Applied Soil Ecology 22 (2003) 29–37 Analysis of the mycorrhizal potential in the rhizosphere of representative plant species from desertification-threatened Mediterranean shrublands C. Azcón-Aguilar a , J. Palenzuela a , A. Roldán b , S. Bautista c , R. Vallejo c , J.M. Barea a,∗ a Departamento de Microbiolog´ ıa del Suelo y Sistemas Simbióticos, Estación Experimental del Zaid´ ın, CSIC, Profesor Albareda 1, 18008 Granada, Spain b Centro de Edafolog´ ıa y Biolog´ ıa Aplicada del Segura (CEBAS-CSIC), Campus Espinardo, 30100 Murcia, Spain c Centro de Estudios Ambientales del Mediterráneo (CEAM), Parque Tecnológico, C/Charles R. Darwin 14, 46980 Paterna, Valencia, Spain Received 19 March 2002; received in revised form 20 July 2002; accepted 22 July 2002 Abstract An evaluation of the mycorrhizal status of desertification-threatened ecosystems has been recommended as a first step in rehabilitation/restoration approaches based on revegetation strategies using arbuscular mycorrhizal (AM) technology. Representative desertified semiarid areas were selected from southeast Spain where the vegetation is dominated by grasses, with Stipa tenacissima usually present, and with some patches of the shrubs Pistacia lentiscus, Rhamnus lycioides, Olea europaea subsp. sylvestris and Retama sphaerocarpa. The objective of this study was to evaluate the mycorrhizal potential in these soils, the contribution of the different species established to the mycorrhizal potential of the soils and to assess the main mycorrhizal propagules involved. There were more AM fungal propagules in the rhizospheres of all the shrub species studied compared with adjacent fallow soils, suggesting that AM propagules can be considered as a functional component of the resource islands developing around plant roots. R. sphaerocarpa and O. europaea had a higher capacity to enhance the development of mycorrhizal propagules in their rhizospheres than R. lycioides and P. lentiscus. Correlation analyses showed that the number of spores of the most representative AM fungal species, i.e. Glomus constrictum, and the total length of extraradical AM mycelium are the propagule sources which were best correlated with the mycorrhizal potential in terms of the number of “infective” AM propagules in the rhizosphere of the target plant species. The contribution of AM symbiosis to the potentiality of S. tenacissima as nurse plant was site dependent. Diversity of AM fungi present in the test area is rather low, indicating the high degree of degradation of the ecosystem. At most, only four AM fungal spore morphoecotypes were consistently detected in the rhizosphere of the target plant species. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Arbuscular mycorrhiza; Degraded Mediterranean ecosystems; Diversity; Restoration ecology; Revegetation strategies ∗ Corresponding author. Tel.: +34-958-121011; fax: +34-958-129600. E-mail address: jmbarea@eez-csic.es (J.M. Barea). 1. Introduction Well-developed, fully functional, “internal sym- bioses” were already recognised in pioneering studies to be fundamental for ecosystem stability and sustain- 0929-1393/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0929-1393(02)00107-5