Environmental and Experimental Botany 53 (2005) 1–11 Effects of water and a nutrient pulse supply on Rosmarinus officinalis growth, nutrient content and flowering in the field J. Sardans a,∗ , F. Rodà b , J. Peñuelas a a Unitat d’Ecofisiologia CSIC-CEAB-CREAF, CREAF (Center of Ecological Research and Forestry Applications) Edifici C, Universitat Autònoma de Barcelona, Bellaterra 08193 (Barcelona), Spain b CREAF (Center of Ecological Research and Forestry Applications), Edifici C, Universitat Autònoma de Barcelona, Bellaterra 08193 (Barcelona), Spain Accepted 23 February 2004 Abstract Rosmarinus officinalis is a dominant shrub species of calcareous Mediterranean communities that has increased its presence in wide areas due to fire frequency increase and field abandonment. We aimed to study the capacity of adult shrubs to respond to nutrient pulses such as those produced by fires and human driven eutrophycation. In a 5 years old post-fire Mediterranean shrubland we conducted an experiment to investigate the effects of irrigation and N and P fertilisation on the growth, nutrient status and flowering effort of adult plants of the dominant shrub R. officinalis in a post-fire shrubland. The responses were monitored during the immediate 3 years after fertilisation. P fertilisation increased plant growth, produced a great increase in P aerial mineralomass and P concentration in leaf and stems and had a slight positive effect on flowering effort. Irrigation increased plant growth, but did not have significant effects on nutrient contents and flowering. The results show that adult individuals of the Mediterranean shrub R. officinalis have a notable capacity to positively respond in growth and in nutritional status to a sudden increase of the limiting nutrient, in this case P, and in a lesser extent, to an increase of water supply. These capacities may be important under the more unpredictable nutrient and water availability conditions expected for the near future; they will allow to take advantage of the pulses of higher nutrient and water availability in the middle of dry periods, thus increasing the community capacity to improve the nutrient retention in the ecosystem. © 2004 Elsevier B.V. All rights reserved. Keywords: Calcareous soil; Flowering; Irrigation; Growth; Mediterranean; Nitrogen; Nutrient content; Nutrient pulse; Phosphorus; Rosmarinus officinalis; Shrubland 1. Introduction The summer drought is the most characteristic trait of Mediterranean ecosystems (Mooney and Parsons, ∗ Corresponding author. Tel.: +93-581-13-12; fax: +93-581-41-51. E-mail address: j.sardans@creaf.uab.es (J. Sardans). 1973; Specht, 1979; Mooney, 1989), but the nutrients play an important role too (Kruger, 1979; Specht, 1979; Carreira et al., 1992). Water and nutrient avail- ability are the main abiotic factors that drive the struc- ture and relations in Mediterranean plant communities (Dunn et al., 1977; Rundel, 1982; Witkowski et al., 1990; Barbault and Doucet, 1993; Lebourgeois et al., 1997; Rodà et al., 1999). Mediterranean ecosystems 0098-8472/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.envexpbot.2004.02.007