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.LinkDoi: 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.
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.LinkDoi: 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.
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.LinkDoi: 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.
Estiarte M., Peñuelas J., López-Martínez C., Pérez-Obiol R. (2008) Holocene palaeoenvironment in a former coastal lagoon of the arid south eastern Iberian Peninsula: Salinization effects on δ15N. Vegetation History and Archaeobotany. 17: 667-674.LinkDoi: 10.1007/s00334-008-0153-y
The palaeoenvironment of a former coastal lagoon in the south eastern Iberian Peninsula (San Rafael, Almeria, Spain) were inferred from one core analyzed for particulate organic matter content (POM) together with its C/N, δ13C, δ15N to depict the biogeochemical record from the Late Glacial to the Holocene. The results, complemented by previously reported pollen assemblages, indicate the appearance of a freshwater lagoon at 7300 b.p. (uncalibrated 14C age), its salinization at 6200 b.p. and its disappearance at 4400 b.p. The period of existence of the lagoon coincided with a period of wetter conditions as inferred from terrestrial vegetation. The lagoon's salinization was not related to a decrease in precipitation but to a stronger maritime influence since there were no parallel changes in terrestrial vegetation. Salinization caused an increase in δ13C, associated with a higher relative presence of C4 plants, and an increase in δ15N, due to a decrease in plant N demand. The late period of the lagoon, from about 5100 to 4400 b.p., shows a progressive drying and salinization not detected in isotopes but reflected in a decrease in POM, and in the pollen records. Increases in δ15N were related to increases in salinity within the lagoon, and are indicative of a more open N cycle, because the absence of changes in terrestrial vegetation rules out changes in the catchment area as the cause for changes in δ15N. © 2008 Springer-Verlag.
Llusià J, Peñuelas J, Alessio GA, Estiarte M (2008) Contrasting species-specific, compound-specific, seasonal, and inter-annual responses of foliar isoprenoid emissions to experimental drought in a Mediterranean shrubland. International Journal of Plant Sciences. 169: 637–645.
Sardans J, Peñuelas J, Estiarte M (2008) El canvi climàtic altera l'activitat enzimàtica als sòls Mediterranis. UAB Medi Ambient i Conservació
Peñuelas J, Filella I, Estiarte M, Ogaya R, Llusià J, Sardans J, Jump A, Garbulsky M, Carrillo B, Stefanescu C, Lloret F, Terradas J (2008) El canvi climàtic altera i alterarà la vida als ecosistemes terrestres Catalans. L'Atzavara 16: 13-28.
Peñuelas J, Filella I, Estiarte M, Ogaya R, LLusià J, Sardans J, Jump A, Garbulsky M, Coll M, Diaz de Quijano M, Seco R, Salvador Blanch J, Owen S, Curiel J, Carnicer J, Boada M, Stefanescu C, Lloret F, Terradas J (2008) Climate change and phenology, adaptation, migration and extinction in plant species.In Climate Change and Systematics, Trinity College Dublin pp. 16.
Peñuelas J, Jump A, Sardans J, Filella I, Estiarte M, Ogaya R, Llusià J, Owen S, Lloret F (2008) From Phosphorous and VOCs to Biodiversity: some studies on the effects of global change inspired by Margalef’s legacy. (2008).. In: F. Valladares, A. Camacho, A. Elosegi, C. Gracia, M. Estrada, J.C. Senar, J.M. Gili (eds.), Unity in Diversity. Reflection s on Ecology after the legacy of Ramon Margalef, pp. 83-94. Fundación BBVA, Bilbao.
Peñuelas J, Sardans J, Ogaya R, Estiarte M (2008) Nutrient stoichiometric relations and biogeochemical niche in coexisting plant species: effect of simulated climate change. Polish Journal of Ecology 56: 613-622.
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