Petit C, Fréville H, Mignot A, Colas B, Riba M, Imbert E, Hurtrez-Boussès S, Virevaire M, Olivieri I (2001) Gene flow and local adaptation in two endemic plant species. Biological Conservation 100:21-34.
Ortiz O (2001) Uso de la materia orgánica como criterio de aplicación de residuos. En Boixadera J, Teira R (eds) Aplicación agrícola de residuos orgánicos. 5º Curso de Ingeniería Ambiental, Universitat de Lleida, Lleida, pp. 279-291.
Ortiz O, Alcañiz JM (2001) Reducció de l'erosionabilitat d'un alfisol mitjançant l'ús de fangs de depuradora o d'adobs minerals per al desenvolupament de la coberta herbàcia. Orsis 16:121-131.
Petit C., Fréville H., Mignot A., Colas B., Riba M., Imbert E., Hurtrez-Boussés S., Virevaire M., Olivieri I. (2001) Gene flow and local adaptation in two endemic plant species. Biological Conservation. 100: 21-34.EnllaçDoi: 10.1016/S0006-3207(00)00204-4
In order to detect the evolutionary potential of two endangered species, Brassica insularis (Brassicaceae) and Centaurea corymbosa (Asteraceae), within and among-population genetic variation for both quantitative traits and allozymic markers was examined. Four populations of each species were studied, representing a large proportion of extant populations. High values of θST (0.213 and 0.364 for B. insularis and C. corymbosa respectively) suggested that low amounts of gene flow occur among the study populations. In each species, the genetic distance based on allozymes (estimated by the ratio (θST/1-θST)) was positively correlated with the geographical distance, indicating isolation by distance. In contrast to previous studies in either outcrossing or selfing plant species, and especially for B. insularis, population differentiation for quantitative traits (QST) was generally found lower than differentiation for allozymes (θST), suggesting that the populations studied were experiencing similar selective forces acting upon the quantitative traits measured. Such forces would be strong enough to counteract local genetic drift. Interestingly, for both species QST's were statistically independent of geographical distance, in contrast to the marginally significant positive isolation by distance shown by θST. Altogether, these results suggest that θST's might not always be used as conservative estimates of QST's, and might instead overestimate the evolutionary potential of endangered species. This would be especially expected in narrow-endemic species, whose ecological niche is often so restricted that indeed homogeneous selective forces are likely to occur, whereas small population sizes and restricted dispersal are likely to produce strong differentiation for neutral variation. In fact, knowledge of both neutral and quantitative diversity patterns allows identification of those traits undergoing natural selection, and could be useful in designing reinforcement or reintroduction programs. However, this approach might have limitations too, in the presence of outbreeding depression due to locally coevolved gene complexes. © 2001 Elsevier Science Ltd.
Peuelas J., Llusià J. (2001) Seasonal patterns of non-terpenoid C6-C10 VOC emission from seven Mediterranean woody species. Chemosphere. 45: 237-244.EnllaçDoi: 10.1016/S0045-6535(00)00572-5
The seasonal pattern of non-terpenoid C6-C10 VOC emission by seven Mediterranean woody species (Bupleurum fruticosum, Cistus albidus, Pinus halepensis, Arbutus unedo, Erica arborea, Quercus coccifera, and Q. ilex) was studied under field conditions. Branch chamber samples were sorbed on carbotrap and analyzed by thermal desorption in combination with GC-MS. These non-terpenoid C6-C10 VOC emissions were large, almost of similar magnitude to those of terpenes. Overall, maximum values were recorded in spring and summer (up to 12 μg g-1 DM h-1 in Q. ilex) and minimum values in autumn and winter (up to 5 μg g-1 DM h-1 in Q. ilex). These C6-C10 VOC emissions represented 2.82% of the photosynthetic C fixation in summer and 0.22% in winter. Some compounds such as 2-ethoxyethyl acetate were emitted by most species, others such as 3-hexen-1-o1, phenol or decanal were significantly emitted only by few species. The greatest diversity of emitted non-terpenoid C6-C10 VOCs was observed in spring and in Q. ilex. Temperature seemed a strong driver of these seasonal changes but other species-specific and seasonal factors seem involved. These results indicate that C6-C10 non-terpenoid VOCs contribute a rather significant fraction of the total biogenic VOC flux from these Mediterranean species, especially in spring and summer, and therefore should be considered in VOC emission inventories and in model predictions of tropospheric chemistry. © 2001 Elsevier Science Ltd. All rights reserved.
Peñuelas J., Filella I. (2001) Herbaria century record of increasing eutrophication in Spanish terrestrial ecosystems. Global Change Biology. 7: 427-433.EnllaçDoi: 10.1046/j.1365-2486.2001.00421.x
Additional biological evidence is presented for the alteration of biogeochemical cycles by human activities. The leaf δ15N and the concentrations of nutrients in herbarium specimens of 24 species of vascular plants and 3 species of bryophytes collected in northern and eastern regions of Spain have substantially changed throughout the XX century. In the second half of the century, when anthropogenic nitrogen fixation and mobilization started to increase rapidly, leaf δ15N values started to decrease strongly, indicating that additional anthropogenic nitrogen is being retained in Spanish terrestrial ecosystems. The concentration of nutrients in vascular plants did not present any clear pattern, but there were increasing concentrations of N and other nutrients (P, K, and S) in the last decades in bryophytes, which are usually better biomonitors of airborne chemicals than vascular plants. Important consequences for ecosystem structure and functioning such as enhancement of the carbon sink or changes in community biodiversity and species distribution may be expected from this increase in eutrophication.
Peñuelas J., Filella I. (2001) Phenology: Responses to a warming world. Science. 294: 793-795.EnllaçDoi: 10.1126/science.1066860
[No abstract available]
Ricotta C., Arianoutsou M., Díaz-Delgado R., Duguy B., Lloret F., Maroudi E., Mazzoleni S., Manuel Moreno J., Rambal S., Vallejo R., Vázquez A. (2001) Self-organized criticality of wildfires ecologically revisited. Ecological Modelling. 141: 307-311.EnllaçDoi: 10.1016/S0304-3800(01)00272-1
Wildfire cumulative frequency-area distributions of Mediterranean landscapes are examined for agreement with self-similar (fractal) behavior. Our results support landscape-specific restricted scaling regions of 1.5-3.5 orders of magnitude in size, which are delimited by breakpoints or 'cut-offs'. By identifying the extent of such regions in the fractal frequency-area distribution of wildfires, fractal statistics may give a deeper insight into the scale-invariant dynamics of fire spread, whereas the observed cut-offs may be related to changes in the process-pattern interactions that control wildfire propagation at the landscape scale. © 2001 Elsevier Science B.V. All rights reserved.
Rouget, M., Richardson, D.M., Lavorel, S., Vayreda, J., Gracia, C., Milton, S.J. (2001) Determinants of distribution of six Pinus species in Catalonia, Spain. Journal of Vegetation Science. 12: 491-502.EnllaçDoi: 10.2307/3237001
Salvador R., Piol J., Tarantola S., Pla E. (2001) Global sensitivity analysis and scale effects of a fire propagation model used over Mediterranean shrublands. Ecological Modelling. 136: 175-189.EnllaçDoi: 10.1016/S0304-3800(00)00419-1
A Global Sensitivity Analysis (GSA) and an analysis of scale effects have been carried out over the equations given by Rothermel (1972), with some additional modifications. Data mainly derived from Mediterranean shrublands and a spatially close meteorological station have been used to derive probability distribution functions for the variables involved. In spite of the abundant non-linearities contained in the equations studied, scale effects found have been relatively unimportant, thus supporting the current usage of spatial averages (i.e. fuel models) in spatially distributed models based on the Rothermel equations. On the other hand, the results of the GSA clearly showed the negligible effect of the variability of three of the model variables (the low heat content, the particle density and the mineral content) on the output values. However, all other input variables had some noticeable effect over the variability of the output, and they cannot be ignored if an optimal use of the model is desired. Finally, caution is recommended if results have to be extrapolated to other types of vegetation or climate. © 2001 Elsevier Science B.V.
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