Testing leaf trade-offs in Mediterranean woody species: Post-fire regenerative strategy links water regulation and Leaf dry matter content.

Saura-Mas S, Shipley B, Lloret F (2009) Testing leaf trade-offs in Mediterranean woody species: Post-fire regenerative strategy links water regulation and Leaf dry matter content. Functional Ecology 23: 103-110.

The Fluctuation Niche in Plants.

Terradas J, Peñuelas J, Lloret F (2009) The Fluctuation Niche in Plants. International Journal of Ecology doi: 10.1155/2009/959702. Article ID 959702.

Exploring species attributes and site characteristics to assess plant invasions in Spain

Gassó N., Sol D., Pino J., Dana E.D., Lloret F., Sanz-Elorza M., Sobrino E., Vilà M. (2009) Exploring species attributes and site characteristics to assess plant invasions in Spain. Diversity and Distributions. 15: 50-58.
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Doi: 10.1111/j.1472-4642.2008.00501.x

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Aim: Biological invasions are a major component of global change with increasing effects on natural ecosystems and human societies. Here, we aim to assess the relationship between plant invader species attributes and the extent of their distribution range size, at the same time that we assess the association between environmental factors and plant invader species richness. Location: Spain, Mediterranean region. Methods: From the species perspective, we calculated the distribution range size of the 106 vascular plant invaders listed in a recently published atlas of alien plant species in Spain. Range size was used as an estimation of the degree of invasion success of the species. To model variation in range size between species as a function of a set of species attributes, we adopted the framework of the generalized linear mixed models because they allow the incorporation of taxonomic categories as nested random factors to control for phylogenetic relationships. From the invaded site perspective, we determined invader plant species richness as the number of species for each 10 × 10 km Universal Transverse Mercator (UTM) grid. For each grid cell, we estimated variables concerning landscape, topography, climate and human settlement. Then, we performed a generalized linear mixed model incorporating a defined spatial correlation structure to assess the relationship between plant invader richness and the environmental predictors. Results: From the species perspective, wind dispersal and minimum residence time appeared to favour invasion success. From the invaded site perspective, we identified high anthropogenic disturbance, low altitude, short distance to the coastline and dry, hot weather as the main correlates to UTM grid cell invader richness. Main conclusions: According to these results, an increasing importance of man-modified ecosystems and global warming in the Mediterranean region should facilitate the expansion of plant invaders, especially wind-dispersed species, leading to the accumulation of invasive species in some sites (i.e. invasion hot spots). © 2008 The Authors.

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Microspatial population genetic structure of the Mediterranean shrub Fumana thymifolia

Jump A.S., Rico L., Lloret F., Peñuelas J. (2009) Microspatial population genetic structure of the Mediterranean shrub Fumana thymifolia. Plant Biology. 11: 152-160.
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Doi: 10.1111/j.1438-8677.2008.00109.x

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Fumana thymifolia (Cistaceae) is an insect-pollinated, gravity-dispersed evergreen shrub, which is a common component of fire-prone Mediterranean shrubland ecosystems. Despite the availability of basic knowledge on its ecology, little is known of its breeding system and no information is available on its population genetic structure. We explored the within-population genetic structure of this species using amplified fragment length polymorphism (AFLP) molecular markers and related this to predictions based on its breeding system, pollen and seed dispersal. Existing information on the reproductive ecology of F. thymifolia was supplemented by artificial pollination experiments. We determined that self-fertilisation can occur in F. thymifolia but results in reduced fruit set. Significant genetic structuring was detected within the population, a likely consequence of localised seed dispersal in combination with a mixed mating system. In a study site covering approximately 0.5 ha, amova revealed that approximately 9% of genetic variability was distributed among population subsamples. Significant spatial genetic structure was detected, with kinship coefficients being significantly elevated above the null expectation in the first six distance classes (maximum 5 m), and a value of Sp of up to 0.0342, comparable with species having similar ecological characteristics. Weak isolation by distance at the plot scale was detected, suggesting that insect-mediated pollen flow is non-random, despite being more extensive than seed dispersal. Fumana thymifolia provides a promising model for the investigation of both short- and long-term population dynamics in relation to fire frequency within this plant community. © 2008 German Botanical Society and The Royal Botanical Society of the Netherlands.

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Plant community changes induced by experimental climate change: Seedling and adult species composition

Lloret F., Peñuelas J., Prieto P., Llorens L., Estiarte M. (2009) Plant community changes induced by experimental climate change: Seedling and adult species composition. Perspectives in Plant Ecology, Evolution and Systematics. 11: 53-63.
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Doi: 10.1016/j.ppees.2008.09.001

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Experimental manipulation of climate provides a powerful tool for studying plant community dynamics with respect to current climate change. We experimentally investigated the vegetation dynamics of a Mediterranean shrubland under directional climate change by manipulating rain and temperature at stand level throughout 7 years. We focused on seedling establishment in relation to the between-year variability of drought conditions. We also compared seedling dynamics to changes in the established adult vegetation to assess the coupling between both dynamics. We used multivariate techniques (principal response curves (PRC) and redundancy analysis (RDA)) to explore changes in the whole community, and Generalized Linear Model (GLZM) to analyse the influence of drought on the abundance and survival of the most abundant species. Drought treatment induced significant changes in the species composition of the seedlings, via a differential decrease in the seedling density of most species. No species was particularly favoured in terms of seedling abundance under water-deficit conditions. Warming only explained a low percentage of the variability in seedling species composition. The emergence of seedlings in control plots - which may be considered an estimation of the between-year variability in the conditions for seedling establishment - was a better predictor of seedling emergence in experimental plots than climate manipulation treatments. The PRC analysis of the adults showed dynamics that were different from those recorded for seedlings, and it also showed that drought treatment significantly explained species composition. This result is reinforced by the change in the relative abundance of seedling and adults of the more common species in the drought and warming treatments, supporting the hypothesis that climatic directional change heightens discrepancies between recruitment and the adult performance. The RDA analysis applied to species composition at the end of the experiment failed, however, to attain any statistical significance. The warming treatment did not produce any significant shifts in adult vegetation. In conclusion, directional climate change - particularly drier conditions in Mediterranean shrublands - would result in a change in the recruitment of the plant community. This change in seedling recruitment tends to be different from the dynamics of adults, suggesting that potential adult mortality would not be compensated by actual seedling recruitment, thus enhancing shifts in community composition. © 2008 Rübel Foundation, ETH Zürich.

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Fire-related traits for plant species of the Mediterranean Basin

Paula S., Arianoutsou M., Kazanis D., Tavsanoglu Ç., Lloret F., Buhk C., Ojeda F., Luna B., Moreno J.M., Rodrigo A., Espelta J.M., Palacio S., Fernández-Santos B., Fernandes P.M., Pausas J.G. (2009) Fire-related traits for plant species of the Mediterranean Basin. Ecology. 90: 1420-0.
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Doi: 10.1890/08-1309.1

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Plant trait information is essential for understanding plant evolution, vegetation dynamics, and vegetation responses to disturbance and management. Furthermore, in Mediterranean ecosystems, changes in fire regime may be more relevant than direct changes in climatic conditions, making the knowledge of fire-related traits especially important. Thus the purpose of this data set was to compile the most updated and comprehensive information on fire-related traits for vascular plant species of the Mediterranean Basin, that is, traits related to plant persistence and regeneration after fire. Data were collected from an extensive literature review and from field and experimental observations. The data source is documented for each value. Since life history traits may vary spatially or with environmental conditions, we did not aggregate them by species; i.e., traits and species are repeated in different records if they were observed by different researchers and/or in different locations. Life history traits included in the data set are: life form, resprouting ability (after fire, after clipping, or after other disturbances that remove all the aboveground biomass), resprouting bud source, heat-stimulated germination, other germination cues, seed bank location and longevity, post-fire seedling emergence and survival, maturity age of resprouts and saplings, and seed mass. Several traits are unknown for many species; consequently, the data set reflects the state of the knowledge on the topic. However, since the ability to resprout is a trait of paramount relevance in fire-prone environments, it was considered a core trait in the data set, and thus species whose resprouting capacity was unknown were not included. Life form is also provided for all taxa. The structure of the database allows different levels of information (and accuracy) for each entry, and thus some traits may include different types of data (quantitative, semi-quantitative, or categorical) from different sources. The data set is structured in 8263 records and 11 columns, obtained from 301 published and unpublished sources of information. It includes 952 taxa determined at specific or infraspecific level, which comprise 859 species, 384 genera, and 79 families. Although this is the most comprehensive data set of fire-relevant plant traits for Mediterranean species, there is still a considerable need for observations and experiments, especially in little-studied Mediterranean areas, such as northern Africa. © 2009 by the Ecological Society of America.

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Experimental drought and warming decrease diversity and slow down post-fire succession in a Mediterranean shrubland

Prieto P., Peñuelas J., Lloret F., Llorens L., Estiarte M. (2009) Experimental drought and warming decrease diversity and slow down post-fire succession in a Mediterranean shrubland. Ecography. 32: 623-636.
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Doi: 10.1111/j.1600-0587.2009.05738.x

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Plant community recovery (species richness, diversity and composition) of a post-fire Mediterranean shrubland was monitored over a seven year period (1998-2005) under experimental drought and warming that simulated the environmental conditions forecast for this area in the coming decades. Species richness and Shannon's index were positively correlated with accumulated precipitation in the growing season and both variables were negatively affected by reduced water availability in drought plots. The relative abundance of the different species in both treatments was linearly correlated with their relative abundance in control plots. Moreover, we found species-specific responses to treatments. Drought and warming treatment reduced the competitive ability of the obligate seeder tree Pinus halepensis against native resprouter shrubs and consequently, the transformation from shrub to pine tree dominated vegetation was slowed down. Conversely, the water use strategy of Globularia alypum may allow this species to maintain a dominant position in drought plots. Therefore, future drier and warmer conditions in Mediterranean areas may severely affect plant community recovery after a disturbance, due to the existence of both abundance-dependent and species-specific responses that may change inter-specific competitive relationships. © 2009 Ecography.

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Linking post-fire regenerative strategy and leaf nutrient content in Mediterranean woody plants

Saura-Mas S., Lloret F. (2009) Linking post-fire regenerative strategy and leaf nutrient content in Mediterranean woody plants. Perspectives in Plant Ecology, Evolution and Systematics. 11: 219-229.
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Doi: 10.1016/j.ppees.2009.04.002

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We explored differences in leaf nutrient contents between species from Mediterranean shrublands with the ability to resprout after disturbances such as fire (resprouters) and others without this capacity (non-resprouters). Since it is to be expected that resprouting capacity is related to a more conservative use of nutrients, we hypothesize that resprouter and non-resprouter species will differ in their leaf nutrient concentrations. We measured the following leaf traits: leaf carbon content (LCC), leaf nitrogen content, leaf phosphorous content (LPC), leaf potassium content, leaf calcium content (LCaC), leaf magnesium content and leaf sodium content, in 30 woody species coexisting in a coastal shrubland. We also considered the influence of species' taxonomic affiliation in our analysis. Non-resprouters had higher LPC and LCaC than resprouter species, and lower LCC, which could be related to their cell and life-history properties. This study also suggests that non-resprouter species have more P in their leaves and are less limited by P than resprouter species. Overall, the differences in leaf nutrient contents suggest that shifts in the proportion of resprouter and non-resprouter species resulting from changes in the fire regime may have effects on the functional properties of the ecosystem. © 2009 Rübel Foundation, ETH Zürich.

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Relationship between post-fire regeneration and leaf economics spectrum in Mediterranean woody species

Saura-Mas S., Shipley B., Lloret F. (2009) Relationship between post-fire regeneration and leaf economics spectrum in Mediterranean woody species. Functional Ecology. 23: 103-110.
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Doi: 10.1111/j.1365-2435.2008.01474.x

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1. Recent work has identified global-scale relationships between key leaf traits (leaf economics spectrum). However, it is important to determine whether this approach can be applied at local scale with smaller subsets of species facing similar environments. Since fire is a key process in Mediterranean shrubland dynamics we analyze whether fire-related life-history traits influence the pattern of correlation between the leaf economic spectrum and leaf moisture traits. 2. Using structural equation modelling and exploratory path analysis, we developed alternative models to test how interspecific leaf traits are related to the seasonal variation of water content (leaves and shoots) and to the type of post-fire regeneration of Mediterranean woody species. 3. This study demonstrates that for these species seasonal variation in water content and fuel moisture would be better predicted by the presence or absence of a trait describing post-fire seedling establishment than by the leaf economic spectrum traits. However, leaf dry matter content (LDMC) is influenced by both the leaf economic spectrum and the post-fire regenerative type. 4. Seeder species (those that recruit via seeds immediately after fire) present lower LDMC and higher relative seasonal variation of relative water content (RWCrsv) than non-seeders. We hypothesize that since seeder species mostly evolved under the Mediterranean climate, they developed a particular strategy of drought tolerance (without causing an effect to the relation between the volume occupied by cytoplasm relative to the volume occupied by cell walls), which is the cause of the observed relation between LDMC and RWCrsv. 5. This study suggests that the leaves of Mediterranean woody species would follow the general leaf economics spectrum (Wright et al. 2004) but that specific selective forces, such as disturbance regime, acting at regional scale also play a relevant role to explain leaf traits related to water content. © 2008 The Authors.

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