Soil quality changes in the Horqin sandy area under different ecological restoration patterns

Ecological restoration is crucial for combatting desertification and mitigating grassland degradation. The assessment of changes in soil quality under different restoration patterns is beneficial for optimizing the development and implementation of local ecological restoration strategies. In this study, five typical restoration patterns of sample plots-plant regenerative sand-barrier land (S2), shrub planted afforested land (S3), aerially seeded afforested land (S4), artificially restored grassland (S5), fenced shrubland (S6), and a control plot (S1)-were selected as research objects in the Horqin sandy area. Four depths of soil samples ranging from 0 to 30 cm were collected from six plots to determine their physicochemical properties, analyze soil primary particle size and nutrient levels in different plots, and propose a soil quality index (SQI) to evaluate the effectiveness of soil restoration under different restoration patterns. The results showed a decrease in sand content under the five restoration patterns, whereas clay and silt content, soil fractal dimension (D value), and SQI increased significantly (P < 0.05). The soil fractal dimension was positively correlated with the contents of clay, slit, and the SQI (P < 0.01). The composite soil quality index from highest to lowest was S6 (0.5877) > S5 (0.5384) > S4 (0.4357) > S3 (0.4068) > S2 (0.1305) > S1 (0.0648). The soil restoration effects were greatest for S5 in the 0-10 cm soil depth, and the soil restoration effects were most effective for S6 in the 10-30 cm soil depth, with SQIs increasing by 11.21 and 7.85 times, respectively, compared with that of the control sample plot. Based on the results at different soil depths, we believe that the restoration pattern of artificially planting shrub-grass combined with fencing may significantly enhance restoration effectiveness on sandy land.