Re-establishment of Retama sphaerocarpa as a target species for reclamation of soil physical and biological properties in a semi-arid Mediterranean area

Re-establishment of the indigenous shrub vegetation is a key step in the restoration of abandoned agricultural semi-arid lands. A field experiment was carried out to evaluate the effect of a composted residue and mycorrhizal inoculation with Glomus intraradices on the viability of Retama sphaerocarpa (L.) Boissier. The influence of the rhizosphere of this shrub legume on the physical-chemical and biological properties of an abandoned semi-arid agricultural area in south-eastern Spain was also assessed. Eighteen months after planting, the combined treatment of mycorrhizal inoculation and composted residue was the most effective for increasing the growth and the N and P contents in shoot tissues of R. sphaerocarpa. There was a highly positive significant correlation between shoot dry weight and the nutrient contents in shoot tissues. Water-soluble C, water-soluble carbohydrates, biomass C contents, and enzyme activities (dehydrogenase, urease, protease-N-alpha-benzoyl-L-argininamide (BAA), and acid phosphatase) measured in the rhizosphere of R. sphaerocarpa were higher than in the bare soil. Rhizosphere aggregate stability of R. sphaerocarpa was about 47% higher than that of bare soil. These improvements in the physical-chemical and biological properties of the rhizosphere soil of R. sphaerocarpa could facilitate the establishment and development of new plants in the surrounding area, which would aid the revegetation of semi-arid ecosystems. (C) 2003 Elsevier Science B.V. All rights reserved.