Toxicity of soil labile aluminum fractions and aluminum species in soil water extracts on the rhizosphere bacterial community of tall fescue

Different forms of aluminum (Al) in soil can be toxic to plants and the bacterial community. In our previous study, the distribution and toxicity to plants of soil Al species and soil labile Al fractions were examined. However, the toxicity of different forms of Al on the bacterial community has not been completely studied. In this study, five soil samples (pH: 4.92, 6.17, 6.62, 6.70, 8.51) were collected from Lichuan, China. Tall fescue was planted in rhizosphere boxes with those soils for 120 days, The toxicity of soil Al species and soil labile Al fractions on the bacterial community of near-rhizosphere (NR) soils and far-rhizosphere (FR) soils were analyzed. The effect of different forms of Al on bacterial community between NR and FR soils was small, but the difference was obvious according to the different spatial distribution of samples. An individual bacterial community has eosinophilia, and most bacterial communities are tolerant of heavy metals (e.g., Cu, Zn, Cd). The toxicity of exchangeable Al has a strong effect on the bacterial community. Meanwhile, the toxicity of Al3+ to the bacterial community is strong. In this study, the key finding was that the toxicity of the Al-F- complex toward the bacterial community and plants was different. AlF2+, AlF2+, AlF3, and AlF4- are toxic for the bacterial community, and the correlation decreases with the addition of F-. This finding is of considerable significance to the treatment of acid-contaminated soil and the study of the tolerance mechanism of plants toward Al.