Revegetation of semi-arid mine dumps: Arbuscular mycorrhizal fungi alleviate water competition in mixed planting systems

Water scarcity is the primary limiting factor for achieving sustainable revegetation and ecological restoration in arid and semi-arid mining areas. The application of arbuscular mycorrhizal fungi (AMF) and mixed planting has proven effective in promoting vegetation establishment and land restoration, thereby supporting sustainable ecological restoration. To investigate the effects of AMF inoculation and mixed planting ( Amorpha fruticosa L. + Medicago sativa L.) on plant physiology, water use strategies, and water use efficiency (WUE), we conducted a field experiment in a large mine dump located in a coal mining area. We measured plant leaf photosynthesis-related indicators, 13 C abundance, and plant and soil water isotopes. The results revealed that mixed planting and AMF inoculation in water-scarce environments significantly optimized the water-use strategy of plants. Using the MixSIAR model, we found that in AMF-inoculated mixed plots, M. sativa obtained more than 60% of its water from the 0–30 cm soil layer, whereas A. fruticosa L. obtained approximately 50% from the 60–100 cm soil layer. Furthermore, compared with the corresponding non-inoculated treatments, AMF shifted the apparent water uptake depth toward deeper soil layers. In A. fruticosa monoculture, compared with the non-inoculated treatment, AMF inoculation increased the net photosynthetic rate, WUE, root biomass, root length density, root mean diameter, root volume density, leaf C content, and leaf N content by 31.7%, 4.8%, 91.7%, 151.8%, 48.9%, 89.1%, 12.5%, and 33.4%, respectively. These data confirmed that AMF inoculation and mixed planting techniques are vital in regulating water distribution within the system under water-scarce conditions. These findings provide valuable insights for improving phytoremediation effectiveness and alleviating water scarcity.