Effects Of Arbuscular Mycorrhizal Fungi On The Growth Of Maize In Three Types Of Coal Mine Spoil

Inner Mongolia is rich in coal resources and coal mining has brought about enormous economic benefits for the country as well as to the local people. However, disorderly discharge of coal gangue and other mining wastes has also caused serious eco-environmental problems to the grassland ecosystem, such as the shrinking of grassland, air and water pollution and soil degradation. Therefore, from the long-term overall situation, considering the protection of ecological environment in the mining area and the maintaining of the grassland ecosystem stability, it is urgent to seek a feasible way to comprehensive control coal mine spoil banks. Revegetation is one of the most cost-effective ways to solve environment problems caused by coal mine spoil. In this study, three types of coal mine spoil were selected as growth substrates. The substrates were recent discharged, weathered and spontaneous combusted coal mine spoils and were collected from Shiguai mine area of Baotou. Effects of arbuscular mycorrhizal (AM) fungi on the growth of maize(Zea mays L.) grown in coal mine spoil and mycorrhizal effects were studied, and the potential role of AM fungi in the vegetation restoration of coal mine spoil banks was investigated.A greenhouse pot experiment was conducted to investigate the influence of AM fungi (G aggregatum, G etunicatum, G. intraradices, G. mosseae or G. versiforme) on the plant growth, nutrient uptake, C:N:P stoichiometric, uptake of metals by maize grown in three types of coal mine spoil. The results indicated that the symbiotic associations were successfully established between five isolates and maize grown in the three substrates, with an average mycorrhizal colonization rate ranging from36%to90%. The colonization of five AM fungi increased the dry weight of maize and the uptake of N, P and K by maize to varying degrees, and the plant had different mycorrhizal dependency in three substrates. Inoculation with G. mosseae, G. intraradices and G. etunicatum exhibited the most obvious role in promoting the growth and nutrient uptake of maize grown in recent discharged, weathered and spontaneous combusted coal mine spoils, respectively. Inoculation with AM fungi also significantly decreased C:P and N:P ratios and adjusted C:N:P ratios, supporting the growth rate hypothesis. In addition, AM fungi had significantly differences on concentrations of Cu, Fe, Mn and Zn in shoots and roots of maize. The results indicated that the five isolates had different mycorrhizal effects on maize in the three substrates, and G. mosseae, G. intraradices and G. etunicatum were more suitable for the revegetation of recent discharged, weathered and spontaneous combusted coal mine spoils, respectively. Based on the comprehensively consideration, G. intraradices played a good role for the plant growth in there substrates, so it was selected as the further study strains. In the following pot experiment, effects of AM fungi G. intraradices on the plant growth, nutrient uptake, C:N:P stoichiometric, uptake of metals by maize and water status of maize grown in three types of coal mine spoil under water stress (80%,60%and40%of water content) were investigated. The results showed maize in three substrates had high root AM colonization rate, ranging from36%to90%, and AM rate was gradually increased with the decrease of substrate water content. Inoculation with G. intraradices significantly promoted the growth of maize grown in spontaneous combusted coal mine spoil under three levels of watering and weathered coal mine spoil under the severe water stress. However, inoculation with AM fungi had no effect on the plant growth in recent discharged coal mine spoil. Colonization by G. intraradices significantly increased the P uptake of maize in there substrates under water stress, especially the other nutrient situations of maize grown in spontaneous combusted coal mine spoil were also improved. With the increase in the degree of water stress, the biomass and nutrient uptake of maize were decreased. Moreover, Inoculation with AM fungi also significantly adjusted C:N:P ratios, supporting the growth rate hypothesis. In this experiment, metal concentrations in maize were significantly affected by inoculation, substrate water contents and substrate types, especially the Cu, Zn and Mn concentrations. In spontaneous combusted and weathered coal mine spoils, inoculation with G. intraradices increased water content of leaf fresh weight and water utilization efficiency of maize, accelerated plant rehydration rate and improved water status and the drought resistance of maize under water stress. G. intraradices did not effectively improved plant water status in recent discharged coal mine spoil. The results indicated that the effect of G. intraradices on plant growth and drought resistance of maize in there substrates were in order:spontaneous combusted> weathered> recent discharged coal mine spoil, and G. intraradices had a potential role in increasing the drought resistance of maize in recent discharged coal mine spoil.The experiments provide a direct basis for the use of AM technology to restore the vegetation of coal mine spoil banks in grassland of arid and semiarid area, and demonstrate that AM fungi have a potential role for maize to enhance the ability to adapt the composite adversity of different types of coal mine spoil and play a positive role in the revegetation of different coal mine spoil banks in grassland ecosystem. Further field experiments should be conducted to evaluate the practical effects of AM fungi on the vegetation restoration of different types of coal mine spoil under field conditions.