Simulating the effects of different disturbance regimes on Cortaderia selloana invasion.

Pausas J, Lloret F, Vilà M (2005) Simulating the effects of different disturbance regimes on Cortaderia selloana invasion. Biological Conservation 128: 128-135

Landscape-scale positive feedbacks between fire and expansion of the large tussock grass, Ampelodesmos mauritanica in Catalan shrublands.

Grigulis K, Lavorel S, Davies ID, Dossantos A, Lloret F, Vilà M (2005) Landscape-scale positive feedbacks between fire and expansion of the large tussock grass, Ampelodesmos mauritanica in Catalan shrublands. Global Change Biology 11: 1042-1053.

Les formes dels éssers vius: formes orgàniques, forma i funció.

Lloret F (2005) Les formes dels éssers vius: formes orgàniques, forma i funció. Seminaris de Morfologia, Centre d'Art i Natura, Farrera, Pallars Sobirà, Lleida.

Effect of vegetation canopy and climate on seedling establishment in a Mediterranean shrubland.

Lloret F, Peñuelas J, Estiarte M (2005) Effect of vegetation canopy and climate on seedling establishment in a Mediterranean shrubland. Journal of Vegetation Science 16: 67-76.

Patterns of plant population dieback and recvery alter drought episodes in Mediterranean forests and shrublands. Climate Change-Forest Ecosystems & Landscape Zvolen (Slovakia).

Lloret F, Peñuelas J, Estiarte M, Ogaya R (2005) Patterns of plant population dieback and recvery alter drought episodes in Mediterranean forests and shrublands. Climate Change-Forest Ecosystems & Landscape Zvolen (Slovakia). Forest Research Institute Zvolen and the European Forest Institute.

Fire regenerative syndromes of forest woody species across fire and climatic gradients

Lloret F., Estevan H., Vayreda J., Terradas J. (2005) Fire regenerative syndromes of forest woody species across fire and climatic gradients. Oecologia. 146: 461-468.
Enllaç
Doi: 10.1007/s00442-005-0206-1

Resum:

Community resilience after fire is determined by species' ability to regenerate through two main mechanisms growth of new sprouts (resprouter species) and germination from surviving seed banks or from seeds arriving from neighbouring populations (seeder species). Both the mechanisms are present in Mediterranean communities. The occurrence of both the types in a community depends on fire history and the bio-geographical history determining the available species pool. Regenerative traits also covary with other functional attributes associated with resource acquisition and stress tolerance. As post-fire regenerative responses can be related to various ecological factors other than fire, we tested the hypothesis of a different proportional representation of post-fire regenerative syndromes in forest woody species along a climatic gradient in Catalonia (NE Spain) ranging from Mediterranean to temperate-boreal climates. Specifically, we expected seeder species to become less common with colder and moister conditions while resprouters would not be so influenced by the climatic gradient. We also tested the hypothesis of change in the relative abundance of regenerative syndromes in relation to recent fire history. We analysed a large database obtained from extensive forestry surveys and remote sensing fire records. After correction for spatial autocorrelation, we found an increase in the proportion of seeder species under more Mediterranean conditions and a decrease in fire-sensitive species (with no efficient mechanisms of post-fire recovery) in moister conditions. Resprouter species were similarly present across the whole gradient. A similar pattern was observed after excluding recently burnt plots. Therefore, post-fire regenerative syndromes segregate along the climatic gradient. Recent fires reduced the occurrence of fire-sensitive species and increased the proportion of seeder species. No significant effect was observed on resprouter species. Fire has a sorting effect, shaping the occurrence of species with different regenerative traits. Overall, fire seems to explain better the variability of the proportion of fire-sensitive species and climate the variability of seeder species. In addition, other factors (forestry practices and the covariation between regenerative and functional attributes) are likely to contribute to the regional pattern of regenerative syndromes. © Springer-Verlag 2005.

Llegeix més

Species attributes and invasion success by alien plants on Mediterranean islands

Lloret F., Médail F., Brundu G., Camarda I., Moragues E., Rita J., Lambdon P., Hulme P.E. (2005) Species attributes and invasion success by alien plants on Mediterranean islands. Journal of Ecology. 93: 512-520.
Enllaç
Doi: 10.1111/j.1365-2745.2005.00979.x

Resum:

1 Species attributes have been used to explain invasion patterns assuming the prevalence of biological mechanisms, although this approach often suffers several methodological and conceptual limitations, such as local idiosyncrasies, differences among habitats, phylogenetic constraints and insufficient sample size. 2 The relative importance of 15 species traits for explaining the abundance over 350 naturalized alien plant species was assessed across five Mediterranean islands (Corsica, Crete, Majorca, Malta and Sardinia). A comparative analysis accounting for phylogeny was used to examine variation in semi-quantitative estimates of species abundance in comparable habitats across the five island floras. 3 Species were divided into those with affinity for semi-natural, agricultural and ruderal habitats. Both vegetative and reproductive attributes were evaluated for individual islands and averaged across all islands. 4 Vegetative propagation, large leaf size, summer flowering, long flowering period and dispersal by wind or vertebrates were positively associated with average alien abundance across all five islands. Fewer significant trends were found in island-specific patterns. 5 The relative importance of a few reproductive traits is reflected in over-representation of Caryophyllales, Asterales and Poales (late flowering, large seed size and anemochory). Although significant covariation in traits was found there was no evidence for well-defined invasive syndromes. 6 Succulence was important in ruderal habitats, long flowering period in agricultural habitats and vertebrate seed dispersal in semi-natural habitats, suggesting that empty niches, avoidance of competitors and exploitation of mutualists, respectively, are important. 7 The study highlights the importance of estimating invasion success across a wide region, but analyses of specific invasion stages are also needed. Reproductive traits, which may be more relevant for long-distance colonization, and vegetative traits, which determine local dominance and persistence, were, nevertheless, both related to abundance within islands. © 2005 British Ecological Society.

Llegeix més

Does fire occurrence modify the probability of being burned again? A null hypothesis test from Mediterranean ecosystems in NE Spain

Salvador R., Lloret F., Pons X., Piñol J. (2005) Does fire occurrence modify the probability of being burned again? A null hypothesis test from Mediterranean ecosystems in NE Spain. Ecological Modelling. 188: 461-469.
Enllaç
Doi: 10.1016/j.ecolmodel.2004.12.017

Resum:

Two main causes have been proposed as drivers of fire regime in Mediterranean-type ecosystems: fuel build-up and weather conditions. If fuel build-up is the main cause, then areas recently burned will not burn again until some years later. Contrarily, if weather is the main cause, then all areas will burn irrespective of their age. We have devised a statistical test aimed to distinguish between these two hypotheses. To use the test is necessary to know the spatial distribution of fires during a period of time as long as possible. Then, a percolation algorithm procedure is applied to mimic the location, extent, and perimeter/area ratio of the real fires, independently of previous fire occurrence. This model is run many times and each run is considered a realization under the null hypothesis that a pixel burns irrespectively of whether it was burnt in the previous years. The actual number of pixels burned twice is then compared to the histogram of the probability density function of pixels burned twice, which is obtained from the simulations. Actual values falling in the right tail of the distribution point to a clumped pattern (fires tend to be more abundant in some locations), while falling in the left tail will indicate a segregated pattern (burning reduces the probability of further fires in the same site). The method was applied to three different areas of Catalonia (NE Spain) by comparing the actual fires from 1975 to 1998 to the pattern obtained from random fire simulations. An aggregated pattern was obtained in two of the studied areas when the origin of the simulated fires was located randomly, indicating that fires were not uniformly distributed in the territory. When the simulations were started at the centroids of the real fires, the null hypothesis of independence from previous fires was not rejected, and the fuel-driven assumption was not supported. In the third area, results were inconclusive because two large fires, occurred in 1994, totally changed the results obtained until then. © 2005 Elsevier B.V. All rights reserved.

Llegeix més

Wind effects on dispersal patterns of the invasive alien Cortaderia selloana in Mediterranean wetlands.

Saura S, Lloret F (2005) Wind effects on dispersal patterns of the invasive alien Cortaderia selloana in Mediterranean wetlands. Acta Oecologica 27: 129-133.