Soil quality and its evaluation under different sand-fixing shrubs in the southern edge of Mu Us Sandy Sand

This study used typical sand-fixing shrub plots in the ecological restoration region of Mu Us Sandy Sand as the research object and sandy land without any sand-fixing shrubs as the control (CK) to investigate the effect of different sand-fixing shrubs on soil quality. The effects of five different sand-fixing shrubs on the physicochemical properties and microbial activities at a soil depth of 0 – 10 cm were analyzed. Additionally, the soil quality under five different sand-fixing shrubs was evaluated using membership function and factor analysis methods. It was found that the shrubland of Caragana korshinskii (N) and the mixed shrubland of C. korshinskii and Corethrodendron scoparium (NH) had the highest clay-silt and very fine sand contents (5.10% and 11.07%, 3.25% and 9.58%, respectively), and the coarse sand content of the two was the lowest (both were 17.88%). Moreover, the soil organic matter content of the five sand-fixing shrub communities was significantly higher than that of CK (P < 0.05), and the total soil carbon content was the highest in the shrubland of C. korshinskii, reaching 6.67 g·kg⁻¹. Available soil nitrogen and total potassium content were the highest in the shrubland of Corethrodendron fruticosum var. mongolicum (Y), which were 4.05 mg·kg⁻¹ and 31.30 g·kg⁻¹, respectively. Furthermore, the number of soil bacteria OTU under Y treatment was significantly lower than that of the other four shrublans (P < 0.05), and the number of soil fungi OTU under NH treatment was significantly higher than that of the other four shrublans (P < 0.05). The results of the correlation analysis showed that the improvement in soil quality was closely related to soil fine grain. Finally, the comprehensive score of the soil quality evaluation was of the following sequence: NH > N > mixed shrubland of C. scoparium and C. mongolicum (HS) > mixed shrubland of C. korshinskii and C. mongolicum (NS) > Y > CK. Therefore, the NH treatment was the most effective sand-fixing shrub for soil quality restoration.