Aragón, Cristina F. , Escudero, Adrian , Valladares, Fernando .
Relationship between physiological status and fitness-related traits in a semi-arid specialist, Helianthemum squamatum, in two contrasting scenarios.
SUMMER drought, entailing high irradiation and air temperature as well as water shortage, is generally considered the primary constraint to the productivity and dynamics of Mediterranean vegetation. However, the knowledge of the implications of these environmental constraints for plant performance under field conditions remains scant. The main goal of this study was to model the relationships between the physiological status and some fitness-related variables such as reproductive output and survival, in a semi arid specialist. We conducted a field study in a gypsum outcrop in central Spain with Helianthemum squamatum (Cistaceae), a semi-arid endemic gypsophyte, in two nearby sites of constrasting slope aspect. Flowering phenology was monitored along the reproductive season, and measurements of maximal photochemical efficiency of PSII were taken at pre-dawn and midday in 5 relevant phenological moments: before flowering, at both the onset and the peak of flowering, at the peak of fruit ripening and at the end of the reproductive period. Soil water content was also determined in all these sampling dates. Pre-dawn values of Fv/Fm remained rather high along all the reproductive period, and despite the generalized diurnal decline, midday values also kept considerably high. The lowest values of midday Fv/Fm were recorded coinciding with the peak of flowering, suggesting a possible vulnerability of plants related to reproductive effort. Although the conditions for plant development are considered to be better in north-facing slopes in Mediterranean ecosystems, midday Fv/Fm values were higher in the south-facing slope plants, except at the end of the reproductive season, likely due to the greater competition for water in the northern site. These results improve our understanding of the functioning of semi-arid Mediterranean shrublands, as well as the evolutionary processes implicated in the adaptation of this species to an adverse environment.
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1 - Universidad Rey Juan Carlos, Biodiversity and Conservation Group, C/ Tulipán s/n, Móstoles, Madrid, 28933, Spain
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, August 1st, 2006
Time: 8:45 AM