 páginas, 3 figuras, 4 tablas. ; Plant-invasive success is one of the most important current global changes in the biosphere. To understand which factors explain such success, we compared the foliar traits of 41 native and 47 alien-invasive plant species in Oahu Island (Hawaii), a location with a highly endemic flora that has evolved in isolation and is currently vulnerable to invasions by exotic plant species. Foliar traits, which in most cases presented significant phylogenetic signal, i.e. closely related species tended to resemble each other due to shared ancestry, separated invasive from native species. Invasive species had lower leaf mass per area and enhanced capacities in terms of productivity (photosynthetic capacity) and nutrient capture both of macro- (N, P, K) and microelements (Fe, Ni, Cu and Zn). All these differences remain highly significant after removing the effects of phylogenetic history. Alien-invasive species did not show higher efficiency at using limiting nutrient resources, but they got faster leaf economics returns and occupied a different biogeochemical niche, which helps to explain the success of invasive plants and suggests that potential increases in soil nutrient availability might favor further invasive plant success. ; This research was supported by the University of Hawaii (G. P. Wilder research funds), and the grants from the Spanish Government (CGL2006-04025/BOS and Consolider-Ingenio Montes CSD2008-00040), the Catalan Government (SGR 2009-458) and the Estonian Ministry of Education and Science (SF1090065s07) and the join collaborative project between Spanish CSIC and the Estonian Academy of Sciences. ; Peer reviewed