Coupling relationship between Hedysarum mongdicum shrub plantation and sand soil based on structural equation model

In order to find out the coupling relationship between Hedysarum mongdicum shrub plantation and sand soil, choosing Hedysarum mongdicum planting sand land with good conservation condition, the structural equation model of the plot location-H. mongdicum shrub plantation-physical properties of sand soil-chemical properties of sand soil was built based on the plots in Hunshandake Sand, Inner Mongolia of northern China. The results showed that after 15 years recovery, H. mongdicum shrub plantation coverage-density, soil physical properties and chemical properties both had spatial heterogeneity of varied degrees; H. mongdicum shrub plantation coverage-density mostly had a positive influence on the soil physical properties and chemical properties of 0-10 cm, 10-20 cm and 20-40 cm soil layers, total path coefficients to physical properties were 0.01, 0.42 and 0.50, and to chemical properties were -0.07, 0.49 and 0.79, respectively; The physical properties had positive influence on the chemical properties at 0-10 cm, 10-20 cm and 20-40 cm soil layers, and the total path coefficients were 0.80, 0.89 and 1.00, respectively; Sample location had an indirect influence on the physical properties through affecting the coverage and density of H. mongdicum shrub plantation at 0-10 cm, 10-20 cm and 20-40 cm soil layers, and the indirect influencing coefficients were -0.01, -0.26 and -0.38, respectively. Sample location had an indirect influence on the chemical properties through affecting the coverage and density of H. mongdicum shrub plantation and physical properties at 0-10 cm, 10-20 cm and 20-40 cm soil layers, and the indirect influencing coefficients were -0.15, -0.02 and -0.30, respectively. The coverage and density of H. mongdicum shrub plantation had an indirect influence on the soil chemical properties through affecting the soil physical properties at 0-10 cm, 10-20 cm and 20-40 cm soil layers, and the indirect influencing coefficients were 0.01, 0.37 and 0.50, respectively. In addition to the natural recovery, ecological restoration of sand vegetation could be promoted by cultivating shrub population such as H. mongdicum to improve the fertility indexes of sand soil, and to speed up the recovery of sand vegetation.