Salix integra Thunb., a fast-growing woody plant species, has been used for phytoremediation in recent years. However, little knowledge is available regarding indigenous soil microbial communities associated with the S. integra phytoextraction process. In this study, we used an Illumina MiSeq platform to explore the indigenous microbial composition after planting S. integra at different lead (Pb) contamination levels: no Pb, low Pb treatment (Pb 500 mg kg −1 ), and high Pb treatment (Pb 1500 mg kg −1 ). At the same time, the soil properties and their relationship with the bacterial communities were analyzed. The results showed that Pb concentration was highest in the root reaching at 3159.92 ± 138.98 mg kg −1 under the high Pb treatment. Planting S. integra decreased the total Pb concentration by 84.61 and 29.24 mg kg −1 , and increased the acid-soluble Pb proportion by 1.0 and 0.75% in the rhizosphere and bulk soil under the low Pb treatment compared with unplanted soil, respectively. However, it occurred only in the rhizosphere soil under the high Pb treatment. The bacterial community structure and microbial metabolism were related to Pb contamination levels and planting of S. integra, while the bacterial diversity was only affected by Pb contamination levels. The dominant microbial species were similar, but their relative abundance shifted in different treatments. Most of the specific bacterial assemblages whose relative abundances were promoted by root activity and/or Pb contamination were suitable for use in plant-microbial combination remediation, especially many genera coming from Proteobacteria. Redundancy analysis (RDA) showed available nitrogen and pH having a significant effect on the bacteria relating to phytoremediation. The results indicated that indigenous bacteria have great potential in the application of combined S. integra-microbe remediation of lead-contaminated soil by adjusting soil properties.
Poor soil quality caused by salinity and sodicity is the main limitation on plant growth and crop production worldwide. This study focused on the change in the physicochemical properties of the coastal saline-sodic soils of Yellow River Delta with different histories of reclamation. Soil samples representing six different reclamation times (RTs) were collected in two soil profiles (0-20 cm and 20-40 cm). The results showed that soil soluble salts (SSs) significantly decreased with increasing reclamation time, and the change were 32.9%-67.6% in the 0-20 cm layer and 39.0%-73.2% in the 20-40 cm layer, respectively. Based on non-liner fitting, the change regulation of SS with RT was expressed by the following functions:(R 2 = 0.93, p<0.01) in the 0-20 cm layer and SS = (R = 0.97, p<0.01) in the 20-40 cm layer, respectively. The other soil properties, such as bulk density, total carbon, total nitrogen, the ratio of carbon and nitrogen, soil organic matter, available phosphorus, and available potassium significantly improved with increasing RT, but EC and pH had the opposite trend. The change in the physical and chemical properties of saline-sodic soil was higher at 0-20 cm soil depth than at the 20-40 cm soil depth, indicating that the effect of reclamation on salinesodic soils occurs mainly in topsoil. In conclusion, reclamation has been shown to be an effective human activity in terms of improving fertilizer and inhibiting the salinity of saline-sodic soils.
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