Espelta JM, Rodrigo A, Habrouk A, Meghelli N, Ordóñez JL, Retana J (2002) Land use changes, natural regeneration patterns, and restoration practices after a large wildfire in NE Spain: Challenges for fire ecology and landscape restoration In Trabaud L, Prodon R (eds) Fire and Biological Processes. Backhuys Publishers, Leiden, pp. 315-324.
Peñuelas J (2002) Síntomas biológicos del cambio climático. Mundo Científico 236:48-51.
Peñuelas J (2002) Símptomes biològics del canvi climàtic. Medi Ambient 31:1-8.
Peñuelas J, Filella I, Estiarte M, Ogaya R, Ribas A, Llorens L, Mangirón M, Munné S, Bruna P, Sardans J, Prieto P, Asensio D (2002) Plant Ecophysiological studies in the frame of global changes: upscaling from molecule to environment, or walking across space and time. 13 th Congress of the Federation of European Societies of Plant Physiology, Crete. Greece 2002.
Peñuelas J, Llusià J (2002) La emisión de compuestos volátiles por las plantas mediterraneas Ecosistemas (edició electrònica). Revista de la Asociación Española de Ecología Terrestre. Any XI, Núm. 1. (http://www.aeet.org/ecosistemas/).
Piñol J, Salvador R, Beven K (2002) Model calibration and uncertainty prediction of fire spread. In Viegas DX (ed) Forest Fire Research & Wildland Fire Safety. Millpress, Rotterdam, pp. 1-13. ISBN 90-77017-72-0.
Klumpp, A., Ansel, W., Klumpp, G., Belluzzo, N., Calatayud, V., Chaplin, N., Garrec, J.P., Gutsche, H.J., Hayes, M., Hentze, H.W., Kambezidis, H., Laurent, O., Peñuelas, J., Rasmussen, S., Ribas, A., Ro-Poulsen, H., Rossi, S., Sanz, M.J., Shang, H., Sifakis, N., Vergne, P. (2002) EuroBionet: A Pan-European biomonitoring Network for Urban Air Quality Assessment. Environmental Science and Pollution Research. 9: 199-203.LinkDoi: 10.1007/BF02987489
Llorens L., Peñuelas J., Emmett B. (2002) Developmental instability and gas exchange responses of a heathland shrub to experimental drought and warming. International Journal of Plant Sciences. 163: 959-967.LinkDoi: 10.1086/342713
The effects of predicted climatic changes on the physiological stress of bilberry (Vaccinium myrtillus L.) were investigated in a field experiment in a heathland of northern Wales (U.K.). In the experiment, drought was increased during the growing season by excluding precipitation, and night warming was created by reducing heat loss. To assess physiological stress, leaf size and leaf fluctuating asymmetry (FA) as integrative measures of stress during leaf development and leaf gas exchange as a classical instantaneous method to detect physiological stress, were measured. Since leaf FA increased with increasing size, comparisons of asymmetries were made for relative rather than absolute asymmetry. Relative leaf FA was calculated as the absolute difference between leaf size (area or width) of left and right halves, corrected for trait size. Drought treatment increased the relative leaf area FA in 2000 and not in 1999, in agreement with a stronger treatment in 2000. Conversely, the warming treatment decreased the relative leaf area FA in 1999 and not in 2000, coinciding with the lower minimum temperatures in the growing season of 1999. Differences in water availability and temperature between years were related with changes in the relative leaf area FA, which were consistent with the treatment effects. In contrast, leaf gas exchange rates and leaf size showed no significant response to the environmental manipulations, although there was a slight decrease of photosynthetic values and leaf size in drought treatments in both years. Leaf FA therefore appeared to be a more sensitive indicator of physiological stress than leaf size or gas exchange measurements. Our results indicate that a future increase in the severity of drought during the growing season will increase physiological stress of V. myrtillus, whereas warming will decrease physiological stress during leaf development because of the alleviation of temperature constraints.
Lloret F., Calvo E., Pons X., Díaz-Delgado R. (2002) Wildfires and landscape patterns in the Eastern Iberian Peninsula. Landscape Ecology. 17: 745-759.LinkDoi: 10.1023/A:1022966930861
The relations between disturbance regime and landscape patterns have been developed from a theoretical perspective, but few studies have tested these relations when forces promoting opposing heterogeneity patterns are simultaneously operating on a landscape. This work provides quantitative evidence of these relations in areas dominated by human activity, showing that landscape heterogeneity decreases disturbance spread. In turn, disturbance introduces a source of landscape heterogeneity, but it is not enough to counterbalance the homogeneity trend due to agricultural abandonment. Land cover changes and wildfire occurrence (fires larger than 0.3 km2) have been monitored in the Tivissa municipality (208.4 km2) (Catalonia, NE Spain) from 1956 to 1993. Land cover maps were obtained from 1956, 1978 and 1993 and they were overlaid with fire occurrence maps obtained for the 1975-1995 period from 60 m resolution remote sensing images, which allow the identification of burned areas by sudden drops in Normalized Difference Vegetation Index (NDVI). Changes in landscape patterns in relation to fire regime have been analyzed considering several parameters: patch density, mean patch size, mean distance to the nearest neighbour of the same category, edge density, and the Shannon diversity index. In the 1956-1993 period there is a trend to increasing landscape homogenization due to the expansion of shrublands linked to a decrease in forest surface, and to the abandonment of agricultural lands. This trend, however, is not constant along all the period. Fires are more likely to occur in woody, homogenous areas, increasing landscape heterogeneity, as observed in the 1978-1993 period. This increase in heterogeneity does not counterbalance the general trend to landscape homogenization as a consequence of agricultural abandonment and the coalescence of natural vegetation patches.
Llusià J., Peñuelas J., Gimeno B.S. (2002) Seasonal and species-specific response of VOC emissions by Mediterranean woody plant to elevated ozone concentrations. Atmospheric Environment. 36: 3931-3938.LinkDoi: 10.1016/S1352-2310(02)00321-7
Although certain factors controlling plant emission rates of volatile organic compounds (VOCs) are reasonably well understood, the influence of elevated ozone concentrations as abiotic stress is mostly unknown. Therefore, we studied the effects of ozone concentrations on seasonal biogenic volatile organic compound (BVOC) emissions by different Mediterranean plant species in open top chambers (OTC). Three ozone treatments were established: filtered air (F), non-filtered air (NF), and fumigated air (NF+) adding 40nll-1 of ozone over NF. We studied the response of VOC emission in saplings of four Mediterranean woody plant species and subspecies: Ceratonia siliqua L., Olea europaea L., Quercus ilex spp. ilex L., and Quercus ilex spp. rotundifolia L. as representative of natural Mediterranean vegetation. No visible symptoms were detected on the leaves. No significant effect was found on net photosynthetic rates or stomatal conductance except for an increase in net photosynthetic rates in Quercus ilex ilex in spring and summer and an overall slight increase in Quercus ilex rotundifolia. Emissions of the total VOCs from Ceratonia siliqua in summer, and from Olea europaea and Quercus ilex rotundifolia in spring increased in ozone fumigated OTC in comparison with F or NF OTC. Decreased emissions were found in Quercus ilex rotundifolia in summer. There were no significant differences between ozone fumigation treatments for the other plant species and seasons. When considering particular VOCs, the results were also variable among species and time of the year. While α-pinene emissions decreased with ozone fumigation in Olea europaea, α-pinene and limonene emissions increased in Quercus ilex ilex. The responses of these particular VOCs did not always match the responses of total VOCs. In spite of this strong variability, when considering overall annual data for all species and seasons, there were increased net photosynthetic rates (37%) and limonene (95%) and total VOC (45%) emission rates in ozone-fumigated plants, whereas stomatal conductance did not change. Since VOCs are precursors of ozone, the increase in BVOC emission as a consequence of elevated tropospheric ozone concentrations may lead to positive feedback mechanisms in ozone formation. © 2002 Elsevier Science Ltd. All rights reserved.
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