We tested the hypothesis that seed availability is a limiting factor for plant colonization of road embankments under Mediterranean climate conditions. Experimental sowing on 10 road embankments was carried out to compare the colonization success of plants that Successfully colonize the road embankment and species that appear only occasionally in the road embankments. After sowing, we measured plant establishment, biomass production, and reproductive capacity of the species. The species that appear only occasionally in the road embankments had lower emergence rates (1.1 +/- 0.3%) than species that were successful colonizers (18.8 +/- 2.9%). None of the species of the former group survived or reproduced. The results did not support the hypothesis that seed availability was the main factor limiting plant colonization in the road embankments. We concluded that the arrival of seeds to road embankments under Mediterranean climate conditions was not enough to ensure colonization success of plants. Other factors, like hydric stress, appeared to affect seedling establishment and plant growth. Reclamation measures such as species selection should be taken in account to ensure revegetation success of road embankments.

We thank the Spanish "Plan Nacional I+D+I del Mnisterio de Ciencia y Tecnología" (project REN2001-2313), "Consejo Superior de Investigaciones Científicas" and "Fundación Bancaja" for their funding. We also thank José Antonio Bellido for his assistance in sowing, plot weeding and seed collecting; Maite Pardo for her assistance in sowing; the staff of the laboratories of the CIDE for soil analyses; Miguel Verdú and David Conesa for their help with statistical analyses; and two anonymous referees for their considerable help in improving the manuscript.

7 páginas, 2 figuras, 2 tablas.

Peer reviewed