To live or to survive in Doñana dunes: Adaptive responses of woody species under a Mediterranean climate

Abstract

The Dune System of Don˜ana National Park (SW Spain) exhibit a mosaic of environmental characteristics, with different plant communities, all under the same Mediterranean climate, creating an interesting field laboratory for the study of plant responses to stressing conditions. Fourteen woody plant populations were selected, belonging to either xerophytic or hygrophytic plant communities on stabilised dunes, where topography causes differences in soil water availability. Plants were tagged and morphological and ecophysiological measurements were recorded in winter and summer of 1999. Seasonal differences in ecophysiological measurements together with morphological variables were used as plant traits to identify the main adaptive responses of the species. Cluster analysis of traits separated three groups of plant strategies: spiny legume species; sclerophyll, and semideciduous species. In addition, another two kind of strategies have been found in the semideciduous group of species, those withstanding water shortages, attaining very negative water potentials, low photochemical efficiency, and leaf proline accumulation in summer, as opposed to those tolerating water deficit, with moderate seasonal differences in water potential, proline content and photochemical efficiency. The results of this study indicate that legume species behave as a different functional group and drought-semideciduous species present different adaptive responses under the same environmental stress. Ecophysiological measurements must be used as plant traits to detect functional groups under Mediterranean climate.

Chlorophyll fluorescence varies more across seasons than leaf water potential in drought-prone plants

“…However, this is true only when the former have access to deeper soil water profi les and/or soil moisture is frequently replenished by rainfall . The Ψ pd of restinga species growing where mean annual rainfall was 1100-1300 mm was higher than for other species occurring in sandy environments where the mean annual rainfall was around 450 mm (-0.1 to -1.70 MPa compared with -1.0 to -5.0 MPa, respectively) (Zunzunegui et al 2005. In comparison with other seasonal environments, the variation in Ψ pd observed in restinga plants, -0.1 to -0.43 MPa in the wet season and -0.19 to -1.70 MPa during the dry season, was not as marked.…”

Acclimatation of three co-occurring tree species to water stress and their role as site indicators in mixed pine-oak forests in the Sierra Madre Oriental, Mexico

“…Differences between the two aspects (N and S), the tree species and the sampling dates (January to August 2006) were examined with three-way analyses of variance (threeway ANOVA), while aspect and species were considered as between-subject factors and sampling date (sd) as within-subject factor (Zar 1999). The three-way ANOVA was conducted for predawn and midday data separately.…”

“…Differences between meteorological conditions at each aspect were compared by one-way ANOVA after proofing true the assumption of normality and homogeneity of variance (Zar 1999;Crawley 2007).…”

“…For these analyses, real data of each species, summarizing both plots, were considered on a seasonal base (Zar 1999;Crawley 2007). On a seasonal basis, regression analysis was performed between averaged soil water content and predawn leaf water potentials (W wpd ) considering mean values of each sampling date (Crawley 2007).…”

“…All species presented their highest values at predawn and their lowest during midday, the value that integrates and reflects all environmental influences on the plants' internal water balance, indicating the least favourable condition for the plant . The water potential of a fully hydrated plant may be close to zero, while water potentials could reach as low as -12 MPa under extreme water stress conditions in the field (Zunzunegui et al 2005).…”