Fuel loading and flammability in the Mediterranean Basin woody species with different post-fire regenerative strategies

12 páginas, 5 figuras, 3 tablas.The flammability and combustibility of plant communities are determined by species features related to growth-form, structure and physiology. In some ecosystems, such as the Mediterranean ones, these characteristics may contribute to the existence of fire-prone species. We measured several parameters associated with the flammability and fuel loading of dominant woody species with different post-fire regenerative strategies ( seeders and non-seeders) in shrublands in the western Mediterranean Basin. Overall, seeder species show lower fuel load but are more prone to burning owing to a higher dead-to-live fuel ratio, live fine-fuel proportion and dead fine-fuel proportion. Moreover, they burst into flame at lower temperatures than non-seeders. In the Mediterranean Basin, most seeder species emerged mainly during the Quaternary, under a highly fluctuating Mediterranean climate and during recurrent fires. We propose that properties related to the combustibility and flammability of seeders may be the result of selective pressures associated with both fire and climate. These results suggest that ecosystems dominated by seeder species are more susceptible to fire risk than those dominated by non-seeder species in the Mediterranean Basin. Therefore, the proportion of these types of species resulting from previous fire or management history is likely to determine the characteristics of future fire events.We thank M. Jané, E. Martí, A. Vilà-Cabrera, J. Garcia, B. Moreira, S. Ribeiro and C. Beseler for helping in the field and in the laboratory work. Also, special thanks are due to J. Piñol for his advice and suggestions, and to J. Peñuelas and G. Alessio for supporting the flammability tests. This study was funded by the Department of Universities, Research and Information Society of the Generalitat de Catalunya, the European social funds, and the Spanish Ministerio de Ciencia y Tecnología (MCYT) projects REN 2003–07198 and CGL2006–01293/BOS. It also contributes to the European research group (GDRE) ‘Mediterranean and mountain ecosystems in a changing world’ funded by the Generalitat de Catalunya and CNRS (Centre National de la Recherche Scientifique). CEAM (Fundación Centro de Estudios Ambientales del Mediterráneo) is supported by the Generalitat Valenciana and Bancaixa.Peer reviewe

Fuel loading and flammability in the Mediterranean Basin woody species with different post-fire regenerative strategies

12 páginas, 5 figuras, 3 tablas.The flammability and combustibility of plant communities are determined by species features related to growth-form, structure and physiology. In some ecosystems, such as the Mediterranean ones, these characteristics may contribute to the existence of fire-prone species. We measured several parameters associated with the flammability and fuel loading of dominant woody species with different post-fire regenerative strategies ( seeders and non-seeders) in shrublands in the western Mediterranean Basin. Overall, seeder species show lower fuel load but are more prone to burning owing to a higher dead-to-live fuel ratio, live fine-fuel proportion and dead fine-fuel proportion. Moreover, they burst into flame at lower temperatures than non-seeders. In the Mediterranean Basin, most seeder species emerged mainly during the Quaternary, under a highly fluctuating Mediterranean climate and during recurrent fires. We propose that properties related to the combustibility and flammability of seeders may be the result of selective pressures associated with both fire and climate. These results suggest that ecosystems dominated by seeder species are more susceptible to fire risk than those dominated by non-seeder species in the Mediterranean Basin. Therefore, the proportion of these types of species resulting from previous fire or management history is likely to determine the characteristics of future fire events.We thank M. Jané, E. Martí, A. Vilà-Cabrera, J. Garcia, B. Moreira, S. Ribeiro and C. Beseler for helping in the field and in the laboratory work. Also, special thanks are due to J. Piñol for his advice and suggestions, and to J. Peñuelas and G. Alessio for supporting the flammability tests. This study was funded by the Department of Universities, Research and Information Society of the Generalitat de Catalunya, the European social funds, and the Spanish Ministerio de Ciencia y Tecnología (MCYT) projects REN 2003–07198 and CGL2006–01293/BOS. It also contributes to the European research group (GDRE) ‘Mediterranean and mountain ecosystems in a changing world’ funded by the Generalitat de Catalunya and CNRS (Centre National de la Recherche Scientifique). CEAM (Fundación Centro de Estudios Ambientales del Mediterráneo) is supported by the Generalitat Valenciana and Bancaixa.Peer reviewe

Diversidad funcional del matorral de Doñana: respuesta a episodios climáticos extremos

Póster presentados a las jornadas citadas que se celebraron del 6-7 de febrero 2014, en Sevilla, España.El funcionamiento y sostenibilidad de un ecosistema en parte depende de su diversidad biológica. Según la teoría ecológica, la diversidad funcional de las comunidades puede modular los efectos que tienen los factores abióticos sobre los ecosistemas. Durante el año 2005, dos eventos climáticos extremos acontecieron en el Parque Nacional de Doñana. Por un lado, tuvo lugar la mayor sequía de los últimos 28 años y por otro, aconteció un invierno muy frío con un elevado número de heladas, lo que dio lugar a un importante daño y mortalidad en la vegetación arbustiva del Parque. Estos eventos climáticos extremos ofrecen un marco único para estudiar la dinámica de la vegetación y la capacidad de resiliencia de estas comunidades mediterráneas de matorral usando una aproximación funcional. En el presente trabajo se ha realizado un seguimiento de la vegetación leñosa en 18 parcelas (de 5 x 5 metros) de "monte blanco" (matorral de la parte más seca de Doñana, dominado fundamentalmente por Cistáceas). Se han medido en 6 individuos de cada una de las especies más abundantes de la comunidad, diferentes rasgos funcionales a nivel de hoja, tallo y raíz. Nuestros objetivos son: (i) evaluar los cambios en los rasgos funcionales y en la diversidad funcional de estas comunidades entre los años 2005, 2007 y 2013, lo cual nos permitirá comprender si la estructura funcional de la comunidad explica la resistencia de la comunidad a estos eventos climáticos extremos; y (ii) comprender la contribución de los individuos supervivientes y de los regenerados a la resiliencia de la comunidad en una escala temporal, para lo cual se cuantificó la diversidad funcional de los adultos y juveniles del año 2007 y su contribución a la diversidad funcional de las comunidades actuales (2013). Estos resultados son de interés para conocer cómo el matorral de Doñana responde a los cambios climáticos extremos y qué incidencia tienen éstos en la dinámica de la vegetación futura, además de poder entender el papel de indicador de estos procesos.PROYECTOS DIVERBOS CGL2011-30285-C02-01 and C02-02 Y SECADIN CGL2012-32965.Peer reviewe

Contribution of species abundance and frequency to aboveground forest biomass along an Andean elevation gradient

Aims: To determine whether species that contribute most to a plot's biomass are the most abundant (high local abundance at plot scale) or the most frequent (occur the most across plots at landscape scale), or both. In the tropical Andes, these patterns may change with elevation. This study assesses the contribution to plot's above-ground biomass (AGB) of the plant community abundance pattern –the prevalence of within-plot dominant species– and the over-occurrence of regionally frequent species, in an elevation gradient. Methods: We considered all trees ≥2.5 cm DBH from 446 0.1 ha plots in an Amazonia-Andes 260–4350 m elevation cline in N Bolivia. Plot AGB was calculated as the sum of AGBs for all stems contained. We grouped plots into four bins segregated by elevation and ran a bootstrap analysis over subsets of 58 random plots per bin with 100 iterations. Simpson evenness index (E) for all species in each plot was used as a measure for its species abundance. Values for each plot's species frequency was calculated as the mean of all species’ in the plot mean frequencies across the bin (i.e. the fraction of plots where each species occurs). We used linear models to correlate plot AGB with (1) elevation and mean annual precipitation (MAP), and (2) E, plot species frequency and elevation. We performed all analyses at the species, genus and family levels. Results: Plot AGB was related negatively with elevation, and thus positively with MAP, and also negatively with plot E and plot species frequency, all significant. Plot species abundance therefore contributes positively to explain the relationship with AGB along elevational gradients, while plot species frequency does so negatively (i.e. less frequent species contribute more to a plot's AGB across elevation). AGB, for both generic and familial levels was also significantly and negatively correlated with E, but not related with plot species frequency biomass at these taxonomic levels. Conclusions: Plot AGB was mainly associated with elevation and floristic composition where species, genera and families tended to be abundant at the local (plot) scale. Species that were less frequent at the regional scale contributed with more AGB regionally, while frequency at generic and familial scales did little to explain AGB patterns. This association seems stronger at lower elevations for all taxonomic levels while decreases toward higher elevation. Our study reveals a relationship between plot structural features like C stocks –influenced by species local abundances– and the distribution of taxa across the landscape

The importance of functional diversity in the stability of Mediterranean shrubland communities after the impact of extreme climatic events

13 páginas.-- 5 figuras.-- 1 tabla.-- referencias.-- Supplementary material is available at Journal of Plant Ecology online. https://doi.org/10.1093/jpe/rtw027Aims Extreme climatic events may have important consequences for plant community structure and composition. In 2005, a severe drought together with a cold winter promoted extensive damage and mortality in shrubland communities of southwest Spain (Doñana National Park). Here, we aim to identify the mechanisms underlying community stability (resistance and resilience) in response to this extreme climatic event, considering changes in the functional structure of these communities. Methods We used a trait-based approach, quantifying variations in 10 functional traits at the community level (community weighted means, CWM) and the functional diversity (functional richness, evenness and divergence) in 18 plots at three different times: predating the climatic event (estimated from the sum of the live and dead volume of each species in 2007), and 2 and 8 years after the 2005 episode. We also quantified the differences in functional traits and functional diversity between adult and recruit stages, which allowed us to better understand the contribution of the recruitment to the maintenance of the functional structure and diversity of the community. Important Findings Communities with higher functional divergence before the climatic event maintained nearly constant their levels of functional divergence 8 years after, but they were more prone to changes in species composition. Community resistance in terms of vegetation cover was positively correlated with root dry matter content, whereas community resilience was positively correlated with leaf chlorophyll (LChl). We also found that some values (weighted means) of functional community traits (such as root dry matter content and LChl) had increased 2 years after the event, returning to the pre-event conditions after 8 years. In addition, there was hardly any establishment of new species in the community and the recruits did not make substantial differences to the community functional structure. Only seed mass differed significantly between the adult and seedling stages. In summary, the extreme climatic event induced rapid vegetation changes, modifying several functional properties of the community, but, in spite of the occurrence of changes in species composition, a rapid convergence of these shrubland communities took place due to the replacement of species with functional redundancy, thus recovering the initial conditions and supporting the existence of strong mechanisms of functional resilience.This study was funded by the Spanish MEC projects DIVERBOS (CGL2011-30285-C02-01 and C02-02), SECADIN (CGL2012-32965) and ECO-MEDIT (CGL2014-53236-R), the Catalonian 2014-SGR-453 grant, the ICTS-Reserva Biológica de Doñana projects 38/2007, 27/2009 and 11/2013 and European FEDER funds. Isotopic analysis was carried out in the LIE of EBD(CSIC), multielemental analysis of soil and plant samples in the IRNAS Analysis Service and leaf N analysis in the SCAI of the University of Córdoba.Peer reviewe

Forest and woodland replacement patterns following drought-related mortality

Forest vulnerability to drought is expected to increase under anthropogenic climate change, and drought-induced mortality and community dynamics following drought have major ecological and societal impacts. Here, we show that tree mortality concomitant with drought has led to short-term (mean 5 y, range 1 to 23 y after mortality) vegetation-type conversion in multiple biomes across the world (131 sites). Self-replacement of the dominant tree species was only prevalent in 21% of the examined cases and forests and woodlands shifted to nonwoody vegetation in 10% of them. The ultimate temporal persistence of such changes remains unknown but, given the key role of biological legacies in long-term ecological succession, this emerging picture of postdrought ecological trajectories highlights the potential for major ecosystem reorganization in the coming decades. Community changes were less pronounced under wetter postmortality conditions. Replacement was also influenced by management intensity, and postdrought shrub dominance was higher when pathogens acted as codrivers of tree mortality. Early change in community composition indicates that forests dominated by mesic species generally shifted toward more xeric communities, with replacing tree and shrub species exhibiting drier bioclimatic optima and distribution ranges. However, shifts toward more mesic communities also occurred and multiple pathways of forest replacement were observed for some species. Drought characteristics, species-specific environmental preferences, plant traits, and ecosystem legacies govern postdrought species turnover and subsequent ecological trajectories, with potential far-reaching implications for forest biodiversity and ecosystem services