203 research outputs found
Carbon and nitrogen balances for six shrublands across Europe
No full textShrublands constitute significant and important parts of European landscapes providing a large number of important ecosystem services. Biogeochemical cycles in these ecosystems have gained little attention relative to forests and grassland systems, but data on such cycles are required for developing and testing ecosystem models. As climate change progresses, the potential feedback from terrestrial ecosystems to the atmosphere through changes in carbon stocks, carbon sequestration, and general knowledge on biogeochemical cycles becomes increasingly important. Here we present carbon and nitrogen balances of six shrublands along a climatic gradient across the European continent. The aim of the study was to provide a basis for assessing the range and variability in carbon storage in European shrublands. Across the sites the net carbon storage in the systems ranged from 1,163 g C m−2 to 18,546 g C m−2, and the systems ranged from being net sinks (126 g C m−2 a−1) to being net sources (−536 g C m−2 a−1) of carbon with the largest storage and sink of carbon at wet and cold climatic conditions. The soil carbon store dominates the carbon budget at all sites and in particular at the site with a cold and wet climate where soil C constitutes 95% of the total carbon in the ecosystem. Respiration of carbon from the soil organic matter pool dominated the carbon loss at all sites while carbon loss from aboveground litter decomposition appeared less important. Total belowground carbon allocation was more than 5 times aboveground litterfall carbon which is significantly greater than the factor of 2 reported in a global analysis of forest data. Nitrogen storage was also dominated by the soil pools generally showing small losses except when atmospheric N input was high. The study shows that in the future a climate-driven land cover change between grasslands and shrublands in Europe will likely lead to increased ecosystem C where shrublands are promoted and less where grasses are promoted. However, it also emphasizes that if feedbacks on the global carbon cycle are to be predicted it is critically important to quantify and understand belowground carbon allocation and processes as well as soil carbon pools, particularly on wet organic soils, rather than plant functional change as the soil stores dominate the overall budget and fluxes of carbon
Physiological and antioxidant responses of Erica multiflora to drought and warming through different seasons
No full textClimate change projections forecast a warming and an associated change in the distribution and intensity of rainfalls. In the case of the Mediterranean area, this will be reflected in more frequent and severe drought periods in the future. Within a long-term (9 years) manipulation experiment, we aimed to study the effect of the soil drought (15-20% decreased soil moisture) and warming conditions (+1A degrees C warming) projected for the next decades onto photosynthetic rates and water relations, and onto the antioxidant and anti-stress defense capacity of Erica multiflora, a common species of the dry Mediterranean coastal scrublands, in two different seasons, spring and summer. Results indicated that none of the applied treatments was severe enough to induce a pronounced negative response of photosynthesis in this species well adapted to harsh Mediterranean conditions, but also highlighted important seasonal differences. Photosynthesis was limited by photoinhibition in spring and by stomatal closure in summer. Isoprenoid emission and the level of enzymatic and non-enzymatic antioxidants were lower in summer than in spring, whereas pigment and total phenolic contents were generally higher in summer. Volatile isoprenoid emissions were largely inhibited by drought and were not stimulated by warming. Drought and warming increased the oxidation state of ascorbate and reduced total glutathione levels in spring, but not in summer. It is concluded that E. multiflora plants can adapt to prolonged drought and warming, at least at the level simulated by our manipulative experiment, through changes in the seasonal physiological and antioxidant response of leaves
Study of pure electric propulsion system and design of the system for a 6 m hull already permited
No full textla indústria de les embarcacions d`esbarjo creix contínuament a causa de la seva popularitat a la societat. A causa d'aquest creixement, les empreses estan desenvolupant nous models amb l`última tecnologia, dissenyant i construint models cada cop més còmodes i econòmics, i la probabilitat d'èxit en el sector està disminuint. per reduir els impactes ambientals a la costa produïts per la navegació d`esbarjo, és molt important reduir les emissions, el soroll i les vibracions dels motors de combustió interna. aquest treball tracta el disseny i el dimensionament d'un sistema de propulsió totalment elèctric per a una embarcació d'esbarjo de 6 m amb un casc de planeig predeterminat. També inclou informació d`última generació sobre noves tecnologies de baixes i zero emissions, motors elèctrics marins, bateries i panells fotovoltaics. per a la realització del treball es va proposar un procediment en dues fases. El primer pas és analitzar la forma del casc per estudiar la seva resistència a les velocitats requerides mitjançant el programari maxsurf. El segon és triar el motor elèctric i la bateria adequats per optimitzar l'energia. Com a cas pràctic s'ha escollit un casc de planeig obtingut de la base de dades delftship, amb 6,1 m d`eslora i capacitat per a 6 persone
Study of pure electric propulsion system and design of the system for a 6 m hull already permited
No full textla indústria de les embarcacions d`esbarjo creix contínuament a causa de la seva popularitat a la societat. A causa d'aquest creixement, les empreses estan desenvolupant nous models amb l`última tecnologia, dissenyant i construint models cada cop més còmodes i econòmics, i la probabilitat d'èxit en el sector està disminuint. per reduir els impactes ambientals a la costa produïts per la navegació d`esbarjo, és molt important reduir les emissions, el soroll i les vibracions dels motors de combustió interna. aquest treball tracta el disseny i el dimensionament d'un sistema de propulsió totalment elèctric per a una embarcació d'esbarjo de 6 m amb un casc de planeig predeterminat. També inclou informació d`última generació sobre noves tecnologies de baixes i zero emissions, motors elèctrics marins, bateries i panells fotovoltaics. per a la realització del treball es va proposar un procediment en dues fases. El primer pas és analitzar la forma del casc per estudiar la seva resistència a les velocitats requerides mitjançant el programari maxsurf. El segon és triar el motor elèctric i la bateria adequats per optimitzar l'energia. Com a cas pràctic s'ha escollit un casc de planeig obtingut de la base de dades delftship, amb 6,1 m d`eslora i capacitat per a 6 persone
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Author Correction: Crowther et al. reply
No full textIn this Brief Communications Arising Reply, the affiliation for author P. H. Templer was incorrectly listed as 'Department of Ecology & Evolutionary Biology, University of California Irvine, Irvine, California 92697, USA' instead of 'Department of Biology, Boston University, Boston, Massachusetts 02215, USA'. This has been corrected online
Effects of resource availability on condensed tannins and nitrogen in two Quercus species differing in leaf life span.
No full text7 páginas, 2 tablas, 2 figuras.[EN]Seedlings of Quercus ilex and Q. cerrioides, an evergreen and a winter-deciduous oak co-occurring in western-Mediterranean forests, were
grown at two light regimes (8 and 36% of photosynthetically active radiation), at two water regimes (500 and 800 mm) and with two nutrient availabilities
(standard substrate and 7% increase in soil N). The concentrations of soluble condensed tannins (CT) and nitrogen in the leaves were analyzed to test
the phenotypic plasticity of these commonly related parameters in two con-generic species with contrasting leaf habit. Q. ilex contains seven times
more CT and a few less N than Q. cerrioides. Light increased CT, whereas neither fertilization nor water had an effect on CT. N concentration was
decreased by light, increased by fertilization and not affected by water treatment. Plant growth was increased by light but not affected by fertilization
or water treatment. CT were negatively correlated with N concentration. CT of the evergreen species exhibited greater plasticity than the deciduous
one as reflected by a steeper negative correlation among nitrogen and CT concentrations in Q. ilex. Given the antiherbivory activity of CT, this implies
that in less shaded environments, e.g. canopy aperture by disturbances, leaf tissue quality for herbivores will be much more reduced in Q. ilex than in
Q. cerrioides. Higher leaf CT in Q. ilex and its higher plasticity to light availability may explain the higher browsing by sheep in Q. cerrioidesthan in
Q. ilex resprouts, as well as the low recruitment rates of seedlings of the former species, reported in other studies.[FR]Effets de la disponibilité de la ressource sur les tanins condensés et l’azote chez deux espèces de Quercus différentes pour la durée de
vie de leurs feuilles. Des semis de Quercus ilex et Quercus cerrioides, une espèce sempervirente et une espèce décidue co-existantes dans les forêts
méditerranéennes occidentales, ont été élevés sous deux régimes lumineux (8 et 36 % de PAR), deux régimes d’alimentation hydrique (500 et 800 mm)
et avec deux niveaux d’alimentation nutritionnelle (substrat standard et substrat avec une augmentation d’azote de 7 %). Les concentrations des tanins
solubles condensés (CT) et d’azote des feuilles ont été analysées pour tester la plasticité phénotypique de ces paramètres couramment rapportés chez
deux espèces de même genre ayant des types différents de feuilles. Quercus ilex contient 7 fois plus de CT et un peu moins d’azote que Quercus
cerrioides. La lumière accroît CT alors que ni la fertilisation ni l’eau ont eu un effet sur CT. La concentration en azote a diminué avec l’augmentation de
la lumière, elle a été augmentée par la fertilisation et n’a pas été affectée par le niveau d’alimentation hydrique. La croissance des semis a été augmentée
par l’augmentation du PAR mais n’a pas été affectée par la fertilisation ou le niveau d’alimentation en eau. CT a été corrélée avec la concentration
en azote. La CT des espèces sempervirentes présente une plus grande plasticité que les espèces décidues comme cela est reflété par une plus forte
corrélation négative entre les concentrations d’azote et de CT chez Quercus ilex. Etant donné l’activité antiherbivore de CT, cela implique que dans les
environnements moins ombragés, par exemple dans les ouvertures de la canopée, la qualité des tissus foliaires sera plus diminuée chez Quercus ilex, que
chez Quercus cerrioides. Une CT plus élevée chez Quercus ilex, et sa plasticité plus grande à la lumière peuvent expliquer un broutage plus important
des rejets par les moutons chez Quercus cerrioides que chez Quercus ilex, de même que le faible taux de recrutement de semis de la première espèce
qui est rapportée dans d’autres études.We greatfully acknowledge funding from the
INTERREG III A project (I3A-1-100-E), Patronat Metropolità
del Parc de Collserola, Spanish Government grants REN2003-
04871/GLO, Catalan government grant SGR2005-00312, the EC
Integrated FP6 ALARM (GOCE-CT-2003-506675) Project, and a
Fundación BBVA 2004 grant. Marc Estiarte acknowledges financial support from the Spanish Ministerio de Educación y Ciencia
(Ramon y Cajal contract).Peer reviewe
The handbook for standardized field and laboratory measurements in terrestrial climate change experiments and observational studies (ClimEx)
No full textDrought advances spring growth phenology of the Mediterranean shrubErica multiflora.
No full text6 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 reviewe
Can current moisture responses predict soil CO2 efflux under altered precipitation regimes?: a synthesis of manipulation experiments
No full textAs a key component of the carbon cycle, soil CO2 efflux (SCE) is being increasingly studied to improve our mechanistic understanding of this important carbon flux. Predicting ecosystem responses to climate change often depends on extrapolation of current relationships between ecosystem processes and their climatic drivers to conditions not yet experienced by the ecosystem. This raises the question of to what extent these relationships remain unaltered beyond the current climatic window for which observations are available to constrain the relationships. Here, we evaluate whether current responses of SCE to fluctuations in soil temperature and soil water content can be used to predict SCE under altered rainfall patterns. Of the 58 experiments for which we gathered SCE data, 20 were discarded because either too few data were available or inconsistencies precluded their incorporation in the analyses. The 38 remaining experiments were used to test the hypothesis that a model parameterized with data from the control plots (using soil temperature and water content as predictor variables) could adequately predict SCE measured in the manipulated treatment. Only for 7 of these 38 experiments was this hypothesis rejected. Importantly, these were the experiments with the most reliable data sets, i.e., those providing high-frequency measurements of SCE. Regression tree analysis demonstrated that our hypothesis could be rejected only for experiments with measurement intervals of less than 11 days, and was not rejected for any of the 24 experiments with larger measurement intervals. This highlights the importance of high-frequency measurements when studying effects of altered precipitation on SCE, probably because infrequent measurement schemes have insufficient capacity to detect shifts in the climate dependencies of SCE. Hence, the most justified answer to the question of whether current moisture responses of SCE can be extrapolated to predict SCE under altered precipitation regimes is "no" – as based on the most reliable data sets available. We strongly recommend that future experiments focus more strongly on establishing response functions across a broader range of precipitation regimes and soil moisture conditions. Such experiments should make accurate measurements of water availability, should conduct high-frequency SCE measurements, and should consider both instantaneous responses and the potential legacy effects of climate extremes. This is important, because with the novel approach presented here, we demonstrated that, at least for some ecosystems, current moisture responses could not be extrapolated to predict SCE under altered rainfall conditions
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