Summary
Trait variability in space and time allows plants to adjust to changing environmental conditions. However, we know little about how this variability is distributed and coordinated at different organizational levels.
For six dominant tree species in northeastern Spain (three Fagaceae and three Pinaceae) we quantified the inter‐ and intraspecific variability of a set of traits along a water availability gradient. We measured leaf mass per area (LMA), leaf nitrogen (N) concentration, carbon isotope composition in leaves (δ13C), stem wood density, the Huber value (Hv, the ratio of cross‐sectional sapwood area to leaf area), sapwood‐specific and leaf‐specific stem hydraulic conductivity, vulnerability to xylem embolism (P50) and the turgor loss point (Ptlp).
Differences between families explained the largest amount of variability for most traits, although intraspecific variability was also relevant. Species occupying wetter sites showed higher N, P50 and Ptlp, and lower LMA, δ13C and Hv. However, when trait relationships with water availability were assessed within species they held only for Hv and Ptlp.
Overall, our results indicate that intraspecific adjustments along the water availability gradient relied primarily on changes in resource allocation between sapwood and leaf area and in leaf water relations.
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.
Groups of species with different post-fire regenerative strategies (seeders and resprouters) have different functional traits related to water use. In addition to the role of phylogenetical constraints, these differences are also likely to be related to the respective life history characteristics. Therefore, the presence and abundance of species with different post-fire regenerative responses influence the functional properties of the communities.
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