Effects of arbuscular mycorrhizal fungi on growth parameters, nutrient absorption, and interspecific competition of herbs on iron tailings

The greenhouse pot experiment was used to study the effects of the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae (FM) and three different planting patterns on growth parameters, mineral nutrient absorption, and inter-species competition of white clover (Trifolium repens) and ryegrass (Lolium perenne) on iron tailings. This study aimed to identify a type of cultivation mode that could not only increase plant colonization but also improve the introduction of pioneer plants in tailings and to provide a theoretical and application basis for plant restoration on iron tailing wasteland. The results showed that FM could establish a symbiotic with the two other plant species and had a higher rhizosphere mycorrhizal infection rate under mixed planting. The rhizosphere mycorrhizal infection rate of mixed planting white clover was the highest, with an average of 47.9%. Inoculation with FM significantly increased the phosphorus concentrations in white clover (168% ~ 357%) (P < 0.05) and the phosphorus concentrations in ryegrass in mixed planting (10.5%) (P < 0.05) as well as the biomass of white clover (by approximately 5 ~ 7 times) (P < 0.05) and ryegrass in mixed mode (1.9 times) (P < 0.05). In mixed planting, plant iron concentrations were significantly higher than that in single species. FM inoculation significantly decreased the iron concentrations in shoots of the white clover (P < 0.05), but the iron concentration in their roots increased. FM inoculation increased the iron absorption of white clover and ryegrass under the single mode and significantly decreased the iron absorption of ryegrass under the mixed mode (P < 0.05). In the mixed planting mode, the two plants had higher iron absorption efficiency, FM inoculation significantly increased the iron absorption efficiency of white clover (P < 0.05) and decreased that of ryegrass. The mixed planting mode significantly increased the zinc concentrations and decreased the copper concentrations of white clover. FM inoculation significantly decreased the manganese concentrations of two plants and significantly increased the copper concentrations of white clover. The white clover and ryegrass hybrid system has a land equivalent ratio greater than 1, which has a mixed advantage. The interspecific competitive ability of ryegrass compared with white clover was greater than 0, indicating a competitive advantage. Mycorrhizal fungi may improve the competitive ability of white clover. Mixed planting can, therefore, significantly promote the growth of ryegrass, whereas inoculation with FM can enhance the competitiveness of white clover. AMFs have great potential for use with pioneer plants to adapt to the complex adversity of iron tailings and to restore tailings pioneer vegetation.