Mycorrhizal inoculum selected under arid conditions promotes plant resource‐use efficiency

Abstract Arid and semi‐arid ecosystems, especially oceanic islands, face increasing degradation that limits plant establishment and challenges restoration. Although arbuscular mycorrhizal fungi (AMF) can enhance plant performance, their effects depend on plant functional traits and inoculum history, and it remains unclear how inocula from contrasting environments shape species‐specific growth and resource‐use efficiency. Understanding these interactions is essential for improving the effectiveness of AMF‐based restoration strategies in drylands. This study hypothesises that (i) plant species with a ‘do‐it‐yourself’ strategy (i.e. relying on their own roots rather than fungal partners for resource acquisition) are less dependent on the temporal variation of the mycorrhizal inoculum, and (ii) inocula shaped by different selection pressures (agricultural vs. natural environments) exert contrasting effects on plant growth and resource‐use efficiency. We grew six plant species with two contrasting inocula (one from an agricultural system and one from a natural arid environment) and a sterilised control. To evaluate the effect of temporal variations on early mycorrhizal colonisation and plant growth responses, a subset of plants was harvested at 3 and 10 months. After 10 months, we quantified a comprehensive set of morphological and physiological traits to assess growth and resource‐use efficiency. Agricultural inoculum increased photosynthetic activity but did not enhance biomass production. In contrast, inoculum from arid natural environments was associated with higher mycorrhizal dependency, improved resource‐use efficiency and increased biomass production. Synthesis and applications. Root traits and the environmental history of AMF communities jointly determine symbiotic outcomes. Our findings provide an evidence‐based framework for selecting AMF inocula according to restoration goals in drylands, highlighting the importance of environmental history when developing microbiome‐based interventions.