Experimental study on effect of soil layer reconstruction and inoculation on plant root hydraulic lift in open-pit coal mine dump

Soil layer reconstruction of open-pit coal mine dump is of great significance for ecological reconstruction. In order to study the effect of inoculation of dark septate endophytes (DSE) on water utilization of corn root system under different reconstructed soil layer models, soil column simulating and culturing test was adopted, with DSE inoculation and control treatment set up under each of the four soil layer types, in a total of 8 groups. The results show that the roots of corn are the longest with the maximum density under the treatment with 20% loess, which are 3.2, 2.4 and 2.8 times that of 0%, 10% and 40% loess respectively. After water stress, the root system has the capability to grow downward and absorb deep water. According to the water source analysis of MixSIAR model based on δ¹⁸O value, the water at the depth of 0-25 cm is mainly used by corn at the water utilization ratio of 80% under the treatment with 0% loess, and the water at the depth of 15-35 cm is mainly used by corn at the water utilization ratio of 64% under the treatment with 10% loess. However, the water utilization ratio of corn is 36% at the depth of 0-25 cm only and 64% at the depth of 25-45 cm under the treatment with 20% loess, indicating that the water in deep soil is mainly used by corn under the treatment with 20% loess. The DSE inoculation improves the capability of plants to absorb deeper water. Specifically, the depth of water used increases by 5 cm under the treatment with 20% loess. The hydraulic lift of plant roots is maximized under drought stress through inoculation treatment in the matrix containing 20% loess, with the total hydraulic lift during the growth period increased by 45% compared with that treatment without DSE inoculation. The hydraulic lift of plant roots mixed with 20% loess is 1.45 times that of 0% loess under the condition without DSE inoculation, while the hydraulic lift of plant roots mixed with 20% loess can reach 1.72 times that of 0% loess under the condition with DSE inoculation. In conclusion, DSE inoculation and soil layer reconstruction have significant effects on improving the hydraulic lift of plants. In addition, the results of this study could provide experimental reference basis for the improvement of soil and water utilization efficiency of plants in the process of soil layer reconstruction of open-pit mine dump.