Oliveira G, Peñuelas J (2004) Effects of winter cold stress on photosynthesis and photochemical efficiency of PSII of the Mediterranean Cistus albidus L. and Quercus ilex L. Plant Ecology 175:179-191.
Peñuelas J (2004) Com canvia la vida en resposta als canvis climàtics i atmosfèrics. In Ponències curs 2002-2003 del Grup Català del Capítol Espanyol del Club de Roma. The Club of Rome, Barcelona, pp. 93-110.
Peñuelas J, Munné-Bosch S, Llusià J, Filella I (2004) Leaf reflectance and photo- and antioxidant protection in field-grown summer-stressed Phillyrea angustifolia. Optical signals of oxidative stress? New Phytologist 162:115-124.
Peñuelas J, Sabaté S, Filella I, Gracia C (2004) Efectos del cambio climático sobre los ecosistemas terrestres: observación, experimentación y simulación. In Valladares F (ed) Ecología del bosque mediterráneo en un mundo cambiante. Ministerio de Medio Ambiente, Madrid, pp. 425-460.
Piñol J (2004) Acumulació de combustible i la paradoxa de l'extinció. In Plana E (ed) Incendis forestals, dimensió socioambiental, gestió del risc i ecologia del foc. Xarxa ALINFO XCT2001-00061, Solsona, pp. 39-43.
Oliveras I, Piñol J, Viegas DX (2004) Experiments per a la validació de models de propagació del foc. In Plana E (ed) Incendis forestals, dimensió socioambiental, gestió del risc i ecologia del foc. Xarxa ALINFO XCT2001-00061, Solsona, pp. 56-59.
Ribes J, Piñol J, Espadaler X, Cañellas N (2004) Heterópteros de un cultivo ecológico de cítricos en Tarragona. Orsis 19:21-35.
Llorens L., Peñuelas J., Beier C., Emmett B., Estiarte M., Tietema A. (2004) Effects of an experimental increase of temperature and drought on the photosynthetic performance of two ericaceous shrub species along a north-south European gradient. Ecosystems. 7: 613-624.EnllaçDoi: 10.1007/s10021-004-0180-1
Plant ecophysiological changes in response to climatic change may be different in northern and southern European countries because different abiotic factors constrain plant physiological activity. We studied the effects of experimental warming and drought on the photosynthetic performance of two ericaceous shrubs (Erica multiflora and Calluna vulgaris) along a European gradient of temperature and precipitation (UK, Denmark, The Netherlands, and Spain). At each site, a passive warming treatment was applied during the night throughout the whole year, whereas the drought treatment excluded rain events over 6-10 weeks during the growing season. We measured leaf gas exchange, chlorophyll a fluorescence, and leaf carbon isotope ratio (δ 13C) during the growing seasons of 1999 and 2000. Leaf net photosynthetic rates clearly followed a gradient from northern to southern countries in agreement with the geographical gradient in water availability. Accordingly, there was a strong correlation between net photosynthetic rates and the accumulated rainfall over the growing season. Droughted plants showed lower leaf gas exchange rates than control plants in the four sites. Interestingly, although leaf photosynthetic rates decreased along the precipitation gradient and in response to drought treatment, droughted plants were able to maintain higher leaf photosynthetic rates than control plants in relation to the accumulated rainfall over the months previous to the measurements. Droughted plants also showed higher values of potential photochemical efficiency (F v/Fm) in relation to controls, mainly at midday. The warming treatment did not affect significantly any of the studied instantaneous ecophysiological variables.
Llorens L., Peñuelas J., Estiarte M., Bruna P. (2004) Contrasting growth changes in two dominant species of a mediterranean shrubland submitted to experimental drought and warming. Annals of Botany. 94: 843-853.EnllaçDoi: 10.1093/aob/mch211
• Background and Aims: Climate projections predict drier and warmer conditions in the Mediterranean basin in the next decades. The possibility of such climatic changes modifying the growth of two Mediterranean species, Erica multiflora and Globularia alypum, which are common components of Mediterranean shrublands, was assessed. • Methods: A field experiment was performed from March 1999 to March 2002 to prolong the drought period and to increase the night-time temperature in a Mediterranean shrubland, where E. multiflora and G. alypum are the dominant species. Annual growth in stem diameter and length of both species was measured and annual stem biomass production was estimated for 1999, 2000 and 2001. Plant seasonal growth was also assessed. • Key Results: On average, drought treatment reduced soil moisture 22 %, and warming increased temperature by 0.7-1.6°C. Erica multiflora plants in the drought treatment showed a 46 % lower annual stem elongation than controls. The decrease in water availability also reduced by 31 % the annual stem diameter increment and by 43 % the annual stem elongation of G. alypum plants. New shoot growth of G. alypum was also strongly reduced. Allometrically estimated biomass production was decreased by drought in both species. Warming treatment produced contrasting effects on the growth patterns of these species. Warmer conditions increased, on average, the stem basal diameter growth of E. multiflora plants by 35 %, raising also their estimated stem biomass production. On the contrary, plants of G. alypum in the warming treatment showed a 14 % lower annual stem growth in basal diameter and shorter new shoots in spring compared with controls. • Conclusions: The results indicate changes in the annual productivity of these Mediterranean shrubs under near future drier and warmer conditions. They also point to alterations in their competitive abilities, which could lead to changes in the species composition of these ecosystems in the long term. © 2004 Annals of Botany Company.
Lloret F., Médail F., Brundu G., Hulme P.E. (2004) Local and regional abundance of exotic plant species on Mediterranean islands: Are species traits important?. Global Ecology and Biogeography. 13: 37-45.EnllaçDoi: 10.1111/j.1466-882X.2004.00064.x
Aim We assess the importance of three relevant and readily obtainable life-history traits (dispersal syndrome, stem height and growth form) and biogeographical origin (European vs. non-European) on the local and regional abundance of over 400 exotic plant species across eight Mediterranean islands. Location The Mediterranean islands of Lesbos, Rhodes, Crete, Malta, Corsica, Sardinia, Majorca and Minorca. Methods We adopt two abundance criteria for each exotic species: the proportion of islands in which the species occurs (regional abundance), and a qualitative estimate of species abundance within each of five islands (local abundance). Subsequently, we assess the relationship between local and regional abundance, as well as the role of key life-history traits on both regional and local abundance. These analyses were undertaken separately for the European exotics and the non-European exotics. Results Only 10.9% of the species occur on more than four islands, and only four species are present on all eight islands. Both local and regional abundances were higher for the non-European than the European species. Local and regional abundances were positively correlated, particularly for exotics with non-European origins. Wind-dispersed species tended to have higher regional abundance than species dispersed by other means but this trend only occurred for local abundance on two islands - Corsica and Majorca. Neither a species' growth form nor its stem height explained trends in regional or local abundance. Conclusions Although wind-dispersed exotics are more widespread in the Mediterranean, plant life-history traits appear to play a lesser role in invasion success than area of biogeographical origin. In general, exotic species of non-European origin were more abundant at both local and regional scales. Invasion patterns should be interpreted at both local and regional scales, but the stochastic nature of biological invasions may limit deterministic interpretations of invasion patterns, especially if islands are studied in isolation. © 2004 Blackwell Publishing Ltd.
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