Alessio G.A., Peñuelas J., Llusià J., Ogaya R., Estiarte M., De Lillis M. (2008) Influence of water and terpenes on flammability in some dominant Mediterranean species. International Journal of Wildland Fire. 17: 274-286.EnllaçDoi: 10.1071/WF07038
In the Mediterranean basin, fires are a major concern for forest and shrubland ecosystems. We studied flammability, its seasonality and its relationship with leaf moisture and volatile terpene content and emission in the dominant species of a Mediterranean shrubland and forest in Catalonia (NE Iberian Peninsula). We measured temperatures and time elapsed between the three flammability phases: smoke, pyrolysis and flame, for four seasons. We sampled twice in spring because of an occasional drought period during this season. Flammability had a significant relationship with leaf hydration, in the shrubland and in the forest. Few and only weak correlations were found between terpene content and flammability. In the future, arid conditions projected by climatic and ecophysiological models will increase fire risk through decreased hydration and subsequent increased flammability of the species. © IAWF 2008.
Avila A. (Coordinadora capítol) (2008) Contaminació atmosfèrica. CREAF 2003-2008 ISBN: 978-84-935221-03.
Avila A, Terradas J (eds) (2008) Aula d’Ecologia. Cicle de Conferències 2007 Servei de Publicacions. Universitat Autònoma de Barcelona. Bellaterra. ISBN: 978-84-490-2532-7.
Rodrigo A, Martínez-Vilalta J, Piñol J, Lloret F, Ribas A, Retana J, Losarcos J (2008) Disseny i aplicació d’una proposta d’aprenentatge cooperatiu dels continguts de l’àrea d’Ecologia mitjançant l’estudi de casos. En “Cap a l’espai europeu d’educació superior. Experiències docents innovadores de la UAB en ciències experimentals i tecnol ogies i en ciències de la salut”. Servei de Publicacions UAB. Bellaterra
Asensio D., Owen S.M., Llusià J., Peñuelas J. (2008) The distribution of volatile isoprenoids in the soil horizons around Pinus halepensis trees. Soil Biology and Biochemistry. 40: 2937-2947.EnllaçDoi: 10.1016/j.soilbio.2008.08.008
We measured the terpene concentration in pentane and water extracts from soil horizons (litter, organic, top and low mineral) and from roots growing in top and low mineral horizons on a distance gradient from Pinus halepensis L. trees growing alone on a grassland. Terpene concentrations in pentane were higher than in water extracts, although β-caryophyllene showed relatively high solubility in water. The litter and roots were important sources of terpenes in soil. Alpha-pinene dominated in roots growing in both "top" (A1) and "low" (B) mineral horizons (123 ± 36 μg g-1 or 14 ± 5 mg m-2) and roots in low mineral horizon (270 ± 91 μg g-1 or 7 ± 2 mg m-2). Beta-caryophyllene dominated in litter (1469 ± 331 μg g-1 or 2004 ± 481 mg m-2). Terpene concentration in soil decreased with increasing distance to the trunk. This is likely to be related to changes in litter and roots type on the distance gradient from pine to grass and herbs. The relative contributions of all compounds, except α-pinene, were similar in the mineral soils and litter. This suggests that litter of P. halepensis is probably the main source of major terpene compounds. However, long-term emissions of α-pinene from P. halepensis roots might also contribute to α-pinene concentrations in rhizosphere soils. © 2008 Elsevier Ltd. All rights reserved.
Asensio D., Peñuelas J., Prieto P., Estiarte M., Filella I., Llusià J. (2008) Interannual and seasonal changes in the soil exchange rates of monoterpenes and other VOCs in a Mediterranean shrubland. European Journal of Soil Science. 59: 878-891.EnllaçDoi: 10.1111/j.1365-2389.2008.01057.x
Information about soil VOC inventories and exchange rates in different soils is very scarce. Seasonality of soil VOC exchange rates is also largely unknown, despite the increasing interest in some soil volatile compounds, such as monoterpenes, because of their important role in soil ecology. We aimed to explore and quantify soil VOC exchange rates in a Mediterranean shrubland and their seasonality. Measurements of soil VOC exchange were taken using GC-MS and PTR-MS techniques, together with soil temperature, soil moisture and soil CO2 efflux measurements, during two annual campaigns with contrasting precipitation. Methanol, acetic acid, ethyl acetate, acetaldehyde, acetone, C3 and C4 carbonyls (such as methyl ethyl ketone), α-pinene and limonene, showed the highest emission rates. Maximum soil monoterpene emission rates were very low (0.003 nmol m-2 s -1) compared with foliar monoterpene emission rates. The emission rates of the other VOCs were also low (maximum 0.8 nmol m-2 s -1) except for methanol (1.2 nmol m-2 s-1). Maximum soil uptake rates for some VOCs, such as methanol and acetonitrile (ranging from -0.1 to -0.5 nmol m-2 s-1) were, however, comparable with foliar uptake rates. Further studies are needed to corroborate these results and the possible importance of the soil VOC sink in regional chemistry-climate models. Long-term severe drought increased soil monoterpene emission rates in this Mediterranean shrubland. The increases seem to be linked to changes in the soil's physical properties induced by low soil moisture. Unlike monoterpenes, other soil VOC emission rates decreased when soil moisture was low. The results suggest a seasonal control of soil temperature on the emission rates of monoterpenes and other VOCs. The emission rates increase with soil temperature. Positive correlations between the VOC exchange rates and the soil CO2 fluxes suggest that phenology of roots and microorganisms also controls seasonal changes in soil VOCs in this Mediterranean shrubland. © 2008 The Authors.
Bartomeus I., Bosch J., Vilà M. (2008) High invasive pollen transfer, yet low deposition on native stigmas in a Carpobrotus-invaded community. Annals of Botany. 102: 417-424.EnllaçDoi: 10.1093/aob/mcn109
• Background and Aims: Invasive plants are potential agents of disruption in plant-pollinator interactions. They may affect pollinator visitation rates to native plants and modify the plant-pollinator interaction network. However, there is little information about the extent to which invasive pollen is incorporated into the pollination network and about the rates of invasive pollen deposition on the stigmas of native plants. • Methods: The degree of pollinator sharing between the invasive plant Carpobrotus affine acinaciformis and the main co-flowering native plants was tested in a Mediterranean coastal shrubland. Pollen loads were identified from the bodies of the ten most common pollinator species and stigmatic pollen deposition in the five most common native plant species. • Key Results: It was found that pollinators visited Carpobrotus extensively. Seventy-three per cent of pollinator specimens collected on native plants carried Carpobrotus pollen. On average 23% of the pollen on the bodies of pollinators visiting native plants was Carpobrotus. However, most of the pollen found on the body of pollinators belonged to the species on which they were collected. Similarly, most pollen on native plant stigmas was conspecific. Invasive pollen was present on native plant stigmas, but in low quantity. • Conclusions: Carpobrotusis highly integrated in the pollen transport network. However, the plant-pollination network in the invaded community seems to be sufficiently robust to withstand the impacts of the presence of alien pollen on native plant pollination, as shown by the low levels of heterospecific pollen deposition on native stigmas. Several mechanisms are discussed for the low invasive pollen deposition on native stigmas. © The Author 2008. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.
Bartomeus I., Vilà M., Santamaría L. (2008) Contrasting effects of invasive plants in plant-pollinator networks. Oecologia. 155: 761-770.EnllaçDoi: 10.1007/s00442-007-0946-1
The structural organization of mutualism networks, typified by interspecific positive interactions, is important to maintain community diversity. However, there is little information available about the effect of introduced species on the structure of such networks. We compared uninvaded and invaded ecological communities, to examine how two species of invasive plants with large and showy flowers (Carpobrotus affine acinaciformis and Opuntia stricta) affect the structure of Mediterranean plant-pollinator networks. To attribute differences in pollination to the direct presence of the invasive species, areas were surveyed that contained similar native plant species cover, diversity and floral composition, with or without the invaders. Both invasive plant species received significantly more pollinator visits than any native species and invaders interacted strongly with pollinators. Overall, the pollinator community richness was similar in invaded and uninvaded plots, and only a few generalist pollinators visited invasive species exclusively. Invasive plants acted as pollination super generalists. The two species studied were visited by 43% and 31% of the total insect taxa in the community, respectively, suggesting they play a central role in the plant-pollinator networks. Carpobrotus and Opuntia had contrasting effects on pollinator visitation rates to native plants: Carpobrotus facilitated the visit of pollinators to native species, whereas Opuntia competed for pollinators with native species, increasing the nestedness of the plant-pollinator network. These results indicate that the introduction of a new species to a community can have important consequences for the structure of the plant-pollinator network. © 2007 Springer-Verlag.
Beier C., Emmett B.A., Peñuelas J., Schmidt I.K., Tietema A., Estiarte M., Gundersen P., Llorens L., Riis-Nielsen T., Sowerby A., Gorissen A. (2008) Carbon and nitrogen cycles in European ecosystems respond differently to global warming. Science of the Total Environment. 407: 692-697.EnllaçDoi: 10.1016/j.scitotenv.2008.10.001
The global climate is predicted to become significantly warmer over the next century. This will affect ecosystem processes and the functioning of semi natural and natural ecosystems in many parts of the world. However, as various ecosystem processes may be affected to a different extent, balances between different ecosystem processes as well as between different ecosystems may shift and lead to major unpredicted changes. In this study four European shrubland ecosystems along a north-south temperature gradient were experimentally warmed by a novel nighttime warming technique. Biogeochemical cycling of both carbon and nitrogen was affected at the colder sites with increased carbon uptake for plant growth as well as increased carbon loss through soil respiration. Carbon uptake by plant growth was more sensitive to warming than expected from the temperature response across the sites while carbon loss through soil respiration reacted to warming in agreement with the overall Q10 and response functions to temperature across the sites. Opposite to carbon, the nitrogen mineralization was relatively insensitive to the temperature increase and was mainly affected by changes in soil moisture. The results suggest that C and N cycles respond asymmetrically to warming, which may lead to progressive nitrogen limitation and thereby acclimation in plant production. This further suggests that in many temperate zones nitrogen deposition has to be accounted for, not only with respect to the impact on water quality through increased nitrogen leaching where N deposition is high, but also in predictions of carbon sequestration in terrestrial ecosystems under future climatic conditions. Finally the results indicate that on the short term the above-ground processes are more sensitive to temperature changes than the below ground processes. © 2008 Elsevier B.V. All rights reserved.
Belmonte J., Alarcón M., Avila A., Scialabba E., Pino D. (2008) Long-range transport of beech (Fagus sylvatica L.) pollen to Catalonia (north-eastern Spain). International Journal of Biometeorology. 52: 675-687.EnllaçDoi: 10.1007/s00484-008-0160-9
Local and long-range transport of beech (Fagus sylvatica) pollen was analysed by using 23-year data (1983-2007) at six stations in Catalonia, Spain, and numerical simulations. Back trajectories and synoptic meteorology indicated a consistent north European provenance during beech pollen peak days. Specifically, the area from northern Italy to central Germany was the most probable source, as indicated by a source-receptor model based on back trajectories. For the event with the highest pollen levels (17 May 2004), back trajectories indicated a source in the Vosges (NE France) and the Schwarzwald (SW Germany) regions. By applying a mesoscale model (MM5) to this event, pollen transport could be further refined, allowing its entrance to Catalonia through the lower easternmost pass of the Pyrenees (the Alberes pass, 500 m a.s.l.) to be described. Hourly counts of Fagus pollen allowed the timing of pollen arrival during this episode to be matched with the model results regarding the above-mentioned passage. This study may help to interpret some results of modern beech genetic diversity and contribute to the understanding of paleopalynological records by taking long-range transport into consideration. © 2008 ISB.
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