Barbeta A., Peñuelas J., Ogaya R., Jump A.S. (2011) Reduced tree health and seedling production in fragmented Fagus sylvatica forest patches in the Montseny Mountains (NE Spain). Forest Ecology and Management. 261: 2029-2037.EnllaçDoi: 10.1016/j.foreco.2011.02.029
Habitat fragmentation results in smaller and more isolated populations that may be at higher risk of extirpation or further decline in comparison with their more continuously distributed progenitors. Risks to fragmented populations have frequently been considered from the perspective of population genetics, however, disruption of normal plant demography may be an equal or greater threat to population persistence. We compared demographic performance and tree health in continuous and fragmented forest plots with similar tree size structure and local climatic and physiographic conditions in order to determine if fragments are characterized by poor health and reproduction. We found that beech forest fragments showed lower seedling density, more tree crown damage and also higher percentage of dead trees. However, mortality of juveniles in the youngest age class was substantially lower in fragments such that long-term population structure remained similar between the two forest types. If reduced mortality compensates for reduced seedling establishment, as our data suggest, then fragmented populations should show greater long-term persistence than would be predicted based on comparison of young age cohorts alone. However, despite such demographic compensation, the decreased health of adult trees may pose an increasing future threat to the fragmented populations. Our results demonstrate the importance of integrating demographic patterns over long time periods and not relying on single year or cohort comparisons and may partly explain population genetic differences previously reported for the same populations. © 2011 Elsevier B.V.
Sardans J, Peñuelas J, Estiarte M, Ogaya R, Llusià J (2011) The world's largest database on wild plants is published. UABdivulga 09/2011.
Peñuelas J, Filella I, Estiarte M, Ogaya R, Llusià J, Sardans J, Jump A, Curiel J, Carnicer J, Rutishauser T, Rico L, Keenan T, Garbulsky M, Coll M, Diaz de Quijano M, Seco R, Rivas-Ubach A, Silva J, Boada M, Stefanescu C, Lloret F, Terradas J (2011) Llebot E. (ed). Impactes, vulnerabilitat i retroalimentacions climàtiques als ecosistemes terrestres catalans. Segon informe sobre el canvi climàtic a Catalunya. Institut d'Estudis Catalans i Generalitat de Catalunya. Barcelona, pp. 373-407.
Peñuelas J, Cabadell J, Ogaya R (2011) L'increment de CO2 no ha fet augmentar el creixement dels arbres. UABdivulga 10/2011.
Kattge J., Diaz S., Lavorel S., Prentice I.C., Leadley P., Bonisch G., Garnier E., Westoby M., Reich P.B., Wright I.J., Cornelissen J.H.C., Violle C., Harrison S.P., Van Bodegom P.M., Reichstein M., Enquist B.J., Soudzilovskaia N.A., Ackerly D.D., Anand M., Atkin O., Bahn M., Baker T.R., Baldocchi D., Bekker R., Blanco C.C., Blonder B., Bond W.J., Bradstock R., Bunker D.E., Casanoves F., Cavender-Bares J., Chambers J.Q., Chapin F.S., Chave J., Coomes D., Cornwell W.K., Craine J.M., Dobrin B.H., Duarte L., Durka W., Elser J., Esser G., Estiarte M., Fagan W.F., Fang J., Fernandez-Mendez F., Fidelis A., Finegan B., Flores O., Ford H., Frank D., Freschet G.T., Fyllas N.M., Gallagher R.V., Green W.A., Gutierrez A.G., Hickler T., Higgins S.I., Hodgson J.G., Jalili A., Jansen S., Joly C.A., Kerkhoff A.J., Kirkup D., Kitajima K., Kleyer M., Klotz S., Knops J.M.H., Kramer K., Kuhn I., Kurokawa H., Laughlin D., Lee T.D., Leishman M., Lens F., Lenz T., Lewis S.L., Lloyd J., Llusia J., Louault F., Ma S., Mahecha M.D., Manning P., Massad T., Medlyn B.E., Messier J., Moles A.T., Muller S.C., Nadrowski K., Naeem S., Niinemets U., Nollert S., Nuske A., Ogaya R., Oleksyn J., Onipchenko V.G., Onoda Y., Ordonez J., Overbeck G., Ozinga W.A., Patino S., Paula S., Pausas J.G., Penuelas J., Phillips O.L., Pillar V., Poorter H., Poorter L., Poschlod P., Prinzing A., Proulx R., Rammig A., Reinsch S., Reu B., Sack L., Salgado-Negret B., Sardans J., Shiodera S., Shipley B., Siefert A., Sosinski E., Soussana J.-F., Swaine E., Swenson N., Thompson K., Thornton P., Waldram M., Weiher E., White M., White S., Wright S.J., Yguel B., Zaehle S., Zanne A.E., Wirth C. (2011) TRY - a global database of plant traits. Global Change Biology. 17: 2905-2935.EnllaçDoi: 10.1111/j.1365-2486.2011.02451.x
Plant traits - the morphological, anatomical, physiological, biochemical and phenological characteristics of plants and their organs - determine how primary producers respond to environmental factors, affect other trophic levels, influence ecosystem processes and services and provide a link from species richness to ecosystem functional diversity. Trait data thus represent the raw material for a wide range of research from evolutionary biology, community and functional ecology to biogeography. Here we present the global database initiative named TRY, which has united a wide range of the plant trait research community worldwide and gained an unprecedented buy-in of trait data: so far 93 trait databases have been contributed. The data repository currently contains almost three million trait entries for 69000 out of the world's 300000 plant species, with a focus on 52 groups of traits characterizing the vegetative and regeneration stages of the plant life cycle, including growth, dispersal, establishment and persistence. A first data analysis shows that most plant traits are approximately log-normally distributed, with widely differing ranges of variation across traits. Most trait variation is between species (interspecific), but significant intraspecific variation is also documented, up to 40% of the overall variation. Plant functional types (PFTs), as commonly used in vegetation models, capture a substantial fraction of the observed variation - but for several traits most variation occurs within PFTs, up to 75% of the overall variation. In the context of vegetation models these traits would better be represented by state variables rather than fixed parameter values. The improved availability of plant trait data in the unified global database is expected to support a paradigm shift from species to trait-based ecology, offer new opportunities for synthetic plant trait research and enable a more realistic and empirically grounded representation of terrestrial vegetation in Earth system models. © 2011 Blackwell Publishing Ltd.
Llusià J., Peñuelas J., Alessio G.A., Ogaya R. (2011) Species-specific, seasonal, inter-annual, and historically-accumulated changes in foliar terpene emission rates in Phillyrea latifolia and Quercus ilex submitted to rain exclusion in the Prades Mountains (Catalonia). Russian Journal of Plant Physiology. 58: 126-132.EnllaçDoi: 10.1134/S1021443710061020
Mediterranean vegetation emits large amounts of terpenes. We aimed to study the effects of the decreases in soil water availability forecast for the next decades by global circulation models and ecophysiological models on the terpene emissions by two widely distributed Mediterranean woody species, Phillyrea latifolia L. and Quercus ilex L. We subjected holm oak forest plots to an experimental soil drought of ca. 20% decrease in soil moisture by partial rainfall exclusion and runoff exclusion. We measured the emission rates throughout the seasons for two years with contrasting precipitation and soil moisture (16.6% average in 2003 vs. 6.4% as average in 2005). Among the detected volatile terpenes, only α-pinene and limonene were present in detectable quantities in all of the studied periods. Total terpene emitted ranged from practically zero (spring 2003) to 3.6 and 58.3 μg/(g dry wt h) (winter 2005 and summer 2003 for P. latifolia and Q. ilex, respectively). A clear seasonality was found in the emission rates (they were the highest in summer in both species) and also in the qualitative composition of the emission mix. Maximum emissions of α-pinene occurred in spring and maximum emissions of limonene in winter. Neither the inter-annual differences in water availability nor the rain exclusion treatment significantly affected the emissions in P. latifolia, but Q. ilex showed by 17% lower emissions during the drier second year of study, 2005, but more than two- and threefold increases with the drought treatment in summer 2003 and in summer 2005, respectively, showing historical accumulated effects. These results, which show increased monoterpene emission under the moderate drought produced by the treatment and decreased emission under the severe second year drought, and a much higher sensitivity to drought in Q. ilex than in P. latifolia, are useful in understanding the behavior of plant volatiles under Mediterranean conditions and in modeling future emission under changing climate conditions. They show that the usage of current models could lead to under- and overestimations of the emission under summer dry conditions, because most current algorithms are based on light and temperature only. © 2011 Pleiades Publishing, Ltd.
Ogaya R., Llorens L., Peñuelas J. (2011) Density and length of stomatal and epidermal cells in "living fossil" trees grown under elevated CO2 and a polar light regime. Acta Oecologica. 37: 381-385.EnllaçDoi: 10.1016/j.actao.2011.04.010
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. © 2011 Elsevier Masson SAS.
Ogaya R., Peñuelas J., Asensio D., Llusià J. (2011) Chlorophyll fluorescence responses to temperature and water availability in two co-dominant Mediterranean shrub and tree species in a long-term field experiment simulating climate change. Environmental and Experimental Botany. 71: 123-127.EnllaçDoi: 10.1016/j.envexpbot.2010.10.016
A rain exclusion experiment simulating drought conditions expected in Mediterranean areas for the following decades (15% decrease in soil moisture) is being conducted since 1999 in a Mediterranean holm oak forest to study its response to the forecasted climatic changes for the coming decades. The maximum PSII quantum yield of primary photochemistry (Fv/Fm) was measured in Quercus ilex, and Phillyrea latifolia, the co-dominant species of the studied forest, from 1999 to 2009 in four plots: two of them were control plots and the other two plots received the rain exclusion treatment. In both species, the Fv/Fm values were highly dependent on air temperatures, and in a second term, in water availability. P. latifolia was the species with the larger decrease in Fv/Fm values induced by low air temperatures, while in hot seasons, the Fv/Fm values in P. latifolia were even higher than in Q. ilex. Rainfall exclusion decrease Fv/Fm values significantly only in few monitoring dates. The most drought resistant species P. latifolia was more affected by the experimental rainfall exclusion than Q. ilex that instead lost number of leaves per tree. There was a synergic effect of drought stress and winter cold in P. latifolia not observed in Q. ilex, but a more conservative strategy in P. latifolia maintaining leaves with a down-regulation of the linear photosynthetic electron transport. These results indicate that, although other physiological and reproductive strategies at whole plant level must be also taken into account, the warmer and drier environment expected for the following decades could favour the species more sensitive to cold and more resistant to drought, the shrub P. latifolia, in detriment of the tree Q. ilex as already observed in the field after severe heat-drought episodes. © 2010 Elsevier B.V.
Ogaya R., Peñuelas J., Asensio D., Llusià J. (2011) Chlorophyll fluorescence responses to temperature and water availability in two co-dominant Mediterranean shrub and tree species in a long-term field experiment simulating climate change. Environmental and Experimental Botany. 73: 89-93.EnllaçDoi: 10.1016/j.envexpbot.2011.08.004
Peñuelas J., Canadell J.G., Ogaya R. (2011) Increased water-use efficiency during the 20th century did not translate into enhanced tree growth. Global Ecology and Biogeography. 20: 597-608.EnllaçDoi: 10.1111/j.1466-8238.2010.00608.x
Aim 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 Δ13C) 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. Location A global range of sites covering all major forest biome types. Methods The analysis encompassed 47 study sites including boreal, wet temperate, mediterranean, semi-arid and tropical biomes for which measurements of tree ring Δ13C and growth are available over multiple decades. Results The iWUE inferred from the Δ13C analyses of comparable mature trees increased 20.5% over the last 40 years with no significant differences between biomes. This increase in iWUE did not translate into a significant overall increase in tree growth. Half of the sites showed a positive trend in growth while the other half had a negative or no trend. There were no significant trends within biomes or among biomes. Main conclusions These results show that despite an increase in atmospheric CO2 concentrations of over 50p.p.m. and a 20.5% increase in iWUE during the last 40 years, tree growth has not increased as expected, suggesting that other factors have overridden the potential growth benefits of a CO2-rich world in many sites. Such factors could include climate change (particularly drought), nutrient limitation and/or physiological long-term acclimation to elevated CO2. Hence, the rate of biomass carbon sequestration in tropical, arid, mediterranean, wet temperate and boreal ecosystems may not increase with increasing atmospheric CO2 concentrations as is often implied by biospheric models and short-term elevated CO2 experiments. © 2010 Blackwell Publishing Ltd.
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