Influence of arbuscular mycorrhizal fungi and water regime on the development of endemic Thymus species in dolomitic soils

Dolomitic soils characteristically contain high levels of magnesium and calcium, and have a low water holding capacity. Such constraints enhance plant speciation and the emergence of endemic species. Thymus granatensis is an example of an endemic species from Southern Spain (Mediterranean climate) and a bioindicator of dolomitic soils that can be found in the Sierra de Baza Natural Park on pure dolomite (PD) soils (those containing more than 90% dolomite). Acknowledging the beneficial role of arbuscular mycorrhizal (AM) symbiosis against abiotic stress factors, this research was established to ascertain the importance of the AM community in supporting the growth of T. granatensis in PD soils. To study this, another Thymus species i.e., T. mastichina, was chosen for comparison. T. mastichina does not grow naturally in PD soils, but it is able to grow in a wide range of soil types including those having lower dolomite content. The results showed that: (i) AM establishment increases the biomass production of both species; (ii) the AM fungal community from PD soil might be fundamental for the growth of T. granatensis in the PD soil, particularly under drought conditions; (iii) the inoculation with AM fungi from the PD soil lowered the shoot Mg and Ca concentrations of both Thymus species growing in PD soil. Accordingly, AM fungi management could be used as a biotechnological tool to address the restoration and conservation of Mediterranean dolomitic habitats. (C) 2011 Elsevier B.V. All rights reserved.