Impact of vegetation restoration techniques in slope ecological engineering on AMF colonization in soils

This study systematically investigated the colonization dynamics of arbuscular mycorrhizal fungi (AMF) and their interactions with soil biochemical properties during slope restoration using vegetation concrete technology. The study aims to understand the mycorrhizal ecological effects in vegetation concrete substrates, and provides valuable information for the subsequent application of AMF in the restoration of slope vegetation, enhancing root-zone environments, and achieving the goal of enhancing the stability of slope ecosystems. The study, conducted in Yichang City, Hubei Province, China, utilized the space-for-time substitution method. Vegetation concrete slopes with different restoration durations (2, 3, 5, and 15 a) were selected, with naturally restored slope (15 a) and secondary forest (30 a) serving as controls. In each plot, five 1 m × 1 m quadrats were randomly selected for vegetation survey, within which five 0.25 m × 0.25 m sub-quadrats were sampled within each quadrat. Root samples collected using a mixed sampling approach based on the biomass proportion of dominant plants was employed to ensure the representativeness of host plants. AMF colonization characteristics were quantified using acetic acid ink staining and microporous membrane filtration. Microbial biomass carbon(MBC), microbial biomass nitrogen(MBN), and microbial biomass phosphorus (MBP) were measured using the chloroform fumigation method, and enzyme activities (invertase, urease, catalase, alkaline phosphatase) were analyzed colorimetrically. Pearson correlation, redundancy analysis, and stepwise regression were employed to identify key environmental driving factors. The results indicated that, except for the C1 and N2, the total AMF colonization rates in the remaining plots were all above 60%, classified as high colonization. Across all the plots, the total AMF colonization rates followed a unimodal curve during the vegetation restoration process, reaching their optimum in the mid-restoration phase (3-5 a), with a rate of 69.93% at 5 years, significantly higher than the 44.09% in secondary forest controls. Among the plots, the hyphal colonization rate contributed the most to the total colonization rate, accounting for 80.03%-98.57%, followed by the vesicular colonization rate, while the arbuscular colonization rate contributed the least to the total colonization rate, with a maximum of only 0.05% of the total colonization. The MBC, MBN, and MBP contents in the vegetation concrete restoration plots ranged from 0.47-1.07, 3.47-16.51, and 14.77-77.60 mg/kg, respectively. The activities of invertase(INV), urease(URE), alkaline phosphatase(ALP), and catalase(CAT) in the vegetation concrete restoration plots ranged from 72.11-179.15, 4.09-12.21, 29.85-34.77, and 8.12-12.16 mg/g, respectively. The correlation analysis between AMF growth and soil environmental factors showed that the total infection rate of AMF was closely related to MBC and INV, while the hyphal density was significantly negatively correlated with soil pH and MBN, and significantly positively correlated with AN and MBP (P<0.05). The spore density was significantly positively correlated with MBP, and CAT (P<0.05). Redundancy analysis and regression equations further validated the results of correlation analysis, simultaneously clarifying that MBC is the direct driving factor influencing the colonization and growth of AMF. Research indicates that during the vegetation restoration process on slopes repaired with vegetation concrete, AMF can infect plant roots to form symbiotic associations. Compared to naturally recovered sites and secondary forests, vegetation concrete restoration measures can promote the colonization and growth of AMF. It is recommended that when using vegetation concrete technology to repair slopes, the colonization of AMF be promoted by regulating substrate moisture and nutrients, and microbial management be strengthened at 3 to 5 years post-restoration to optimize ecological benefits. This study provides a theoretical basis and quantitative indicators for the application of mycorrhizal technology in slope engineering.