1.College of Hydraulic & Environmental Engineering,China Three Gorges University,Yichang,Hubei 443002,China
2.Hubei Provincial Engineering Research Center for Cement-based Ecological Restoration Technology,China Three Gorges University,Yichang,Hubei 443002,China
3.College of Biological & Pharmaceutical Sciences,China Three Gorges University,Yichang,Hubei 443002,China
Objective To explore the influencing mechanisms of biological soil crusts on the distribution and stability characteristics of soil aggregates in slope ecological restoration. Methods Soils from vegetation concrete slopes mulched with different types of biological soil crusts (algal crusts, mixed crusts, and moss crusts) were used as research objects, with soils without crust mulching as the control group (CK). The Le Bissonnais (LB) method was applied to investigate the distribution and stability of soil aggregates and the physicochemical properties of different soil layers (0-2 cm and 2-5 cm). Results 1) Compared with CK, the content of >0.25 mm aggregates (R0.25) increased by 12.53%, 21.97%, and 30.20% in the 0-2 cm layer and by 20.11%, 32.00%, and 44.34% in the 2-5 cm layer under algal crust, mixed crust, and moss crust mulching, respectively. This indicated that biological soil crusts had a significant effect on soil aggregate stability and R0.25, with moss crusts showing the best effect in improving aggregate stability. 2) In the three wetting treatments of LB method (fast wetting-FW, slow wetting-SW, and wetting stirring-WS), the soil aggregate stability in different soil layers and under different types of biological soil crust mulching showed the trend of MWDFW<MWDWS<MWDSW and GMDFW<GMDWS<GMDSW, and the mean weight diameter (MWD) and geometric mean diameter (GMD) decreased with increasing soil depth. This indicated that SW caused the least destruction to soil aggregates, while FW had the greatest effect. 3) Biological soil crusts had more pronounced effects on increasing surface soil organic carbon (SOC), calcium-bound organic carbon (Ca-SOC), clay, and silt content. Correlation analysis showed that soil aggregate stability indicators (MWD, GMD, R0.25) were extremely significantly positively correlated with SOC, clay content, and Ca-SOC (p<0.01), and extremely significantly negatively correlated with relative slaking index (RSI), relative mechanical breakdown index (RMI), and sand content (p<0.01). The correlation with silt content was positive but not significant. These results suggested that biological soil crusts influenced aggregate stability by affecting soil particle composition, SOC, and Ca-SOC. Conclusion Biological soil crusts can effectively enhance soil erosion resistance, and promote the formation of large aggregates from smaller ones, thereby improving aggregate stability and soil structure. Thus, the biological soil crusts play a crucial role in soil erosion control during slope ecological restoration and ecosystem stabilization and can provide scientific support for the construction and species selection for vegetation concrete slopes.
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